Nonlinear encoding of tactile patterns in the barrel cortex.
Nowhere is the sparse nature of neuronal coding more evident than in the sensory cortex, where neuronal response becomes increasingly tuned to specific features of the sensory environment. For such situations, where rate modulation schemes do not accurately describe the neuronal response to sensory stimuli, statistical descriptions based on point process events are particularly appropriate. Here, intensity measures derived from experimental data in the rat somatosensory cortex enable the direct analysis of statistical structure within spike trains, as well as inter-relationships between tactile stimuli and neuronal response. Intensity measures capture structure in spontaneous as well as driven activity, reflecting the interplay between excitatory and suppressive influences on neuronal firing. Second-order intensity estimates reveal strong dependencies upon patterns of tactile stimulation, which define the neuronal response characteristics to temporally structured stimuli.