[What the whiskers tell the tactile brain]

The rodent whisker system became one of the main system models for the study of the functional properties of sensory neurons. This is due on one hand to the detailed knowledge that we have on the afferent pathways linking the mechanoreceptors in the follicles to the primary somatosensory cortex and on the other hand to the possibility of controlling the sensory input at a micrometer and millisecond scale. The observation of the natural use of the whiskers by rodents indicates that exploration of objects and textures imply multiple contacts with tens of whiskers simultaneously. We have studied the neural code in the barrel cortex, which receives tactile information from the whiskers. By combining multi-electrode recordings and controlled multiwhisker tactile stimulation with theoretical analysis, we have observed a dependence of neural responses on the statistics of the sensory input. Several classes of neuronal responses, similar to those described in a number of cortical visual areas, were observed in the same cortical volume, indicating that various coding schemes are implemented in the same cortical network and can be put into play differentially to cope with the changing statistics of the peripheral stimuli.