Murray and Mishkin (1985) observed severe effects of bilateral amygdalectomy in a cross-modal task in which animals had
to match the feel of an object with the sight of the object. They
suggested that the amygdala might be specifically important for
cross-modal sensory associations. Their hypothesis accommo-
dates well the present results since the task of the present experiment
provided a strong within-modal association. Also, their
hypothesis is consistent with the effects of bilateral amygdalectomy
in Gaffan and Harrison’s (1987) experiment, with auditory
secondary reinforcers; these auditory stimuli, and the reactions
they evoked because of their association with primary reinforcement,
were all nonvisual events. However, their hypothesis cannot
readily explain the effects of disconnection in Gaffan and
Harrison’s experiment. In that experiment, visual cortex was
isolated from the amygdala without any decrement in learning
ability. We conclude from this that the cross-modal associations
of visual stimuli with the reactions to the secondary reinforcer
were not dependent on the interaction of the visual cortex with
the amygdala. Instead, a specific subset of cross-modal associations,
i.e., the association of the auditory secondary reinforcer
with the incentive value of the primary reward, was dependent
on the amygdala in that experiment.