[Show abstract][Hide abstract] ABSTRACT: Patients with category specific recognition impairments for living and non living things have played a crucial role in developing current theories of semantic memory and object recognition. This paper reviews a number of the classic cases and discusses the theories that have been developed to account for these impairments. The first reports of patients with category specific recognition impairments for living and non living things were documented by Nielsen, who argued that they arose because living and non living things were stored in functionally and anatomically separate systems. Although this hypothesishas been reiterated in some recent papers, the most widespread view hasbeen that they emerge because living andnon living thingshave contrasting processing demands. The latter accounts include those which stress the relative importance of: the 'weighting of sensory and functional features associated with living and non living things; the role of structural similarity between objects; the role of direct experience with objects; direct links between perceptual and functional features; and category structure. These theories are reviewed before outlining our own view on why category specific recognition impairments emerge following brain damage.
Aphasiology 08/2010; March 1(1999):169-193. · 1.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We examined eye movements in a patient, FK, who has action disorganisation syndrome (ADS), as he performed the everyday task of making a cup of tea. We compared his eye movements with those of a person with Alzheimer's disease and with healthy volunteers. Despite showing very disorganised behaviour many aspects of FK's eye movements were relatively normal. However, unlike normal participants FK made no advance glances to objects that were about to be used, and he made increased numbers of fixations to irrelevant objects during the task. There were also differences in the durations of his eye movements during correct actions and during his perseverative and task-addition responses. We discuss the implications for understanding ADS and the cognitive processes required for correctly performing everyday tasks.
[Show abstract][Hide abstract] ABSTRACT: We describe a patient (J.M.) who showed "refractory" behavior in picture-word matching tasks--that is, his performance became poorer when items were repeated. This contrasts with the facilitatory effects of repetition usually observed in normal participants. We show for the first time that there can be facilitatory effects of repetition on some tasks, even though refractory behavior is shown on the same items in other tasks. In particular, in Experiments 1 and 2, we demonstrate that J.M. showed contrasting effects of repetition across different components of the language system: There were facilitatory effects of repetition priming on lexical decision but refractory behavior on picture-word matching. In Experiments 3 and 4, we demonstrate that J.M. showed contrasting effects of repetition within the same system (semantic memory). His performance became refractory when items were repeated in picture-word matching (Experiment 3), but it was facilitated when items were repeated in superordinate categorization (Experiment 4). These contrasting patterns of facilitation and interference from repetition priming have implications for understanding the nature of refractory behavior and for constraining theoretical accounts of semantic memory.
[Show abstract][Hide abstract] ABSTRACT: We report a study on a patient (DW) with integrative visual agnosia and a category-specific recognition impairment for living things. We assessed DW's local and global processing and tested if his integrative agnosia could have led directly to his category-specific impairment. The main findings were: (i) DW was faster at identifying local compared to global letters. (ii) DW showed no local-to-global (or global-to-local) interference effects in selective attention tasks. (iii) DW showed a congruency effect in a divided attention task, suggesting that, when his attention was cued to both levels, he could process information simultaneously and integrate local and global information. (iv) Controls were poorer at naming nonliving compared to living things when presented with silhouettes. These data suggest that local and global information are differentially weighted in the visual recognition of living and nonliving things, and that an impairment in processing the overall shape of an object can lead to a category-specific deficit for living things. Crucially, this implies that category-specific impairments do not necessarily reflect damage to the semantic system, and models of semantic memory based on this assumption need to be revised.
[Show abstract][Hide abstract] ABSTRACT: We report data on patient FK, who presented with a marked deficit in accessing semantic knowledge about objects when tested across a range of input and output modalities. FK also showed a high degree of item-specific consistency in object identification, over and above effects due to object familiarity. We show that, despite being better at naming some objects than others, FK was equally poor at discriminating the superordinate categories of the stimuli. Also, he tended to be better at matching nameable items to a base-level label than to a superordinate-level label. We discuss the implications of the data for models of semantic memory.
[Show abstract][Hide abstract] ABSTRACT: Recognition of orally spelt words is an unusual task, not commonly encountered in everyday life, but it can be surprising well preserved in patients with brain damage. There is, however, considerable debate over the cognitive abilities that are required to successfully perform this task. The main controversy has centred on whether oral spelling recognition is parasitic on the processes normally involved in spelling aloud or in reading. We describe a patient (FL) who showed a similar pattern of performance on reading and oral spelling recognition and was better at both tasks relative to spelling. We describe a second patient (FK) who was good at reading and reasonable at spelling but poor at reverse spelling. The patient data are not consistent with either of the following hypotheses: that oral spelling recognition is dependent either on a reading system that is functionally separate from a spelling system, or on a spelling system that is functionally separate from reading. We propose that the findings can, however, be accommodated by a model in which spelling and reading are not functionally independent systems, but share important cognitive components such as a graphemic buffer.
[Show abstract][Hide abstract] ABSTRACT: We report data on stored knowledge of everyday tasks in a patient, FK, with 'action disorganisation syndrome'. In section 1, we analysed his explicit knowledge of the component actions, and their temporal order. FK showed generally impaired knowledge of everyday tasks relative to controls, and, when knowledge of the temporal order of the actions was probed, he showed particular impairments for the actions making up the final steps in tasks. In section 2 we assessed FK's implicit knowledge of the tasks, by evaluating how knowledge of the tasks influenced his ability to act out sets of instructions. We demonstrate that FK had some implicit knowledge of the tasks, but also, when actions had to be performed in the order as instructed, there was better knowledge of order for actions performed early rather than late in the task. We suggest that disordered task schema contributed to FK's deficits, with impairments on 'end' actions being vulnerable when task order was important for performance.
[Show abstract][Hide abstract] ABSTRACT: Using group functional Magnetic Resonance Imaging (fMRI) and group Magnetoencephalography (MEG) we studied two cognitive paradigms: A language task involving covert letter fluency and a visual task involving biological motion direction discrimination. The MEG data were analyzed using an adaptive beam-former technique known as Synthetic Aperture Magnetometry (SAM), which provides continuous 3-D images of cortical power changes. These images were spatially normalized and averaged across subjects to provide a group SAM image in the same template space as the group fMRI data. The results show that frequency-specific, task-related changes in cortical synchronization, detected using MEG, match those areas of the brain showing an evoked cortical hemodynamic response with fMRI. The majority of these changes were event-related desynchronizations (ERDs) in the 5-10 Hz and 15-25 Hz frequency ranges. Our study demonstrates how SAM, spatial normalization, and intersubject averaging enable group MEG studies to be performed. SAM analysis also allows the MEG experiment to have exactly the same task design as the corresponding fMRI experiment. This new analysis framework represents an important advance in the use of MEG as a cognitive neuroimaging technique and also allows mutual cross-validation with fMRI.
[Show abstract][Hide abstract] ABSTRACT: We report a 12-year longitudinal case study on a 60-year-old male patient (DW) with category-specific agnosia. The extent to which DW's impairment has changed over time was evaluated using identical tests at time 1 (1988) and time 2 (2000). In particular, we assessed his ability to identify pictures and real objects, to draw from memory, and to access stored semantic information about living and non-living things. The principal findings were: (i). DW was significantly better at identifying real objects in comparison with line drawings. (ii). DW presented with a category-specific impairment for living things that remained consistent over the 12-year period. (iii). He significantly improved in his ability to identify real non-living objects over the 12-year period but real living objects remained at floor. (iv). His ability to access stored visual knowledge declined over time. On the basis of these data, we suggest that visual perception is required to maintain intact visual memories over a period of time. We also suggest that integrative visual agnosia co-occurs with a category-specific impairment for living things because the recognition of these items requires more global processing than for non-living things. In addition, we suggest that degradation to stored visual knowledge can cause category-specific naming impairments for living compared with non-living things because naming living things requires access to more detailed visual knowledge.
[Show abstract][Hide abstract] ABSTRACT: In this paper we examine the role of stored semantic knowledge in recall from short-term memory. We assessed the performance of a patient (FK), who showed a consistent lack of semantic knowledge for some words ('unknown') but not others ('known') on a range of serial recall tasks using both spoken and written words. Overall, FK was significantly better at recalling lists of known compared with unknown words. His recall of unknown words was characterized by numerous phonological errors, such as repeating 'bear skunk' as 'bunk scare'. FK showed a relatively normal primacy effect in immediate recall, but a striking lack of a recency effect. This pattern of performance is useful for constraining theoretical accounts of language production and verbal short-term memory and for understanding the role that long-term semantic knowledge may play in maintaining information in short-term memory.
[Show abstract][Hide abstract] ABSTRACT: We present a single case study of a patient, FK, who was severely impaired on routine, everyday tasks, such as preparing a cup of tea. We used the action coding system developed by Schwartz et al. to provide quantitative and qualitative measures of his performance in a number of experimental manipulations. In section A, we established FK's baseline performance on a range of tasks with (a) task-congruent objects only and (b) task-congruent objects and semantic distracters. In section B, we aimed to facilitate FK's performance by (a) giving him a pictorial representation of the goal, (b) giving him a set of written commands to follow, (c) giving him one command at a time, (d) demonstrating how the task should be performed and (e) dividing the task into smaller subgoals. We compared FK's performance with another patient, HG, to establish if there are qualitative differences between patients with 'action disorganization syndrome'. In section C, we aimed to hinder FK's performance by interrupting his execution of routine tasks. By comparing the factors that facilitated and impaired FK's performance in sections B and C, we hoped to isolate the key cognitive processes required to generate and control routine behaviour. In section D, we investigated how task demands impact on our ability to complete different everyday activities. The results of these experiments have important clinical implications for rehabilitation programmes for patients with action disorganization syndrome and can also help to distinguish between contemporary theoretical accounts of routine behaviour. In particular, we propose that patients who can be classified under the umbrella term of 'action disorganization syndrome' do not all have a reduction to 'non-specific cognitive resources' but can have qualitatively different impairments to a specialized action production system.
[Show abstract][Hide abstract] ABSTRACT: Category-specific impairments of object recognition and naming are among the most intriguing disorders in neuropsychology, affecting the retrieval of knowledge about either living or nonliving things. They can give us insight into the nature of our representations of objects: Have we evolved different neural systems for recognizing different categories of object? What kinds of knowledge are important for recognizing particular objects? How does visual similarity within a category influence object recognition and representation? What is the nature of our semantic knowledge about different objects? We review the evidence on category-specific impairments, arguing that deficits even for one class of object (e.g., living things) cannot be accounted for in terms of a single information processing disorder across all patients; problems arise at contrasting loci in different patients. The same apparent pattern of impairment can be produced by damage to different loci. According to a new processing framework for object recognition and naming, the hierarchical interactive theory (HIT), we have a hierarchy of highly interactive stored representations. HIT explains the variety of patients in terms of (1) lesions at different levels of processing and (2) different forms of stored knowledge used both for particular tasks and for particular categories of object.
[Show abstract][Hide abstract] ABSTRACT: We summarise and respond to the main points made by the commentators on our target article, which concern: (1) whether structural similarity can play a causal role in normal object identification and in neuropsychological deficits for living things, (2) the nature of our structural knowledge of the world, (3) the relations between sensory and functional knowledge of objects, and the nature of our functional knowledge about living things, (4) whether we need to posit a “core” semantic system, (5) arguments that can be marshalled from evidence on functional imaging, (6) the causal mechanisms by which category differences can emerge in object representations, and (7) the nature of our knowledge about categories other than living and nonliving things. We also highlight points raised in our article that seem to be accepted.
[Show abstract][Hide abstract] ABSTRACT: We present a single case study of a patient, HG, who was severely impaired on routine everyday tasks, such as cleaning his teeth and preparing a cup of tea. We used the Action Coding System developed by Schwartz et al. (1991) to provide quantitative and qualitative measures of his performance in a number of experimental manipulations: (a) with task-congruent objects only, (b) with task-congruent objects and semantic distractors, (c) with a set of written commands to follow, (d) when he was given one command at a time, (e) when he was shown how the task should be performed before starting himself, and (f) when the task was divided into smaller subgoals. In general, the majority of HG's errors were step omissions, perseverations, sequence errors, and semantic errors. These semantic errors are particularly interesting since HG was able to name, gesture to, and define all the objects when they were presented in isolation or in task-congruent arrays. We suggest that semantic errors may arise for a number of reasons: (1) impaired access from semantic memory to a network representing action schema, (2) degradation of stored schema, and (3) behavior that is abnormally driven by the goal, by preceding actions, or by salient objects rather than by an appropriate association between these elements in working memory.
Brain and Cognition 12/2000; 44(2):214-52. · 2.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A single case study is presented of a global aphasic patient, JM, who shows similar impairments to other patients in the literature classified as "access dysphasics": On auditory word-written word matching tasks, JM's performance is inconsistent, it declines over repetitions, and it is sensitive to presentation rate and to the semantic relatedness of distractors (Forde & Humphreys, 1995). The deleterious effects of stimulus repetition can be attributed to JM's access to semantic information becoming refractory following activation of a target word or object. This paper examines the locus of the refractoriness by comparing JM's performance on tasks requiring access to presemantic perceptual representations or to semantic information. When both words and pictures were used as stimuli, JM was unimpaired on tasks thought to tap presemantic representations, such as visual lexical decision and unusual views matching, but performance became refractory on tasks that required access to fine-grained semantic information about specific items (e.g. associative matching). In addition, we found that the refractoriness spread across modalities when the targets changed from pictures to words. We discuss the implication of these findings for understanding the underlying nature of semantic representations of words and objects, and for the access-storage distinction in neuropsychology.
[Show abstract][Hide abstract] ABSTRACT: Why living things, such as animals, fruit, and vegetables, can pose recognition or naming problems compared to nonliving things for certain patients has intrigued neuropsychologists for a number of years. We report a further case study of a patient (SRB) with a category-specific impairment in naming living things, which occurred in naming from vision, taste, touch, and when auditory definitions stressed the visual properties of objects. In addition, SRB was particularly poor at retrieving the perceptual attributes of living things when asked to draw from memory, make perceptual comparisons, or name associated colours. In contrast to this, SRB's performance on standard tests of semantic memory was relatively unimpaired, although when asked to give definitions about living things (and faces) he showed interference effects from visually and semantically similar exemplars from the same category. Also, the problem in naming was not necessarily confined to living things, but also occurred with faces and when nonliving things had to be named at a subordinate level. We suggest that SRB was impaired on tasks requiring fine differentiation between the representations of objects with similar perceptual structures, allowing both base-level naming of nonliving things, and semantic categorisation tasks to be performed relatively well. In a follow-up study, after naming accuracy had recovered, we demonstrated a remaining problem in response latencies to living things. Thus, though performance may recover to some degree in such patients, residual difficulties can still occur.
[Show abstract][Hide abstract] ABSTRACT: We investigated four paranoid schizophrenic patients diagnosed with Frégoli delusion, and four matched psychotic controls. Neuropsychological testing included visual and verbal recognition memory, in addition to a comparison of left and right hemispheric processing of two different classes of stimuli, animate and inanimate objects. Performance on the recognition memory test failed to discriminate between the two psychotic groups on the basis of facial recognition, however, the patients with Frégoli delusion failed to show the right hemisphere processing advantage for the animate class of stimuli found for the set of norms and also present in the psychotic control group. These results are discussed in the context of both current theories of the delusional misidentification syndromes in general, and models of facial recognition in particular.
[Show abstract][Hide abstract] ABSTRACT: A single case study is reported of a global aphasic patient, JM, with impaired access to semantic information which was particularly severe for the class of proper names. JM's ability to perform matching tasks with printed words and pictures to auditory words deteriorated when items were repeated, especially when the response-stimulus interval was short. Performance was also inconsistent across items. The effect of repeated testing on items generalised to other, previously untested members of the same category. Despite this, JM was able to access general semantic information about stimuli from the affected categories (e.g. to categorise boys' and girls' names), and showed good ability to access an input lexicon concerning these stimuli. There was also a close relationship between the categories affected when he was tested with pictures and printed words. We propose that JM's deficit can be attributed to his semantic system entering an abnormal refractory state once semantic access for a particular item has been achieved, and with this stage being isolated from the procedures providing access to stored lexical knowledge. Furthermore, the representations affected seem common to pictures and printed words. We discuss the implications of the results for understanding the nature of semantic representations in general and for proper names in particular, and for the distinction between access and storage deficits in neuropsychology.