Different roles of alpha and beta band oscillations in anticipatory sensorimotor gating.

Verena N Buchholz,W Pieter Medendorp,Ole Jensen

doi:10.3389/fnhum.2014.00446

Abstract

Alpha (8–12 Hz) and beta band (18–30 Hz) oscillations have been implicated in sensory anticipation and motor preparation. Here, using magneto-encephalography, we tested whether they have distinct functional roles in a saccade task that induces a remapping between sensory and motor reference frames. With a crossed hands posture, subjects had to saccade as fast and accurate as possible toward a tactile stimulus delivered to one of two non-visible index fingers, located to the left or right of gaze. Previous studies have shown that this task, in which the somatotopic stimulus must be remapped to activate oculomotor system in the opposing hemisphere, is occasionally preceded by intrahemispheric remapping, driving a premature saccade into the wrong direction. To test whether the brain could anticipate the remapping, we provided auditory predictive cues (80% validity), which indicated which finger is most likely to be stimulated. Both frequency bands showed different lateralization profiles at central vs. posterior sensors, indicating anticipation of somatosensory and oculomotor processing. Furthermore, beta band power in somatosensory cortex correlated positively with saccade reaction time (SRT), with correlation values that were significantly higher with contralateral vs. ipsilateral activation. In contrast, alpha band power in parietal cortex correlated negatively with SRT, with correlation values that were significantly more negative with ipsilateral than contralateral activation. These results suggest distinct functional roles of beta and alpha band activity: (1) somatosensory gating by beta oscillations, increasing excitability in contralateral somatosensory cortex (positive correlation); and (2) oculomotor gating by posterior alpha oscillations, inhibiting gaze-centered oculomotor regions involved in generating the saccade to the wrong direction (negative correlation). Our results show that low frequency rhythms gate upcoming sensorimotor transformations.

Highlights

Saccadic eye movements serve to bring objects of interest into our focus
Alpha band power in parietal cortex correlated negatively with saccade reaction time (SRT), with correlation values that were significantly more negative with ipsilateral than contralateral activation. These results suggest distinct functional roles of beta and alpha band activity: (1) somatosensory gating by beta oscillations, increasing excitability in contralateral somatosensory cortex; and (2) oculomotor gating by posterior alpha oscillations, inhibiting gaze-centered oculomotor regions involved in generating the saccade to the wrong direction
Mean saccadic reaction time (SRT) of correct responses did not differ between stimuli presented to the left and right hand (t-test, P > 0.05)

Summary

Introduction

Saccadic eye movements serve to bring objects of interest into our focus To make these movements, the object’s sensory coordinates must be converted into gaze-based oculomotor coordinates. Making saccades toward something felt on the skin, e.g., to inspect the insect landed on your hand, involves a more complex transformation. In this case, the tactile information, as sensed in a body-based somatotopic frame (i.e., relative to the body’s surface), must be transformed into the oculomotor representation, which depends on the position of both hand and gaze (Groh and Sparks, 1996; Ren et al, 2006; Azañón et al, 2010; Harrar and Harris, 2010).

Methods

Results

Conclusion