Objective: Investigate the effect of orbitofrontal cortex (OFC) lesions on taste aversion learning and the ability of conditioned stimuli to access representational information about incentive value of associated reinforcement
Materials & Equipment Checklist
6 items1 from ConductScience
Gather these items before starting the experiment. Check off items as you prepare.
Equipment4
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Protocol Steps
View Abstract
Clinical evidence indicates that damage to ventromedial prefrontal cortex disrupts goal-directed actions that are guided by motivational and emotional factors. As a consequence, patients with such damage characteristically engage in maladaptive behaviors. Other research has shown that neurons in the corresponding orbital region of prefrontal cortex in laboratory animals encode information regarding the incentive properties of goals or expected events. The present study investigates the effect of neurotoxic orbitofrontal cortex (OFC) lesions in the rat on responses that are normally influenced by associations between a conditioned stimulus (CS) and the incentive value of reinforcement. Rats were first trained to associate a visual CS with delivery of food pellets to a food cup. As a consequence of learning, rats approached the food cup during the CS in anticipation of reinforcement. In a second training phase, injection of LiCl followed consumption of the food unconditioned stimulus (US) in the home cage, a procedure used to alter the incentive value of the US. Subsequently, rats were returned to the conditioning chamber, and their responding to the CS in the absence of the food US was tested. Lesions of OFC did not affect either the initial acquisition of a conditioned response to the light CS in the first training phase or taste aversion learning in the second training phase. In the test for devaluation, however, OFC rats exhibited no change in conditioned responding to the visual CS. This outcome contrasts with the behavior of control rats; after devaluation of the US a significant decrease occurred in approach to the food cup during presentation of the CS. The results reveal an inability of a cue to access representational information about the incentive value of associated reinforcement after OFC damage.
1
Initial Conditioned Response Training
Rats were trained to associate a visual conditioned stimulus (CS) with delivery of food pellets to a food cup. This training established a conditioned approach response where rats approached the food cup during presentation of the CS in anticipation of reinforcement.
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Note: This is the first training phase establishing the baseline conditioned response
View evidence from paper
“Rats were first trained to associate a visual CS with delivery of food pellets to a food cup. As a consequence of learning, rats approached the food cup during the CS in anticipation of reinforcement”
2
Taste Aversion Learning (US Devaluation)
In the home cage, injection of lithium chloride (LiCl) was administered following consumption of the food unconditioned stimulus. This procedure was designed to alter the incentive value of the food US by creating a taste aversion.
Note: This is the second training phase that devalues the US through classical conditioning
View evidence from paper
“In a second training phase, injection of LiCl followed consumption of the food unconditioned stimulus (US) in the home cage, a procedure used to alter the incentive value of the US”
3
Devaluation Test
Rats were returned to the conditioning chamber and their responding to the visual CS was tested in the absence of the food US. Approach behavior to the food cup during CS presentation was measured to assess whether the devaluation of the US affected conditioned responding.
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Note: This test measures whether the CS can access representational information about the changed incentive value of the US
View evidence from paper
“Subsequently, rats were returned to the conditioning chamber, and their responding to the CS in the absence of the food US was tested”
