Subcortical correlates of consciousness with human single neuron recordings

Subcortical brain structures such as the basal ganglia or the thalamus are involved in regulating motor and cognitive behavior. However, their contribution to perceptual consciousness is still unclear, due to the inherent difficulties of recording subcortical neuronal activity in humans. Here, we asked neurological patients undergoing surgery for deep brain stimulation to detect weak vibrotactile stimuli applied on their hand while recording single neuron activity from the tip of a microelectrode. We isolated putative single neurons in the subthalamic nucleus and thalamus. A significant proportion of neurons modulated their activity while participants were expecting a stimulus. We isolated a subset of neurons for which we had sufficiently good behavior to contrast neuronal activity between detected and undetected stimuli. We found that the firing rate of 23% of these neurons differed between detected and undetected stimuli. Our results provide direct neurophysiological evidence of the involvement of subcortical structures in for the detection of vibrotactile stimuli, thereby calling for a less cortico-centric view of the neural correlates of consciousness.