| Abstract No.: | B-G2186 |
| Country: | Canada |
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| Title: | ARTIFICIAL REARING SELECTIVELY MODULATES ANTICIPATORY RESPONDING IN AN INSTRUMENTAL TASK |
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| Authors/Affiliations: | 1 Anna M. Lomanowska*; 1 Gary W. Kraemer;
1 University of Toronto at Mississauga, ON, Canada;
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| Content: | Objectives: Experiences during early life are crucial in shaping the development of the nervous system. In humans, adverse early life experience, such as child abuse or neglect, have been associated with adulthood mental and behavioural disorders, including drug addiction. A prominent characteristic of this disorder is the progression from acute drug abuse to compulsive drug-taking. This process may reflect the loss of control over goal-directed actions and the promotion of habitual, stimulus driven behaviour. This study used an animal model to investigate whether early rearing in a deprived environment affects the transition from goal-directed to habitual responding in an instrumental conditioning paradigm.
Materials and methods: Rats were reared either by the mother (maternally reared; MR, n=24) or in complete isolation from the mother and litter using the “pup-in-a-cup” method (artificially reared; AR, n=24) until weaning. In adulthood, rats were tested in two instrumental devaluation tasks to examine their transition from goal-directed to habitual responding towards a naturally rewarding food stimulus. They were trained in an instrumental chamber to press a lever to obtain food pellets presented in a recessed magazine. Once lever pressing stabilized on a random interval 60s schedule, a novel pellet (sucrose) was introduced. For half of the rats in each rearing group, this novel instrumental outcome was devalued by pairing its presentation with LiCl-induced nausea. One week later, all rats were reintroduced to the initial instrumental outcome (food pellets) for several sessions on a RI60s schedule. This instrumental outcome was subsequently devalued in half of the rats from each rearing group by pre-feeding them with food pellets for one hour prior to lever pressing (specific satiety). Lever pressing and magazine entries following outcome devaluation were measured during extinction sessions.
Results: Devaluation by LiCl-induced nausea reduced both lever pressing and magazine entries, while subsequent devaluation by specific satiety only reduced magazine entries. These results indicate that the rats shifted towards habitual responding during the second devaluation procedure. There were no differences between AR and MR rats on these measures, indicating that their instrumental responding was equally sensitive to reward devaluation. However, AR rats showed a consistently higher proportion of magazine entries per lever press throughout the experiment.
Conclusion: The current results suggest that artificial rearing in a deprived environment does not affect the progression from goal-directed to habitual responding in an instrumental task. However, artificial rearing does appear to affect other aspects of behaviour that may be related to the expectation of reward following an instrumental action. Thus, behavioural responding in anticipation of reward may be selectively modified by adverse early life experiences. Supported by NSERC.
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