Development of a vocabulary of object shapes in a child with a very-early-acquired visual agnosia: A unique case

We report a longitudinal study of an exceptional child (S.R.) whose early-acquired visual agnosia, following encephalitis at 8 weeks of age, did not prevent her from learning to construct an increasing vocabulary of visual object forms (drawn from different categories), albeit slowly. S.R. had problems perceiving subtle differences in shape; she was unable to segment local letters within global displays; and she would bring complex scenes close to her eyes: a symptom suggestive of an attempt to reduce visual crowding. Investigations revealed a robust ability to use the gestalt grouping factors of proximity and collinearity to detect fragmented forms in noisy backgrounds, compared with a very weak ability to segment fragmented forms on the basis of contrasts of shape. When contrasts in spatial grouping and shape were pitted against each other, shape made little contribution, consistent with problems in perceiving complex scenes, but when shape contrast was varied, and spatial grouping was held constant, S.R. showed the same hierarchy of difficulty as the controls, although her responses were slowed. This is the first report of a child's visual–perceptual development following very early neurological impairments to the visual cortex. Her ability to learn to perceive visual shape following damage at a rudimentary stage of perceptual development contrasts starkly with the loss of such ability in childhood cases of acquired visual agnosia that follow damage to the established perceptual system. Clearly, there is a critical period during which neurological damage to the highly active, early developing visual–perceptual system does not prevent but only impairs further learning.     

Damasio's error – Prosopagnosia with intact within‐category object recognition

The sudden inability to recognize individual faces following brain damage was first reported in a scientific journal 150 years ago and termed ‘prosopagnosia’ 70 years ago. While the term originally identified a face‐selective neurological condition, it is now obscured by a sequence of imprecisions. First, prosopagnosia is routinely used to define symptoms of individual face recognition (IFR) difficulties in the context of visual object agnosia or other neurological conditions, or even in the normal population. Second, this over‐expansive definition has lent support to a long‐standing within‐category recognition account of prosopagnosia, that is, that the impairment of IFR reflects a general impairment in recognizing within‐category objects. However, stringent experimental studies of classical cases of prosopagnosia following brain damage show that their core impairment is not in recognizing physically similar exemplars within non‐face object categories. Instead, the impairment presents specifically for recognizing exemplars of the category of faces. Moreover, compared to typical observers, the impairment appears even more severe for recognizing individual faces against physically dissimilar than similar distractors. Here, I argue that we need to limit accordingly our definition of prosopagnosia to a clinical (i.e., neurological) condition in which there is no basic‐level object recognition impairment. Other criteria for prosopagnosia are proposed, with the hope that this conservative definition enables the study of human IFR processes in isolation, and supports progress in understanding the nature of these processes.     

Characteristics of auditory agnosia in a child with severe traumatic brain injury: a case report

We present a case that is unusual in many respects from other documented incidences of auditory agnosia, including the mechanism of injury, age of the individual, and location of neurological insult. The clinical presentation is one of disturbance in the perception of spoken language, music, pitch, emotional prosody, and temporal auditory processing in the absence of significant deficits in the comprehension of written language, expressive language production, or peripheral auditory function. Furthermore, the patient demonstrates relatively preserved function in other aspects of audition such as sound localization, voice recognition, and perception of animal noises and environmental sounds. This case study demonstrates that auditory agnosia is possible following traumatic brain injury in a child, and illustrates the necessity of assessment with a wide variety of auditory stimuli to fully characterize auditory agnosia in a single individual.     

Interhemispheric functional relationships in auditory agnosia : An analysis of the preconditions and a conceptual model

A statistical analysis revealed the following concerning auditory agnosia. (1) Bilateral temporal lobe lesions prevailed; in a minority of cases unilateral lesions were verified. (2) The syndrome occurred as a result of repeated insults. (3) There was a statistically significant correlation between the side of the first insult and the predilective type of the syndrome, i.e., agnosia preferably for linguistic with respect to nonlinguistic material. On the basis of these results we discuss the principle of contralateral compensation and the hypothesis of lesional interference. In doing so a conceptual model of interhemispheric functional relationships is developed. We made use of a set theory-oriented interpretation of Kinsbourne's “attention-model” (M. Kinsbourne, 1970, Acta Psychologica 33, 193–201).     

Visual object agnosia without prosopagnosia or alexia: Evidence for hierarchical theories of visual recognition

Abstract

A single case study is presented of a patient, Mr. W, with a selective deficit in recognizing pictures and real objects, linked to impaired stored visual knowledge about objects. Despite this, Mr. W maintained a preserved ability both to read aloud printed words and to recognize famous faces, when compared with age-matched control subjects. In addition, his access to semantic information from words was superior to that from pictures. The data provide evidence that visual agnosia can occur without alexia or prosopagnosia, contrary to recent proposals (Farah 1990, 1991). This finding is consistent with a hierarchical model of visual object recognition in which agnosia can reflect impaired stored knowledge of objects without accompanying perceptual deficits. The selective recognition deficit for objects further indicates that stored knowledge concerning different classes of visual stimuli (common objects, faces, and words) is separately represented in the brain.     

Case Study Evidence for an Irreducible Form of Knowing How to: An Argument Against a Reductive Epistemology

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.

Perception of dynamic acoustic patterns by an individual with unilateral verbal auditory agnosia

Previous studies have found that subjects diagnosed with verbal auditory agnosia (VAA) from bilateral brain lesions may experience difficulties at the prephonemic level of acoustic processing. In this case study, we administered a series of speech and nonspeech discrimination tests to an individual with unilateral VAA as a result of left-temporal-lobe damage. The results indicated that the subject's ability to perceive steady-state acoustic stimuli was relatively intact but his ability to perceive dynamic stimuli was drastically reduced. We conclude that this particular aspect of acoustic processing may be a major contributing factor that disables speech perception in subjects with unilateral VAA.     

Object Recognition Difficulty in Visual Apperceptive Agnosia

Two patients with visual apperceptive agnosia were examined on tasks assessing the appreciation of visual material. Elementary visual functioning was relatively preserved, but they had profound difficulty recognizing and naming line drawings. More detailed evaluation revealed accurate recognition of regular geometric shapes and colors, but performance deteriorated when the shapes were made more complex visually, when multiple-choice arrays contained larger numbers of simple targets and foils, and when a mental manipulation such as a rotation was required. The recognition of letters and words was similarly compromised. Naming, recognition, and anomaly judgments of colored pictures and real objects were more accurate than similar decisions involving black-and-white line drawings. Visual imagery for shapes, letters, and objects appeared to be more accurate than visual perception of the same materials. We hypothesize that object recognition difficulty in visual apperceptive agnosia is due to two related factors: the impaired appreciation of the visual perceptual features that constitute objects, and a limitation in the cognitive resources that are available for processing demanding material within the visual modality.     

The importance of identifying underlying process abnormalities in alexithymia: Implications of the three-process model and a single case study illustration

We present an in-depth case study of a rare individual (whom we will refer to as “Jane”) who reported an inability to experience emotion. Jane completed a range of assessments measuring alexithymia, emotional awareness, and emotion recognition ability. She, along with 22 control participants, also underwent skin conductance (SC) measurement and facial electromyography (EMG) during exposure to affective images, and self reported the valence/arousal of their responses to those images. Jane scored high on alexithymia and low on emotional awareness; yet she performed well on emotion recognition measures and showed a typical pattern of valence ratings. Her SC responses and subjective arousal ratings were atypically low, and some of her EMG responses were also atypical. Jane’s deficit profile highlights the dissociability of self-focused emotional awareness and other-focused emotion recognition ability, as well as the dissociability between the generation and representation of valence and arousal (with both subjective and objective measures).     

Now you see it,now you don't: The context dependent nature of category-effects in visual object recognition

In two experiments, we test predictions regarding processing advantages/disadvantages for natural objects and artefacts in visual object recognition. Varying three important parameters—degree of perceptual differentiation, stimulus format, and stimulus exposure duration—we show how different category-effects can be provoked in normal subjects on the same task. We interpret the results in light of the Pre-semantic Account of Category Effects (PACE; Gerlach, 2009), and conclude that category-effects do not reflect absolute processing differences between categories. Rather, category-effects are products of common operations which are differentially affected by the structural similarity among objects (with natural objects being more structurally similar than artefacts). The potentially most important aspect of the present study is the demonstration that category-effects are very context dependent; an aspect which has been neglected in earlier literature on category-specificity. PACE provides a useful framework in this respect, as it specifies how category-effects are influenced by changes in task and stimulus characteristics.     

Covert processing of faces in prosopagnosia is restricted to facial expressions: evidence from cross-modal bias

We present a single case study of a brain-damaged patient, AD, suffering from visual face and object agnosia, with impaired visual perception and preserved mental imagery. She is severely impaired in all aspects of overt recognition of faces as well as in covert recognition of familiar faces. She shows a complete loss of processing facial expressions in recognition as well as in matching tasks. Nevertheless, when presented with a task where face and voice expressions were presented concurrently, there was a clear impact of face expressions on her ratings of the voice. The cross-modal paradigm used here and validated previously with normal subjects (de Gelder & Vroomen, 1995, 2000), appears as a useful tool in investigating spared covert face processing in a neuropsychological perspective, especially with prosopagnosic patients. These findings are discussed against the background of different models of the covert recognition of face expressions.     

Visual object agnosia as a problem in integrating parts and part relations

Current models of vision generally assume that the recognition of visual objects is achieved by encoding their component parts, as well as the spatial relations among parts. The current study examined how the processing of parts and their configurations may be affected in visual agnosia due to brain damage. Both a visual agnosic patient (AR) and healthy control subjects performed a visual search task in which they had to discriminate between targets and distractors that varied according to whether they shared their parts and/or their configuration. The results show that AR's visual search rates are disproportionally slow when targets and distractors share the same configuration than when they have different configurations. AR is also found to be disproportionately slow in discriminating targets and distractors that share identical parts when the targets and distractors share the same configuration. With differently configured targets and distractors, AR shows no part sharing effect. For controls, in contrast, the part and configuration sharing effects occur independently of one another. It is concluded that AR's object recognition deficit arises from difficulties in discriminating objects that share their configuration, and from an abnormal dependency of part information processing upon object configuration.     

Is the Right Anterior Temporal Variant of Prosopagnosia a Form of ‘Associative Prosopagnosia’ or a Form of ‘Multimodal Person Recognition Disorder’?

The construct of associative prosopagnosia is strongly debated for two main reasons. The first is that, according to some authors, even patients with putative forms of associative visual agnosia necessarily present perceptual defects, that are the cause of their recognition impairment. The second is that in patients with right anterior temporal lobe (ATL) lesions (and sparing of the occipital and fusiform face areas), who can present a defect of familiar people recognition, with normal results on tests of face perception, the disorder is often multimodal, affecting voices (and to a lesser extent names) in addition to faces. The present review was prompted by the claim, recently advanced by some authors, that face recognition disorders observed in patients with right ATL lesions should be considered as an associative or amnestic form of prosopagnosia, because in them both face perception and retrieval of personal semantic knowledge from name are spared. In order to check this claim, we surveyed all the cases of patients who satisfied the criteria of associative prosopagnosia reported in the literature, to see if their defect was circumscribed to the visual modality or also affected other channels of people recognition. The review showed that in most patients the study had been limited to the visual modality, but that, when the other modalities of people recognition had been taken into account, the defect was often multimodal, affecting voice (and to a lesser extent name) in addition to face.     

On the relationship between autobiographical memory and perceptual learning

Although the majority of research on human memory has concentrated on a person's ability to recall or recognize items as having been presented in a particular situation, the effects of memory are also revealed in a person's performance of a perceptual task. Prior experience with material can make that material more easily identified or comprehended in perceptually difficult situations. Unlike with standard retention tests, effects of prior experience on a perceptual task do not logically require that a person be aware that he or she is remembering. Indeed, amnesic patients purportedly show effects of practice in their subsequent performance of a perceptual or motor task even though they profess that they do not remember having engaged in that prior experience. The experiments that are reported were designed to explore the relationship between the more aware autobiographical form of memory that is measured by a recognition memory test and the less aware form of memory that is expressed in perceptual learning. Comparisons of effects on perceptual learning and recognition memory reveal two classes of variables. Variables such as the level of processing of words during study influenced recognition memory, although they had no effect on subsequent perceptual recognition. A study presentation of a word had as large an effect on its later perceptual recognition when recognition memory performance was very poor as it did when recognition memory performance was near perfect. In contrast, variables such as the number and the spacing of repetitions produced parallel effects on perceptual recognition and recognition memory. Following Mandler and others, it is suggested that there are two bases for recognition memory. If an item is readily perceived so that it seems to "jump out" from the page, a person is likely to judge that he or she has previously seen the item in the experimental situation. Variables that influence ease of perceptual recognition, then, can also have an effect on recognition memory, so parallel effects are found. The second basis for recognition memory involves elaboration of a word's study context and depends on such factors as level of processing during study--factors that are not important for perceptual recognition of isolated words. Comparisons of perceptual recognition and recognition memory are shown to be useful for determining how a variable has its effect. Effects of study on perceptual recognition appear to be totally due to memory for physical or graphemic information. Results reported are also relevant to theories of perceptual learning. A single presentation of an item is shown to have large and long-lasting effects on its later perceptual recognition. At least partially, effects of study on perceptual recognition depend on the same variables as do effects on more standard memory tests.     

Impairment of voice and face recognition in patients with hemispheric damage

Voice and face recognition were tested in 21 left- and 9 right-hemisphere-damaged patients. Test materials were photographs and recordings of famous political and entertainment personalities. Pathological face recognition (prosopagnosia) and voice recognition (phonagnosia) were both significantly more prevalent in the right-hemisphere group. Only one instance of prosopagnosia and one of phonagnosia were observed in the left-hemisphere group, all of whom were aphasic. Of the right-hemisphere cases, there were four instances of each agnosia, with three patients showing a dual impairment. These findings are discussed in relation to differential modes of processing by the two cerebral hemispheres.     

Shape Integration for Visual Object Recognition and Its Implication in Category-Specific Visual Agnosia

A series of experiments was conducted on a patient (ELM) with bilateral inferior temporal lobe damage and category-specific visual agnosia in order to specify the nature of his functional impairment. In Experiment 1, ELM performed a task of picture/word matching that used line drawings of fruits and vegetables as stimuli. The pattern of confusions exhibited by the patient suggested a failure in processing the full range of shape features necessary for the unique specification of the target relative to other structurally related items. This hypothesis of a shape integration impairment was tested and verified by subsequent visual recognition experiments (Experiments 2-4), which used synthetic stimuli with shapes precisely defined on the dimensions of elongation, curvature, and tapering. Furthermore, it was determined (Experiment 5) that the integration deficit is specific to the retrieval of shape knowledge from memory and does not affect the encoding of the properties of visual stimuli. It is argued that these findings have critical implications for cognitive theories of visual object recognition and for an interpretation of the visual function of the inferior temporal cortex. Finally, it was shown that the patient's deficit for structural knowledge integration is modulated by the semantic properties of the objects (Experiment 6), thereby demonstrating the applicability of the present findings to an explanation of category-specific visual agnosia.     

The role of sensory-motor information in object recognition: evidence from category-specific visual agnosia

The role of sensory-motor representations in object recognition was investigated in experiments involving AD, a patient with mild visual agnosia who was impaired in the recognition of visually presented living as compared to non-living entities. AD named visually presented items for which sensory-motor information was available significantly more reliably than items for which such information was not available; this was true when all items were non-living. Naming of objects from their associated sound was normal. These data suggest that both information about object form computed in the ventral visual system as well as sensory-motor information specifying the manner of manipulation contribute to object recognition.     

Optic aphasia, optic apraxia, and loss of dreaming

A 47-year-old man with a left temporo-occipital infarct in the area of the posterior cerebral artery is presented. The neuropsychological examination did not reveal aphasia or gross mental deficits. The patient presented with alexia without agraphia, color agnosia, but few visual perceptual deficits. The main impairment was in confrontation naming; he was incapable of naming objects and pictures, not from lack of recognition (excluding visual agnosia) but from lack of access to the appropriate word (optic aphasia). The patient also exhibited a deficit in the evocation of gesture from the visual presentation of an object (optic apraxia) and a difficulty in "conjuring up" visual images of objects (impaired visual imagery) and loss of dreams. The fundamental deficit of this patient is tentatively explained in terms of visuoverbal and visuogestural disconnection and a deficit of mental imagery.     

Speech discrimination and lip reading in patients with word deafness or auditory agnosia

The purpose of this study was to assess the ability of four patients with word deafness or auditory agnosia to discriminate speech by reading lips. The patients were studied using nonsense monosyllables to test for speech discrimination, a lip reading test, the Token Test for auditory comprehension, and the Aphasia test. Our results show that patients with word deafness or auditory agnosia without aphasia can improve speech comprehension by reading lips in combination with listening, as compared with lip reading or listening alone. In conclusion, lip reading was shown to be useful for speech comprehension among these patients.     

Cortical auditory disorders: a case of non-verbal disturbances assessed with event-related brain potentials

In the auditory modality, there has been a considerable debate about some aspects of cortical disorders, especially about auditory forms of agnosia. Agnosia refers to an impaired comprehension of sensory information in the absence of deficits in primary sensory processes. In the non-verbal domain, sound agnosia and amusia have been reported but are frequently accompanied by language deficits whereas pure deficits are rare. Absolute pitch and musicians' musical abilities have been associated with left hemispheric functions. We report the case of a right handed sound engineer with the absolute pitch who developed sound agnosia and amusia in the absence of verbal deficits after a right perisylvian stroke. His disabilities were assessed with the Seashore Test of Musical Functions, the tests of Wertheim and Botez (Wertheim and Botez, Brain 84, 1961, 19-30) and by event-related potentials (ERP) recorded in a modified 'oddball paradigm'. Auditory ERP revealed a dissociation between the amplitudes of the P3a and P3b subcomponents with the P3b being reduced in amplitude while the P3a was undisturbed. This is interpreted as reflecting disturbances in target detection processes as indexed by the P3b. The findings that contradict some aspects of current knowledge about left/right hemispheric specialization in musical processing are discussed and related to the literature concerning cortical auditory disorders.