Hyperdirect connectivity of opercular speech network to the subthalamic nucleus

Abstract

How the basal ganglia participate in the uniquely human behavior of speech is poorly understood, despite their known role in modulating critical aspects of cognitive and motor behavior. The subthalamic nucleus (STN) is well positioned to facilitate basal ganglia functions critical for speech. Using electrocorticography in patients undergoing awake deep brain stimulation (DBS) surgery, evidence is reported for a left opercular hyperdirect pathway in humans via stimulating the STN and examining antidromic-evoked activity in the left temporal, parietal, and frontal opercular cortex. These high-resolution cortical and subcortical mapping data provide evidence for hyperdirect connectivity between the inferior frontal gyrus and the STN. In addition, evoked potential data are consistent with the presence of monosynaptic projections from areas of the opercular speech cortex that are primarily sensory, including the auditory cortex, to the STN. These connections may be unique to humans, evolving alongside the ability for speech.

Keywords: Broca's area; basal ganglia; deep brain stimulation; electrocorticography; hyperdirect pathway; inferior frontal gyrus; speech production; subthalamic nucleus; superior temporal gyrus.