[Ronald de Sousa] Taking literally the concept of emotional truth requires breaking the monopoly on truth of belief-like states. To this end, I look to perceptions for a model of non-propositional states that might be true or false, and to desires for a model of propositional attitudes the norm of which is other than the semantic satisfaction of their propositional object. Those models inspire a conception of generic truth, which can admit of degrees for analogue representations such as emotions; (...) belief-like states, by contrast, are digital representations. I argue that the gravest problem-objectivity-is not insurmountable. /// [Adam Morton ] It is accuracy rather than truth itself that is valuable. Emotional truth is a dubious though attractive notion, but emotional accuracy is much easier to make sense of. My approach to accuracy goes via an account of what makes a story accurate. Stories can be accurate but not true, and emotions can be accurate whether or not they are true. The capacity for emotional accuracy, for emotions that fit a person's situation, is an aspect of emotional intelligence, which is as important an aspect of rational human agency as the intelligent formation of beliefs and desires. (shrink)

Despite the fact that common sense taxes emotions with irrationality, philosophers have, by and large, celebrated their functionality. They are credited with motivating, steadying, shaping or harmonizing our dispositions to act, and with policing norms of social behaviour. It's time to restore emotion's bad rep. To this end, I shall argue that we should expect that some of the “norms” enforced by emotions will be unevenly distributed among the members of our species, and may be dysfunctional at the individual, social, (...) moral, or even species levels. I”ll adduce three considerations in support of that pessimistic view: The fallacy of adaptive fixation, the moral randomness of group selection, and the lack of fit between “natural norms” set up by evolution and those moral and social norms we would like philosophy to justify. (shrink)

Abstract (German version follows): -/- This paper develops a new proposal for a coherentist business ethic in which ethically justified and empirically supported proposed solutions to economic problems are developed through a coherentist process of adjustments between the three levels of (1) conception of problem and its solution, (2) positive economic theory, and (3) ethical theories. Using an example, it illustrates how in this framework, Homann's business ethics gains in validity and relevance but loses its claim to universality. // -/- (...) Diese Arbeit entwickelt eine kohärentistische Wirtschaftsethik, in der ethisch begründete und empirisch gestützte Lösungsvorschläge für ökonomische Probleme durch einen kohärentistischen Anpassungsprozess zwischen den drei Ebenen (1) Auffassung von Problem und Lösungsansatz, (2) positive ökonomische Theorie, sowie (3) ethischen Theorien erarbeitet werden. Anhand eines Beispiels wird illustriert, wie Homanns Wirtschaftsethik in diesem Rahmen an Validität und Relevanz gewinnt, jedoch ihren Universalitätsanspruch verliert. (shrink)

In this paper we examine to what extent the lengths of the links in an animated articulated figure can be changed without the viewer being aware of the change. This is investigated in terms of a framework that emphasizes the role of attention in visual perception. We conducted a set of five experiments to establish bounds for the sen-sitivity to changes in length as a function of several parameters and the amount of attention available. We found that while length changes (...) of 3% can be perceived when the relevant links are given full attention, changes of over 20% can go unnoticed when attention is not focused in this way. These results provide general guidelines for algorithms that produce or process character motion data and also bring to light some of the potential gains that stand to be achieved with attention-based algorithms. (shrink)

In this paper we suggest a revisionist perspective on two significant figures in early modern life science and philosophy: William Harvey and John Locke. Harvey, the discoverer of the circulation of the blood, is often named as one of the rare representatives of the ‘life sciences’ who was a major figure in the Scientific Revolution. While this status itself is problematic, we would like to call attention to a different kind of problem: Harvey dislikes abstraction and controlled experiments (aside from (...) the ligature experiment in De Motu Cordis), tends to dismiss the value of instruments such as the microscope, and emphasizes instead the privileged status of ‘observed experience’. To use a contemporary term, Harvey appears to rely on, and chiefly value, ‘tacit knowledge’. Secondly, Locke’s project is often explained with reference to the image he uses in the Epistle to the Reader of his Essay, that he was an “underlabourer” of the sciences. In fact, despite the significant medical phase of his career, Locke’s ‘empiricism’ turns out to be above all a practical (i.e. ‘moral’) project, which focuses on the delimitation of our powers in order to achieve happiness, and rejects the possibility of naturalizing knowledge. When combined, these two cases suggest a different view of some canonical moments in early modern natural philosophy. (shrink)

Résumé Charles Wolfe vient de publier Lire le matérialisme (ENS Éditions, 2020), où il esquisse une histoire des différentes formes de matérialisme, y compris le matérialisme vitaliste et les versions du XXe et du XXIe siècle. Pierre-François Moreau, auteur de la préface de l’ouvrage, entame ici une discussion sur les problèmes et les ressources d’une telle histoire.

A presente pesquisa visa caracterizar o método empregado por Aristóteles na Ethica Nicomachea a partir de uma análise que contrasta duas interpretações: de um lado, a tese já tradicional que busca ver na filosofia prática do Estagirita um método estritamente dialético; de outro, a tese alternativa, explorada apenas recentemente, que aponta o uso, na EN, de um procedimento filosófico próximo das prescrições sugeridas nos Segundos Analíticos para a busca definicional nas ciências. O núcleo da primeira tese deverá ser analisado sob (...) duas perspectivas: (i) examinando um conjunto de textos que revelam o teor dialético da filosofia aristotélica; e (ii) avaliando o processo de expansão da noção de dialética e suas implicações para os estudos aristotélicos. Alternativamente, (i) será examinado como um modelo de tipo definicional pode reaproximar a ética do registro científico dos Segundos Analíticos sem necessariamente se valer de argumentos dialéticos. Por fim (ii), proponho uma versão deflacionária do que deve contar como método dialético em Aristóteles. (shrink)

RAAAF [Rietveld Architecture-Art-Affordances] is an interdisciplinary studio that operates at the crossroads of visual art, experimental architecture and philosophy. RAAAF makes location- and context-specific artworks, an approach that derives from the respective backgrounds of the founding partners: Prix de Rome laureate Ronald Rietveld and Socrates Professor in Philosophy Erik Rietveld.

Sensibility, in any of its myriad realms – moral, physical, aesthetic, medical and so on – seems to be a paramount case of a higher-level, intentional property, not a basic property. Diderot famously made the bold and attributive move of postulating that matter itself senses, or that sensibility (perhaps better translated ‘sensitivity’ here) is a general or universal property of matter, even if he at times took a step back from this claim and called it a “supposition.” Crucially, sensibility is (...) here playing the role of a ‘booster’: it enables materialism to provide a full and rich account of the phenomena of conscious, sentient life, contrary to what its opponents hold: for if matter can sense, and sensibility is not a merely mechanical process, then the loftiest cognitive plateaus are accessible to materialist analysis, or at least belong to one and the same world as the rest of matter. This was noted by the astute anti-materialist critic, the Abbé Lelarge de Lignac, who, in his 1751 Lettres à un Amériquain, criticized Buffon for “granting to the body [la machine, a common term for the body at the time] a quality which is essential to minds, namely sensibility.” This view, here attributed to Buffon and definitely held by Diderot, was comparatively rare. If we look for the sources of this concept, the most notable ones are physiological and medical treatises by prominent figures such as Robert Whytt, Albrecht von Haller and the Montpellier vitalist Théophile de Bordeu. We then have, or so I shall try to sketch out, an intellectual landscape in which new – or newly articulated – properties such as irritability and sensibility are presented either as an experimental property of muscle fibers, that can be understood mechanistically (Hallerian irritability, as studied recently by Hubert Steinke and Dominique Boury) or a property of matter itself (whether specifically living matter as in Bordeu and his fellow montpelliérains Ménuret and Fouquet, or matter in general, as in Diderot). I am by no means convinced that it is one and the same ‘sensibility’ that is at issue in debates between these figures (as when Bordeu attacks Haller’s distinction between irritability and sensibility and claims that ‘his own’ property of sensibility is both more correct and more fundamental in organic beings), but I am interested in mapping out a topography of the problem of sensibility as property of matter or as vital force in mid-eighteenth-century debates – not an exhaustive cartography of all possible positions or theories, but an attempt to understand the ‘triangulation’ of three views: a vitalist view in which sensibility is fundamental, matching up with a conception of the organism as the sum of parts conceived as little lives (Bordeu et al.); a mechanist, or ‘enhanced mechanist’ view in which one can work upwards, step by step from the basic property of irritability to the higher-level property of sensibility (Haller); and, more eclectic, a materialist view which seeks to combine the mechanistic, componential rigour and explanatory power of the Hallerian approach, with the monistic and metaphysically explosive potential of the vitalist approach (Diderot). It is my hope that examining Diderot in the context of this triangulated topography of sensibility as property sheds light on his famous proclamation regarding sensibility as a universal property of matter. (shrink)

The materialist approach to the body is often, if not always understood in ‘mechanistic’ terms, as the view in which the properties unique to organic, living embodied agents are reduced to or described in terms of properties that characterize matter as a whole, which allow of mechanistic explanation. Indeed, from Hobbes and Descartes in the 17th century to the popularity of automata such as Vaucanson’s in the 18th century, this vision of things would seem to be correct. In this paper (...) I aim to correct this inaccurate vision of materialism. On the contrary, the materialist project on closer consideration reveals itself to be, significantly if not exclusively, (a) a body of theories specifically focused on the contribution that ‘biology’ or rather ‘natural history’ and physiology make to metaphysical debates, (b) much more intimately connected to what we now call ‘vitalism’ (a case in point is the presence of Théophile de Bordeu, a prominent Montpellier physician and theorist of vitalism, as a fictional character and spokesman of materialism, in Diderot’s novel D’Alembert’s Dream), and ultimately (c) an anti-mechanistic doctrine which focuses on the unique properties of organic beings. To establish this revised vision of materialism I examine philosophical texts such as La Mettrie’s Man a Machine and Diderot’s D’Alembert’s Dream; medical entries in the Encyclopédie by physicians such as Ménuret and Fouquet; and clandestine combinations of all such sources (Fontenelle, Gaultier and others). (shrink)

Der Aufsatz beschäftigt sich am Beispiel des deutschen "Kopftuchstreits" mit der rechtlich-politischen Auseinandersetzung um subjektive Rechte innerhalb des liberalen Rechtsstaats. Wie Christoph Menke in seiner Deutung der für den politischen Liberalismus wesentlichen politischen Konflikte gezeigt hat, bezieht sich diese Auseinandersetzung vorrangig auf zwei Fragen: Wer sollte Anspruch darauf genießen, ein politisches Subjekt zu sein, das heißt, als Gleiche oder Gleicher berücksichtigt zu werden? Welche Ansprüche politischer Subjekte könneen als schützenswerte Verwirklichung subjektiver Rechte gelten? Der vorliegende Beitrag beschäftigt sich vorwiegend mit (...) der Frage, wie die politischen Konflikte des letztgenannten Typs auf die rechtliche Auseinandersetzung um Grundrechte abfärben. Damit wende ich mich gegen ein Verständnis der Grundrechte, das diese als Garant der ethischen Neutralität eines liberalen Gemeinwesens ansieht. Ich möchte zeigen, dass der Sinn subjektiver Rechte in der liberalen Demokratie zwar unter anderem genau darin besteht, dass sie partikulare ethische Wertvorstellungen neutralisieren und die Bürgerinnen und Bürger innerhalb eines vernünftigen Rahmens vor Unterdrückung schützen. Wie eine Analyse der Entscheidungen des Bundesverfassungsgerichts (BVerfG) zum "Kopftuchstreit" zeigt, wird diese Funktion aber stets zugleich durch die partikulare Interpretation gleicher Rechte unterminiert. Dies bezeichne ich als die Dekonstruktion der Neutralität, die sich im Recht vollzieht. (shrink)

ABSTRACT: GEORGES CANGUILHEM’S BIOPHILOSOPHY The eminent French biologist and historian of biology, François Jacob, once notoriously declared «On n’interroge plus la vie dans les laboratoires»: laboratory research no longer inquires into the notion of “Life”. Certain influential French philosophers of science of the mid‐century such as Georges Canguilhem would disagree, or at least seek to resist some of Jacob’s diagnosis. Not by imposing a different kind of research program in laboratories, but by an unusual combination of historical and philosophical inquiry (...) into the foundations of the life sciences. Canguilhem speaks of «defending vitalist biology» and declares that Life cannot be grasped by logic. Is this history and philosophy of biology? Is it vitalism? It definitely is a different project from current philosophy of biology. One short‐lived term for it was “biophilosophy”. In this paper I explore the content of this term as it relates to the above questions. (shrink)

Locke and Leibniz deny that there are any such beings as ‘monsters’ (anomalies, natural curiosities, wonders, and marvels), for two very different reasons. For Locke, monsters are not ‘natural kinds’: the word ‘monster’ does not individuate any specific class of beings ‘out there’ in the natural world. Monsters depend on our subjective viewpoint. For Leibniz, there are no monsters because we are all parts of the Great Chain of Being. Everything that happens, happens for a reason, including a monstrous birth. (...) But what about materialism? Well, beginning with the anatomical interest into ‘monstrous births’ in the French Académie des Sciences in the first three decades of the eighteenth century, there is a shift away from ‘imaginationist’ claims such as those of Malebranche, that if a woman gives birth to a monstrous child it is a consequence of something she imagined. Anatomists such as Lemery and Winslow try to formulate a strictly mechanical explanation for such events, rejecting moral and metaphysical explanations. Picking up on this work, materialist thinkers like Diderot are compelled to reject the very idea of monsters. We are all material beings produced according to the same mechanisms or laws, some of us are more ‘successful’ products than others, i.e. some live longer than others. In his late Eléments de physiologie he says “L’homme est un effet commun, le monstre un effet rare.” Ultimately he arrives at a materialist version of Leibniz’s position: there are no monsters, we are all monsters in each other’s eyes, at one time or another. This conclusion is a pregnant one in light of twentieth century interest in the problem of ‘the normal and the pathological’ (Canguilhem), and the broader question of how materialism relates to the biological world. (shrink)

The concept of self has preeminently been asserted (in its many versions) as a core component of anti-reductionist, antinaturalistic philosophical positions, from Descartes to Husserl and beyond, with the exception of some hybrid or intermediate positions which declare rather glibly that, since we are biological entities which fully belong to the natural world, and we are conscious of ourselves as 'selves', therefore the self belongs to the natural world (this is characteristic e.g. of embodied phenomenology and enactivism). Nevertheless, from Cudworth (...) and More’s attacks on materialism all the way through twentieth-century argument against naturalism, the gulf between selfhood and the world of Nature appears unbridgeable. In contrast, my goal in this paper is to show that early modern materialism could yield a theory of the self according to which (1) the self belongs to the world of external relations (Spinoza), such that no one fact, including supposedly private facts, is only accessible to a single person; (2) the self can be reconstructed as a sense of “organic unity” which could be a condition for biological individuality (a central text here is Diderot’s 1769 Rêve de D’Alembert); yet this should not lead us to espouse a Romantic concept of organism as foundational or even ineffable subjectivity (a dimension present in Leibniz and made explicit in German idealism); (3) what we call 'self' might simply be a dynamic process of interpretive activity undertaken by the brain. This materialist theory of the self should not neglect the nature of experience, but it should also not have to take at face value the recurring invocations of a better, deeper “first-person perspective” or “first-person science.”. (shrink)

The eminent French biologist and historian of biology, François Jacob, once notoriously declared “On n’interroge plus la vie dans les laboratoires”: laboratory research no longer inquires into the notion of ‘Life’. Nowadays, as David Hull puts it, “both scientists and philosophers take ontological reduction for granted… Organisms are ‘nothing but’ atoms, and that is that.” In the mid-twentieth century, from the immediate post-war period to the late 1960s, French philosophers of science such as Georges Canguilhem, Raymond Ruyer and Gilbert Simondon (...) returned to Jacob’s statement with an odd kind of pathos: they were determined to reverse course. Not by imposing a different kind of research program in laboratories, but by an unusual combination of historical and philosophical inquiry into the foundations of the life sciences (particularly medicine, physiology and the cluster of activities that were termed ‘biology’ in the early 1800s). Even in as straightforwardly scholarly a work as La formation du concept de réflexe aux XVIIe et XVIIIe siècles (1955), Canguilhem speaks oddly of “defending vitalist biology,” and declares that Life cannot be grasped by logic (or at least, “la vie déconcerte la logique”). Was all this historical and philosophical work merely a reassertion of ‘mysterian’, magical vitalism? In order to answer this question we need to achieve some perspective on Canguilhem’s ‘vitalism’, notably with respect to its philosophical influences such as Kurt Goldstein. (shrink)

From Hegel to Engels, Sartre and Ruyer (Ruyer, 1933), to name only a few, materialism is viewed as a necropolis, or the metaphysics befitting such an abode; many speak of matter’s crudeness, bruteness, coldness or stupidity. Science or scientism, on this view, reduces the living world to ‘dead matter’, ‘brutish’, ‘mechanical, lifeless matter’, thereby also stripping it of its freedom (Crocker, 1959). Materialism is often wrongly presented as ‘mechanistic materialism’ – with ‘Death of Nature’ echoes of de-humanization and hostility to (...) the Scientific Revolution (which knew nothing of materialism!), also a powerful Christian theme in Cudworth, Clarke and beyond (Overhoff, 2000). Here I challenge this view, building on some aspects of Israel’s Radical Enlightenment concept (Israel, 2001), which has been controversial but for my purposes is a useful claim about the dissemination of a home-grown Spinozism, sometimes reformulated as an ontology of the life sciences, an aspect Israel does not address (compare Secrétan et al., eds., 2007; Citton, 2006). First, I examine some ‘moments’ of radical Enlightenment materialism such as La Mettrie and Diderot (including his Encyclopédie entry “Spinosiste”), but also anonymous, clandestine texts such as L’Âme Matérielle, to emphasize their distinctive focus on the specific existence of organic beings. Second, I show how this ‘embodied’, non-mechanistic character of Enlightenment ‘vital materialism’ makes it different from other episodes, and perhaps more of an ethics than is usually thought (also via the figure of the materialist as ‘laughing philosopher’). Third, I reflect on what this implies for our image of the Enlightenment – no longer a Frankfurt School and/or Foucaldian vision of ‘discipline’, regimentation and order (as in Mayr, 1986) – but ‘vital’, without, conversely, being a kind of holist vitalism “at odds with the universalizing discourse of Encyclopedist materialism, with its insistence on the uniformity of nature and the universality of physical laws” (Williams, 2003): vital materialism is still materialism. Its ethics tends towards hedonism, but its most radical proponents (Diderot, La Mettrie and later Sade) disagree as to what this means. (shrink)

Sind die Menschenrechte primär Ausdruck einer politischen Praxis und die Idee der Menschenrechte eine Art „Überbau“, den die Praxis epiphänomenal hervorbringt? Oder ist die Praxis der Menschenrechte das Ergebnis der Verwirklichung einer normativen Idee, die unabhängig von ihr existiert? Ist die Idee der Menschenrechte die Bedingung dafür, dass es die Praxis der Menschenrechte geben kann? Oder gibt es einen Vorrang der Praxis vor der Idee? In meinem Aufsatz argumentiere ich für zwei These: 1. These: Menschenrechte sind prinzipiell unabhängig von jeder (...) bestehenden rechtlichpolitischen Praxis und sind zugleich untrennbar an bestimmte rechtlich-politische Praktiken geknüpft. Darin besteht der konstitutive Widerspruch der Menschenrechte. 2. These: Aus diesem Widerspruch folgt nicht, dass wir aufhören sollten über Menschenrechte nachzudenken und eine Politik der Menschenrechte anzustreben. Der Widerspruch hat keine lähmende Wirkung, sondern ist theoretisch und praktisch produktiv. Um diese Thesen zu plausiblisieren, werde ich zunächst einige Grundzüge von Arendts Diskussion der Menschenrechte rekapitulieren (Abschnitt 2) und ihr Postulat eines den Menschenrechten vorgelagerten „Rechts, Rechte zu haben“ diskutieren (Abschnitt 3). Ausgehend von einer kritischen Diskussion der diskurstheoretischen Weiterentwicklung von Arendts These zu einem „Recht auf Rechtfertigung“ im diskurstheoretischen Konstruktivismus von Seyla Benhabib und Rainer Forst (Abschnitt 4) werde ich einen rechtfertigungstheoretischen Dekonstruktivismus vorstellen, der das Verhältnis von Praxis und Idee der Menschenrechte als produktiven Widerspruch fasst (Abschnitt 5). (shrink)

an essay on monsters, science and categories from Diderot to Baudelaire.

Ce livre étudie, à travers une série d'épisodes allant de la philosophie des Lumières à notre époque, le problème du matérialisme dans l'histoire de la philosophie et l’histoire des sciences. Comment comprendre les spécificités de l’histoire du matérialisme, des Lumières à nos jours, au sein de la grande histoire de la philosophie et de l’histoire des sciences ? Quelle est l’actualité de l’opposition classique entre le corps et l’esprit ? Qu’est-ce que le rire ou le rêve peuvent nous apprendre du (...) matérialisme ? En traversant l’histoire de ce concept jusqu’à l’émergence d’un « nouveau matérialisme » contemporain, l’ouvrage vise à revitaliser le matérialisme et sa lecture. -/- . (shrink)

Is justice (merely) an expression of particular values or is it to be understood as a (universal) cross-cultural standard of validity? Following the ideas of Jacques Derrida, this book provides a new answer to this question: Justice is to be explained as a process of deconstruction. To arrive at this conclusion, I proceed from a critical discussion of Martin Heidegger's approach to social philosophy in Being and Time which I connect with a detailed analysis of the implications of Derrida's writings (...) on practical philosophy aspiring to provide a variety of insights, both critical and constructive, into the cultural and normative foundations of democracy. Thematically, the book bridges the frontiers between the philosophy of law, cultural and social philosophy, ethics and political theory, focusing on fundamental questions of the constitution of normativity, responsibility and justification. In this way, my reading of Heidegger and Derrida aims to shed light on the nature of the political problems that concern our societies today. The file contains the table of contents and the first two (introductory) chapters, the introductions of the remaining chapters, as well as the concluding remarks (in German). (shrink)

It is now well-known that Newton–Cartan theory is the correct geometrical setting for modelling the quantum Hall effect. In addition, in recent years edge modes for the Newton–Cartan quantum Hall effect have been derived. However, the existence of these edge modes has, as of yet, been derived using only orthodox methodologies involving the breaking of gauge-invariance; it would be preferable to derive the existence of such edge modes in a gauge-invariant manner. In this article, we employ recent work by Donnelly (...) and Freidel in order to accomplish exactly this task. Our results agree with known physics, but afford greater conceptual insight into the existence of these edge modes: in particular, they connect them to subtle aspects of Newton–Cartan geometry and pave the way for further applications of Newton–Cartan theory in condensed matter physics. (shrink)

When looking at a scene, observers feel that they see its entire structure in great detail and can immediately notice any changes in it. However, when brief blank fields are placed between alternating displays of an original and a modified scene, a striking failure of perception is induced: identification of changes becomes extremely difficult, even when changes are large and made repeatedly. Identification is much faster when a verbal cue is provided, showing that poor visibility is not the cause of (...) this difficulty. Identification is also faster for objects mentioned in brief verbal descriptions of the scene. These results support the idea that observers never form a complete, detailed representation of their surroundings. In addition, results also indicate that attention is required to perceive change, and that in the absence of localized motion signals it is guided on the basis of high-level interest. (shrink)

Five aspects of visual change detection are reviewed. The first concerns the concept of change itself, in particular the ways it differs from the related notions of motion and difference. The second involves the various methodological approaches that have been developed to study change detection; it is shown that under a variety of conditions observers are often unable to see large changes directly in their field of view. Next, it is argued that this “change blindness” indicates that focused attention is (...) needed to detect change, and that this can help map out the nature of visual attention. The fourth aspect concerns how these results affect our understanding of visual perception—for example, the implication that a sparse, dynamic representation underlies much of our visual experience. Finally, a brief discussion is presented concerning the limits to our current understanding of change detection. (shrink)

One of the more powerful impressions created by vision is that of a coherent, richly-detailed world where everything is present simultaneously. Indeed, this impression is so compelling that we tend to ascribe these properties not only to the external world, but to our internal representations as well. But results from several recent experiments argue against this latter ascription. For example, changes in images of real-world scenes often go unnoticed when made during a saccade, flicker, blink, or movie cut. This "change (...) blindness" provides strong evidence against the idea that our brains contain a picture-like representation of the scene that is everywhere detailed and coherent. (shrink)

Large changes that occur in clear view of an observer can become difficult to notice if made during an eye movement, blink, or other such disturbance. This change blindness is consistent with the proposal that focused visual attention is necessary to see change, with a change becoming difficult to notice whenever conditions prevent attention from being automatically drawn to it. -/- It is shown here how the phenomenon of change blindness can provide new results on the nature of visual attention, (...) including estimates of its capacity and the extent to which it can bind visual properties into coherent descriptions. It is also shown how the resultant characterization of attention can in turn provide new insights into the role that it plays in the perception of scenes and events. (shrink)

Large changes in a scene often become difficult to notice if made during an eye movement, image flicker, movie cut, or other such disturbance. It is argued here that this _change blindness_ can serve as a useful tool to explore various aspects of vision. This argument centers around the proposal that focused attention is needed for the explicit perception of change. Given this, the study of change perception can provide a useful way to determine the nature of visual attention, and (...) to cast new light on the way that it is?and is not?involved in visual perception. To illustrate the power of this approach, this paper surveys its use in exploring three different aspects of vision. The first concerns the general nature of _seeing_. To explain why change blindness can be easily induced in experiments but apparently not in everyday life, it is proposed that perception involves a _virtual representation_, where object representations do not accumulate, but are formed as needed. An architecture containing both attentional and nonattentional streams is proposed as a way to implement this scheme. The second aspect concerns the ability of observers to detect change even when they have no visual experience of it. This _sensing_ is found to take on at least two forms: detection without visual experience (but still with conscious awareness), and detection without any awareness at all. It is proposed that these are both due to the operation of a nonattentional visual stream. The final aspect considered is the nature of visual attention itself?the mechanisms involved when _scrutinizing_ items. Experiments using controlled stimuli show the existence of various limits on visual search for change. It is shown that these limits provide a powerful means to map out the attentional mechanisms involved. (shrink)

A set of visual search experiments tested the proposal that focused attention is needed to detect change. Displays were arrays of rectangles, with the target being the item that continually changed its orientation or contrast polarity. Five aspects of performance were examined: linearity of response, processing time, capacity, selectivity, and memory trace. Detection of change was found to be a self-terminating process requiring a time that increased linearly with the number of items in the display. Capacity for orientation was found (...) to be about 5 items, a value comparable to estimates of attentional capacity. Observers were able to filter out both static and dynamic variations in irrelevant properties. Analysis also indicated a memory for previously-attended locations. These results support the hypothesis that the process needed to detect change is much the same as the attentional process needed to detect complex static patterns. Interestingly, the features of orientation and polarity were found to be handled in somewhat different ways. Taken together, these results not only provide evidence that focused attention is needed to see change, but also show that change detection itself can provide new insights into the nature of attentional processing. (shrink)

Experiments are presented showing that visual search for Mueller-Lyer (ML) stimuli is based on complete configurations, rather than component segments. Segments easily detected in isolation were difficult to detect when embedded in a configuration, indicating preemption by low-level groups. This preemption—which caused stimulus components to become inaccessible to rapid search—was an all-or-nothing effect, and so could serve as a powerful test of grouping. It is shown that these effects are unlikely to be due to blurring by simple spatial filters at (...) early visual levels. It is proposed instead that they are due to more sophisticated processes that rapidly bind contour fragments into spatially-extended assemblies. These results support the view that rapid visual search cannot access the primitives formed at the earliest stages of visual processing; rather, it can access only higher-level, more ecologically-relevant structures. (shrink)

TRANSPORTE DE GAMETAS, FERTILIZAÇÃO E SEGMENTAÇÃO -/- • _____OBJETIVO -/- O entendimento do desenvolvimento embrionário nos estágios iniciais, desde a deposição dos espermatozoides na fêmea, passando pela fertilização deste no ovócito e na formação do zigoto, é de suma importância para diferenciar especialistas em reprodução e manejo reprodutivo no mercado de trabalho e, também, durante a vida acadêmica. Compreender os processos que levam à formação do zigoto na fêmea é essencial para avaliar a capacidade reprodutiva dos animais e, mediante técnicas, (...) avaliar o trato reprodutivo da fêmea e o desenvolvimento do embrião até a formação do feto e, por fim, em um novo animal sadio na propriedade. Com esse trabalho, o estudante de veterinária ou zootecnia, que deseja se aprofundar na fisiologia da reprodução animal, identificará os mecanismos que são envolvidos no transporte dos gametas, bem como os processos que estes últimos devem completar para alcançar a fertilização e para desencadear as divisões iniciais do embrião. -/- • _____INTRODUÇÃO -/- A fertilização ou fecundação é o processo pelo qual os gametas masculino (espermatozoide) e feminino (ovócito) se fundem para gerar um novo indivíduo. Seu êxito depende da culminação adequada dos diferentes processos que devem sofrer os gametas durante sua maduração e percurso; do transporte oportuno destes no trato reprodutivo da fêmea, assim como de uma série de adaptações dos órgãos genitais internos da mãe. A segmentação refere-se às primeiras divisões celulares do embrião. -/- • _____TRANSPORTE DO OVÓCITO -/- O ovócito que é liberado na ovulação, e que se encontra coberto pelas células do cumulus (figura 1), é capturado pela fímbria do infundíbulo ao aderir aos cílios. Esse processo é altamente eficaz, inclusive em espécies onde os ovários possuem várias formações globosas, por exemplo nas porcas, onde os ovidutos capturam entre 95 e 100% dos ovócitos que são ovulados. As contrações das camadas musculares do oviduto e o movimento intenso dos cílios da mucosa faz com que as secreções fluam em direção ao útero, transportando assim o complexo cumulus-ovócito. Esse transporte é relativamente rápido até alcançar a junção da ampola com o istmo (que é considerado o local de fertilização do espermatozoide e ovócito) a partir do qual se torna lento. Devido a fêmea estar em estro, o processo está sob controle endócrino, isto é, controle hormonal através do estradiol. Nas fêmeas domésticas, ao contrário das mulheres, o transporte ao longo do oviduto é extremamente eficiente, pois os embriões passam para o útero sem dificuldade, de modo que gestações ectópicas (tubárias ou em cavidade) são quase inexistentes. A égua, frequentemente, retém por muito tempo os ovócitos não fertilizados no oviduto, provavelmente devido a não secreção de substâncias (como a prostaglandina E) que poderiam favorecer sua passagem, como se propõe que aconteça com os embriões. A figura 2 apresenta um ovócito com suas respectivas estruturas. Figura 1: ovócitos de uma vaca madurados in vitro. Nota-se as células do cumulus que os recobre. -/- Figura 2: estruturas do ovócito de uma ovelha que se encontra na etapa de ovócito secundário, depois da ovulação. Elaborado pelo autor. • _____TRANSPORTE ESPERMÁTICO -/- Para que os espermatozoides sejam capazes de fertilizar o ovócito, deverão sofrer uma série de mudanças bioquímicas e morfológicas ao longo de sua passagem pelo aparelho reprodutor tanto masculino como feminino. Uma vez produzidos na parede do túbulo seminífero, os espermatozoides são liberados em direção ao lúmen tubular e transportados passivamente para uma estrutura ramificada conhecida como rede testicular (rete testis). Dessa rede são conduzidos em direção ao epidídimo passando através de 10 a 20 ductos eferentes localizados no polo superior do testículo. O epidídimo é dividido em três seções denominadas cabeça, corpo e cauda; é constituído por um só ducto longo e tortuoso que continua com o canal deferente. Ao final desemboca nas ampolas seminais, no ducto ejaculatório e na uretra. As funções do epidídimo são as de maduração, transporte e armazenamento dos espermatozoides. O transporte através do epidídimo é lento, aproximadamente de 10 dias em touros, e segue sendo passivo. Os espermatozoides tomados da cabeça do epidídimo são ainda imaturos e incapazes de fertilizar, enquanto os armazenados na cauda são completamente maduros. Durante o trânsito pelo epidídimo os espermatozoides adquirem motilidade e o potencial para fertilizar, o acrossomo é remodelado e a gota citoplasmática migra para o flagelo e é liberada. Quando um macho ejacula com muita frequência, é possível observar espermatozoides com gota citoplasmática no sêmen, já que não há tempo suficiente para que completem sua maduração. Os espermatozoides são expulsados fora do organismo durante a cópula, na masturbação ou em emissões espontâneas. Na ejaculação, os espermatozoides que se encontram suspensos nos fluidos do testículo e do epidídimo, misturam-se ao chegar na uretra com as secreções das glândulas acessórias para formar o sêmen. Essas secreções denominadas plasma seminal, proporcionam substâncias para manter o metabolismo energético das células espermáticas, e integram suas membranas elementos que impedem uma capacitação prematura. Durante a cópula, o sêmen é depositado na vagina ou no útero, variando entre as espécies (tabela 1). Na monta natural, geralmente, o serviço ocorre no momento propício, já que está definido pela fase do ciclo estral em que a fêmea é receptiva ao macho. No entanto, na inseminação artificial, é o macho que deverá determinar o momento ideal, e para isso é importante considerar a vida média dos gametas, ao qual é muito curta no caso dos ovócitos (tabela 1). -/- Tabela 1: local de depósito do sêmen, volume da ejaculação e vida média dos gametas. Espécie Local de deposição Volume (ml) Velocidade de ejaculação Vida média do ovócito Vida média do espermatozoide Bovinos Intravaginal 2 1 – 3 seg 8 h 30 – 48 h Caninos Intravaginal 2 – 30 (10 média) 6 – 45 min 48 – 72 h 9 – 11 d Equinos Intrauterina 50 – 200 20 – 60 seg 6 – 8 h 72 – 120 h Humanos Intravaginal 3 - - 5 – 6 d Ovinos Intravaginal 1 1 – 2 seg 16 – 24 h 30 – 48 h Suínos Intrauterina 200 – 400 5 – 20 min 8 – 10 h 24 – 48 h Onde d = dias; h = horas. A vida fértil do ovócito é muito curta, portanto, o momento do serviço é de grande importância para obter altos índices de fertilização. -/- Independentemente do local em que os espermatozoides sejam depositados no aparelho reprodutor feminino, serão expostos às secreções genitais e sofrem uma série de mudanças em seu trajeto até o local de fertilização antes de penetrar no ovócito. Nas espécies em que o sêmen é depositado na parte cranial da vagina, uma parte do mesmo penetra através da cérvix, enquanto outra parte é eliminada do aparelho genital da fêmea, em pouco tempo, através do fluxo retrógrado. O meio vaginal não é adequado e imobiliza os espermatozoides em pouco tempo, pelo qual deverão entrar no útero onde o ambiente é mais propício. O transporte espermático na fêmea é o resultado da alta contratilidade, do movimento ciliar e o fluido do aparelho genital durante o estro, ao qual está sob controle endócrino e do sistema nervoso. Esse transporte é favorecido pelas características especiais do muco estral, cujas moléculas formam uma espécie de canais que facilitam a passagem dos espermatozoides. Pelo contrário, durante a fase lútea seu transporte é dificultado. Além do meio vaginal, a cérvix também atua como barreira natural para limitar a passagem dos espermatozoides, diminuindo assim a possibilidade de polispermia. Funciona, também, como um filtro que seleciona os espermatozoides aptos dos que não o são, uma vez que somente os primeiros possuem uma motilidade vigorosa que lhes permite passar pelo muco altamente hidratado. Na vaca a cérvix é considerada como um reservatório espermático. Quando atravessam a cérvix, os espermatozoides seguem sua deslocação tanto por movimento próprio como pelas contrações uterinas e tubárias. Nas espécies em que o local de depósito do sêmen do macho na fêmea é intrauterino, como equinos, a principal barreira que os espermatozoides enfrentam é a união ou junção útero-tubárica. A união entre o útero e o oviduto (istmo do oviduto) serve como reservatório funcional dos espermatozoides nas espécies domésticas. Poucos minutos depois da cópula, é possível encontrar alguns espermatozoides no oviduto, que é conhecido como fase de transporte rápido. No entanto, esses espermato-zoides não são os que participam do processo de fertilização e podem apresentar certas anormalidades. Existe um segundo tipo de transporte denominado fase sustentada, a qual consiste na migração prolongada dos espermatozoides em direção as partes mais craniais do aparelho genital feminino, que conduzem à colonização do reservatório funcional e na liberação gradual dos espermatozoides dos reservatórios espermáticos, incluindo este último. O reservatório do istmo fornece aos espermatozoides um ambiente propício, protegendo-os contra a fagocitose, prolongando assim a sua viabilidade. Aqui os esper-matozoides permanecem aderidos a superfície das células ciliadas do epitélio até a finalização de sua capacitação, depois da qual são liberados quando alteram seu padrão de motilidade flagelada, fenômeno conhecido como hipermotilidade, e migram em ondas em direção ao local da fertilização. Dos milhões de espermatozoides ejaculados, somente alguns milhares alcançarão o istmo do oviduto e um número sumamente pequeno será encontrado nas imediações do ovócito no momento da fertilização. -/- • _____CAPACITAÇÃO ESPERMÁTICA E REAÇÃO ACROSSÔMICA -/- A capacitação é um processo gradual e essencial para a fertilização. Os espermato-zoides devem passar por um dado tempo de “incubação” no aparelho genital da fêmea e sofrer uma série de mudanças antes de serem capazes de fecundar o ovócito. A capacita-ção dos espermatozoides começa quando eles entram em contato com as secreções do aparelho genital da fêmea e termina no istmo do oviduto. Durante esse percurso a superfície da cabeça do espermatozoide se modifica já que algumas moléculas como o colesterol são removidas da membrana plasmática, aumentando sua fluidez e alterando suas propriedades bioquímicas. Entre outras coisas, essa reorganização dos lipídios facilita a entrada de cálcio extracelular pelos canais iônicos e ocasiona a desestabilização da membrana, tornando-a mais fusogênica. Também são eliminados outros fatores (conhecidos genericamente como fatores descapacitantes) que expõem receptores membranais indispensáveis para a realização da união entre o espermatozoide e o ovócito durante a fertilização. Os espermatozoides capacitados apresentam um padrão de hipermotilidade e uma maior atividade metabólica, características que devem obter para que sejam capazes de penetrar as camadas do ovócito. A capacitação é necessária para que ocorra a reação acrossômica. A reação acrossomal ou acrossômica (RA) é um fenômeno de exocitose que é desencadeada pela ligação entre as proteínas e receptores localizados na membrana do espermatozoide e a zona pelúcida do ovócito (figura 3). Envolve a fusão da membrana plasmática do espermatozoide com a membrana externa de seu acrossomo; formando, assim, pequenas vesículas, cujo conteúdo de enzimas hidrolíticas, como a hialuronidase e a acrosina, é liberado em direção ao seu exterior, facilitando a penetração da zona pelúcida. A adesão do espermatozoide à zona pelúcida é específica da espécie e depende de glicoproteínas presentes na membrana dos ovócitos maduros; a cabeça do espermatozoide se une com essas glicoproteínas mediante receptores específicos e atravessam em direção oblíqua a zona pelúcida até chegar ao espaço perivitelino. Nos mamíferos, particularmente em roedores e nos humanos, algumas dessas glicoproteínas são conhecidas como ZP1, ZP2 e ZP3. Pensa-se que a união da membrana espermática a esta última é o que desencadeia a reação acrossomal. Posteriormente, as vilosidades do ovócito entram em contato com o espermatozoide e a membrana presente na secreção equatorial da cabeça do espermatozoide, que tem proteínas fusogênicas específicas, une-se a membrana plasmática do ovócito, fusionando-se e permitindo a entrada do núcleo espermático ao citoplasma (figura 4). A capacitação dos espermatozoides é fundamental para o êxito da fertilização, uma vez que apenas os aptos estarão perfeitos e íntegros para que a união e percepção das glicoproteínas presentes nos mesmos possam ocorrer de forma ideal para a penetração deste no ovócito, fertilizá-lo e formar um zigoto. Figura 3: estrutura do espermatozoide. Nota: a membrana é acrossomal e não acrossonal. Elaborado pelo autor. -/- Figura 4: eventos que ocorrem durante a fertilização. A – depois de passar através das células do cumulus, o espermatozoide entra em contato com a zona pelúcida, onde receptores da membrana plasmática reconhecem as proteínas da zona pelúcida; B – é desencadeada, então, a reação acrossomal; C – para que o espermatozoide penetre na zona pelúcida; D – ao atravessar a zona pelúcida e entrar no espaço perivitelino, a cabeça do espermatozoide entra em contato com a membrana vitelina; ambas membranas se fusionam graças ao reconhecimento de proteínas fusogênicas que estão no segmento equatorial. E – ocorre, então, que o núcleo do espermatozoide penetra no citoplasma do ovócito; uma das consequências da fusão da membrana com a cabeça do espermatozoide é a reação cortical, em que os grânulos corticais do ovócito liberam seu conteúdo em direção ao espaço perivitelino, o que resulta na alteração da estrutura da zona pelúcida e da membrana vitelina para bloquear a polispermia. Elaborado pelo autor. • _____CONSEQUÊNCIAS DA PENETRAÇÃO -/- Bloqueio da polispermia -/- A fusão das membranas dos gametas durante a penetração permite a entrada da fosfolipase C zeta (PLCζ) – fator solúvel que provém do espermatozoide – que desencadeia liberação e oscilações de Ca2+ no retículo endoplasmático. Isso, por sua vez, provoca a migração e fusão dos grânulos corticais, com a consequente liberação de enzimas, que mudam tanto a estrutura da zona pelúcida (por exemplo a inativação de ZP3), como a da membrana vitelina. Desse modo, impede-se que outros espermatozoides as penetrem, evitando assim a polispermia (figura 5). -/- Figura 5: os grânulos corticais que encontram-se na periferia do citoplasma, debaixo da superfície da membrana do ovócito, migram e fusionam-se sobre a mesma, liberando seu conteúdo no espaço perivitelino imediatamente depois da penetração do espermatozoide. A – como conse-quência, tanto a membrana vitelina como a zona pelúcida são modificadas, impedindo a entrada de mais espermatozoides, o que evita a polispermia. B – o ovócito retoma, então, sua segunda divisão meiótica, que ocasiona a expulsão do segundo corpúsculo polar, e na formação dos pronúcleos feminino e masculino. C – continuando, os pronúcleos migram, suas membranas se dissolvem e os cromossomos de ambos se condensam e se unem. Completa-se, assim, a singamia e forma-se, então, o zigoto. Elaborado pelo autor baseado nos livros de embriologia e fisiologia da reprodução conforme vida bibliografia. -/- Ativação do ovócito e formação de pronúcleos -/- Na maioria das fêmeas domésticas, com exceção da cadela, o ovócito encontra-se suspenso na metáfase II da segunda meiose no momento da ovulação. A entrada da PLCζ do espermatozoide no citoplasma do ovócito, e a consequente liberação de Ca2+, faz com que o ovócito se ative, terminando a segunda divisão meiótica e expulse o segundo corpo polar. Posteriormente, o material nuclear do ovócito se reorganiza para formar o pronú-cleo feminino. Entretanto, a membrana nuclear do espermatozoide se dissolve, a cromatina descondensa-se, as protaminas são substituídas por histonas, e se forma uma nova membrana nuclear, dando lugar ao pronúcleo masculino. -/- Singamia -/- Uma vez que os pronúcleos feminino e masculino são formados, migram para o centro do ovócito, aproximam-se, suas membranas se dispersam e os cromossomos paternos e maternos se associam, com o qual recupera a condição diploide e dá origem ao zigoto (figura 5). -/- • _____DESENVOLVIMENTO EMBRIONÁRIO -/- Poucas horas após a fertilização ocorre a primeira divisão do zigoto em duas, depois em 4, 8, 16 e 32 células, denominadas blastômeros. Essas divisões mitóticas são conhecidas como divisões de segmentação ou clivagem (figura 6), uma vez que são realizadas sem aumento do citoplasma, de modo que com cada divisão os blastômeros se tornam menores. A partir das 16 células o embrião se chama mórula, e é visto como uma massa celular compacta. A compactação deve-se a informação de proteínas de ligação entre os blastômeros. O embrião acumula líquido em seu interior, formando uma cavidade denominada blastocele. Esse processo é conhecido como blastulação; o embrião, assim, passa a ser chamado de blastocisto. Nessa etapa é possível diferenciar duas populações de células embrionárias: a massa celular interna, embrioblasto ou botão embrionário (que dará origem ao embrião), e a massa celular externa, células superficiais ou trofoblasto, do qual se originam a maioria das membranas fetais. Ao continuar a multiplicação das células e a acumulação de líquido, o blastocisto aumenta de tamanho, convertendo-se em blastocisto expandido. A zona pelúcida torna-se mais fina e, finalmente, o embrião eclode; isto é, o embrião é liberado da zona pelúcida. -/- • _____FERTILIZAÇÕES ATÍPICAS -/- Polispermia -/- É a penetração de dois ou mais espermatozoides no óvulo. Esta condição é letal nos mamíferos, já que o número cromossômico desse zigoto é maior que 2n, o envelheci-mento do ovócito da porca, como consequência do serviço tardio, favorece a apresentação da polispermia, por isso, é comum ver números de nascimentos de média de 10 a 12 leitões por parição nessa espécie. Nas aves, no entanto, a penetração de mais de um espermatozoide é normal, embora apenas um pronúcleo masculino se formará, fundindo-se com o feminino. -/- Figura 6: etapas do processo de segmentação/clivagem. Fonte: aula de reprodução da professora Domenica Palomaris, UFT. -/- Ginogênese -/- É o desenvolvimento de um embrião a partir de um óvulo normal fecundado por um espermatozoide, mas sem a fusão dos cromossomos masculinos com os da fêmea. A função do espermatozoide, nesse caso, é a de ativação do ovócito para que este inicie seu desenvolvimento, mas não há fusão com o núcleo do espermatozoide. Ocorre em plantas, em nematódeos e em algumas espécies de peixes, por exemplo a Poecilia formosa, espécie em que os ovócitos das fêmeas são ativados por machos de outra espécie relacio-nada. -/- Partenogênese -/- Consiste no desenvolvimento do embrião sem a participação do espermatozoide. Ocorre em alguns insetos, o zangão, por exemplo, é partenogenético. Também pode apresentar-se em perus, cujos embriões são machos e, geralmente, morrem antes da eclosão. -/- • _____GÊMEOS -/- Existem dois tipos de gêmeos: idênticos ou monozigóticos e os não idênticos ou dizigóticos. -/- Idênticos ou monozigóticos -/- Originam-se do mesmo zigoto, sendo assim, possuem o mesmo genótipo e um fenótipo similar e, portanto, são do mesmo sexo. Em laboratório é possível gerá-los ao seccionar uma mórula em duas ou mais partes, por meio de um micromanipulador. Uma vez que possuem o mesmo genótipo, os produtos resultantes são clones. -/- Não idênticos ou dizigóticos -/- Provêm da fertilização de dois óvulos distintos por espermatozoides diferentes. Possuem, portanto, genótipos e fenótipos diferentes, e podem ser de sexo diferente. -/- REFERÊNCIAS BIBLIOGRÁFICAS -/- ALBERTS, Bruce et al. Biologia molecular da célula. Artmed Editora, 2010. AUSTIN, Colin Russell; SHORT, Roger Valentine. Reproduction in Mammals, Book I: Germ Cells and Fertilization. 1982. BEARDEN, Henry Joe et al. Reproducción animal aplicada. México: Manual Moderno, 1982. BOSCH, P.; WRIGHT JR, R. W. The oviductal sperm reservoir in domestic mammals. Archivos de medicina veterinaria, v. 37, n. 2, p. 95-105, 2005. CAPALLEJAS, Roberto Brito; RODRÍGUEZ, Lourdes Tagle. Fisiología de la reproducción animal: con elementos de biotecnología. Editorial Félix Varela, 2010. CROXATTO, Horacio B. Physiology of gamete and embryo transport through the fallopian tube. Reproductive biomedicine online, v. 4, n. 2, p. 160-169, 2002. CUPPS, Perry T. (Ed.). Reproduction in domestic animals. Elsevier, 1991. DIEDRICH, Smidt et al. Endocrinología y Fisiología de la Reproducción de los Animales Zootécnicos. 1972. DUKES, Henry Hugh; SWENSON, Melvin J.; REECE, William O. Dukes fisiologia dos animais domésticos. Editora Guanabara Koogan, 1996. FERREIRA, A. de M. Reprodução da fêmea bovina: fisiologia aplicada e problemas mais comuns (causas e tratamentos). Juiz de Fora: Minas Gerais–Brasil, p. 422, 2010. HAFEZ, Elsayed Saad Eldin; HAFEZ, Bahaa. Reprodução animal. São Paulo: Manole, 2004. HUNTER, Ronald Henry Fraser. The Fallopian tubes in domestic mammals: how vital is their physiological activity?. Reproduction Nutrition Development, v. 45, n. 3, p. 281-290, 2005. HUNTER, R. H. F.; RODRIGUEZ‐MARTINEZ, H. Capacitation of mammalian spermatozoa in vivo, with a specific focus on events in the Fallopian tubes. Molecular Reproduction and Development: Incorporating Gamete Research, v. 67, n. 2, p. 243-250, 2004. GALINA, Carlos; VALENCIA, Javier. Reproducción de los animales domésticos. 2006. HOPPER, Richard M. (Ed.). Bovine reproduction. John Wiley & Sons, 2014. HYTTEL, Poul; SINOWATZ, Fred; VEJLSTED, Morten. Embriologia veterinária. Elsevier Brasil, 2012. KÖLLE, Sabine; REESE, Sven; KUMMER, Wolfgang. New aspects of gamete transport, fertilization, and embryonic development in the oviduct gained by means of live cell imaging. Theriogenology, v. 73, n. 6, p. 786-795, 2010. MCKINNON, Angus O. et al. (Ed.). Equine reproduction. John Wiley & Sons, 2011. OLIVERA, Martha et al. El espermatozoide, desde la eyaculación hasta la fertilización. Revista Colombiana de Ciencias Pecuarias, v. 19, n. 4, p. 426-436, 2006. PLANT, Tony M.; ZELEZNIK, Anthony J. (Ed.). Knobil and Neill's physiology of reproduction. New York: Academic Press, 2014. RODRIGUEZ-MARTINEZ, Heriberto. Role of the oviduct in sperm capacitation. Theriogenology, v. 68, p. S138-S146, 2007. SAAVEDRA LEOS, María Dolores. Estudio de la composición de los gránulos corticales y del oolema de ovocitos porcinos y bovinos madurados y fecundados in vitro. Proyecto de investigación:, 2010. SENGER, Phillip L. et al. Pathways to pregnancy and parturition. Current Conceptions, Inc, 2004. SUAREZ, Susan S. The oviductal sperm reservoir in mammals: mechanisms of formation. Biology of Reproduction, v. 58, n. 5, p. 1105-1107, 1998. VALENCIA MÉNDEZ, Javier de J. Fisiología de la reproducción porcina. 1986. -/- FIXAÇÃO DO ASSUNTO -/- 1. Defina e diferencie fertilização e segmentação. -/- 2. Disserte sobre o transporte do ovócito. Por que no istmo o transporte do ovócito se torna lento? -/- 3. Fale sobre a eficiência do transporte do gameta no trato genital da fêmea e sobre a retenção de ovócitos pela égua. -/- 4. Defina as células do cumulus e explique seu papel sobre o ovócito. -/- 5. Quais as estruturas que compõem o ovócito? Qual a função de cada uma? -/- 6. Todos os ovócitos das fêmeas domésticas são iguais? Justifique. -/- 7. Disserte sobre o papel dos hormônios e das secreções sobre o transporte do ovócito no trato genital da fêmea. -/- 8. Disserte sobre o transporte do espermatozoide. Por que há transporte rápido e lento dos espermatozoides? -/- 9. Fale sobre o local de deposição do sêmen nas espécies domésticas e como esse influen-cia na eficiência da reprodução. -/- 10. Por que a vida média do espermatozoide canino é maior que as outras espécies? -/- 11. Quais as mudanças que os espermatozoides precisam sofrer para conseguir êxito na fertilização e por quê? -/- 12. Defina fase de transporte rápido, fase sustentada e hipermotilidade. Qual a importân-cia de cada um? -/- 13. Como ocorre a reação acrossômica? -/- 14. O que é polispermia e como ocorre seu bloqueio? 15. Como ocorre a ativação do ovócito e como se formam os pronúcleos? -/- 16. O que é e qual a importância da singamia? -/- 17. Disserte sobre as divisões de segmentação e qual a importância destas para o êxito da reprodução. -/- 18. Defina e diferencia mórula e blastocisto. -/- 19. Defina e diferencie ginogênese e partenogênese. -/- 20. Qual o papel endócrino e quais hormônios e enzimas atuam sobre o transporte de gametas, sobre a fertilização e sobre a segmentação? (shrink)

It has often been assumed that when we use vision to become aware of an object or event in our surroundings, this must be accompanied by a corresponding visual experience (i.e., seeing). The studies reported here show that this assumption is incorrect. When observers view a sequence of displays alternating between an image of a scene and the same image changed in some way, they often feel (or sense) the change even though they have no visual experience of it. The (...) subjective difference between sensing and seeing is mirrored in several behavioral differences, suggesting that these are two distinct modes of conscious visual perception. (shrink)

We show that early vision can use monocular cues to rapidly complete partially-occluded objects. Visual search for easily detected fragments becomes difficult when the completed shape is similar to others in the display; conversely, search for fragments that are difficult to detect becomes easy when the completed shape is distinctive. Results indicate that completion occurs via the occlusion-triggered removal of occlusion edges and linking of associated regions. We fail to find evidence for a visible filling-in of contours or surfaces, but (...) do find evidence for a "functional" filling-in that prevents the constituent fragments from being rapidly accessed. As such, it is only the completed structures—and not the fragments themselves—that serve as the basis for rapid recognition. (shrink)

It is suggested that the relationship between visual attention and conscious visual experience can be simplified by distinguishing different aspects of both visual attention and visual experience. A set of principles is first proposed for any possible taxonomy of the processes involved in visual attention. A particular taxonomy is then put forward that describes five such processes, each with a distinct function and characteristic mode of operation. Based on these, three separate kinds—or possibly grades—of conscious visual experience can be distinguished, (...) each associated with a particular combination of attentional processes. (shrink)

When brief blank fields are placed between alternating displays of an original and a modified scene, a striking failure of perception is induced: the changes become extremely difficult to notice, even when they are large, presented repeatedly, and the observer expects them to occur (Rensink, O'Regan, & Clark, 1997). To determine the mechanisms behind this induced "change blindness", four experiments examine its dependence on initial preview and on the nature of the interruptions used. Results support the proposal that representations at (...) the early stages of visual processing are highly volatile, and that focused attention is needed to stabilize them sufficiently to support the perception of change. (shrink)

Our visual experience of the world is one of diverse objects and events, each with particular colors, shapes, and motions. This experience is so coherent, so immediate, and so effortless that it seems to result from a single system that lets us experience everything in our field of view. But however appealing, this belief is mistaken: there are severe limits on what can be visually experienced. -/- For example, in a display for air-traffic control it is important to track all (...) moving items. For a single item, this can be done without problem. Three or four can also be tracked, although some degree of effort may be needed. As the number is increased further, accurate tracking becomes more and more difficult—and eventually, impossible. Performance is evidently affected by a factor within the observer which enables certain kinds of perception to occur, but is limited in some way. This factor is generally referred to as attention. -/- At various times, attention has been associated with clarity of perception, intensity of perception, consciousness, selection, or the allocation of a limited “resource” enabling various operations (see Hatfield, 1998). During the past several decades, considerable progress has been achieved by focusing on the idea of selection (Broadbent, 1982). In particular, attention can be productively viewed as contingently selective processing. This can be embodied in various ways by various processes—there need not be a single quantity identified with all forms of attention, or a single site where it operates (Allport, 1993; Tsotsos, 2011). Although “paying attention” is often considered to be a unitary operation, it may simply refer to the control of one or more selective processes, ideally in a co-ordinated way. While this view has some cost in terms of conceptual simplicity, it can help make sense of a large set of phenomena. -/- This article surveys several of the major issues in our understanding of attention and how it relates to perception. It focuses on vision, since many—if not all—considerations are similar for all sensory modalities, and the level of understanding achieved in this domain is currently the most advanced. (shrink)

Three separate churches erected in Constantinople were all dedicated to the wisdom of Christ and erected on the same site one after the other. These churches were built between 360 and 537 AD by three different emperors: Constantius II, Theodosius the Younger, and Justinian I. The first two churches were consumed in flames after relatively short lives, but the final and greatest church still stands today, despite a history of extensive damage. This final edifice is the main focus of this (...) paper, owing to its 1500 year longevity and unprecedented architecture. If the entire History of Justinian's church is to considered, it is inaccurate to refer to it as a “church,” because although it remained a church for the first 900 years after its audacious construction, it was later converted into a mosque. Today it is a museum, in remembrance of its long history. (24). (shrink)

Over the centuries, magicians have developed extensive knowledge about the manipulation of the human mind—knowledge that has been largely ignored by psychology. It has recently been argued that this knowledge could help improve our understanding of human cognition and consciousness. But how might this be done? And how much could it ultimately contribute to the exploration of the human mind? We propose here a framework outlining how knowledge about magic can be used to help us understand the human mind. Various (...) approaches—both old and new—are surveyed, in terms of four different levels. The first focuses on the methods in magic, using these to suggest new approaches to existing issues in psychology. The second focuses on the effects that magic can produce, such as the sense of wonder induced by seeing an apparently impossible event. Third is the consideration of magic tricks—methods and effects together—as phenomena of scientific interest in their own right. Finally, there is the organization of knowledge about magic into an informative whole, including the possibility of a science centered around the experience of wonder. (shrink)

Human vision briefly retains a trace of a stimulus after it disappears. This trace—iconic memory—is often believed to be a surrogate for the original stimulus, a representational structure that can be used as if the original stimulus were still present. To investigate its nature, a flicker-search paradigm was developed that relied upon a full scan (rather than partial report) of its contents. Results show that for visual search it can indeed act as a surrogate, with little cost for alternating between (...) visible and iconic representations. However, the duration over which it can be used depends on the type of task: some tasks can use iconic memory for at least 240 ms, others for only about 190 ms, while others for no more than about 120 ms. The existence of these different limits suggests that iconic memory may have multiple layers, each corresponding to a particular level of the visual hierarchy. In this view, the inability to use a layer of iconic memory may reflect an inability to maintain feedback connections to the corresponding representation. (shrink)

Religious faith may manifest itself, among other things, as a mode of seeing the ordinary world, which invests that world imaginatively (or inspiredly) with an unseen depth of divine intention and spiritual significance. While such seeing may well be truthful, it is also unavoidably constructive, involving the imagination in its philosophical sense of the capacity to organize underdetermined or ambiguous sense date into a whole or gestalt. One of the characteristic ways in which biblical narratives inspire and teach is by (...) renewing their characters’ and readers’ imagination. The texts do so not inexorably but in a similar way as (other) works of art. This paper therefore investigates the ways in which works of art engage and develop the imagination, and thereby enable renewed perceptual and cognitive engagement with the world. The paper introduces predictive processing as a helpful psychological theory for analyzing this dynamic, and outlines questions for further research. (shrink)

We show that cast shadows can have a significant influence on the speed of visual search. In particular, we find that search based on the shape of a region is affected when the region is darker than the background and corresponds to a shadow formed by lighting from above. Results support the proposal that an early-level system rapidly identifies regions as shadows and then discounts them, making their shapes more difficult to access. Several constraints used by this system are mapped (...) out, including constraints on the luminance and texture of the shadow region, and on the nature of the item casting the shadow. Among other things, this system is found to distinguish between line elements (items containing only edges) and surface elements (items containing visible surfaces), with only the latter deemed capable of casting a shadow. (shrink)

Traditionally, vision science and information/data visualization have interacted by using knowledge of human vision to help design effective displays. It is argued here, however, that this interaction can also go in the opposite direction: the investigation of successful visualizations can lead to the discovery of interesting new issues and phenomena in visual perception. Various studies are reviewed showing how this has been done for two areas of visualization, namely, graphical representations and interaction, which lend themselves to work on visual processing (...) and the control of visual operations, respectively. The results of these studies have provided new insights into aspects of vision such as grouping, attentional selection and the sequencing of visual operations. More generally yet, such results support the view that the perception of visualizations can be a useful domain for exploring the nature of visual cognition, inspiring new kinds of questions as well as casting new light on the limits to which information can be conveyed visually. (shrink)

First, I briefly characterize Dretske’s particular naturalization project, emphasizing his naturalistic reconstruction of the notion of representation. Second, I note some apparent similarities between his notion of representation and Husserl’s notion of intentionality, but I find even more important differences. Whereas Husserl takes intentionality to be an intrinsic, phenomenological feature of thought and experience, Dretske advocates an “externalist” account of mental representation. Third, I consider Dretske’s treatment of qualia, because he takes it to show that his representational account of mind (...) succeeds in naturalizing even the “subjective” features of experience. I claim that Dretske's argument for his account of qualia turns on an ambiguous characterization of qualia. I conclude that he succeeds in naturalizing qualia only if qualia are understood as nonphenomenological features of experience and that he therefore has less to say than he thinks about the subjective life of beings such as us. (shrink)

Several studies (e.g., Becklen & Cervone, 1983; Mack & Rock, 1998; Neisser & Becklen, 1975) have found that observers attending to a particular object or event often fail to report the presence of unexpected items. This has been interpreted as inattentional blindness (IB), a failure to see unattended items (Mack & Rock, 1998). Meanwhile, other studies (e.g., Pashler, 1988; Phillips, 1974; Rensink et al., 1997; Simons, 1996) have found that observers often fail to report the presence of large changes in (...) a display when these changes occur simultaneously with a transient such as an eye movement or flash of the display. This has been interpreted as change blindness (CB), a failure to see unattended changes (Rensink et al., 1997). In both cases there is a striking failure to report an object or event that would be quite visible under other circumstances. And in both cases there is a widespread (although not universal) belief that the underlying cause has to do with the absence of attention. The question then arises as to how these effects might be related. Is CB the same thing as IB? If not, what is the relation between them? And given that these phenomena deal with failures of subjective perception, what can they teach us about the nature of our visual experience? In particular, what can they teach us about the role played by visual attention? (shrink)

In the not-too-distant past, vision was often said to involve three levels of processing: a low level concerned with descriptions of the geometric and photometric properties of the image, a high level concerned with abstract knowledge of the physical and semantic properties of the world, and a middle level concerned with anything not handled by the other two. The negative definition of mid-level vision contained in this description reflected a rather large gap in our understanding of visual processing: How could (...) the here-and-now descriptions of the low levels combine with the enduring knowledge of the high levels to produce our perception of the surrounding world? A number of experimental and theoretical efforts have been made over the past few decades to solve this "mid-level crisis". One of the more recent of these is based on the phenomenon of change blindness—the difficulty in seeing a large change in a scene when the transients accompanying that change no longer convey information about its location (Rensink, O'Regan, & Clark, 1997; Rensink, 2000a). Phenomenologically, this effect is quite striking: the change typically is not seen for several seconds, after which it suddenly snaps into awareness. During the time the change remains "invisible", there is an apparent disconnection of the low-level descriptions (which respond to the change) from subjective visual experience (which does not). As such, this effect would seem to have the potential to help us understand how mid-level mechanisms might knit low- and high-level processes into a coherent representation of our surroundings. -/- It is argued here that this potential can indeed be realized, and that change blindness can teach us much about the nature of mid-level vision.3 A number of studies are first reviewed showing that the perception of a scene does not involve a steady buildup of detailed representation: rather, it is a dynamic process, with focused attention playing one of the main roles, viz., forming coherent object representations whenever needed. It is then argued that change blindness can also shed considerable light on the nature of focused attention itself, such as its speed, capacity, selectivity, and ability to bind together visual properties into coherent structures. (shrink)

The past few years have seen a resurgence of interest in the scientific study of magic. Despite being only a few years old, this “new wave” has already resulted in a host of interesting studies, often using methods that are both powerful and original. These developments have largely borne out our earlier hopes (Kuhn et al., 2008) that new opportunities were available for scientific studies based on the use of magic. And it would seem that much more can still be (...) done along these lines. -/- But in addition to this, we also suggested that it might be time to consider developing an outright science of magic—a distinct area of study concerned with the experience of wonder that results from encountering an apparently impossible event1. To this end, we proposed a framework as to how this might be achieved (Rensink and Kuhn, 2015). A science can be viewed as a systematic method of investigation involving three sets of issues: (i) the entities considered relevant, (ii) the kinds of questions that can be asked about them, and (iii) the kinds of answers that are legitimate (Kuhn, 1970). In the case of magic, we suggested that this could be done at three different levels, each focusing on a distinct set of issues concerned with the nature of magic itself: (i) the nature of magical experience, (ii) how individual magic tricks create this experience, and (iii) organizing knowledge of the set of known tricks in a more comprehensive way (Rensink and Kuhn, 2015). Our framework also included a base level focused on how the methods of magic could be used as tools to investigate issues in existing fields of study. -/- Lamont (2010) and Lamont et al. (2010) raised a number of concerns about the possibility of such a science, which we have addressed (Rensink and Kuhn, 2015). More recently, Lamont (2015) raised a new objection, arguing that although base-level work (i.e., applications of magic methods) might be useful, there is too little structure in magic tricks for them to be studied in a systematic way at the other levels, ruling out a science of magic. We argue here, however, that although this concern raises some interesting challenges for this science, it does not negate the possibility that it could exist, and could contribute to the study of the mind. (shrink)

I critically evaluate the influential new wave account of theory reduction in science developed by Paul Churchland and Clifford Hooker. First, I cast doubt on claims that the new wave account enjoys a number of theoretical virtues over its competitors, such as the ability to represent how false theories are reduced by true theories. Second, I argue that the genuinely novel claim that a corrected theory must be specified entirely by terms from the basic reducing theory is in fact too (...) restrictive for scientific practice and should be rejected. Basic theories co-evolve with nonbasic theories in a mutually interactive way, and thus the basic theories incorporate the concepts and concerns of nonbasic theories. Third, I show that once its ontological consequences are duly noted, the reductive part the new wave account collapses into the classical theory developed within the logical empiricist tradition. As such, it still falls prey to standard anti-reductionist argument based upon multiple realizability and the cross-classification of special science and physical science terms. (shrink)

A computational theory is developed that explains how line drawings of polyhedral objects can be interpreted rapidly and in parallel at early levels of human vision. The key idea is that a time-limited process can correctly recover much of the three-dimensional structure of these objects when split into concurrent streams, each concerned with a single aspect of scene structure.