Temporal Patterns of Field Potentials in Vibrissa/Barrel Cortex Reveal Stimulus Orientation and Shape (original) (raw)

Topographic analysis of field potentials in rat vibrissa/barrel cortex

Brain Research, 1991

An 8 x 8 multichannei microelectrode array was used to simultaneously record epicortical field potentials, evoked by displacement of contralateral vibrissae, from a 4 x 4 mm 2 area of vibrissa/barrel cortex in 4 rats. The epicortical responses began with early positive(P1)and negative (N1) sharp waves, followed by slower positive (P2) and negative (N2) waves. The potential complex systematically shifted toeation with vibrissa stimulated, in accordance with the known somatotopic anatomy of vibrissa/barrel cortex. Topographical distributions of potentials at the P1, N1, P2 and N2 peaks were approximately concentric, but had distinct spatial extents, suggesting that they were generated by different but overlapping neuronal subpopulations. We propose that the SEP in the vibrissa/barrel cortex is produced by both sequential and parallel processing of somatosensory information, and that all components of the epicortical SEP are generated only in primary somatosensory cortex of the rat. Applications and weaknesses of topographic analysis methods are discussed.

Late Emergence of the Vibrissa Direction Selectivity Map in the Rat Barrel Cortex

Journal of Neuroscience, 2011

In the neocortex, neuronal selectivities for multiple sensorimotor modalities are often distributed in topographical maps thought to emerge during a restricted period in early postnatal development. Rodent barrel cortex contains a somatotopic map for vibrissa identity, but the existence of maps representing other tactile features has not been clearly demonstrated. We addressed the issue of the existence in the rat cortex of an intra-barrel map for vibrissa movement direction using in vivo two photon imaging. We discovered that the emergence of a direction map in rat barrel cortex occurs long after all known critical periods in the somatosensory system. This map is remarkably specific, taking a pinwheel-like form centered near the barrel center and aligned to the barrel cortex somatotopy. We suggest that this map may arise from intra-cortical mechanisms and demonstrate by simulation that the combination of spike-timing-dependent plasticity at synapses between layer 4 and layer 2/3 and realistic pad stimulation is sufficient to produce such a map. Its late emergence long after other classical maps suggests that experience-dependent map formation and refinement continue throughout adult life.