Direct current stimulation (tDCS) reveals parietal asymmetry in local/global and salience-based selection

Bardi, Lara, Kanai, Ryota, Mapelli, Daniela and Walsh, Vincent (2012) Direct current stimulation (tDCS) reveals parietal asymmetry in local/global and salience-based selection. Cortex, 49 (3). pp. 850-860. ISSN 0010-9452

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Abstract

Data from neuropsychology and neuroimaging studies indicate hemispheric asymmetries in processing object's global form versus local parts. However the attentional mechanisms subtending visual selection of different levels of information are poorly understood. The classical left hemisphere/local-right hemisphere/global dichotomy has been recently challenged by studies linking the asymmetry of activation in the posterior parietal cortex (PPC) with the relative salience of the stimulus rather than with the local/global level. The present study aimed to assess hemispheric asymmetry in local-global and salience-based selection in hierarchical stimuli by using transcranial direct current stimulation (tDCS). To this end, tDCS has been applied to the PPC of both the hemispheres. Our data revealed that tDCS did affect the selection of the target on the basis of its relative salience in a manner that depended on the tDCS polarity applied to the two hemispheres. This result is in line with previous findings that the left PPC is critically involved in attention for low-salience stimuli in the presence of high-salience distractor information, while right PPC is involved in attending to more salient stimuli. Hemispheric asymmetries were also found in local/global selection. Overall the results suggest that neural activation in the PPC is related to both the salience and the level of stimulus representations mediating responses to hierarchical stimuli. The comparison of the results from Experiments 1 and 2 in local/global-based selection suggests that the effect of stimulation could be completely opposite depending on subtle differences in demands of attentional control (sustained attention vs task switching).

Item Type: Article
Schools and Departments: School of Psychology > Psychology
Subjects: R Medicine > RC Internal medicine > RC0321 Neurosciences. Biological psychiatry. Neuropsychiatry
Depositing User: Ryota Kanai
Date Deposited: 11 Mar 2013 12:36
Last Modified: 21 May 2013 11:12
URI: http://sro.sussex.ac.uk/id/eprint/43887
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