Posner & Raichle's (1994) exciting, wonderfully illustrated book describes the past successes and future potential of the relatively noninvasive imaging of the nervous systems of living people. The focus has been on cognitive processes but there is no reason why emotional and motivational systems cannot also be tapped. Although the authors do not formally address such contentious issues as consciousness and the private experience of other species, imaging methods may hold promise for helping us to understand these phenomena, as well (...) as to integrate psychological processes into ethological and phylogenetic research in general. (shrink)

We divided the many diverse comments on our book into categories. These are: theory, scope and goals of our project, methods, comments on specific anatomical areas, the concept of attention, consciousness and cognitive control, and finally other issues. Although many of the points of the critics are certainly well taken, we believe studies that have emerged since our book provide strong evidence that the general approach taken in our book is now yielding important new data on the relation of cognitive (...) processes to underlying brain activity. (shrink)

In Posner & Raichle's (1994) book, two essential and strictly related limitations of cognitive neurophysiology are not sufficiently enhanced: (1) The problem of “coding,” namely the capability of a natural brain to redefine its own “basic symbols” as a function of a changing environment; (2) the inadequacy of a Hebbian rule to reckon with complex computational problems such as those solved by real brains.

Amit defines cell assemblies aslocal cortical neuron populationswith strong internal connections. However, Hebb himself proposed that cell assemblies are distributed over different cortical areas (nonlocal ortranscortical assemblies). We review evidence from cognitive neuroscience and neuropsychology supporting the assumption that cell assemblies are transcortical.

A distinction should be made between the formation of stimulus-driven associations and cognitive concepts. To test the learning mode of a neural network, we propose a simple and classic input-output test: the discrimination shift task. Feed-forward PDP models appear to form stimulus-driven associations. A Hopfield network should be extended to apply the test.

Amit's Hebbian model risks being overexplanatory, since it does not depend on specific physiological modelling of cortical ANNs, but concentrates on those phenomena which are modelled by a large class of ANNs. While offering a strong demonstration of the presence of Hebb's “cell assemblies,” it does not offer an equal account of Hebb's “phase sequence” concept.

Amit's work addresses a critical issue in cognitive science: the structure of neural representations. The use of Hebbian cell assemblies is a positive step, and we now need to consider its role in a larger cognitive theory. When considering the dynamics of a system built out of attractors, a more limited version of reverberation becomes necessary.

Recurrent excitation is experimentally well documented in cortical populations. It provides for intracortical excitatory biases that linearize negative feedback interactions and induce macroscopic state transitions during perception. The concept of the local neighborhood should be expanded to spatial patterns as the basis for perception, in which large areas of cortex are bound into cooperative behavior with near-silent columns as important as active columns revealed by unit recording.

This commentary questions the target articles inferences from a limited set of empirical data to support this model and conceptual scheme. Especially questionable is the attribution of internal representation properties to an assembly of cells in a discrete cortical module firing at a discrete attractor frequency. Alternative inferences are drawn from cortical cooling and cell-firing data that point to the internal representation as a broad and specific cortical network defined by cortico-cortical connectivity. Active memory, it is proposed, consists in the (...) sustained activation of the component neuron populations of the network. (shrink)

We present an information theoretic account of models as scientific representations, where scientific models are understood as information carrying artifacts. We propose that the semantics of models should be based on this information coupling of the model to the world. The information theoretic account presents a way of avoiding the need to refer to agents' intentions as constitutive of the semantics of scientific representations, and it provides a naturalistic account of model semantics, which can deal with the problems of asymmetry, (...) relevance and circularity that afflict other currently popular naturalistic proposals. (shrink)

In Furnishing the mind, Prinz defends a view of concept representation that assumes all representations are rooted in perception. This view is attractive, because it makes clear how concepts could be learned from experience in the world. In this paper, we discuss three limitations of the view espoused by Prinz. First, the central proposal requires more detail in order to support the claim that all representations are modal. Second, it is not clear that a theory of concepts must make a (...) realist assumption. Third, the arguments focus on object categories that can be described by features, which are only one of many types of categories. Despite the flaws in the book, however, it clearly highlights a road that can be taken by those interested in defending an empiricist view of concepts. (shrink)

The discussion about a difference between brain and soul or mind is now at the center of the anthropological debate. It seems that the pioneers in this current polemic have a reductionistic view of human nature, inherited from the Cartesian solution to mind-body problem and the modern materialistic explanation of reality. This view – dualistic or monistic – about the opposition between material and immaterial structure of the person, claims that as a consequence of scientific progress, the human brain in (...) the future could be completely explained in naturalistic terms. On the other hand, according to the new results of scientific research, this situation reveals the possibility to develop a new, more adequate paradigm of man as an incarnated person. This change was called by many researchers “the passage from the mind-body problem to the person-body problem”. It seems that the Aristotelian-Thomistic approach is the most suitable to describe this “paradigm shift”. Aristotelian-Thomistic philosophy undoubtedly encourages lively dialogue between philosophy and contemporary sciences through its dual ontology. Thus, it can give suitable answers for questions about the nature of human reason ; unity of composition of the human brain and the role of causality in natural processes. (shrink)

Social externalism is a thesis about the individuation-conditions of thoughts. Actually, the thesis applies only to a special category of ‘trained’ thoughts, thoughts which issue from trained thinking. It isn't that the thinker of such a thought has to have had special training about the subject-matter. It is rather that he or she needs to have acquired certain basic linguistic skills and values. For trained thoughts are thoughts whose contents are tailored to the demands of communication. Social externalism, as I (...) understand it, says that people who are competent in a public language are equipped to have certain thoughts whose contents are fixed by the lexical semantic norms of their language. (shrink)

ABSTRACT:This essay describes three commitments that have become central to the author's philosophical outlook, namely, to liberal naturalism, to metaphysical realism, and to the epistemic and ontological objectivity of normative judgments.Liberal naturalismis contrasted with familiar scientistic versions of naturalism and their project of forcing explanations in every field into models derived from one or another particular science. The form ofmetaphysical realismthat the author endorses rejects every form of verificationism, including the author's one-time ‘internal realism’, and insists that our claims about (...) the world are true or false and not just epistemically successful or unsuccessful and that the terms they contain typically refer to real entities. ‘Representationalism is no sin’. The central part of the essay is an account oftruthbased on a detailed analysis of Tarski's theory of truth and of the insights we can get from it as well as of the respects in which Tarski is misleading. The account ofthe objectivity of the normativein this essay draws on insights from Dewey as well as Scanlon. (shrink)

The approach adopted by Posner & Raichle in this book, with its strong emphasis on the cognitive level of description, is ideally suited to the study of psychotic illnesses. However, their discussion of depression and schizophrenia is based on a very small number of studies and involves ad hoc arguments derived largely from neuroanatomy. Their conclusions are almost certainly wrong.

This is an excellent book but it lacks a detailed presentation and formulation of images of memory. Positron emission tomography (PET) findings sometimes raise more enigmatic questions than they answer, with differences between studies and differences with established lesion evidence. Perhaps the book could have been more critical in its analysis of these enigmas, covering more of the basic issues and assumptions underlying PET research.

Posner & Raichle (1994) is a nice addition to the Scientific American Library and the average reader will both enjoy the book and learn a great deal. As an activeresearcher, however, I find the book disappointing in many respects. My two major disappointments are in the illusion of computation that is created throughout the volume and in the inadequate perspective of the presentation on visual attention.

The authors ofImages of mindhave been highly successful in unravelling the neural basis of complex brain functions. Their emphasis on top-down processingin experimental neuroscience is especially important and, it is hoped, influential. Tracking brain activation accurately botli in space and in time would benefit from studiesofindividual subjects without relying on grand average data.

Every immediate memory is unique; it is therefore unlikely to consist of an attractor or even a combination of attractors. In the present state of knowledge about the chemistry of synaptic transmission, there is no reason to look beyond neurons that directly receive sensory afferents for the afterdischarges that correspond to active memories.

Este ensayo busca mostrar que la ciencia macroeconómica desde hace mucho tiempo no es una disciplina cuyas investigaciones están encuadradas dentro del denominado empirismo lógico y tampoco sus controversias se dirimen dentro del algúnparadigma al estilo de Thomas Kuhn, sino que está conformada por un conjunto de propuestas teóricas que conforman lo que Laudan denomina como “tradiciones de investigación”. Aunque los fenómenos que estudia la macroeconomía son externos a la consciencia del investigador, del diseñador de política económica y del público (...) en general, sus realizaciones tienden más hacia las propuestas de un realismo perspectivistade corte naturalista y que sus hallazgos expresan verdades acerca de las “tendencias” y “capacidades” que subyacen en los fenómenos económicos.This essay tries to show that macroeconomic science from a long time rather to make economic research taking account neo positivist principles and point of view is a discipline with different perspectives and theories within “research traditions” as Larry Laudan said. Although, whether the macroeconomic phenomena is outside of researchers, public policy makers, and people in general, the understanding of macroeconomic as a science trends to be a form of perspective realism with a methodological commitment to naturalism, using models as primary representational entities of economic problems, and where truth are about its trends and capacities as suggested Ronald GiereandNancy Cartwright. (shrink)

Some have suggested that there is no fact to the matter as to whether or not a particular physical system relaizes a particular computational description. This suggestion has been taken to imply that computational states are not real, and cannot, for example, provide a foundation for the cognitive sciences. In particular, Putnam has argued that every ordinary open physical system realizes every abstract finite automaton, implying that the fact that a particular computational characterization applies to a physical system does not (...) tell oneanything about the nature of that system. Putnam''s argument is scrutinized, and found inadequate because, among other things, it employs a notion of causation that is too weak. I argue that if one''s view of computation involves embeddedness (inputs and outputs) and full causality, one can avoid the universal realizability results. Therefore, the fact that a particular system realizes a particular automaton is not a vacuous one, and is often explanatory. Furthermore, I claim that computation would not necessarily be an explanatorily vacuous notion even if it were universally realizable. (shrink)

The paper analyses theoretical presuppositions of the predominant form of semantic naturalism in contemporary analytic philosophy. The aim is to show that irrespective of the fact that the doctrine of semantic naturalism is grounded in ontological and epistemological naturalism, and is developed on the basis of semantic externalism, this conception of foundational semantics rests on internalist premises, and therefore should be construed as Cartesian. Theories and their interrelations that are assumed by semantic naturalism are explicated by relying on the tripartite (...) interpretation of “the problem of intentionality”. The Cartesian aspects of the assumed theories – and thus of the form of semantic naturalism that is analysed – are then specified in the context of Hilary Putnam’s version of semantic externalism. (shrink)

This project provides a detailed examination and critique of current philosophical, linguistic, and cognitive accounts of first language acquisition. In particular, I focus on the concept of "innate" and how it is embraced, marginally utilized, or abandoned altogether in efforts to describe the way that a child comes to be a competent user of a language. A central question that naturally falls out of this general inquiry is therefore what exactly is supposed to be "innate," according to various theories? Philosophically, (...) the theory of innate ideas put forth to explain human learning has existed for centuries and hence, this thesis as it relates to language is discussed. The revival of nativism by linguists like Chomsky is thus a central theme of the first chapter. Universal Grammar and the various arguments for it are closely scrutinized, and I close this chapter with what I take to be the commitments of linguistic nativism, how its proponents conceive of "innate," and several possible objections to the arguments they put forth. Just as the theory of innate ideas has had its contesters throughout the history of philosophy, so too have linguists and cognitive scientists rejected Universal Grammar and other forms of linguistic nativism. Thus, the second chapter presents several of these alternative explanations of language acquisition. Namely, I divide the chapter into three sections, Usage-Based Linguistics, Emergentism, and Sociolinguistic Acquisition, as it is my suggestion that most of the anti-UG attacks are levied from one of these three fields. In discussing the details of each, two distinctions become of particular concern: first, a large part of the differing conceptions of "innate" seem to hinge on what is meant by "learning" and "acquiring," and therefore second, a fine line between UBL and Emergentism can be drawn, a relationship that is otherwise conflated in the literature. Because chapter two involves a brief account of the way in which connectionist simulations are often utilized to model or represent language acquisition, particularly from an Emergentist perspective, chapter three begins by examining this feature of Emergentism in more detail. Due to its explanatory power, ability to be effectively modeled, and the evidentiary support found in neuroscience, Emergentism would appear to be the most tenable position to maintain regarding language acquisition. This possibility seems further strengthened when we take into account the neuroscientific data often used to bolster anti-nativist claims. Nevertheless, reflecting on the overarching concern of the project, regarding what is really meant by "innate," it is shown that this attack on nativism might stand on shakier ground than was originally assumed. Finally, based on these considerations, a case is made for an intermediary position, a theory of "Minimally Innate Ideas.". (shrink)

Images of mindis an exciting book, well-written and wellorganized, but many of the connections the authors draw between PET scan results and more general psychological issues are somewhat strained.

Posner & Raichle's book presents methods and data that increase support for mind-brain unity and provide a method for studying and verifying brain dysfunction objectively. Their incorporation into the assessment technology of neuropsychology should accordingly constitute a major advance. In addition, these techniques may help clarify longstanding controversies in cognitive psychology such as whether perception is multimodal or amodal.

Posner & Raichle's book is a superbly presented and wellwritten overview of a fast-developing and important field in contemporary neuroscience. It suffers from being an overview, however, because it does not go into sufficient detail or depth in many of the issues that it raises. It also neglects many other important areas of current research, for example, technical advances in other areas, learning and memory, and lesion analysis of brain function.

The cell assembly as a simple attractor cannot explain many cognitive phenomena. It must be a highly structured network that can sustain highly structured excitation patterns. Moreover, a cell assembly must be more widely distributed in space than on a square millimeter.

The Miyashita experiments are very interesting and the results should be examined from a viewpoint of attractor dynamics. Amit's target article shows a path toward realistic modeling by artificial neural networks (ANN), but it is not necessarily the only one. I introduce another model that can explain a substantial part of the empirical observations and makes an interesting prediction. This model consists of such units that have nonmonotonic input-output characteristics with local inhibition neurons.

Functionalism, which views consciousness as the product of the processing of stimuli by the brain, is perhaps the dominant view among researchers in the cognitive sciences and associated fields. However, as a workable scientific model of consciousness, it has been marred by a singular lack of tangible success, except at the broadest levels of explanation. This paper argues that this is not an accident, and that in its standard construal it is simply too unwieldy to assume the burden of full-fledged (...) theory. In its place, a reduced functionalism is introduced by applying the principle of parsimony successively to the elements of standard functionalism until only a minimal framework remains. This simpler account states that consciousness is a function of instantaneous causal relations between processing elements rather the putative algorithm such relations are instantiating. It is then argued as a corollary that the only such relations that matter are those in which reciprocal influences are at play. Thus, purely afferent and efferent causal relations are pruned from consideration. The theory resulting from the addition of this corollary is shown to have good correspondence with a number of recent neurophysiologically-motivated approaches to consciousness, including those that stress the importance of reentry, those that view synchrony as a key independent variable, and those that highlight the importance of the accessibility of conscious contents to multiple processing modules. In addition, the theory is shown to be consistent with recent results in the literature on masking, and those in the literature on binocular rivalry. The paper concludes by arguing that the theoretical and empirical difficulties inherent in consciousness research imply that the principle of parsimony must occupy a more central role in consciousness research than it would in ordinary scientific discourse. (shrink)

Summary Searle claims that for a machine to have intentional states it is not sufficient that a formal programme be instantiated. Various types of objections to this claim have been brought up by Searle's critics. Searle's replies to some of these objections are analysed. It turns out that it is more to these objections than Searle wants to make us believe. What is crucial, however, is that Searle's „Gedankenexperiment results in a dilemma. At the outset of the dilemma there are (...) two ways of not understanding. According to one of these ways a person (Searle's homunculus) does not understand something without knowing that s/he does not understand. While in the other mode the person knows that s/he doesn't understand. In the first case the inference from facts about the homunculus to facts about the computer is not valid whereas in the second case one would attribute mental states to the computer. Thereby Searle's claim turns out to be unfounded. (shrink)

While recognizing the theoretical importance of context, current research has treated naming as though semantic meaning were invariant and the same mapping of category exemplars and names should exist across experimental contexts. An assumed symmetry or bidirectionality in naming behavior has been implicit in the interchangeable use of tasks that ask subjects to match names to stimuli and tasks that ask subjects to match stimuli to names. Examples from the literature are discussed together with several studies of color naming and (...) basic emotion naming in which no such symmetry was found. A more complete model of naming is proposed to account for flexible mapping of names to items. Principles of naming are suggested to describe effects of stimulus sampling, differing access to terms, task demands, and other impacts on naming behavior. (shrink)

Can information theory be used to understand neural signaling? Yes, but assumptions have to be made about the nature of that signaling. The traditional view is that the individual neural spike is an all-or-none phenomenon, which allows neural spikes to be viewed as discrete, binary pulses, similar in kind to the signals in digital computers. Under this assumption, the tools of information theory can be used to derive results about the properties of neural signals. However, new results from neuroscience demonstrate (...) that the precise shape of the individual spike can be functionally significant, thus violating the assumption that spikes can always be treated as a binary pulse. Instead, spikes must sometimes be viewed as a continuous signal. Fortunately, information-theoretic tools exist for the study of continuous signals; unfortunately, their use in the continuous domain is very different from their use in the discrete domain, and not always well understood. Researchers interested in making precise claims about the nature of the information used, stored, and processed in neural systems must pay careful attention to these differences. (shrink)

In recent papers, Eric Schwitzgebel argues that if physicalism is true, then the United States is probably conscious. My primary aim here is to demonstrate that the source of Schwitzgebel’s conditional argument is the “Problem of Other Minds,” which is a general problem; wherefore, Schwitzgebel’s conclusion should be revised and applied not only to physicalism, but to most contemporary theories of the mind. I analyze the difference between Schwitzgebel’s argument and other arguments against functionalism, arguing that the difference between them (...) is rooted in referring to the causal role of the whole system, rather than referring to the casual role of the system’s parts. This key difference between functionalism and behaviorism explains why the source of Schwitzgebel’s argument stems from the problem of other minds. I conclude that however counterintuitive from a metaphysical point of view, the United States may have its own stream of consciousness, but it has nothing to do with physicalism in particular. (shrink)

It is now generally accepted that human beings are naturally, possibly even essentially, intersubjective. This chapter offers a robust defence of an enhanced and extended intersubjectivity, criticising the paucity of individuating notions of agency and emphasising the community and reciprocity of our affective co-existence with other living organisms and things. I refer to this modified intersubjectivity, which most closely expresses the implicit intricacy of our pre-reflective neuro-muscular experiential entanglement, as ‘enkinaesthesia’. The community and reciprocity of this entanglement is characterised as (...) dialogical, and in this dialogue, as part of our anticipatory preparedness, we have a capacity for intentional transgression, feeling our way with our world but, more particularly, co-feeling our way with the mind and intentions of the other. Thus we are, not so much ‘mind’-reading, as ‘mind’-feeling, and it is through this enkinaesthetic ‘mind’-feeling dialogue that values-realising activity originates and we uncover the deep roots of morality. (shrink)