Francesca Borgo

When Living Things and Other ‘Sensory Quality’ Categories Behave in the Same Fashion: a Novel Category Specificity Effect.

In this study, the performance on semantic tests of five patients with a diagnosis of probable herpes simplex encephalitis was examined. Only one of the patients, MU, showed a marked category-specific deficit for living things, unlike the other patients. Results which closely mirrored those obtained with the category living things were found in each of the five patients for the other categories, edible substances, materials, and liquids, selected for a priori theoretical reasons. The processing of these additional categories was investigated with tasks involving naming abilities in different modalities, matching to sample, and questionnaires exploring the status of the patients’ knowledge about the semantic features of both living things and exemplars of novel ‘sensory quality’ categories. MU showed in all tasks a comparable impairment for both living things and the other three new categories, in spite of a performance closely equivalent to that of the other four patients with man-made artefacts. This finding supports an explanation of MU’s performance in terms of an impairment relating to categories highly dependent on the sensory quality of stimuli. In addition, his difficulty involved all aspects of the processing of the impaired categories.

Proper names in patients with early Alzheimer's disease.

The objective of this study was to seek evidence of the particular sensitivity of proper name retrieval and to check the usefulness of proper names as diagnostic material in the early stages of Alzheimer’s disease (AD). Whether a generalized naming deficit is an early symptom of AD it is not yet clear. Previous studies suggest that proper names might be the category of names that is indeed more sensitive to AD. Seventy AD patients (subdivided into “very mild”, “mild” and “moderate”) and 47 control subjects participated in the study. The performances in two short distinct tests requiring proper name retrieval (Naming People on Definition and Naming Faces), one test of common name retrieval, short (MMSE, 3MS) and long (MODA) batteries for the detection of dementia were compared. Proper name retrieval tests were shown to be more sensitive to early AD than any other tests and batteries that failed to distinguish “very mild” AD from controls. These findings suggest that proper name retrieval tasks might be profitably included in diagnostic tools for the early diagnosis of AD.

Category specificity and feature knowledge: evidence from new sensory-quality categories

Category-specific deficits and their relation to types of feature knowledge are addressed with respect to three semantic domains: artefacts, living things, and mass-kinds. The performance of a herpes encephalitic patient with a classic category-specific pattern of knowledge, MU, was compared to that of the other HSE patients and normal subjects. In a feature verification task involving over 4000 questions, MU showed a severe impairment with the mass-kind category, where his sensory features knowledge was at chance and much worse than his functional knowledge. In the feature production task, however, MU was grossly impaired with respect to sensory relative to functional features across all categories. Control experiments suggest that the deficits were of knowledge. Overall, these findings give some support to the sensory-functional theory, and are difficult to explain on the domain-specific knowledge theory. However, an account is still needed of the differences observed in MUs performance between the two paradigms.

Updating and inhibition processes in working memory: A comparison between Alzheimer’s type dementia and frontal lobe focal damage

A large debate has recently focused on the componential nature of the working-memory system (), as evidenced by functional-imaging studies and by using more sophisticated experimental paradigms. The present work aims at further disentangling the role and effects of central executive (CE) and of phonological loop (PL). It is suggested that maintaining active verbal information mostly relates to an intact PL, while the inhibition of interfering information preponderantly involves the CE. To distinguish these effects, two groups of brain damaged patients were administered with an updating task. Frontal lobe patients showed major difficulties in inhibiting interfering information, an ability requiring an involvement of the CE component. In contrast, Alzheimers dementia patients evidenced a relative impairment in maintaining relevant information, requiring the intervention of the PL.

Proper names in the early stages of Alzheimer's disease

Normal participants display a leftward bias when bisecting horizontal lines. It has been proposed that bisection errors can be affected by representational biases. We investigated the possibility that this effect could also be explained as the result of perceptual cueing. Participants bisected horizontal lines with identical arrows arranged around the lines, all pointing to the same end. The arrows significantly affected bisection placement, although participants bisected significantly away from the direction the arrows pointed to. The findings favor the hypothesis that cueing, rather than representation, can affect bisection errors.  2000 Academic Press

Progressive knowledge loss: A longitudinal case study

The evolution of the progressive loss of semantic knowledge of a patient, VZ, with lesions mainly affecting the infero-medial temporal lobes, was followed for two years. At the beginning of the study VZs performance was mainly characterized by a category-specific deficit for living things and a modality-specific deficit for perceptual attribute knowledge. As time went on, VZs disorder affected all categories by changing the relationship between category and attribute knowledge. Data show that dissociations may change in the course of progressive cognitive breakdown, depending on both degeneration stage and task demands. VZs performance is discussed in the light of the most influential theoretical accounts. Methodological suggestions regarding longitudinal studies of degenerative patients are also put forward.

Semantic access processing in a supra-modal deficit: a single case study.

The case is presented of a semantic dementia patient, who shows a deficit selective for (i) conceptual class (living things), (ii) attribute processing (visual features) and affecting (iii) input-output modalities at the same processing stage (matching stored representation to attributes). The first experimental part aims at exploring the specific stage/process at which semantic knowledge breaks down through multi-modality tasks, devised to tap different levels within the semantic elaboration flow. The second focuses on the differences between category vs. attribute knowledge across various modalities. The core nature of the patients deficit is investigated through a close comparison of her damage to a specific processing stage across modalities in the light of her class and attribute-specific impairment. The complex pattern of findings is discussed according to current theoretical accounts of semantic memory organization. Finally, the relevance of the adoption of a broad perspective when dealing with semantic memory impairments is highlighted.