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What's the role of the basolateral amygdala?

Shamim Khaliq shamim at khaliq.intensive.co.uk
Wed Dec 13 10:42:50 EST 2000

What's the role of the basolateral amygdala? I thought it was important in
classical conditioning of fear responses, i.e. associating a neutral
stimulus with an internal aversive affective state generated by an
unconditioned aversive stimulus. But I'm reading Depue's paper where he says
it's important in stimulus-reinforcement conditioning, with lesions
impairing association of stimuli with reinforcement (appetitive stimuli). Is
the basolateral amygdala then also important in associating a neutral
stimulus with an internal appetitive affective state?

And then why have I heard about conditioned fear responses and not
conditioned pleasure responses?

I include two contradictory quotes about the role of the basal amygdala

"In both monkey and human, the basolateral amygdala plays a critical role in
classical stimulus-reinforcement conditioning (Aggleton 1992; Bechara,
Tranel, Damascio, Adolphs, Rockland & Damascio 1995; Cahill & McGaugh 1990;
Everitt & Robbins 1992; Gaffan 1992; LeDoux 1996; LeDoux, Cicchetti,
Xagoraris & Romanski 1990; Selden, Everitt, Jarrad & Robbins 1991).
Bilateral basolateral amygdala lesions specifically impair the association
of discrete stimuli with reinforcement, whereas the motivational efficacy of
food rewards or of DA injections in the NAS (nucleus accumbens) remains
intact (Aggleton 1992; Everitt & Robbins 1992; Gaffan 1992). This indicates
that the basolateral amygdala performs stimulus-reinforcement associative
functions, whereas DA release in the NAS modulates an incentive motivational
influence. Nevertheless, lesions of either the basolateral amygdala or NAS
impair responding for reward, suggesting that these two structures are
serially connected (Everitt & Robbins 1992; Mogenson et al. 1993)."

"The CTA (conditioned taste aversion) can be differentiated from the CCP
(conditioned place preference) in two ways. First, in contrast to the CCP,
CTAs are not readily elicited by conditioned external cues (Garcia &
Koelling, 1966; Reicher & Holman, 1977; Shennan et al., 1980b; Stefurak,
Martin & van der Kooy, 1990). Neutral or even rewarding taste cues are most
easily conditioned in the CTA paradigm, suggesting that these conditioned
incentive cues elicit aversive internal states. Secondly, CTAs are blocked
by lesions of the basolateral nucleus of the amygdala (Nachman & Ashe, 1974;
Elkins, 1980; Dunn & Everitt, 1988; Yamamoto & Fujimoto, 1991), while the
CCP is eliminated by lesions of the lateral nucleus of the amygdala
(McDonald & White, 1993). This difference suggests that positive and
negative incentive learning are mediated by different neural substrates."

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