Modulation of intracranial field potential responses in the human large-scale attention network during a spatial attention task

Abstract

Spatial attention is mediated through a large-scale network that includes occipital, temporal, parietal and frontal cortical regions. While the network architecture has been well characterized using neuroimaging methods, less is known about the temporal dynamics in local regions and across the network. Here, we explored the modulatory effects of spatial attention throughout this cortical network by analyzing intracranial field potentials recorded from 538 ECoG electrodes implanted in 6 epilepsy patients. We examined the effects of attention using a variant of the Eriksen flanker task, where subjects were cued by an exogenous stimulus to the spatial location of an upcoming target stimulus which, after a variable delay period, was presented embedded in a circular array of shapes. Subjects had to differentiate between barrel or bowtie target stimuli flanked either by congruent or incongruent shapes. Using our probabilistic atlas of the human visual system, we localized the recorded ECoG signals to topographically organized brain areas and linked them to functional brain imaging data from normal subjects. We found spatially constrained visual response fields in 175 electrodes, as indicated by differential cue-related activity, obtained from both induced broadband power and evoked potentials. We examined response modulation from those electrodes during the delay period of the task when subjects either attended to or away from the response field. Further, we related these results to changes in the BOLD signal measured in normal subjects performing the same task. We found that covert spatial attention affected evoked event-related potentials and induced low frequency (4-20Hz) and broadband high gamma (50-200Hz) power differentially along the dorsal pathway through nodes of the fronto-parietal attention network, from V1 through intraparietal sulcus areas IPS0-IPS5 and the frontal eye fields. Meeting abstract presented at VSS 2015