Fig. 1.

Sensory representations in neocortex are focused during activation. A, Schematic representation of the location of the 16 channel silicon probe placed at a 135° angle in the barrel cortex to record field potential responses through an extension of layers IV–III of the barrel neocortex. B, Contour plot of the amplitude of the negative field potential recorded from 16 sites (100 μm intervals) along layers IV–III of the barrel cortex in response to stimulation of a single whisker. Note the spread of activity under control conditions and the suppression of spread and focusing of the representation after brainstem reticular formation stimulation (RF Stim.).