Food and intracranial stimulation responding suppressed with regular-interval shock

Area of Science:

• Neuroscience
• Behavioral Psychology
• Psychopharmacology

Background:

• Conditioned suppression is a behavioral paradigm used to measure the aversive effects of stimuli.
• Intracranial stimulation (IS) and food reinforcement are primary reinforcers that can maintain operant responding.
• Comparing the effects of different reinforcers under aversive conditions can elucidate their relative motivational properties.

Purpose of the Study:

• To compare the degree of conditioned suppression produced by intracranial brain stimulation (IS) versus food reinforcement.
• To investigate the relative response strength of behaviors maintained by IS and food.

Main Methods:

• Rats were trained on a multiple schedule of reinforcement, with response rates for IS and food-food reinforcement equalized.
• Foot shock was introduced during timeout periods to elicit conditioned suppression.
• Response rates during IS and food components were compared before and after component duration was altered.

Main Results:

• Responding maintained by IS showed significantly less suppression to foot shock compared to food-reinforced responding.
• Shortening component durations did not alter the differential suppression between IS and food reinforcement.
• The data suggest that IS may support a stronger behavioral response than food reinforcement.

Conclusions:

• The attenuated suppression during IS is unlikely due to neural disruption, stimulus blocking, or analgesic properties.
• Behaviors maintained by IS appear to have a greater response strength relative to those maintained by food reinforcement.
• These findings have implications for understanding the motivational properties of different reward systems in the brain.