Saccade-related modulation of oscillatory activity in primary auditory cortex
The auditory and visual sensory systems are both used by the brain to obtain and organize information from our external environment, yet there are fundamental differences between these two systems. Visual information is acquired using systematic patterns of fixations and saccades, which are controlled by internal motor commands. Sensory input occurs in volleys that are tied to the timing of saccades. In contrast, the auditory system does not use such an overt motor sampling routine so the relationship between sensory input timing and motor activity is less clear. Previous studies of primary visual cortex (V1) in nonhuman primates (NHP) have shown that there is a cyclical modulation of excitability tied to the eye movement cycle and suggests that this excitability modulation stems from the phase reset of neuronal oscillations. We hypothesized that if saccades provide a supramodal temporal context for environmental information then we should also see saccade-related modulation of oscillatory activity in primary auditory cortex (A1) as NHPs shift their gaze around their surroundings. We used linear array multielectrodes to record cortical laminar neuroelectric activity profiles while subjects sat in a dark or dimly lit and silent chamber. Analysis of oscillatory activity in A1 suggests that saccades lead to a phase reset of neuronal oscillations in A1. Saccade-related phase reset of delta oscillations were observed across all layers while theta effects occurred primarily in extragranular layers. Although less frequent, alpha oscillations also showed saccade-related phase reset within the extragranular layers. Our results confirm that saccades provide a supramodal temporal context for the influx of sensory information into A1 and highlight the importance of considering the effects of eye position on auditory processing. Significance StatementUsing laminar multielectrodes, the current study examined saccade-related neuronal activity during resting state while NHPs sat in a dark or dimly lit room. Our results confirm that saccade-related modulation of delta band oscillatory activity occurs across all layers of A1. Interestingly, our data also show a saccade-related phase reset of theta and alpha bands that preferentially occurs in extragranular layers. These results confirm that saccades provide a supramodal temporal context for the influx of environmental information into A1 and emphasizes the importance of considering eye position when examining auditory processing.