Probing the missing link between sources and targets of attentional control: a concurrent TMS/fMRI study of visuospatial selection

Abstract

Converging evidence from neuroimaging, neuropsychological, and TMS studies suggests that selective spatial attention is controlled by a cortical network including the posterior parietal cortex (angular gyrus, intra-parietal sulcus) and prefrontal cortex (frontal eye field, inferior frontal gyrus). At the same time, neuroimaging studies have established that activity in human striate and extrastriate visual cortex (V1–V5) is modulated by the spatial distribution of visual, auditory and somatosensory attention. Crucially, however, there is little direct evidence connecting sources of attentional control in frontoparietal cortex with sensory gating in visual cortex. Here we probed this missing link by establishing simultaneously the effects of Angular Gyrus (AG) stimulation on spatial orienting behaviour (TMS) and the corresponding BOLD response to behaviourally relevant stimuli in visual cortex (fMRI). Human participants undertook a covert-orienting task in a concurrent TMS/fMRI environment. On each trial, a coloured letter target flanked by distractors was preceded by a peripheral and behaviourally irrelevant spatial cue. To disrupt spatial reorienting of attention between the cue and target (required only on invalid trials), a rapid train of TMS was delivered to the right AG synchronously with target onset. At the same time, the target-related BOLD response was measured in areas V1–V5. Of particular interest was the relationship between the TMS-induced deficit of spatial attention and corresponding changes in the retinotopic representation of behaviourally relevant targets. Results provide new insights into the causal link between attentional control processes in the parietal cortex and sensory selection at various levels of the human visual system.

Footnotes

 This research was supported by the Biotechnology and Biological Sciences Research Council (BBSRC, UK), through a David Phillips fellowship held by C.D. Chambers.