Crossmodal spatial representations: behavioural and electrophysiological evidence on the effects of vision and posture on somatosensory processing in normal population and in right-brain-damaged patients

Sambo, C.F. (2009). Crossmodal spatial representations: behavioural and electrophysiological evidence on the effects of vision and posture on somatosensory processing in normal population and in right-brain-damaged patients. (Unpublished Doctoral thesis, City University London)

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Abstract

Interactions between different sensory modalities can affect processing of unisensory information, at both a perceptual and a neural level. The studies reported in this thesis address the effects of crossmodal interactions between vision and touch on tactile processing. In particular, these studies provide new behavioural and neural (ERP; event related potentials) evidence showing that: i) crossmodal interactions enhance tactile processing when (task-irrelevant) visual stimuli are presented, simultaneously with touch, at the same location as tactile stimuli compared to a different location in near or in far space; ii) crossmodal interactions between spatial congruent visual and tactile stimuli enhance tactile processing compared to incongruent visuo-tactile stimulation, also when (task-irrelevant) visual stimuli presented near the body are observed indirectly in a mirror (i.e., appearing in far space), although in this condition these crossmodal spatial modulations are delayed compared to direct viewing of the visual stimuli; iii) vision of the body (i.e., the hands) facilitates tactile-spatial attentional selection, as compared to no visual input (blindfolded condition), and also compared to visual-spatial information only (i.e., when the hands are hidden from view); iv) in rightbrain- damaged patients with tactile neglect and/or extinction, vision of the stimulated hand may further improve speed processing of contralesional tactile stimuli when the left, contralesional hand is placed in the right, 'intact' hemispace, under crossed posture.

In these studies, visual modulations of touch were present at early time intervals (i.e., early ERP components), suggesting that crossmodal spatial interactions can affect processing in cortical areas that have been considered 'modality-specific', namely, the secondary somatosensory cortex (SII). Taken together, the findings from the studies in this thesis provide new behavioural and ERP evidence in support of crossmodal spatial representations of the body and ofthe space surrounding the body (i.e., peripersonal space) in humans.

Item Type: Thesis (Doctoral)
Subjects: B Philosophy. Psychology. Religion > BF Psychology
R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
Divisions: City University London PhD theses
School of Social Sciences > Department of Psychology
URI: http://openaccess.city.ac.uk/id/eprint/19615

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