August 2009
Volume 9, Issue 8
Free
Vision Sciences Society Annual Meeting Abstract  |   August 2009
Up and down-regulation of visual cortex by posterior parietal cortex modulates selection-by-saliency: Evidence from combined TMS-fMRI
Author Affiliations
  • Carmel Mevorach
    Behavioural Brain Sciences Centre, School of Psychology, The university of Birmingham
  • Harriet Allen
    Behavioural Brain Sciences Centre, School of Psychology, The university of Birmingham
  • John Hodsoll
    Behavioural Brain Sciences Centre, School of Psychology, The university of Birmingham
  • Lilach Shalev
    Division of Learning Disabilities, School of Education, Hebrew University of Jerusalem
  • Glyn Humphreys
    Behavioural Brain Sciences Centre, School of Psychology, The university of Birmingham
Journal of Vision August 2009, Vol.9, 82. doi:10.1167/9.8.82
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      Carmel Mevorach, Harriet Allen, John Hodsoll, Lilach Shalev, Glyn Humphreys; Up and down-regulation of visual cortex by posterior parietal cortex modulates selection-by-saliency: Evidence from combined TMS-fMRI. Journal of Vision 2009;9(8):82. doi: 10.1167/9.8.82.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Objective: Using TMS over the parietal cortex, we have recently shown (Mevorach et al., 2006) that selection and suppression of saliency are lateralised in the brain with the right pIPS critical for the selection of salient targets and left pIPS critical for the suppression of salient but irrelevant information. It is not known, however, whether TMS applied over the parietal cortex also results in changes of brain activity in other functionally related areas which are combined to bring about the change in behaviour. In the present study we combined offline TMS with functional brain imaging to assess the differences in brain activity induced by TMS that underlie the changes in behaviour.

Methods: In two sessions participants performed a Global/Local task where the relative saliency of target and distractor levels was manipulated. In each session participants performed the task twice while functional brain imaging data were collected. In between those scans 20 minutes of offline TMS was applied over either the left or right pIPS.

Results: The behavioural data indicated dissociable effects for left and right IPS stimulation in accordance with the left and right pIPS being critical for the suppression and the selection of saliency, respectively. In addition, the imaging data revealed differential effects of left and right pIPS stimulation on visual cortex, with increased activity following TMS over the left pIPS compared with TMS over right pIPS.

Conclusion: The data support the notion that TMS over a particular site can lead to activation change in other remote (but functionally related) brain regions. In particular it suggests that selection of salient information benefits from an increase in brain activity in visual cortex (which is modulated by the right pIPS), whereas suppression of saliency benefits from a reduction in brain activity in visual cortex (which is modulated by the left pIPS).

Mevorach, C. Allen, H. Hodsoll, J. Shalev, L. Humphreys, G. (2009). Up and down-regulation of visual cortex by posterior parietal cortex modulates selection-by-saliency: Evidence from combined TMS-fMRI [Abstract]. Journal of Vision, 9(8):82, 82a, http://journalofvision.org/9/8/82/, doi:10.1167/9.8.82. [CrossRef]
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