We examined the effect of large, controlled whisker movements, delivered at a high speed, on the amplitude and spread of depolarization in the anesthetized mouse barrel cortex. The stimulus speed was varied between 1500 to 6000 degrees per second and the extent of movement was varied between 4–16 degrees. The rate of rise of the response was linearly related to the rate of rise of the stimulus. The initial spatial extent of cortical activation was also related to the rate of rise of the stimulus: that is the faster the stimulus onset, the faster the rate of rise of the response, the larger the extent of cortex activated initially. The spatial extent of the response and the rate of rise of the response were not correlated with changes in the deflection amplitude. But slower, longer lasting stimuli produced an Off response, making the actual extent of activation larger for the slowest rising stimuli. These results indicate that the spread of cortical activation depends on stimulus features.
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