Saccadic modulation of neural activity in the human anterior thalamus during visual active sensing

Humans and other primates explore visual scenes by , using saccadic eye movements to relocate the fovea and sample different bits of information multiple times per second. Recent reports indicate that saccades induce a phase reset of ongoing neuronal oscillations in a distributed network including primary and higher-order visual cortices and medial temporal lobe. As a result, neuron ensembles in these regions are shifted to a momentary high excitability state at the time visual input enters the system; i.e., just after fixation; among other things, this would amplify the neuronal response to visual input. The extent of the brain’s circuitry modulated by saccades is not yet known. Here, we evaluate the possibility that saccadic phase reset impacts the anterior nuclei of the thalamus (ANT) using field potential recordings in the ANT in three surgical patients undergoing deep brain stimulation for treatment of epilepsy. Given that ANT are strongly connected to frontal/prefrontal cortex, hippocampus and cingulate cortex - brain networks that support active sensing, we hypothesized that ANT would display similar saccade-related modulation of excitability. In all three patients, we found saccade-related phase concentration, peaking at 3-4 Hz, coincident with suppression of Broadband High frequency Activity (BHA; 70-150Hz), a signal that correlates with local neuronal spiking activity. Our results provide evidence for saccade-related modulation of neuronal excitability dynamics in the ANT, consistent with the idea that these nuclei are part of the brain circuitry underlying visual active sensing.