Neural Substrate of Body Size: Illusory Feeling of Shrinking of the Waist

The perception of the size and shape of one's body (body image) is a fundamental aspect of how we experience ourselves. We studied the neural correlates underlying perceived changes in the relative size of body parts by using a perceptual illusion in which participants felt that their waist was shrinking. We scanned the brains of the participants using functional magnetic resonance imaging. We found that activity in the cortices lining the left postcentral sulcus and the anterior part of the intraparietal sulcus reflected the illusion of waist shrinking, and that this activity was correlated with the reported degree of shrinking. These results suggest that the perceived changes in the size and shape of body parts are mediated by hierarchically higher-order somatosensory areas in the parietal cortex. Based on this finding we suggest that relative size of body parts is computed by the integration of more elementary somatic signals from different body segments

The neural basis of central proprioceptive processing in older versus younger adults: An important sensory role for right putamen

Our sense of body position and movement independent of vision (i.e., proprioception) relies on muscle spindle feedback and is vital for performing motor acts. In this study, we first sought to elucidate age‐related differences in the central processing of proprioceptive information by stimulating foot muscle spindles and by measuring neural activation with functional magnetic resonance imaging. We found that healthy older adults activated a similar, distributed network of primary somatosensory and secondary‐associative cortical brain regions as young individuals during the vibration‐induced muscle spindle stimulation. A significant decrease in neural activity was also found in a cluster of right putamen voxels for the older age group when compared with the younger age group. Given these differences, we performed two additional analyses within each group that quantified the degree to which age‐dependent activity was related to (1) brain structure and (2) a behavioral measure of proprioceptive ability. Using diffusion tensor imaging, older (but not younger) adults with higher mean fractional anisotropy were found to have increased right putamen neural activity. Age‐dependent right putamen activity seen during tendon vibration was also correlated with a behavioral test of proprioceptive ability measuring ankle joint position sense in both young and old age groups. Partial correlation tests determined that the relationship between elderly joint position sense and neural activity in right putamen was mediated by brain structure, but not vice versa. These results suggest that structural differences within the right putamen are related to reduced activation in the elderly and potentially serve as biomarker of proprioceptive sensibility in older adults. Hum Brain Mapp, 2012. © 2011 Wiley Periodicals, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90522/1/21257_ftp.pd

Proprietes biomecaniques et modalites d'activation volontaire et reflexe des unites motrices des muscles extenseurs du carpe chez l'homme

SIGLEINIST T 74083 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Bases représentationnelles et neurales des processus de localisation des parties du corps

Selon le modèle dominant, la désignation des parties du corps engage un système de représentations "partagées", qui encode les caractéristiques visuospatiales communes à son propre corps et à celui d'autrui. Sur la base d'une double dissociation observée chez deux sujets cérébro-lésés, nous avons émis l'hypothèse que le LPS gauche était concerné par l'analyse du corps propre et le LPI gauche par celle du corps d'autrui. Deux expérimentations en IRMF étudient ces hypothèses. La première montre que la désignation de parties du corps propre engage le LPS gauche, quel que soit le côté de la partie du corps à localiser. La deuxième expérimentation montre que la désignation de parties du corps humain engage le LPI gauche. Cette activation ne s'observe qu'en réponse à des stimuli dynamiques. L'ensemble de ces éléments suggère que les LPS et LPI gauches participent à la construction d'une représentation différentielle entre soi et autruiAIX-MARSEILLE1-BU Sci.St Charles (130552104) / SudocSudocFranceF

INTENSITY TO FORCE TRANSLATION - A NEW EFFECT OF STIMULUS-RESPONSE COMPATIBILITY REVEALED BY ANALYSIS OF RESPONSE-TIME AND ELECTROMYOGRAPHIC ACTIVITY OF A PRIME MOVER

International audienceno abstrac

Benefits of computer-based memory and attention training in healthy older adults

International audienceMultifactorial cognitive training programs have a positive effect on cognition in healthy older adults. Among the age-sensitive cognitive domains, episodic memory is the most affected. In the present study, we evaluated the benefits on episodic memory of a computer-based memory and attention training. We targeted consciously controlled processes at encoding and minimizing processing at retrieval, by using more familiarity than recollection during recognition. Such an approach emphasizes processing at encoding and prevents subjects from reinforcing their own errors. Results showed that the training improved recognition performances and induced near transfer to recall. The largest benefits, however, were for tasks with high mental load. Improvement in free recall depended on the modality to recall; semantic recall was improved but not spatial recall. In addition, a far transfer was also observed with better memory self-perception and self-esteem of the participants. Finally, at 6-month follow up, maintenance of benefits was observed only for semantic free recall. The challenge now is to corroborate far transfer by objective measures of everyday life executive functioning