The sensory contribution of a single vibrissa's cortical barrel.

The sensory contribution of the cortex containing the cortical barrel of the C1 vibrissa was studied in rats using the ablation-behavior method. Three independent experiments were performed, each requiring stimulus transduction by the C1 vibrissa but varying in their perceptual demands. The first required detection of sinusoidal oscillations of the vibrissa generated by an oscillating airstream directed vertically onto the vibrissa tip. The second required detection of a change in rate of the oscillation. The third required the blinded rat to jump a gap in an elevated runway after palpating the far side with its vibrissa. Psychophysical determinations of the single vibrissa system's thresholds before and after ablation of the cortex containing its barrel show that normal sensitivity either for detecting an oscillation or for detecting a change in oscillation frequency are not dependent on either the contralateral or the ipsilateral cortical barrelfield. In contrast to the lack of effect of barrelfield ablation on the spatial and temporal acuity of the vibrissa, the third experiment shows that a rat's ability to collect situation-relevant information with the vibrissa is lost after ablation of the cortex containing its contralateral barrel but not after ablation of the cortex containing its homologous ipsilateral barrel. The results of repeated retesting of an individual rat's ability to make a jump-no jump decision on the basis of vibrissa-transduced information at each stage of a series of successive single-vibrissa removals and unilateral barrelfield ablations show that the loss of the cortex containing the vibrissa's contralateral barrel is tantamount to loss of the vibrissa itself.