Human single-neuron correlates of somatosensation

Deciphering the neural correlates of consciousness has long been a challenging pursuit in neuroscience, with ongoing discourse surrounding which cortical regions are responsible for subjective sensory experiences. The posterior parietal cortex (PPC) and primary somatosensory cortex (S1) are frequently cited as potential cortical substrates for neural correlates of consciousness within the realm of tactile perception, owing to their significant roles in somatosensory processing.

However, the extent to which these regions contribute to conscious tactile perception remains uncertain. To shed light on this matter, researchers employed chronic intracortical recordings to simultaneously monitor the activity of numerous single neurons in grasp-related cortical areas from three individuals with tetraplegia while exposing them to natural vibrotactile stimuli on a sensate region of the upper limb.

The findings reveal that a harmonized neural activity pattern emerged across the grasp-related parietal-frontal network near the threshold of perception. The researchers then honed in on PPC and S1 within this distributed network. While S1 responses exhibited a direct correlation with the physical stimulus amplitude, PPC activity demonstrated a stronger covariation with awareness and confidence.

This single-neuron evidence underscores the complementary neural codes of PPC and S1, suggesting that PPC converts physical stimulation into conscious perception, while S1 exhibits heightened sensitivity to stimulus amplitude.