Thalamocortical interactions shape hierarchical neural variability during stimulus perception

The brain is hierarchically organized to process sensory signals. But, to what extent do functional connections within and across areas shape this hierarchical order? We addressed this problem in the thalamocortical network, while monkeys judged the presence or absence of a vibrotactile stimulus. We quantified the variability and a directed connectivity measure in simultaneously recorded neurons sharing the same cutaneous receptive field from the somatosensory thalamus (VPL) and areas 3b and 1 from the somatosensory cortex. During the stimulus presence, neuronal variability increased along the network VPL-3b-1. Furthermore, VPL and area 3b display fast dynamics with rapid feedforward interactions. In contrast, area 1 shows slower timescales with persistent intra-area interactions. Our results suggest that the lower variability of VPL and area 3b facilitates feedforward thalamocortical communication, while the higher variability of area 1 supports intra-cortical interactions during sensory processing. These results provide evidence of a hierarchical order along the thalamocortical network.