Midlatency evoked potentials attenuation and augmentation reflect different aspects of sensory gating

A broad definition of sensory gating refers to the ability of the brain to modulate its sensitivity to incoming sensory stimuli. This definition allow s the concept of gating to include both the capacities to minimize or stop responding to incoming irrelevant stimuli (gating out) and to re-respond wh en a novel stimulus is presented or a change occurs in ongoing stimuli (gat ing in). In order to further characterize the function of sensory gating, w e examined the attenuation (decreased responding) and augmentation (increas ed responding) of the P50 EP amplitudes in 22 normal volunteers. Three EP p aradigms, each including a number of conditions, designed to examine both E P habituation (inhibition) and dishabituation (excitation) were administere d to each subject. In conditions designed to examine habituation (identical pairs of clicks or trains of repetitive identical clicks), the P50 behaved , as expected, with decrease of the amplitude with repetition. In condition s designed to examine dishabituation the amplitude of the P50, EP did not d ecrease as much (and frequently increased) with stimulus change. The result s suggest that the P50 EP is sensitive to the effects of stimulus repetitio n and stimulus change and can be used to study the different aspects of sen sory gating. Biol Psychiatry 1999;45:917-922 (C) 1999 Society of Biological Psychiatry.