Single-neuron interactions between the somatosensory thalamo-cortical circuits during perception

Sensory thalamo-cortical interactions are key components of the neuronal chains associated with stimulus perception, but surprisingly, they are poorly understood. We addressed this problem by evaluating a directional measure between simultaneously recorded neurons from somatosensory thalamus (VPL) and somatosensory cortex (S1) sharing the same cutaneous receptive field, while monkeys judged the presence or absence of a tactile stimulus. During the stimulus-presence, feedforward (VPL[->]S1) interactions increased, while pure feedback (S1[->]VPL) interactions were unaffected. Remarkably, bidirectional interactions (VPL{leftrightarrow}S1) emerged with high stimulus amplitude, establishing a functional thalamo-cortical loop. Furthermore, feedforward interactions were modulated by task context and error trials. Additionally, significant stimulus modulations were found on intra-cortical (S1[->]S1) interactions, but not on intra-thalamic (VPL[->]VPL) interactions. Thus, these results show the directionality of the information flow between the thalamo-cortical circuits during tactile perception. We suggest that these interactions may contribute to stimulus perception during the detection task used here.