Arrangement de scripts dans la maladie de Huntington

The neural substrates of script knowledge deficits as revealed by a PET study in Huntington's disease

INTRODUCTION

Previous neuropsychological investigations have suggested that both the prefrontal cortex and the basal ganglia are involved in the management of script event knowledge required in planning behavior.

METHODS

This study was designated to map, the correlations between resting-state brain glucose utilization as measured by FDG-PET (positron emission tomography) and scores obtained by means of a series of script generation and script sorting tasks in 8 patients with early Huntington's disease.

RESULTS

These patients exhibited a selectively greater impairment for the organizational aspects of scripts compared to the semantic aspects of scripts. We showed significant negative correlations between the number of sequencing, boundary, perseverative and intrusion errors and the metabolism of several cortical regions, not only including frontal, but also posterior regions.

CONCLUSION

Our findings suggest that, within the fronto-striatal system, the cortical frontal regions are more crucial in script retrieval and script sequencing than the basal ganglia.

Intuition, insight, and the right hemisphere: Emergence of higher sociocognitive functions

Intuition is the ability to understand immediately without conscious reasoning and is sometimes explained as a 'gut feeling' about the rightness or wrongness of a person, place, situation, temporal episode or object. In contrast, insight is the capacity to gain accurate and a deep understanding of a problem and it is often associated with movement beyond existing paradigms. Examples include Darwin, Einstein and Freud's theories of natural selection, relativity, or the unconscious; respectively. Many cultures name these concepts and acknowledge their value, and insight is recognized as particularly characteristic of eminent achievements in the arts, sciences and politics. Considerable data suggests that these two concepts are more related than distinct, and that a more distributed intuitive network may feed into a predominately right hemispheric insight-based functional neuronal architecture. The preparation and incubation stages of insight may rely on the incorporation of domain-specific automatized expertise schema associated with intuition. In this manuscript the neural networks associated with intuition and insight are reviewed. Case studies of anomalous subjects with ability-achievement discrepancies are summarized. This theoretical review proposes the prospect that atypical localization of cognitive modules may enhance intuitive and insightful functions and thereby explain individual achievement beyond that expected by conventionally measured intelligence tests. A model and theory of intuition and insight's neuroanatomical basis is proposed which could be used as a starting point for future research and better understanding of the nature of these two distinctly human and highly complex poorly understood abilities.

Generalised script sequencing deficits following frontal lobe lesions

Neuropsychological investigations have consistently shown that frontal cortices are relevant in processing temporal and sequential features of actions. However, one of the main theoretical issues that has been discussed in the last 25 years is whether these brain areas store some abstract representations of actions or, conversely, act upon action representations stored within other posterior associative cortices. We administered to 19 patients with frontal lobe lesions and 19 normal controls, script sequencing and generating tasks concerning actions, natural events and "époques" (ordered events such as the days of the week). The main findings from frontal lobe patients were a generalised sequencing deficit concerning actions and natural phenomena (and not what we labelled "époques") with almost intact ability to verbally generate, from the long-term memory, scripts' sequences. These findings are discussed within two of the main theoretical frameworks on frontal lobes: the "processing" perspective of the Supervisory Attentional System, SAS (Norman and Shallice, 1986) and the "representational" one represented by the Structure Event Complex (SEC) theory (Grafman, 2002).

Arithmetic word-problem-solving in Huntington’s disease

The purpose of this study was to examine executive functioning in patients with Huntington's disease using an arithmetic word-problem-solving task including eight solvable problems of increasing complexity and four aberrant problems. Ten patients with Huntington's disease and 12 normal control subjects matched by age and education were tested. Patients with Huntington's disease performed the solvable problems significantly worse than the normal control subjects, but there was no difference in performance between the two groups in inhibiting aberrant problems. These results suggest that early Huntington's disease patients exhibit a precocious impairment in their ability to plan the resolution of complex arithmetic word problems without deficit in their ability to eliminate aberrant problems. This dissociation of performance fits with what we have found in such patients using script-sequencing tasks (Allain et al., 2004) and with neuropsychological data obtained by Watkins et al. (2000). These results are consistent with what is known about the neuropathological progression of Huntington's disease in which neuronal loss progresses in a dorso-to-ventral direction and with what was shown in patients with circumscribed frontal lobe damage. In these patients, impairments in planning solvable word problems were more frequent when lesions were in the lateral prefrontal regions.