| ENHANCEMENT OF AUDITORY RESPONSES IN THE LATERAL AMYGDALA
FOLLOWING COACTIVATION OF CS AND US PATHWAYS |
| T. Sigurdsson1*; V. Doyere1,2;
J.E. LeDoux1 |
| 1. Ctr Neural Sci, NYU, New York, NY, USA |
| 2. Universite Paris-Sud, Orsay, France |
|
During auditory fear conditioning, an auditory
conditioned stimulus (CS) comes to elicit fear responses after being paired
with an aversive unconditioned stimulus (US). Several lines of evidence
suggest that this form of learning is mediated by an increase in the strength
of synapses that transmit CS information to the lateral amygdala (LA).
Such synaptic changes could occur during learning if activation of CS
inputs to the LA coincides with strong depolarization of LA neurons generated
by inputs mediating the US. We investigated this possibility in anesthetized
rats by pairing auditory stimuli with electrical stimulation of the posterior
thalamus, which receives spino-thalamic afferents transmitting US information
and sends projections to the LA. The intensity of thalamic stimulation
was adjusted to elicit field potentials in the LA that were larger than
those evoked by the auditory stimulus alone. Preliminary results suggest
that such pairings lead to an increase in the amplitude of the field potential
evoked in the LA by the auditory stimulus. In contrast, no increase is
observed when auditory and thalamic stimulation is delivered in an unpaired
fashion. These results demonstrate an associative enhancement of auditory
responses in the LA following pairing of auditory stimuli with activation
of a US pathway, suggesting that such temporal CS-US convergence may mediate
the synaptic changes believed to underlie auditory fear conditioning.
Supported by: MH58911, MH38774, MH46516 and MH00956
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