A study was made of neuronal responses in the rabbit visual cortex to patterned visual stimuli and their change during non-specific activation reaction. Non-specific activation while only slightly affecting the background neuronal activity, enhances the responses of most units to patterned visual stimuli. A comparison of responses with a different degree of inhibition participation shows that the depression of inhibitory processes may act as a mechanism of facilitation of the responses during non-specific activation. After facilitated responses evoked by the action of the stimulus during non-specific activation, the neurones retain a state of enhanced excitability. Repetition of stimuli not attended with non-specific activation leads to the diminution of excitability. The possible connection of the indicated effects with extinction processes is discussed.