Right hemisphere dominance directly predicts both baseline V1 cortical excitability and the degree of top-down modulation exerted over low-level brain structures. (17th December 2015)

• Record Type: Journal Article
• Authors: Arshad, Q.; Siddiqui, S.; Ramachandran, S.; Goga, U.; Bonsu, A.; Patel, M.; Roberts, R.E.; Nigmatullina, Y.; Malhotra, P.; Bronstein, A.M.
• Is Part Of: Neuroscience. Volume 311(2015)
• Page Start: 484
• Page End: 489
• Publication Date: 2015-12-17
• Subjects: tDCS trans-cranial direct current stimulation -- TMS trans-cranial magnetic stimulation -- VOR vestibular-ocular reflex; right hemisphere dominance -- visual cortical excitability -- vestibular–ocular reflex -- line bisection -- top-down modulation; Neurochemistry -- Periodicals; Neurophysiology -- Periodicals; Neurology -- Periodicals; Neurochimie -- Périodiques; Neurophysiologie -- Périodiques; Neurochemistry; Neurophysiology; Electronic journals; Periodicals; Electronic journals; 612.8
• DOI: 10.1016/j.neuroscience.2015.10.045
• Languages: English
• ISSNs: 0306-4522

Abstract

Highlights: Line bisection predicts V1 excitability. Line bisection predicts degree of VOR modulation. Line bisection correlates with tDCS-mediated vestibular-nystagmus suppression. Degree of nystagmus suppression is a bio-marker of right hemisphere dominance. Abstract: Right hemisphere dominance for visuo-spatial attention is characteristically observed in most right-handed individuals. This dominance has been attributed to both an anatomically larger right fronto-parietal network and the existence of asymmetric parietal interhemispheric connections. Previously it has been demonstrated that interhemispheric conflict, which induces left hemisphere inhibition, results in the modulation of both (i) the excitability of the early visual cortex (V1) and (ii) the brainstem-mediated vestibular–ocular reflex (VOR) via top-down control mechanisms. However to date, it remains unknown whether the degree of an individual's right hemisphere dominance for visuospatial function can influence, (i) the baseline excitability of the visual cortex and (ii) the extent to which the right hemisphere can exert top-down modulation. We directly tested this by correlating line bisection error (or pseudoneglect), taken as a measure of right hemisphere dominance, with both (i) visual cortical excitability measured using phosphene perception elicited via single-pulse occipital trans-cranial magnetic stimulation (TMS) and (ii) the degree of trans-cranial direct current stimulation (tDCS)-mediated VOR suppression, following left hemisphere inhibition. We found that those individuals with greater right hemisphere dominance had a less excitable early visual cortex at baseline and demonstrated a greater degree of vestibular nystagmus suppression following left hemisphere cathodal tDCS. To conclude, our results provide the first demonstration that individual differences in right hemisphere dominance can directly predict both the baseline excitability of low-level brain structures and the degree of top-down modulation exerted over them.