Rearrangement of receptive field topography after intracortical and peripheral stimulation: the role of plasticity in inhibitory pathways.

Intracortical microstimulation (ICMS) of a single site in the somatosensory cortex of rats and monkeys for 2-6 h increases the number of neurons responsive to the skin region corresponding to the ICMS-site receptive field (RF), with very little effect on the position and size of the ICMS-site RF, and the response evoked at the ICMS site by tactile stimulation. Large changes in RF topography are also observed following several weeks of repetitive stimulation of a restricted skin region during tactile frequency discrimination training in monkeys. It has been suggested that these changes in RF topography are caused by competitive learning in excitatory pathways. This paper analyses the possible role of lateral inhibitory synaptic plasticity in producing cortical plasticity after ICMS and peripheral conditioning in adult animals. The 'EXIN' (afferent excitatory and lateral inhibitory) synaptic plasticity rules are used to model RF changes after ICMS and peripheral stimulation. The EXIN model produces RF topographical changes similar to those observed experimentally. It is shown that lateral inhibitory pathway plasticity is sufficient to model RF changes and increase in position discrimination after peripheral stimulation. Several novel and testable predictions are made based on the EXIN model.