Roughness coding in the somatosensory system.
Roughness perception is coded in the somatosensory system by neurons in the type I slowly adapting (SAI) system. When the fingers scan a surface, an isomorphic representation of the surface is encoded in the discharge patterns of SAI afferents. Central neurons in area 3b of primary somatosensory (SI) cortex spatially filter the peripheral image to compute local spatial variation. The outputs from these neurons converge onto neurons in area 1 and onto neurons in secondary somatosensory (SII) cortex which we believe is the critical processing pathway underlying roughness perception.