The present results are relevant to the interpretation of behavioral
effects of amygdalectomy in the Wisconsin General
Test Apparatus, in which many previous investigations ofamygdalar
function have been carried out. In that apparatus, a monkey
displaces a visual stimulus object and, if the chosen object
is the correct one, finds a piece of food directly underneath it.
As a result of this event, the animal might remember a sensory
association between the visual discriminandum and the visual
properties of the reward underneath it. Monkeys can rapidly
learn associations between displayed stimuli and the visual
properties of non-food objects found under the displaced stimuli
(Gaffan and Bolton, 1983). It is possible therefore that the same
type of association might be formed between a displaced stimulus
and the visual properties (as distinct from the incentive
value) of a piece of food found underneath it. Our present results
imply that that type of association is not dependent on the
amygdala. This could explain why amygdalectomy produces
variable and sometimes quite mild effects upon visual discrimination
learning for food reward in the Wisconsin General Test
Apparatus. [Gaffan and Harrison (1987) briefly review and discuss
the results from this apparatus.]