A case series analysis of "category-specific" deficits of living things:the hit account

We report a case series analysis of a group of seven patients with apparent "category-specific" disorders affecting living things. On standard diagnostic tests, a range of deficits were apparent, with some cases appearing to have impaired visual access to stored knowledge, some with impaired semantic knowledge (across modalities), and some with an impairment primarily at a name retrieval stage. Patients with a semantic deficit were impaired for both visual and associative/functional knowledge about living things, whilst patients with a modality-specific access deficit showed worse performance when stored visual knowledge was probed. In addition, patients with impaired access to visual knowledge were affected when perceptual input was degraded by masking, and all patients showed an interaction between perceptual similarity and category when matching pictures to names or defining statements. We discuss the results in terms of the Hierarchical Interactive Theory (HIT) of object recognition and naming (Humphreys & Forde, 2001). We also discuss evidence on lesion sites in relation to research from functional brain imaging on category differences in object identification in normal observers.     

A CASE SERIES ANALYSIS OF “CATEGORY-SPECIFIC” DEFICITS OF LIVING THINGS:THE HIT ACCOUNT

We report a case series analysis of a group of seven patients with apparent “category-specific” disorders affecting living things. On standard diagnostic tests, a range of deficits were apparent, with some cases appearing to have impaired visual access to stored knowledge, some with impaired semantic knowledge (across modalities), and some with an impairment primarily at a name retrieval stage. Patients with a semantic deficit were impaired for both visual and associative/functional knowledge about living things, whilst patients with a modality-specific access deficit showed worse performance when stored visual knowledge was probed. In addition, patients with impaired access to visual knowledge were affected when perceptual input was degraded by masking, and all patients showed an interaction between perceptual similarity and category when matching pictures to names or defining statements. We discuss the results in terms of the Hierarchical Interactive Theory (HIT) of object recognition and naming (Humphreys & Forde, 2001). We also discuss evidence on lesion sites in relation to research from functional brain imaging on category differences in object identification in normal observers.     

Analysis of the semantic representations of living and nonliving concepts: A normative study

Current feature-based semantic memory models assume that the semantic representations of concepts differ systematically across living and nonliving categories and that such differences account for the emergence of category-specific semantic deficits in brain-damaged people. To assess some of the different models' main assumptions about structural differences at the semantic feature level in the two major semantic domains, we administrated a feature-listing task to normal young volunteers on 64 concepts drawn from living and nonliving semantic categories. We investigated whether feature correlation, a variable with a crucial role in the emergence of category-specific deficits, should be computed as a concept-dependent or as a concept-independent measure, and we chose the former. We also addressed the issue of a psychological counterpart of feature production frequency. Finally, we analysed the database obtained from the feature-listing tasks, looked at cross-domain differences for correlation, feature frequency, distinctiveness, and feature type, and discussed the implications of these findings for current semantic memory models.     

Analysis of the semantic representations of living and nonliving concepts: A normative study

Current feature-based semantic memory models assume that the semantic representations of concepts differ systematically across living and nonliving categories and that such differences account for the emergence of category-specific semantic deficits in brain-damaged people. To assess some of the different models' main assumptions about structural differences at the semantic feature level in the two major semantic domains, we administrated a feature-listing task to normal young volunteers on 64 concepts drawn from living and nonliving semantic categories. We investigated whether feature correlation, a variable with a crucial role in the emergence of category-specific deficits, should be computed as a concept-dependent or as a concept-independent measure, and we chose the former. We also addressed the issue of a psychological counterpart of feature production frequency. Finally, we analysed the database obtained from the feature-listing tasks, looked at cross-domain differences for correlation, feature frequency, distinctiveness, and feature type, and discussed the implications of these findings for current semantic memory models.     

Temporally graded semantic memory loss in amnesia and semantic dementia: Further evidence for opposite gradients

This paper reports an investigation into an apparent category-specific disorder in a young woman whose semantic memory was impaired following a road accident. In Experiment 1, an impairment for processing specific items in tasks of naming pictures and defining words was related to a selective impairment for living things and also to the familiarity level of the items. In Experiment 2, a difference in semantic category (living or nonliving) was pitted against a difference in familiarity (high or low) in a picture-naming task. A significant effect of familiarity was found, but no effect of semantic category. It was shown that, in a widely used set of published pictures, living things were generally of lower familiarity than nonliving things. Moreover, measures of familiarity were shown to be confounded with some reported evidence in support of a selective impairment to living things. It was concluded that, at present, there is no convincing evidence to support the theory that semantic memory is organised into dissociable categories of living and nonliving things.     

THE NOUN/VERB DISSOCIATION IN LANGUAGE PRODUCTION: VARIETIES OF CAUSES

Abstract

We report the performance of two patients who presented with complementary deficits in naming nouns relative to verbs: EA performed far worse with nouns than verbs, while MR performed worse with verbs than nouns. The two patients' grammatical category-specific deficits could not easily be explained in terms of damage to specific types of semantic knowledge prototypically associated with nouns (visual properties) and verbs (action features). One of the two patients, MR, also presented with a selective deficit in processing verbal as opposed to nominal morphology, in line with her impairment in naming verbs. The other patient, EA, showed no impairment in producing nominal and regular verbal morphology. The contrasting patterns of grammatical category-specific deficits in naming and morphological processing, along with other recently reported patterns, are interpreted as providing support for the claim that semantic and grammatical properties independently contribute to the organisation of lexical processes in the brain.     

Neuroanatomical basis in the temporal lobes for processing living things

Category-specific impairment in living things was examined in patients with temporal lobe damage to investigate whether specific neuroanatomical regions could be identified in processing the knowledge of specific categories. Tasks involving more effortful retrieval naming and less effortful attribute judgment were administered to 3 groups of patients with either bilateral, unilateral left, or unilateral right temporal lobe damage. Category-specific impairment in living things was observed for patients with unilateral or bilateral damage, results that are consistent with previous findings. Depending on its site and extent, the damage in the temporal lobe might lead to deficits in processing or loss of semantic knowledge for living things. Therefore, intact category-specific semantic processes may involve associations among different neural substrates in the temporal lobe.     

On the Links between Visual Knowledge and Naming: a Single Case Study of a Patient with a Category-specific Impairment for Living Things

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.     

SEMANTIC DEMENTIA WITH CATEGORY SPECIFICITY:ACOMPARATIVE CASE-SERIES STUDY

Patients with semantic dementia, the temporal variant of frontotemporal dementia, are relevant to both the neuroanatomical and neuropsychological debates in the category-specific literature. These patients present with a selective and progressive semantic deficit consequent on circumscribed atrophy of the inferolateral polar temporal lobes bilaterally, including the inferotemporal gyrus. In this study, a patient KH with a significant advantage for artefacts over living things was compared to five other semantic dementia patients with commensurate levels of semantic impairment. KH demonstrated a consistent category difference in favour of artefacts across all the expressive and receptive semantic tests. This difference was reliable even when familiarity, frequency, and other potential confounding factors were controlled. While KH demonstrated an association between poor knowledge of sensory attributes and a consistently greater impairment on living things than artefacts, the other patients did not. As observed in a number of previous studies, all five of the patients, contrasted to KH, exhibited an advantage for functional/associative over sensory attributes but without demonstrating the category-specific deficit that the sensory-functional theory (and the locus of their atrophy) might predict. The results of this and other studies are discussed in relation to four accounts of category specificity: the sensory-functional theory, domain-specific knowledge systems, intercorrelated features, and individual differences.     

Semantic dementia with category specificity:acomparative case-series study

Patients with semantic dementia, the temporal variant of frontotemporal dementia, are relevant to both the neuroanatomical and neuropsychological debates in the category-specific literature. These patients present with a selective and progressive semantic deficit consequent on circumscribed atrophy of the inferolateral polar temporal lobes bilaterally, including the inferotemporal gyrus. In this study, a patient KH with a significant advantage for artefacts over living things was compared to five other semantic dementia patients with commensurate levels of semantic impairment. KH demonstrated a consistent category difference in favour of artefacts across all the expressive and receptive semantic tests. This difference was reliable even when familiarity, frequency, and other potential confounding factors were controlled. While KH demonstrated an association between poor knowledge of sensory attributes and a consistently greater impairment on living things than artefacts, the other patients did not. As observed in a number of previous studies, all five of the patients, contrasted to KH, exhibited an advantage for functional/associative over sensory attributes but without demonstrating the category-specific deficit that the sensory-functional theory (and the locus of their atrophy) might predict. The results of this and other studies are discussed in relation to four accounts of category specificity: the sensory-functional theory, domain-specific knowledge systems, intercorrelated features, and individual differences.     

GENETIC AND ENVIRONMENTAL INFLUENCES ON THE ORGANISATION OF SEMANTIC MEMORY IN THE BRAIN:IS “LIVING THINGS” AN INNATE CATEGORY?

The organisation of semantic memory into separately lesionable or imageable components must be determined by some combination of genetic and environmental factors. Little is known about the relative contributions of these two factors in establishing the functional architecture of semantic memory. By assessing the semantic memory impairment of an individual who sustained brain damage as a newborn, it is possible to place an upper bound on the contribution of post-natal experience. The present case study demonstrates a profound and enduring impairment in knowledge of “living things” following posterior cerebral artery infarctions at approximately 1 day of age. The design of the two experiments reported here allows us to characterise the subject's semantic memory impairment in terms of its scope and selectivity. The impairment affects both the naming of pictures of living things and the retrieval of verbal information about living things. It cannot be accounted for by differences in the difficulty of retrieving knowledge of living and nonliving things, as the living and nonliving items were equated for difficulty in each experiment. When visual and nonvisual information were queried separately for living and nonliving things, the impairment was manifest for both kinds of information about living things, but for neither kind of information about nonliving things. Because this impairment resulted from brain damage sustained too early for experience to have contributed to the organisation of semantic memory, this case study supports a genetic basis for the living-nonliving distinction in semantic memory.     

Genetic and environmental influences on the organisation of semantic memory in the brain:is "living things" an innate category?

The organisation of semantic memory into separately lesionable or imageable components must be determined by some combination of genetic and environmental factors. Little is known about the relative contributions of these two factors in establishing the functional architecture of semantic memory. By assessing the semantic memory impairment of an individual who sustained brain damage as a newborn, it is possible to place an upper bound on the contribution of post-natal experience. The present case study demonstrates a profound and enduring impairment in knowledge of "living things" following posterior cerebral artery infarctions at approximately 1 day of age. The design of the two experiments reported here allows us to characterise the subject's semantic memory impairment in terms of its scope and selectivity. The impairment affects both the naming of pictures of living things and the retrieval of verbal information about living things. It cannot be accounted for by differences in the difficulty of retrieving knowledge of living and nonliving things, as the living and nonliving items were equated for difficulty in each experiment. When visual and nonvisual information were queried separately for living and nonliving things, the impairment was manifest for both kinds of information about living things, but for neither kind of information about nonliving things. Because this impairment resulted from brain damage sustained too early for experience to have contributed to the organisation of semantic memory, this case study supports a genetic basis for the living-nonliving distinction in semantic memory.     

A common processing system for the concepts of artifacts and actions? Evidence from a case of a disproportionate conceptual impairment for living things

We report the results of a single-case study carried out with a brain-damaged patient, G.C., whose conceptual knowledge of living things (animals and plants) was significantly more impaired than his knowledge of artifacts and his knowledge of actions, which were similarly impaired. We examined whether this pattern of conceptual impairment could be accounted for by the "sensory/functional" or the "manipulability" account for category-specific conceptual impairments advocated within the feature-based organization theory. To this end, we assessed, first, the patient's knowledge of sensory compared to functional and motor features and, second, his knowledge of nonmanipulable compared to manipulable items. The findings showed that the patient's disproportionate impairment for living things compared to both artifacts and actions was not associated with a disproportionate impairment of sensory compared to functional or motor knowledge or with a relative sparing of manipulable compared to nonmanipulable items. We then discuss how alternative theories of conceptual knowledge organization could account for G.C.'s pattern of category-specific deficit.     

A case of impaired knowledge for fruit and vegetables

In this paper, we report the case of RS, a brain-damaged patient presenting with a disproportionate conceptual impairment for fruit and vegetables in comparison to animals and artefacts. We argue that such a finer-grained category-specific deficit than the living/nonliving dichotomy provides a source of critical evidence for assessing current alternative theories of conceptual organisation in the brain. The case study was designed to evaluate distinct expectations derived from the categorical and the knowledge-specific accounts for category-specific semantic deficits. In particular, the integrity of object-colour knowledge has been assessed in order to determine whether the patient's deficit for fruit and vegetables was associated with a deficit for that kind of knowledge, which has been claimed to be highly diagnostic for fruit and vegetables. The results showed that the patient's pattern of performance is consistent with theories assuming a topographical category-like organisation of conceptual knowledge in the brain.     

A CASE OF IMPAIRED KNOWLEDGE FOR FRUIT AND VEGETABLES

In this paper, we report the case of RS, a brain-damaged patient presenting with a disproportionate conceptual impairment for fruit and vegetables in comparison to animals and artefacts. We argue that such a finer-grained category-specific deficit than the living/nonliving dichotomy provides a source of critical evidence for assessing current alternative theories of conceptual organisation in the brain. The case study was designed to evaluate distinct expectations derived from the categorical and the knowledge-specific accounts for category-specific semantic deficits. In particular, the integrity of object-colour knowledge has been assessed in order to determine whether the patient's deficit for fruit and vegetables was associated with a deficit for that kind of knowledge, which has been claimed to be highly diagnostic for fruit and vegetables. The results showed that the patient's pattern of performance is consistent with theories assuming a topographical category-like organisation of conceptual knowledge in the brain.