Visual Agnosia is a comprehensive and up-to-date review of disorders of higher vision that relates these disorders to current conceptions of higher vision from cognitive science, illuminating both the neuropsychological disorders and the nature of normal visual object recognition.Brain damage can lead to selective problems with visual perception, including visual agnosia the inability to recognize objects even though elementary visual functions remain unimpaired. Such disorders are relatively rare, yet they provide a window onto (...) how the normal brain might accomplish the complex task of vision. Visual Agnosia reviews a century of case studies of higher-level visual deficits following brain damage, places them in the general context of current neuroscience, and draws relevant conclusions about the organization of normal visual processing. It is unique in drawing on research in cognitive psychology, computational vision, visual neurophysiology, and neuropsychology to interpret the agnosias and draw inferences from them about visual object recognition.Following a historical account of agnosia research, Visual Agnosia offers a taxonomy of a wide range of agnosia syndromes, describing and interpreting the syndromes in terms of the latest theoretical models of visual processing and ultimately bringing them to bear as evidence on a variety of questions in the study of higher vision.Martha J. Farah is Associate Professor of Psychology at Carnegie Mellon University. Visual Agnosia is included in the Issues in Biology of Language and Cognition series, edited by John Marshall. (shrink)

Common sense says that visual agnosia is impossible. It ought not exist. If an object like a safety pin or a bar of white soap is in full view, you see it, and you know what a "safety pin" or a "bar of soap" is, then you cannot fail to recognize what you see. If you identify the safety pin as "something silver and shiny like a watch or a nail clipper," or you identify the bar of white (...) soap as "a piece of paper," then common sense would dictate that either you fail to see the object, or your knowledge is somehow deficient. But visual agnosics, who make such responses, clearly do--in some sense--"see" the objects in question. Often they can, for example, make accurate and recognizable drawings of what they see. Some lack measurable visual field defects; they have a full visual field. And they clearly know what a "safety pin" or a "bar of soap" is: if allowed to touch the object, or its use is pantomimed, correct identification is immediate. "I see it now," they may say. We get a failure specifically in visual recognition, even though sufficient sensory functions and cognitive functions are demonstrably intact. Such is the mystery of visual agnosia. (shrink)

The cortical visual mechanisms involved in processing spatial relationships remain subject to debate. According to one current view, the ''dorsal stream'' of visual areas, emanating from primary visual cortex and culminating in the posterior parietal cortex, mediates this aspect of visual processing. More recently, others have argued that while the dorsal stream provides egocentric coding of visual location for motor control, the separate ''ventral'' stream is needed for allocentric spatial coding. We have assessed the (...) class='Hi'>visual form agnosic patient DF, whose lesion mainly affects the ventral stream, on a prehension task requiring allocentric spatial coding. She was presented with transparent circular disks. Each disk had circular holes cut in it. DF was asked to reach out and grasp the disk by placing her fingers through the holes. The disks either had three holes (for forefinger, middle finger, and thumb) or two holes (for forefinger and thumb). The distance between the forefinger and thumb holes, and the orientation of the line formed by them, were independently varied. DF was quite unable to adjust her grip aperture or her hand orientation in the three-hole task. Although she was able to orient her hand appropriately for the two-hole disks, she still remained unable to adjust her grip aperture to the distance between the holes. These findings are consistent with the idea that allocentric processing of spatial information requires a functioning ventral stream, even when the information is being used to guide a motor response. (shrink)

Visual Associative agnosia is a rare perceptual impairment generally resulting from lesions in the infero temporal cortex. Patients suffering from associative agnosia are able to make accurate copies of line drawings, but they are unable to visually recognize objects - including those represented in line drawings - as belonging to familiar high-level kinds. The Rich Content View claims that visual experience can represent high-level kind properties. The phenomenon of associative agnosia appears to present us with (...) a strong case for the Rich Content View. There are reasons for thinking that the experiences of an agnosic patient differ from those of a healthy subject. Given that there is a phenomenal contrast between the experiences of an associative agnosic and those of a healthy perceiver, one may argue that this contrast is due to differences in abilities to represent high-level kinds. I claim that there is indeed a phenomenal contrast between the visual experiences of an agnosic and those of a healthy perceiver. However, the explanation of this contrast that best fits the empirical data is compatible with the view that visual experience does not represent high-level kinds. (shrink)

Examines the philosophy, psychology, and neuroscience behind visual experience. Chapters on attention, illusions, aftereffects, binocular rivalry, hemispheric differences, attentional blink, agnosias and other disorders. Particular attention paid to consciouseness. The systematic review of key topics and the multitude of perspectives make this book an ideal primary or ancillary text for graduate courses in perception, vision, consciousness, or philosophy of mind.

Neuropsychological deficits have been widely used to elucidate normal cognitive functioning. Can patients with such deficits also be used to understand conscious visual experience? In this paper, we ask what it would be like to be a patient with apperceptive agnosia . Philosophical analyses of such questions have suggested that subjectively experiencing what another person experiences would be impossible. Although such roadblocks into the conscious experience of others exist, the experimental study of both patients and neurologically normal subjects (...) can be used to understand visual processing mechanisms. In order to understand the visual processes damaged in apperceptive agnosia, we first review this syndrome and present a case study of one such patient, patient J.W. We then review several theoretical accounts of apperceptive agnosia, and we conclude that studies of the patients themselves may not allow us to discriminate between the various explanations of the syndrome. To test these accounts, we have simulated apperceptive agnosia in neurologically normal subjects. The implications of our results for understanding both apperceptive agnosia and normal visual processing are discussed. (shrink)

Over recent years, there has been a resurgence of interest in arguments favouring intellectualism—the view that Ryle’s epistemic distinction is invalid because knowing how is in fact nothing but a species of knowing that. The aim of this paper is to challenge intellectualism by introducing empirical evidence supporting a form of knowing how that resists such a reduction. In presenting a form of visuomotor pathology known as visual agnosia, I argue that certain actions performed by patient DF can (...) be distinguished from a mere physical ability because they are (1) intentional and (2) knowledge-based; yet these actions fail to satisfy the criteria for propositional knowledge. It is therefore my contention that there exists a form of intentional action that not only constitutes a genuine claim to knowledge but, in being irreducible to knowing that, resists the intellectualist argument for exhaustive epistemic reduction. (shrink)

Integration information theories posit that the integration of information is necessary and/or sufficient for consciousness. In this paper, we focus on three of the most prominent information integration theories: Information Integration Theory, Global Workspace Theory, and Attended Intermediate-Level Theory. We begin by explicating each theory and key concepts they utilize. We then argue that the current evidence indicates that the integration of information is neither necessary nor sufficient for consciousness. Unlike GWT and AIR, IIT maintains that conscious experience is both (...) necessary and sufficient for consciousness. We present empirical evidence indicating that simple features are experienced in the absence of feature integration and argue that it challenges IIT’s necessity claim. In addition, we challenge IIT’s sufficiency claim by presenting evidence from hemineglect cases and amodal completion indicating that contents may be integrated and yet fail to give rise to subjective experience. Moreover, we present empirical evidence from subjects with frontal lesions who are unable to carry out simple instructions and argue that they are irreconcilable with GWT. Lastly, we argue that empirical evidence indicating that patients with visual agnosia fail to identify objects they report being conscious of present a challenge to AIR’s necessity claim. (shrink)

Neuropsychological patients exhibiting category-selective visual agnosias provide unique insights into the cognitive functions of the human brain. Transcranial magnetic stimulation, in contrast, can be used to draw causal inferences, as one of the effects of the cortical disruption induced by magnetic stimulation is to act as a “virtual lesion” lasting from tens of milliseconds up to approximately one hour, depending on the type of stimulation. This specificity offers a unique advantage in psychological testing as TMS can be used to (...) test where and when cognitive computations are performed. This article briefly describes TMS, considers the small but growing number of studies that use TMS to disrupt face processing. It discusses how TMS can be used in the future to understand better how faces are cortically represented in the human brain. (shrink)

There is tension between commonly held views concerning phenomenal imagery on the one hand and our first-person epistemic access to it on the other. This tension is evident in many individual issues and experiments in philosophy and psychology (e.g. inattentional and change blindness, the speckled hen, dream coloration, visual periphery). To dissolve it, we can give up either (i) that we lack full introspective access to the phenomenal properties of our imagistic experiences, or (ii) that phenomenal imagery is fully (...) determined, or (iii) that phenomenal imagery does not exist. Which option is preferable? I explore the feasibility of option (ii) in more details by distinguishing between di erent kinds of indeterminacy. One of the most often proclaimed versions of indeterminacy is tied to Representationalism. However, I argue that in this context, Representationalism appears to be the least satisfying option, for which I give ten reasons. By abduction, we should reject Representationalism in favour of (i) or (iii)—the most parsimonious option being eliminativism, and the most conservative being the rejection of privileged access. The decision between these two, however, should be made on a case-by-case basis, depending on which is most adequate given the data. I illustrate this with the comparison between visual agnosia and Charles-Bonnet-Syndrome. (shrink)

In this paper, I explore how best to conceptualize the nature of alexithymia. I argue that the condition is best understood as a dimensional construct; as such, it is likely that there exist various degrees of alexithymia. Moreover, I explore the merits of two analogies that others have used to try to understand the nature of alexithymia: one characterizes the condition as an analogue of associative visual object agnosia, and the other characterizes it as the emotional equivalent of (...) blindsight. I argue that the analogy with blindsight more adequately portrays the processing deficit involved in mild alexithymia, but that neither the analogy with blindsight nor the analogy with associative visual object agnosia is able to account for the deficit involved in severe alexithymia. Instead, I argue that the deficit involved in severe alexithymia is best understood through an analogy with apperceptive visual agnosia. (shrink)

The aim of this paper is to draw the attention of those conducting research on imagery to the different kinds of visual information deployed by expert drawers compared to non-expert drawers. To demonstrate this difference I draw upon the cognitive science literature on vision and imagery to distinguish between three different ways that visual phenomena can be represented in memory: structural descriptions, denotative descriptions, and configural descriptions. Research suggests that perception and imagery deploy the same mental processes and (...) that the drawing of one's imagery would require the simultaneous deployment of these very processes. I reason that drawing a picture of one's imagery is not possible. I hypothesize that when required to draw a picture from memory, both expert and non-expert drawers access their denotative description of the object rather than their imagery. I then suggest how my hypothesis could be tested and if accurate, how this finding would impact upon the design and interpretation of experiments on imagery when drawing is involved. I also suggest why the constraints that perception places upon the simultaneous deployment of imagery appear not to cause the same constraints in autistic savant drawers and visual agnosia patients. (shrink)

Open-minded people should endorse dogmatism because of its explanatory power. Dogmatism holds that, in the absence of defeaters, a seeming that P necessarily provides non-inferential justification for P. I show that dogmatism provides an intuitive explanation of four issues concerning non-inferential justification. It is particularly impressive that dogmatism can explain these issues because prominent epistemologists have argued that it can’t address at least two of them. Prominent epistemologists also object that dogmatism is absurdly permissive because it allows a seeming to (...) provide justification even if the seeming was caused in some apparently inappropriate way. I conclude by disarming this objection. (shrink)

Blindsight is the term commonly used to describe visually guided behaviour elicited by a stimulus falling within the scotoma (blind area) caused by a lesion of the striate cortex. Such is normally held to be unconscious and to be mediated by subcortical pathways involving the superior colliculus. Blindsight is of considerable theoretical importance since it suggests that destriate man is more like destriate monkey than had been previously believed and also because it supports the classical notion of two visual (...) systems. It is also of potential clinical importance, since it has been claimed recently that systematic practice in blindsight can lead to the recovery of normal visual function in patients with cortical lesions. From a review of the literature it is concluded that all of the phenomena of blindsight can be attributed either to light scatter into unimpaired parts of the visual field or to residual vision resulting from spared striate cortex. The possible contribution f other factors is also considered. It is concluded that blindsight studies have generally failed to control for such nonblindsight interpretations partly because of poor methodology and partly because of difficulties in defining the term. (shrink)

Psychogenic depersonalization is an altered mental state consisting of an unusual discontinuity in the phenomenological perception of personal being; the individual is engulfed by feelings of unreality, self-detachment and unfamiliarity in which the self is felt to lack subjective perspective and the intuitive feeling of personal embodiment. A new sub-feature of depersonalization is delineated. 'Prosthesis' consists in the thought that the thinker is a 'mere thing'. It is a subjectively realized sense of the specific and objective 'thingness' of the particular (...) object thought about. I show that prosthesis is an important cognitive feature of depersonalization, and may be psychologically connected with the tendency of depersonalized individuals to report 'philosophical' types of thinking. Indeed, several philosophical issues concerning the identity of the self appear to have been enhanced by prosthesis experiences. Thus, far more efficient than William James's experimental attempts to uncover philosophical truths under the influence of nitrous oxide intoxication, prosthesis may be a safe and recommended experience for philosophers. The history of depersonalization theories is presented from Krishaber to Freud, and the main approaches to prosthesis criticized. Finally, a fresh approach to psychogenic depersonalization is outlined on the basis of certain cognitive similarities with visual agnosia. This paper may be understood as continuing the Jamesian tradition 'experimental abnormal psychology', that is, of examining extraordinary mental states with an eye to their philosophical implications. (shrink)

I respond to three arguments aimed at establishing that natural kind properties — a kind of high-level properties — occur in the experiential content of visual perceptual experience: the argument from phenomenal difference, the argument from mandatory seeing, and the argument from associative agnosia. I conclude with a simple argument against the view that natural kind properties occur in the experiential content of visual experience.

In this dissertation, I reaffirm one aspect of the traditional divide between perception and belief, by arguing that perception and belief can can be distinguished by their rational roles. Partly relying on this proposed rational difference between perception and belief, I reject a different aspect of the traditional picture, on which perception cannot represent conceptually sophisticated features. Focusing on the visual modality, I argue that visual experience can represent at least some features other than shape, color, and movement. (...) More particularly: I consider and criticize some extant arguments for high-level perception, including an argument from introspection and an argument from agnosia. I develop a new reason to think that beliefs are necessarily rationally revisable in a certain way, and I ultimately argue that in some cases, we have literal visual experiences as of others' mental states, such as their proximal intentions. (shrink)

I critically examine Adams and Garrison’s proposed necessary condition for the mark of the cognitive (Adams and Garrison in Minds Mach 23(3):339–352, 2013). After a brief presentation of their position, I argue not only that their proposal is in need of additional support, but also that it is too restrictive.

David Milner and Melvyn Goodale, and the many psychologists and philosophers who have been influenced by their work, claim that ‘the visual system that gives us our visual experience of the world is not the same system that guides our movements in the world’. The arguments that have been offered for this surprising claim place considerable weight on two sources of evidence — visual form agnosia and the reaching behaviour of normal subjects when picking up objects (...) that induce visual illusions. The present article shows that, if we are careful to consider the possibility that a demonstrative gesture can contribute content to a conscious experience, then neither source of evidence is compelling. (shrink)

This book explains the key concepts that surround the issue as well as the nature of the hard problem and the several approaches to it. It gives a comprehensive treatment of the phenomenon, incorporating its main metaphysical and epistemic aspects as well as recent empirical findings, such as the phenomena of blindsight, change blindness, visual-form agnosia and optic ataxia, mirror recognition in other primates, split-brain cases, and visual extinction.

We present a technique called Random Image Structure Evolution (RISE) for use in experimental investigations of high‐level visual perception. Potential applications of RISE include the quantitative measurement of perceptual hysteresis and priming, the study of the neural substrates of object perception, and the assessment and detection of subtle forms of agnosia. In simple terms, RISE involves the measurement of perceptual and/or neural responses as visual stimuli are systematically transformed—in particular, as recognizable objects evolve from, then dissolve into, (...) randomness. Points along the sequences corresponding to the onset and offset of subjects' percepts serve as markers for quantitatively and objectively characterizing several perceptual phenomena. Notably, these image sequences are created in a manner that strictly controls a number of important low‐level image properties, such as luminance and frequency spectra, thus reducing confounds in the analysis of high‐level visual processes. Here we describe the RISE paradigm, report the results of a few basic RISE experiments, and discuss a number of experimental and clinical applications of this approach. (shrink)

This paper concentrates on the basic properties of ''consciousness'' that temporal coding is postulated to relate to. A description of phenomenal consciousness based on what introspection tells us about its contents is offered. This includes a consideration of the effect of various brain lesions that result in cortical blindness, apperceptive and associative agnosia, and blindsight, together with an account of the manner in which sight is regained after cortical injuries. I then discuss two therories of perception-Direct Realism and the (...) Representative Theory. This includes a discussion of the concept of the body-image, phantom limbs, the alleged projection of sensations, the ontological status of phenomenal space, the homunculus argument, the validity of topographic coding, the difference between the stimulus field and the visual field, and two theories of brain-mind relationship-the Identity Theory and the Bohr-Heisenberg theory of brain-mind complementarity. Finally I suggest that the binocular rivalry obtained in the case of the stroboscopic patterns that result from intermittent photic stimulation of one eye, when used in animal expeiments with unit recording, offers a good experimental method of investigating the binding problem. (shrink)

How can the fine-grained phenomenology of conscious experience arise from neural processes in the brain? How does a set of action potentials (nerve impulses) become like the feeling of pain in one's experience? Contemporary neuroscience is teaching us that our mental states correlate with neural processes in the brain. However, although we know that experience arises from a physical basis, we don't have a good explanation of why and how it so arises. The problem of how physical processes give rise (...) to experience is called the 'hard problem' of consciousness and it is the contemporary manifestation of the mind-body problem. This book explains the key concepts that surround the issue as well as the nature of the hard problem and the several approaches to it. It gives a comprehensive treatment of the phenomenon incorporating its main metaphysical and epistemic aspects, as well as recent empirical findings, such as the phenomenon of blindsight, change blindness, visual-form agnosia and optic ataraxia, mirror recognition in other primates, split-brain cases and synaesthesia. (shrink)

Although Wayne Wu correctly identifies a flaw in the way in which my 2009 article frames the debate about ‘zombie action’, he fails in his attempts to strengthen the case for thinking that our actions are under less conscious control than we usually imagine. His argument, like the arguments that my earlier paper addressed, can be blocked by allowing that an embodied demonstrative concept can contribute contents to a visual experience.

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)

Background: Visual technologies are central to youth culture and are often the preferred communication means of adolescents. Although these tools can be beneficial in fostering relations, adolescents’ use of visual technologies and social media also raises ethical concerns. Aims: We explored how school public health nurses identify and resolve the ethical challenges involved in the use of visual technologies in health dialogues with adolescents. Research design: This is a qualitative study utilizing data from focus group discussions. Participants (...) and research context: We conducted focus group discussions using two semi-structured discussion guides with seven groups of public health nurses (n = 40) working in Norwegian school health services. The data were collected during January and October 2016. Discussions were audio recorded, transcribed, and coded into themes and subthemes using systematic text condensation. Ethical considerations: The leader of the public health nursing service who agreed to provide access for the study and the Norwegian Center for Research Data that reviewed and approved the study. All participants gave informed consent. Findings: In adolescents’ use of visual materials with public health nurses, ethical concerns were raised regarding suicide ideations, socially unacceptable content, violation of privacy, and presentations of possible child neglect. The nurses utilized their professional knowledge and experience when identifying and navigating these ethical dilemmas; they resolved ethical uncertainties through peer discussion and collaboration with fellow nurses and other professionals. Discussion: We discussed the findings in light of Annemarie Mol’s interpretation of the ethics of care. Mol expands the notion of ethical care to include the action of technologies. Conclusion: Although the increasing use of visual technologies offered benefits, school nurses faced ethical challenges in health dialogues with adolescents. To address and navigate these ethical issues, they relied on their experience and caring practices based on their professional ethics. Uncertainties were resolved through peer dialogue and guidance. (shrink)

Anosognosia for visual deficits—cases where significant visual deficits go unnoticed—challenges the view that our own conscious experiences are what we know best. We review these widespread and striking failures of awareness. Anosognosia can occur with total blindness, visual abnormalities induced by brain lesions, and eye diseases. We show that anosognosia for visual deficits is surprisingly widespread. Building on previous accounts, we introduce a framework showing how apparently disparate forms of anosognosia fit together. The central idea is (...) that, to notice a deficit, individuals need to form expectations about normal vision, compare expectations and visual input, and judge any mismatch at the metacognitive level. A failure in any of these three steps may lead to unawareness of visual deficits. (shrink)

In this paper, I take up the conciliatory-steadfast debate occurring within social epistemology in regards to the phenomenon of peer disagreement. I will argue, because the conciliatory perspective al-lows us to understand argumentation pragmatically—as a method of problem-solving within a community rather than as a method for obtaining the truth—that in most cases, we should not simply agree to disagree.

Background: Primary open-angle glaucoma patients exhibit widespread white matter degeneration throughout their visual pathways. Whether this degeneration starts at the pre- or post-geniculate pathways remains unclear. In this longitudinal study, we assess the progression of WM degeneration exhibited by the pre-geniculate optic tracts and the post-geniculate optic radiations of POAG patients over time, aiming to determine the source and pattern of spread of this degeneration.Methods: Diffusion-weighted MRI scans were acquired for 12 POAG patients and 14 controls at two time-points (...) 5.4 ± 2.1 years apart. Fiber density, an estimate of WM axonal density, was computed for the OTs and ORs of all participants in an unbiased longitudinal population template space. First, FD was compared between POAG patients and the controls at time-point 1 and time-point 2 independently. Secondly, repeated measures analysis was performed for FD change in POAG patients between the two time-points. Finally, we compared the rate of FD change over time between the two groups.Results: Compared to the controls, POAG patients exhibited significantly lower FD in the left OT at TP1 and in both OTs and the left OR at TP2. POAG patients showed a significant loss of FD between the time-points in the right OT and both ORs, while the left OR showed a significantly higher rate of FD loss in POAG patients compared to the controls.Conclusions: We find longitudinal progression of neurodegenerative WM changes in both the pre- and post-geniculate visual pathways of POAG patients. The pattern of changes suggests that glaucomatous WM degeneration starts at the pre-geniculate pathways and then spreads to the post-geniculate pathways. Furthermore, we find evidence that the trans-synaptic spread of glaucomatous degeneration to the post-geniculate pathways is a prolonged process which continues in the absence of detectable pre-geniculate degenerative progression. This suggests the presence of a time window for salvaging intact post-geniculate pathways, which could prove to be a viable therapeutic target in the future. (shrink)

Resenha do livro PATTON, Pamela A.. Envisioning Others: Race, Color, and the Visual in Iberia and Latin America [Tradução do título: Imaginado os/as outros/as: raça, cor e o visual na Ibéria e América Latina ] Leiden, Bel. / Boston, EUA: Brill, 2016. 382p com índice de 6p 63 imagens [Coletânea: The Medieval and Early Modern Iberian World, vol. 62]. ISBN 978-90-04-26917-0 ; ISBN 978-90-04-30215-0.

Previous research has successfully used feature integration theory to operationalise the predictions of Perceptual Load Theory, while simultaneously testing the predictions of both models. Building on this work, we test the extent to which these models hold up in a 3D world. In two experiments, participants responded to a target stimulus within an array of shapes whose apparent depth was manipulated using a combination of monoscopic and stereoscopic cues. The search task was designed to test the predictions of feature integration (...) theory, as the target was identified by a single feature or a conjunction of features and embedded in search arrays of varying size, and perceptual load theory, as the task included congruent and incongruent distractors presented alongside search tasks imposing high or low perceptual load. Findings from both experiments upheld the predictions of feature integration theory, regardless of 2D/3D condition. Longer search times in conditions with a combination of monoscopic and stereoscopic depth cues suggests that binding features into three-dimensional objects requires greater attentional effort. This additional effort should have implications for perceptual load theory, yet our findings did not uphold its predictions; the effect of incongruent distractors did not differ between conjunction search trials and feature search trials. Individual differences in susceptibility to the effects of perceptual load were evident and likely explain the absence of load effects. Overall, our findings suggest that feature integration theory may be useful for predicting attentional performance in a 3D world. (shrink)