Journal of Neuroscience, Vol 9, 558-564, Copyright © 1989 by Society for Neuroscience
Visual-visual associative learning and reward-association learning in monkeys: the role of the amygdala
D Gaffan, EA Gaffan and S Harrison
Department of Experimental Psychology, Oxford University, England.
Three Cynomolgus monkeys (Macaca fascicularis) took part in an experiment
on visual learning set in an automatic apparatus. Each new visual
discrimination problem was solved using a visual secondary reinforcer
consisting of a white line. If the monkey chose the correct stimulus (by
touching it), the white line appeared over the correct stimulus. Primary
food reward was delivered only after a new problem was solved to a
criterion, and the problem was then replaced by a new one. Thus,
within-problem learning did not rely on primary reinforcement but on the
visual secondary reinforcer. The animals were trained preoperatively in
visual learning set with this procedure and were assessed postoperatively
for their ability to learn new visual discriminations with the same
procedure. Bilateral amygdalectomy did not significantly impair the
animals' learning ability in this task. Learning remained unimpaired when
transection of the uncinate fascicle and of the fornix was added to
amygdalectomy. The effect of bilateral amygdalectomy in this task was much
less severe than in a similar task we previously studied, with auditory
secondary reinforcers. The results show that the involvement of the
amygdala in processes of secondary reinforcement depends on the sensory
properties of the secondary reinforcer. From these and other recent
results, we conclude that the sensory attributes of a reinforcer are easily
associated with a discriminative stimulus when they are in the same
modality and same spatial location as the discriminative stimulus and that
this sensory- sensory association is independent of the amygdala.
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