Role of the mesoamygdaloid dopamine projection in emotional learning
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Amygdala dopamine is crucially involved in the acquisition of Pavlovian associations, as measured via conditioned approach to the location of the unconditioned stimulus (US). However, learning begins before skeletomotor output, so this study assessed whether amygdala dopamine is also involved in earlier ‘emotional’ learning.
A variant of the conditioned reinforcement (CR) procedure was validated where training was restricted to curtail the development of selective conditioned approach to the US location, and effects of amygdala dopamine manipulations before training or later CR testing assessed.
Experiment 1a presented a light paired (CS+ group) or unpaired (CS− group) with a US. There were 1, 2 or 10 sessions, 4 trials per session. Then, the US was removed, and two novel levers presented. One lever (CR+) presented the light, and lever pressing was recorded. Experiment 1b also included a tone stimulus. Experiment 2 applied intra-amygdala R(+) 7-OH-DPAT (10 nmol/1.0 µl/side) before two training sessions (Experiment 2a) or a CR session (Experiment 2b).
For Experiments 1a and 1b, the CS+ group preferred the CR+ lever across all sessions. Conditioned alcove approach during 1 or 2 training sessions or associated CR tests was low and nonspecific. In Experiment 2a, R(+) 7-OH-DPAT before training greatly diminished lever pressing during a subsequent CR test, preferentially on the CR+ lever. For Experiment 2b, R(+) 7-OH-DPAT infusions before the CR test also reduced lever pressing.
Manipulations of amygdala dopamine impact the earliest stage of learning in which emotional reactions may be most prevalent.
KeywordsAmygdala Dopamine Learning and memory Emotion Associative learning Behaviour Classical conditioning Consolidation Retrograde
This work was supported by Project Grants from the Medical Research Council and Wellcome Trust.
- Colwill RM, Motzkin DK (1994) Encoding of the unconditioned stimulus in Pavlovian conditioning. Anim Learn Behav 22:384–394Google Scholar
- Konorski J (1967) Integrative activity of the brain. University of Chicago Press, University of Chicago PressGoogle Scholar
- Lennartz RC, Weinberger NM (1992) Analysis of response systems in Pavlovian conditioning reveals rapidly versus slowly acquired conditioned responses: support for two factors, implications for behavior and neurobiology. Psychobiology 20:93–119Google Scholar
- Müller GE, Pilzecker A (1900) Experimentalle Beiträge zur Lehre vom Gedächtniss. Zeitschrift Fur Psychologie 1:1–288Google Scholar
- Ostlund SB, Winterbauer NE, Balleine B (2009) Theory of reward systems. In: Byrne JH (ed) Concise learning and memory. Academic, Amsterdam, pp 483–502Google Scholar
- Paxinos G, Watson C (1986) The rat brain in stereotaxic coordinates, 2nd edn. Academic Press, Academic PressGoogle Scholar
- Sokoloff P, Giros B, Martres MP, Andrieux M, Besancon R, Pilon C, Bouthenet ML, Souil E, Schwartz JC (1992) Localization and function of the D(3) dopamine receptor. Arzneimittel-Forschung/Drug Res 42:224–230Google Scholar
- Wagner AR (1978) Expectancies and the priming of STM. In: Hulse SH, Fowler H, Hoenig WK (eds) Cognitive processes in animal behavior. Erlbaum, HillsdaleGoogle Scholar
- Wagner AR, Brandon SE (1989) Evolution of a structured connectionist model of Pavlovian conditioning (AESOP). In: Klein SB, Mowrer RR (eds) Contemporary learning theories: Pavlovian conditioning and the status of traditional learning theory. Erlbaum, Hillsdale, pp 149–189Google Scholar
- Winer BJ (1971) Statistical principles in experimental design. McGraw-Hill, McGraw-HillGoogle Scholar