Food and intracranial stimulation responding suppressed with regular-interval shock.

Attenuation of conditioned suppression during intracranial stimulation was compared with that during food reinforcement. Response rates controlled by food and by brain stimulation were equalized on a multiple schedule by adjusting the stimulating current. When foot shock was delivered during timeout periods separating response components, responding for food was significantly more suppressed than responding for brain stimulation. When components were shortened from 10 to 2 minutes, responding maintained by either food or brain stimulation showed a similar temporal pattern of suppression preceding each shock, but responding in the component involving food remained significantly more suppressed. Explanations for the attenuated suppression during brain stimulation based on neural disruption, stimulus blocking, and analgesic properties were questioned. The increased responding during brain stimulation seemed to reflect greater response strength relative to food reinforced responding.