Task and Regions Specific Top-Down Modulation of Alpha Rhythms in Parietal Cortex

Abstract

Alpha (8-12 Hz) power desynchronization is strongly associated to visual perception but has been observed in a large variety of tasks, indicating a general role in task anticipation. We previously reported in human observers that interference by repetitive transcranial magnetic stimulation (rTMS) of core regions of the dorsal attention network (DAN) disrupts both anticipatory alpha desynchronization and performance during a visuospatial attention (VSA) task. Here, we test the hypothesis that alpha desynchronization is task specific, and can be selectively modulated by interfering with activity in different higher-order parietal regions. We contrast the effects of rTMS on alpha rhythms and behavior on 2 different tasks: a VSA and a semantic decision task, by targeting the posterior intraparietal sulcus (pIPS), a core region of the DAN, or the angular gyrus (AG), a core region of the default mode network (DMN). We found that both performance and anticipatory alpha desynchronization were affected by stimulation of IPS only during VSA, and of AG only during semantic decisions. These findings indicate the existence of multiple dedicated parietal channels for the modulation of anticipatory alpha rhythms, which in turn reflect task-specific modulation of excitability in human parieto-occipital cortex.

High-alpha band synchronization across frontal, parietal and visual cortex mediates behavioral and neuronal effects of visuospatial attention

“…Participants who exhibited stronger high-alpha phase synchronization also exhibited stronger lateralization of low-alpha amplitudes during attention shifting. Highalpha phase synchronization between frontal and parietal cortices could thus mediate attention-related low-alpha band suppression, similar to structural connectivity (Marshall et al, 2015a) and perturbation of frontoparietal cortex with TMS (Capotosto et al, 2009(Capotosto et al, , 2016(Capotosto et al, , 2012Marshall et al, 2015b). In addition, participants with stronger high-alpha phase synchronization exhibited a stronger behavioral benefit of visuospatial attention when detecting low-contrast but not high contrast stimuli in the right hemifield.…”

High-alpha band synchronization across frontal, parietal and visual cortex mediates behavioral and neuronal effects of visuospatial attention

“…Participants who exhibited stronger high-alpha phase synchronization also exhibited stronger lateralization of low-alpha amplitudes during attention shifting. High-alpha phase synchronization between frontal and parietal cortices could thus mediate attention-related low-alpha band suppression, similar to structural connectivity (Marshall et al, 2015a) and perturbation of frontoparietal cortex with TMS (Capotosto et al, 2009;Capotosto et al, 2016;Capotosto et al, 2012;Marshall et al, 2015b). In addition, participants with stronger high-alpha phase synchronization exhibited a stronger behavioral benefit of visuospatial attention when detecting low-contrast but not high contrast stimuli in the right hemifield.…”

The contribution of the human posterior parietal cortex to episodic memory

“…Causal support for a segregation of parietal regions that are involved in memory (albeit semantic) retrieval and perceptual attention comes from a recent study 35 that combined electroencephalography (EEG) with the inhibitory effect of repetitive transcranial magnetic stimulation 36,37 (rTMS) during task anticipation. We found that both performance and anticipatory desynchronization of oscillations in the alpha band were affected by stimulation of the pIPS only during the perceptual attention task and of the AG only during the semantic retrieval task, demonstrating a double dissociation between PPC regions and task demands.…”