Fig. 2.

Brief mechanical single whisker deflection causes a center-surround triphasic response. A, Frame sequence showing averaged cortical activation maps in response to brief (1 msec) mechanical stimulation of whisker D2 (4.8 msec/frame;n = 92 trials). B, Three time courses showing the averaged values from a ring-like shape at different distances from the barrel center. During the hyperpolarization phase, the response in the surround is more negative than the response in the center. The opposite is true for the earlier depolarization response.C, The net hyperpolarization gradually disappears on changing the duration of the stimulation from 1 msec to 30 msec.