Marie-Pierre de Partz

Domain-specific reorganization of semantic processing after extensive damage to the left temporal lobe

We investigated with fMRI the cortical correlates of recovery of semantic processing in a patient (DL) with left temporal damage. Names of animals, plant, and artifacts (semantic conditions) and reversed words (baseline condition) were auditorily presented to the patient and nine control subjects in a category monitoring task. Data analyses showed large differences between the patterns of domain-specific semantic activation observed in DL and the control subjects, which could be attributed to a cortical reorganization compensating for the damaged part of the semantic processing system in DL. Such reorganization relied on three main mechanisms, first, upholding of a subset of the structurally intact domain-specific regions, second, functional changes (both decreases and increases) of the domain specificity in several structurally intact regions that are normally engaged in the domain-specific network and, third, recruitment of supplementary domain-specific areas. Thus, in DL, animal-specific processing engaged supplementary areas in the left lingual gyrus and right cuneus, which correspond to animal-specific regions usually engaged in more demanding semantic tasks whereas the supplementary areas recruited for artifact-specific processing within the left superior/middle occipital lobe and right angular gyrus probably are endowed with a related but not domain-specific, semantic function. In contrast, no supplementary area contributed to plant-specific processing in DL. These findings suggest that the pattern of cortical reorganization consecutive to damage to the semantic processing network depends on the particular domain-specific function sustained by the damaged areas and the capacity of the remaining areas to assume this function.

Multiple levels of letter representation in written spelling: evidence from a single case of dysgraphia with multiple deficits.

In this paper, we report a detailed analysis of the impaired performance of a dysgraphic individual, AD, who produced similar rates of letter-level errors in written spelling, oral spelling, and typing. We found that the distribution of various letter error types displayed a distinct pattern in written spelling on the one hand and in oral spelling and typing on the other. In particular, noncontextual letter substitution errors (i.e., errors in which the erroneous letter that replaces the target letter does not occur elsewhere within the word) were virtually absent in oral spelling and typing and mainly found in written spelling. In contrast, letter deletion errors and multiple-letter errors were typically found in oral spelling and very exceptional in written spelling. Only contextual letter substitution errors (i.e., errors in which the erroneous letter that replaces the target letter is identical to a letter occurring earlier or later in the word) were found in similar proportions in the three tasks. We argue that these contrasting patterns of letter error distribution result from damage to two distinct levels of letter representation and processing within the spelling system, namely, the amodal graphemic representation held in the graphemic buffer and the letter form representation computed by subsequent writing-specific processes. Then, we examined the relationship between error and target in the letter substitution errors produced in written and oral spelling and found evidence that distinct types of letter representation are processed at each of the hypothetized levels of damage: symbolic letter representation at the graphemic level and representation of the component graphic strokes at the letter form processing level.

Lorange, Cest-le-fruitier-de-lorangine - a Case of Morphological Impairment

Abstract In this paper, we report the case of a patient who produced many errors in productive tasks that are analysable as a function of morphological properties of the target and/or the response. We propose a quantitative and a qualitative analysis of the derivational errors produced in a picture-naming task, in order to determine whether these errors result from a morphological impairment. The analysis is conducted with reference to minimal predictions that can be inferred from current models of morphological decomposition. It is shown that the morphological errors made by the patient are explainable without appealing to a morphological organisation of the lexicon. More precisely, we account for these errors in the context of a general two-stage retrieval mechanism that applies both to affixed and unaffixed words.

The Re-education of Aphasics: Between theory and Practice

Any general presentation of the rationale of aphasia re-education runs the risk of overemphasizing the theoretical and methodological principles underlying the practices of speech therapists and neuropsychologists. At the same time it risks underemphasizing what, aside from theory, the practices effectively are. This difficulty results from two main sources: The tendency to idealize in any theoretical presentation, and the tendency to neglect the institutional, sociological, medical, and economic constraints that surround effective practices in any specific re-educative setting.

A case study about the interplay between language control and cognitive abilities in bilingual differential aphasia : behavioral and brain correlates

The current study examines the hypothesis that differential aphasia may be due to a problem with language control rather than with language-specific impairment and how this is related to non-linguistic cognitive control abilities. To this end, we report a case study of an L2 dominant French-English bilingual aphasia patient with larger impairments in French than in English. We assessed cross-language interactions using cognates in three lexical decision (LD) tasks, and non-linguistic cognitive control with a flanker task. We also examined functional connectivity between brain regions crucial for language control and language processing. We observed the preservation of cognate effects in a generalized lexical decision task requiring little language control, which indicates intact functionality (and cross-lingual interactivity) of lexical representations. On the other hand, we found diminished linguistic as well as non-linguistic control abilities, suggesting a domain general control impairment. Resting-state functional Magnetic Resonance Imaging (rs-fMRI) analysis revealed altered connectivity between the patients language control and processing network, consistent with the behavioral data. Altogether, these results are in line with the hypothesis that differential aphasia may originate from general cognitive control difficulties.

Residual knowledge of objects in semantic dementia: Semantic or "semantic-like"?

It has been consistently noted that patients with semantic dementia are still able to complete daily domestic activities in spite of the sometimes severe impairment of single object knowledge demonstrated in formal assessments. Several factors, that are notmutually exclusive,may give rise to this apparent paradox. First, the objects encountered by the patient in her daily activities might be more familiar to her than the ones probed in formal tests of object knowledge, and premorbid object familiarity has been shown to be an important factor in predicting the impact of progressive semantic impairment on the integrity of conceptual representations (Lambon Ralph, Graham, Ellis, & Hodges, 1998). Second, patients may have some residual superordinate or/and broad functional knowledge that may suffice to permit correct use for at least some items, particularly if encountered in their usual location and together with objects serving the same purpose (e.g., encountering a toothbrush with toothpaste on bathroom sink). Third, the patient’s current repeated experiencewith her own objects could helpmaintaining at least personally relevant knowledge for these objects (Snowden, Griffiths, & Neary, 1994). These accounts have in common the notion that the appropriate use of personal objects by semantic dementia patients would be based on some residual semantic knowledge. In contrast, Graham, Lambon Ralph, and Hodges (1999) suggested that the information these patients could retrieve about frequently encountered objects is only ‘‘semanticlike.’’ It is based on the patients having learnt an association between a perceptual representation of an object, a particular motor skill and a specific context. Thus, it differs from ‘‘true’’ semantic information by being highly specific, nonabstract, and nongeneralizable across similar items. In this study, we assessed residual object knowledge in a patient with semantic dementia with the aim of determining whether the knowledge she demonstrated with her own objects was generalizable or not to new and alternative exemplars of the same items.