Somatosensory Cortical Neurons Decode Tactile Input Patterns and Location from Both Dominant and Non-dominant Digits

For neurons of the primary somatosensory cortex, the anatomy of the thalamocortical connections supports a digit-wise specialization, whereas the intracortical connections suggest cross-digit integration. To evaluate the digit-wise specialization in individual somatosensory neurons, we explored the decoding of eight spatiotemporally complex tactile input patterns delivered to two non-adjacent digits in the anaesthetized rat. A striking finding was a good decoding performance for the eight input patterns to the non-dominant digit of the neuron, which in some cases was even better than for the same inputs to the dominant digit. Moreover, individual neurons decoded not only the pattern received but also to which digit it was delivered. These neuronal decoding properties were uniform throughout the cortical layers. Our results indicate that non-trivial tactile inputs to a single digit engage a wide processing circuitry throughout the digit region and suggest a low impact for somatotopy on the organization of the information processing.