Source Paper
Dissociation in Effects of Lesions of the Nucleus Accumbens Core and Shell on Appetitive Pavlovian Approach Behavior and the Potentiation of Conditioned Reinforcement and Locomotor Activity byd-Amphetamine
John A. Parkinson, Mary C. Olmstead, Lindsay H. Burns, Trevor W. Robbins, Barry J. Everitt
Journal of Neuroscience • 1999
Instrumental Conditioning with Conditioned Reinforcer
Objective: To test acquisition of a new instrumental response that produces a conditioned stimulus (CS) acting as a conditioned reinforcer, and to examine the effects of intra-nucleus accumbens amphetamine infusions on this conditioned reinforcement
Gather these items before starting the experiment. Check off items as you prepare.
Materials2
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Protocol Steps
Initial Pavlovian Conditioning
Rats were trained to associate a neutral stimulus (conditioned stimulus, CS) with food reinforcement (unconditioned stimulus, US)
Note: This establishes the CS as a predictor of food reward before lesion surgery
View evidence from paper
“Rats were initially trained to associate a neutral stimulus (Pavlovian CS) with food reinforcement (US)”
Excitotoxic Lesion Surgery
Animals underwent excitotoxic lesions that selectively destroyed either the nucleus accumbens core or shell
Note: Lesions were performed between initial Pavlovian training and retraining sessions
View evidence from paper
“After excitotoxic lesions that selectively destroyed either the NAcc core or shell, animals underwent additional CS–US training sessions”
Pavlovian Retraining Sessions
After lesion recovery, animals underwent additional CS-US training sessions to reestablish the Pavlovian association
Note: Core-lesioned animals showed impairment during these retraining sessions
View evidence from paper
“After excitotoxic lesions that selectively destroyed either the NAcc core or shell, animals underwent additional CS–US training sessions”
Instrumental Conditioning Test
Animals were tested for acquisition of a new instrumental response (lever press) that produced the CS acting as a conditioned reinforcer
Note: Two levers were present: one that produced the CS (CR lever) and one nonreinforced control lever
View evidence from paper
“then were tested for the acquisition of a new instrumental response that produced the CS acting as a conditioned reinforcer (CR)”
Amphetamine Infusion During Testing
Before each instrumental conditioning session, animals received intra-nucleus accumbens infusions of d-amphetamine at one of five doses
Note: Dose-response design with 5 dose levels including vehicle control (0 μg)
View evidence from paper
“Animals were infused intra-NAcc with d-amphetamine (0, 1, 3, 10, or 20 μg) before each session”
Measurement of Responding
Responses on both the CR lever (producing conditioned reinforcer) and the control nonreinforced lever were recorded during instrumental conditioning sessions
Note: Selectivity of amphetamine effects was assessed by comparing responding on reinforced versus nonreinforced levers
View evidence from paper
“intra-NAcc amphetamine infusions dose-dependently increased responding on both the CR lever and a nonreinforced (control) lever”
Measurement of Locomotor Activity
Locomotor activity was measured during sessions to assess amphetamine-induced psychomotor stimulation
Note: Shell lesions produced hypoactivity and attenuated amphetamine-induced activity; core lesions resulted in hyperactivity and enhanced amphetamine locomotor effects
View evidence from paper
“Shell lesions produced hypoactivity and attenuated amphetamine-induced activity. In contrast, core lesions resulted in hyperactivity and enhanced the locomotor-stimulating effect of amphetamine”