Effects of prefrontal cortex lesions on visual evoked potential augmenting/reducing

Visual evoked potentials to 4 stimulus intensities were recorded from Fz, Cz, and Oz, all referred to A2, in 23 neurologically normal subjects and 21 neurosurgical patients with prefrontal lesions. The response amplitude as a function of intensity was evaluated for P1/N1 and N1/P2 components. At the Oz lead, the EP amplitude consistently increased with brighter stimuli more rapidly in the prefrontal group than in the controls. Similar, though less consistent, effects were seen at Fz and Cz. These findings suggest that the phenomenon of augmenting/reducing is at least partially influenced by prefrontal-mediated inhibition of sensory processes.