Towards a network theory of cognition
Neural Networks - Special issue on the global brain: imaging and modelling
Timing of Target Discrimination in Human Frontal Eye Fields
Journal of Cognitive Neuroscience
Journal of Cognitive Neuroscience
Electrophysiological Correlates of Conscious Vision: Evidence from Unilateral Extinction
Journal of Cognitive Neuroscience
Visualization and Measurement of the Cortical Surface
Journal of Cognitive Neuroscience
Attentional Preparation for a Lateralized Visual Distractor: Behavioral and fMRI Evidence
Journal of Cognitive Neuroscience
Mental rotation meets the motion aftereffect: The role of hv5/mt+ in visual mental imagery
Journal of Cognitive Neuroscience
When less is more: Evidence for a facilitative cathodal tdcs effect in attentional abilities
Journal of Cognitive Neuroscience
Neuromodulation of early multisensory interactions in the visual cortex
Journal of Cognitive Neuroscience
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We used concurrent TMS-fMRI to test directly for hemispheric differences in causal influences of the right or left fronto-parietal cortex on activity (BOLD signal) in the human occipital cortex. Clinical data and some behavioral TMS studies have been taken to suggest right-hemisphere specialization for top-down modulation of vision in humans, based on deficits such as spatial neglect or extinction in lesioned patients, or findings that TMS to right (vs. left) fronto-parietal structures can elicit stronger effects on visual performance. But prior to the recent advent of concurrent TMS and neuroimaging, it was not possible to directly examine the causal impact of one (stimulated) brain region upon others in humans. Here we stimulated the frontal or intraparietal cortex in the left or right hemisphere with TMS, inside an MR scanner, while measuring with fMRI any resulting BOLD signal changes in visual areas V1-V4 and V5/MT+. For both frontal and parietal stimulation, we found clear differences between effects of right-versus left-hemisphere TMS on activity in the visual cortex, with all differences significant in direct statistical comparisons. Frontal TMS over either hemisphere elicited similar BOLD decreases for central visual field representations in V1-V4, but only right frontal TMS led to BOLD increases for peripheral field representations in these regions. Hemispheric differences for effects of parietal TMS were even more marked: Right parietal TMS led to strong BOLD changes in V1-V4 and V5/MT+, but left parietal TMS did not. These data directly confirm that the human frontal and parietal cortex show right-hemisphere specialization for causal influences on the visual cortex.