Because the visual system cannot process all of the objects, colors, and features present in a visual scene, visual attention allows some visual stimuli to be selected and processed over others. Most research on visual attention has focused on spatial or location-based attention, in which the locations occupied by stimuli are selected for further processing. Recent research, however, has demonstrated the importance of objects in organizing (or segregating) visual scenes and guiding attentional selection. Because of the long history of spatial (...) attention research, theories of spatial attention are more mature than theories of other visual processes, such as object segregation and object attention. In the present paper, I outline a biased competition account of object segregation and attention, following similar accounts that have been developed for spatial attention (Desimone and Duncan, 1995). In my biased competition account, I seek to understand how some objects can be segregated and selected over other objects in a complex visual scene. Under this account, there are two sources of visual information that allow an object to be processed over other objects: bottom-up information carried by the physical stimulus and top-down information based on an observer's goals. I use the biased competition account to combine many diverse findings from the object segregation and attention literatures into a common framework. (shrink)

To understand schizophrenia, a linking hypothesis is needed that shows how brain mechanisms lead to behavioral functions in normals, and also how breakdowns in these mechanisms lead to behavioral symptoms of schizophrenia. Such a linking hypothesis is now available that complements the discussion offered by Phillips & Silverstein (P&S).

Advances in neuroscience implicate reentrant signaling as the predominant form of communication between brain areas. This principle was used in a series of masking experiments that defy explanation by feed-forward theories. The masking occurs when a brief display of target plus mask is continued with the mask alone. Two masking processes were found: an early process affected by physical factors such as adapting luminance and a later process affected by attentional factors such as set size. This later process is called (...) masking by object substitution, because it occurs whenever there is a mismatch between the reentrant visual representation and the ongoing lower level activity. Iterative reentrant processing was formalized in a computational model that provides an excellent fit to the data. The model provides a more comprehensive account of all forms of visual masking than do the long-held feed-forward views based on inhibitory contour interactions. (shrink)

The basis of perception is the processing and categorization of perceptual stimuli from the environment. Much progress has been made in the science of perceptual categorization. Yet there is still no consensus on how the brain generates sensory individuals, from sensory input and perceptual categories in memory. This chapter argues that perceptual categorization is highly variable across perceivers due to their use of different perceptual strategies for solving perceptual problems they encounter, and that the perceptual system structurally adjusts to the (...) strategies that are most successful. Despite this variability, the different sensory individuals that result when different perceivers rely on different strategies nonetheless correspond to actual external world objects/features. This view is called 'perceptual pluralism'. (shrink)

Whether visual perceptual consciousness is gradable or dichotomous has been the subject of fierce debate in recent years. If perceptual consciousness is gradable, perceivers may have less than full access to—and thus be less than fully phenomenally aware of—perceptual information that is represented in working memory. This raises the question: In virtue of what can a subject be less than fully perceptually conscious? In this chapter, we provide an answer to this question, according to which inexact categorizations of visual input (...) may result in a representation of the visual information in working memory that is less than fully available to the perceiver, and of which the perceiver is therefore less than fully phenomenally aware. The latter proposal is a natural extension of a theory of perception we have proposed in previous works, namely, the template tuning theory (TTT). We argue that although TTT is compatible with both gradable and dichotomous conceptions of perceptual consciousness, the available empirical evidence favours a gradable conception of perceptual consciousness. (shrink)

The use and acquisition of knowledge appears to be influenced by what humans pay attention to. Thus, looking at attention will tell us something about the mechanisms involved in knowledge (usage). According to the present review, attention reflects selectivity in information processing and it is not necessarily also reflected in a user’s consciousness, as it is rooted in skill memory or other implicit procedural memory forms–that is, attention is rooted in the necessity of human control of mental operations and actions. (...) The main assumption is that what is true of processing in general is also true of knowledge: Its usage cannot be understood, unless we have the means to study all mechanisms involved, including knowledge hidden from direct introspection and knowledge that participants are not willing to share with interrogators. Reviewing work done in this context, I argue that experimental research on selectivity and bias in human information processing is a promising road to learn about the principles governing knowledge (usage) and to reflect upon them. (shrink)

In the contextual cueing task, visual search is faster for targets embedded in invariant displays compared to targets found in variant displays. However, it has been repeatedly shown that participants do not learn repeated contexts when these are irrelevant to the task. One potential explanation lays in the idea of associative blocking, where salient cues block the learning of invariant associations in the task-irrelevant subset of items. An alternative explanation is that the associative blocking rather hinders the allocation of attention (...) to task-irrelevant subsets, but not the learning per se. The current work examined these two explanations. In two experiments, participants performed a visual search task under a rapid presentation condition in Experiment 1, or under a longer presentation condition in Experiment 2. In both experiments, the search items within both old and new displays were presented in two colors which defined the irrelevant and task-relevant items within each display. The participants were asked to search for the target in the relevant subset in the learning phase. In the transfer phase, the instructions were reversed and task-irrelevant items became task-relevant. In line with previous studies, the search of task-irrelevant subsets resulted in no cueing effect post-transfer in the longer presentation condition; however, a reliable cueing effect was generated by task-irrelevant subsets learned under the rapid presentation. These results demonstrate that under rapid display presentation, global attentional selection leads to global context learning. However, under a longer display presentation, global attention is blocked, leading to the exclusive learning of invariant relevant items in the learning session. (shrink)

Video gaming, specifically action video gaming, seems to improve a range of cognitive functions. The basis for these improvements may be attentional control in conjunction with reward-related learning to amplify the execution of goal-relevant actions while suppressing goal-irrelevant actions. Given that EEG alpha power reflects inhibitory processing, a core component of attentional control, it might represent the electrophysiological substrate of cognitive improvement in video gaming. The aim of this study was to test whether non-video gamers, non-action video gamers and action (...) video gamers exhibit differences in EEG alpha power, and whether this might account for differences in visual information processing as operationalized by the theory of visual attention. Forty male volunteers performed a visual short-term memory paradigm where they memorized shape stimuli depicted on circular stimulus displays at six different exposure durations while their EEGs were recorded. Accuracy data was analyzed using TVA-algorithms. There was a positive correlation between the extent of post-stimulus EEG alpha power attenuation and speed of information processing across all participants. Moreover, both EEG alpha power attenuation and speed of information processing were modulated by an interaction between group affiliation and time on task, indicating that video gamers showed larger EEG alpha power attenuations and faster information processing over time than NVGs – with AVGs displaying the largest increase. An additional regression analysis affirmed this observation. From this we concluded that EEG alpha power might be a promising neural substrate for explaining cognitive improvement in video gaming. (shrink)

One popular theory of moral responsibility locates responsible agency in exercises of control. These control-based theories often appeal to tracing to explain responsibility in cases where some agent is intuitively responsible for bringing about some outcome despite lacking direct control over that outcome’s obtaining. Some question whether control-based theories are committed to utilizing tracing to explain responsibility in certain cases. I argue that reflecting on certain kinds of negligence shows that tracing plays an ineliminable role in any adequate control-based theory (...) of responsibility. (shrink)

In the visual search paradigm, participants’ task is to detect the presence or absence of a target item, which is presented in an array of distractor items. Usually it is found that performance is dependent on specific properties of the visual display, for example, the number of items to be searched or the similarity between display items. However, recent research has demonstrated that memory mechanisms can also affect search behaviour. Further, it was found that memory mechanisms can, in principle, be (...) either facilitatory or inhibitory, that is, that the processing of the item locations, features, or search objects themselves can be improved or impeded, respectively. This thesis investigated the effects of facilitatory and inhibitory memory mechanisms based on the element positions within the search display; facilitatory memory mechanisms based on the features of the search elements; and inhibitory memory mechanisms based on the search objects themselves. (shrink)

Research in vision science, developmental psychology, and the foundations of cognitive science has led some theorists to posit referential mechanisms similar to indices. This hypothesis has been framed within a Fodorian conception of the early vision module. The article shows that this conception is mistaken, for it cannot handle the ‘interface problem’—roughly, how indexing mechanisms relate to higher cognition and conceptual thought. As a result, I reject the inaccessibility of early vision to higher cognition and make some constructive remarks on (...) the perception–cognition interface. -/- 1 The Case for Visual Indices 1.1 Preliminary assumptions 1.2 Transcendental arguments 1.3 Evidence from vision science 2 Visual Indices, Object Files, and Fodorian Modularity 3 The Interface Problem 3.1 Top-down attention and modularity 3.2 Selective attention and information 4 Revising the Indexing Hypothesis 4.1 Revising the perception–cognition interface 4.2 Revising the modularity of early vision 5 Concluding Remarks. (shrink)

Prominent models of attentional control assert a dichotomy between top-down and bottom-up control, with the former determined by current selection goals and the latter determined by physical salience. This theoretical dichotomy, however, fails to explain a growing number of cases in which neither current goals nor physical salience can account for strong selection biases. For example, equally salient stimuli associated with reward can capture attention, even when this contradicts current selection goals. Thus, although 'top-down' sources of bias are sometimes defined (...) as those that are not due to physical salience, this conception conflates distinct - and sometimes contradictory - sources of selection bias. We describe an alternative framework, in which past selection history is integrated with current goals and physical salience to shape an integrated priority map. (shrink)

The past 25 years have witnessed an increasing awareness of the importance of cognitive control in the regulation of complex behavior. It now sits alongside attention, memory, language, and thinking as a distinct domain within cognitive psychology. At the same time it permeates each of these sibling domains. This introduction reviews recent work on cognitive control in an attempt to provide a context for the fundamental question addressed within this topic: Is cognitive control to be understood as resulting from the (...) interaction of multiple distinct control processes, or are the phenomena of cognitive control emergent? (shrink)

Numerous searches have failed to identify a single co-occurrence of total blindness and schizophrenia. Evidence that blindness causes loss of certain NMDA-receptor functions is balanced by reports of compensatory gains. Connections between visual and anterior cingulate NMDA-receptor systems may help to explain how blindness could protect against schizophrenia.

N-methyl-d-aspartate receptor (NMDAR) dysfunction plays a crucial role in schizophrenia, leading to impairments in cognitive coordination. NMDAR agonists (e.g., glycine) ameliorate negative and cognitive symptoms, consistent with NMDAR models. However, not all types of cognitive coordination use NMDAR. Further, not all aspects of cognitive coordination are impaired in schizophrenia, suggesting the need for specificity in applying the cognitive coordination construct.

This commentary compares clinical aspects of ketamine with the amphetamine model of schizophrenia. Hallucinations and loss of insight, associated with amphetamine, seem more schizophrenia-like. Flat affect encountered with ketamine is closer to the clinical presentation in schizophrenia. We argue that flat affect is not a sign of schizophrenia, but rather, a risk factor for chronic schizophrenia.

We are highly tuned to each other's visual attention. Perceiving the eye or hand movements of another person can influence the timing of a saccade or the reach of our own. However, the explanation for such spatial orienting in interpersonal contexts remains disputed. Is it due to the social appearance of the cue—a hand or an eye—or due to its social relevance—a cue that is connected to another person with attentional and intentional states? We developed an interpersonal version of the (...) Posner spatial cueing paradigm. Participants saw a cue and detected a target at the same or a different location, while interacting with an unseen partner. Participants were led to believe that the cue was either connected to the gaze location of their partner or was generated randomly by a computer (Experiment 1), and that their partner had higher or lower social rank while engaged in the same or a different task (Experiment 2). We found that spatial cue‐target compatibility effects were greater when the cue related to a partner's gaze. This effect was amplified by the partner's social rank, but only when participants believed their partner was engaged in the same task. Taken together, this is strong evidence in support of the idea that spatial orienting is interpersonally attuned to the social relevance of the cue—whether the cue is connected to another person, who this person is, and what this person is doing—and does not exclusively rely on the social appearance of the cue. Visual attention is not only guided by the physical salience of one's environment but also by the mental representation of its social relevance. (shrink)

In the following sections, English summaries of the three studies presented in this dissertation are given. For a detailed German synopsis of the present work, see chapter 8. Research in the field of aging and dementia is a main concern as the population of elderly people is growing continuously due to increasing life expectancy and thus, an accumulative number of people who live well beyond 65 years of age run a risk of developing age-associated neurodegenerative disorders of cognitive function, such (...) as Alzheimer’s disease, emerging as a major health problem. The present work is based on growing evidence that deficits in visual selective attention occur early in the progression to AD and therefore might be present as the first non-memory deficits at the early prodromal stage of mild cognitive impairment. The present dissertation was performed to contribute to the still ongoing debate as to whether certain aspects of visual selective attention are par-ticularly vulnerable or preserved, especially at the stage of MCI, and whether attentional func-tioning might be qualitatively and/ or quantitatively different from attentional performance at the AD stage on the one hand or normal functioning on the other hand. As theoretical basis, Bundesen’s theory of visual attention was employed to assess several latent, mathematically independent and quantitative parameter es-timates which are derived from two highly comparable paradigms – computerized whole re-port and partial report of briefly presented visual letter arrays. Central conclusions arising out of TVA-based investigations point at four central strengths of this tool for attentional assessment – the quality criteria sensitivity, specificity, reliability and validity. Study 1: In AD, the amyloid cascade hypothesis assumes that rising plaque and tangle burden invokes loss of nerve cells through direct and indirect effects on synaptic, neuronal and neuritic function, resulting in progressive intellectual decline. Thus, sensitive biomarkers loading functionally on the neural alterations invoked by AD from early on, might improve the possibility to identify at risk subjects in time, providing a chance for effective treatment. The first study examined whether cognitive parameters for estimating the capacity of visual attention might serve that purpose. Based on Bundesen’s TVA, visual information uptake was analyzed in 18 subjects with probable AD, 18 subjects with amnestic MCI, and 18 healthy elderly control subjects. Groups were matched for gender, age, and education. From a whole report task requiring ver-bal report of briefly presented letters, four parameters were derived, characterizing different aspects of visual processing capacity: perceptual threshold t0, iconic memory μ, processing speed C, and visual short-term memory storage capacity K. Comparison of these attentional parameters between groups revealed an elevation of the per-ceptual threshold already in MCI subjects, while processing speed and VSTM storage capacity showed a significant decline for AD patients, only. AD patients on medication with acetyl-choline esterase inhibitors had higher processing speed, but were still below the level of MCI patients. Perceptual threshold values were significantly correlated with disease duration, but not with cognitive measures. Conversely, speed and VSTM were significantly related to cog-nitive scores, but not to disease duration. In particular, VSTM storage was related to neurop-sychological tasks applying visual material, while speed showed an additional relationship also to measures of verbal memory. These results indicate a staged pattern of deficits affecting pre-attentive visual processing in MCI, and attentive processing in AD. They fit into the amyloid cascade hypothesis according to which the neuropathology of AD is characterized by a net accumulation and deposition of β-amyloid in the initial phase, giving rise to neuronal and neuritic dysfunction. Later, gradual neuronal loss and transmitter disturbances finally cause the increasing intellectual de-cline during further progression of the disease. A threshold elevation may thus be considered as a possible index of impaired neuronal functioning prior to cell death, while speed and VSTM deficits may be indicative already of a substantial loss of neuronal cell assemblies and a degeneration of neurotransmitter systems. Study 2: AD is the most frequent form of dementia which appears both as a familial and a sporadic va-riant. In the by far more frequent sporadic form, a genetic risk factor is also implicated, in that carriers of the apolipoprotein E ε4 allele have a 3 to 15 times higher risk of develop-ing the disease, compared to non-carriers. Using an identical TVA-based partial report paradigm as in the present study, Finke et al. had found a close relationship between the severity of the underlying genetic pathology in another neurodegenerative, namely Huntington’s, disease and the direction and degree of spatial attentional weighting. Sensitive tools for assessing selective visual attention might serve as early cognitive markers in the course of AD and therefore enhance the identification rate of at-risk subjects at the MCI stage as well as of subjects with underlying genetic risk. The second study aimed at examining whether attentional parameters of visuospatial and task-related selection are appropriate means for that purpose. Visual selective attention was investigated in 32 patients with amnestic MCI, 16 patients with probable AD, and 36 healthy elderly control subjects. Groups were matched for age, gender and educational level. In combination with Bundesen’s TVA, two mathematically in-dependent and quantitative parameter estimates were derived from a partial report of briefly presented letter arrays: top-down control of attentional selection, representing task-related at-tentional weighting for prioritizing relevant visual objects, and spatial distribution of atten-tional weights across the left and right visual hemifield. Compared to controls, MCI patients showed significantly reduced top-down controlled selec-tion which further deteriorated in AD subjects. Moreover, attentional weighting was signifi-cantly unbalanced across hemifields in MCI and tended to be more lateralized in AD. The ma-jority of patients was biased to the left. Across MCI and AD patients, ApoE4 carriers revealed a leftward spatial bias. The leftward bias was the more pronounced the younger the ApoE4-positive patients and the earlier disease onset. ApoE4-negative subjects showed balanced attentional weighting. These results indicate that impaired top-down control may be linked to early dysfunction of cortico-cortical networks connecting parietal and frontal lobes. Accompanying, an early inter-hemispheric asymmetry in temporo-parietal cortical interactions might cause a pathological spatial bias. As the inheritance of ApoE4 is associated with an interhemispheric imbalance in parietal cortical interactions, a pathological spatial bias may function as early cognitive marker for detecting subjects at risk for probable AD. Study 3: In the latter study, the TVA-based partial report paradigm proved to be a sensitive tool for ve-rifying that both, deficits in task-related selection and a pathological attentional imbalance, are already present at the early stage of amnestic MCI and increase further at the AD stage. It was hypothesized that these deficiencies in selective attention may result from an early disconnection syndrome and an interhemispheric imbalance in cortical interactions, respectively, in the fronto-parietal attention network, before gradual neuronal loss leads to further decline in selective attentional and intellectual functions at later stages. In the third study, these hypotheses were tested by investigat-ing the relationship of both partial report parameters, top-down control α and especially the laterality index of attentional weighting wλ, to regional glucose metabolism measured by rest-ing-state positron emission tomography in a sample of 30 amnestic MCI or mild AD patients. Hypometabolism across all patients was slightly increased in the left hemisphere. Interestingly, the more reduced the metabolism in the left temporo-parietal junction the more pro-nounced was the top-down control deficit. Accordingly, hypometabolism in the left TPJ pre-dicted the magnitude of the spatial bias. Furthermore, relative hypometabolism in the left TPJ and left inferior parietal lobe as compared to the right TPJ and right IPL, respectively, was correlated with direction and degree of spatial bias. Taken together, PET imaging results support the hypotheses that, one the one hand, early def-icits in task-related weighting may result from a fronto-parietal disconnection syndrome al-ready at the stage of MCI. On the other hand, very early AD seems to be also associated with an interhemispheric imbalance of metabolism, particularly in the temporo-parietal cortices, resulting in a correspondingly directed and distinctive visuo-spatial attentional bias. Conclusions and outlook: This dissertation intended to investigate the probable valuable contribution of the whole and partial report of briefly presented letter arrays based on Bundesen’s theory of visual attention in assessing am-nestic MCI and AD patients in comparison to healthy elderly control subjects. The results of the three presented studies suggest a staging model of visual selective atten-tional impairments in MCI and AD. Deficits of pre-attentive processing, task-related and spatial weighting were already detectable in MCI patients, while aspects of processing capacity were still intact. At a later stage of the disease, further deterioration of top-down control α and increasing lateralization of spatial weighting wλ accompanied impairments in perceptual processing speed C and VSTM storage capacity K. In conclusion, the TVA-based assessment of selective visual attention proved to be a sensitive diagnostic tool for revealing subtle deficits already at the stage of MCI which might exhibit the capability of an early cognitive marker for the identification of subjects at risk of AD. To address this question, this survey needs to be complemented by longitudinal studies. (shrink)

The claim that the disorganized subtype of schizophrenia results from glutamate hypofunction is enhanced by consideration of current subtypology of schizophrenia, symptom definition, interdependence of neurotransmitters, and the nature of the data needed to support the hypothesis. Careful specification clarifies the clinical reality of disorganization as a feature of schizophrenia and increases the utility of the subtype.

Phillips & Silverstein emphasize the gain-control properties of NMDA synapses in cognitive coordination. We endorse their view and suggest that NMDA synapses play a crucial role in biased attentional competition and (visual) working memory. Our simulations show that NMDA synapses can control the storage rate of visual objects. We discuss specific predictions of our model about cognitive effects of NMDA-antagonists and schizophrenia.

Phillips & Silverstein offer an exciting synthesis of ongoing efforts to link the clinical and cognitive manifestations of schizophrenia with cellular accounts of its pathophysiology. We applaud their efforts but wonder whether the highly inclusive notion of “context” adequately captures some important details regarding schizophrenia and NMDA/glutamate function that are suggested by work on language processing and cognitive electrophysiology.

The visual attention (VA) span is defined as the amount of distinct visual elements which can be processed in parallel in a multi-element array. Both recent empirical data and theoretical accounts suggest that a VA span deficit might contribute to developmental dyslexia, independently of a phonological disorder. In this study, this hypothesis was assessed in two large samples of French and British dyslexic children whose performance was compared to that of chronological-age matched control children. Results of the French study show (...) that the VA span capacities account for a substantial amount of unique variance in reading, as do phonological skills. The British study replicates this finding and further reveals that the contribution of the VA span to reading performance remains even after controlling IQ, verbal fluency, vocabulary and single letter identification skills, in addition to phoneme awareness. In both studies, most dyslexic children exhibit a selective phonological or VA span disorder. Overall, these findings support a multi-factorial view of developmental dyslexia. In many cases, developmental reading disorders do not seem to be due to phonological disorders. We propose that a VA span deficit is a likely alternative underlying cognitive deficit in dyslexia. (shrink)

Impairments in cognitive coordination in schizophrenia are supported by phenomenological data that suggest deficits in the processing of visual context. Although the target article is sympathetic to such a phenomenological perspective, we argue that the relevance of phenomenological data for a wider understanding of consciousness in schizophrenia is not sufficiently addressed by the authors.

Neurophysiological investigations of the past two decades have consistently demonstrated a deficit in sensory gating associated with schizophrenia. Phillips & Silverstein interpret this impairment as being consistent with cognitive coordination dysfunction. However, the physiological mechanisms that underlie sensory gating have not been shown to involve gamma-band oscillations or NMDA-receptors, both of which are critical neural elements in the cognitive coordination model.

It is proposed that cortical activity is normally coordinated across synaptically connected areas and that this coordination supports cognitive coherence relations. This view is consistent with the NMDA- hypoactivity hypothesis of the target article in regarding disorganization symptoms in schizophrenia as arising from disruption of normal interareal coordination. This disruption may produce abnormal contextual effects in the cortex that lead to anomalous cognitive coherence relations.

When a person decides to do something in the future, she forms an intention and her intention persists. Philosophers have thought about the rational requirement that an agent’s intention persists until its execution. But philosophers have neglected to think about the causal memory mechanisms that could enable this kind of persistence and its role in rational long-term agency. Our aim of this paper is to fill this gap by arguing that memory for intention is a specific kind of memory. We (...) do this by evaluating and rejecting standard declarative accounts of memory for intention and arguing for the plausibility of an alternative model of memory for intention. We argue for the alternative by spelling out a number of computational principles that could enable retaining and retrieving intentions from long-term memory. These principles could explain a number of core features of intentions. (shrink)