*V. DOYERE1, L. R. JOHNSON2, M. HOU2, A. PONCE3, L. GRIBELYUK2, H. H. ALPHS2, L. ALBERT2, J. E. LEDOUX2; 1NAMC-UMR8620, Univ. Paris-Sud, Orsay, FRANCE, 2CNS, NYU, NY, NY, 3Namc-umr8620, Univ. Paris-Sud, Orsay, FRANCE.

The dorsal lateral amygdala (LAd) is a vital nucleus for the formation of associations between aversive unconditioned stimuli (US) and neutral stimuli, such as auditory tones, which can become conditioned (CS) to the US through temporal pairing. Important aspects of CS-US associations are believed to occur within the LAd, however relatively little is known about the temporal behavior of local LAd networks. Information about the CS and US enters the LA via a rapid and direct thalamic input and a longer latency cortical path. We developed a novel methodology for the identification and extraction of polysynaptic temporal structure, and identified systematically reoccurring polysynaptic potentials in LAd in response to thalamic afferent activation in awake animals and in an in vitro slice preparation. In awake animals up to nine peaks were identified. We compared the temporal structure of these peaks to responses elicited from the same brain areas in vitro. The first five potentials in LAd-d were preserved in vitro, demonstrating they reflect recurrent activity in a local network. Simultaneous recordings from LAd-d and LAd-v revealed functional but independent micro-networks, with faster polysynaptic activity in LAd-v. Physically isolating the LAd-d from the LAd-v showed that the second and the fifth polysynaptic potentials in LAd-d were dependent upon synaptic input from the LAd-v. The temporal window for the recurrent LAd-v to LAd-d network projection coincides with known cortico-amygdala latencies. Sustained activity in this recurrent network was disrupted by NMDA receptor blockade. This internal recurrent network of the LAd is plastic, as polysynaptic responses are depressed in response to induction of LTP. Depression of the recurrent network may be a homeostatic mechanism to prevent runaway excitation within the recurrent network. In sum, using a novel analysis methodology, we identified a NMDA sensitive and plastic recurrent network within the LAd. In the Hebbian postulate, coincidence detection is facilitated by network activity. The structured recurrent reentry of thalamic mediated sensory information we observed in LAd may facilitate temporal associativity of sensory inputs during aversive learning.
Support Contributed By:NSF-CNRS17089,CNRS-PICS;NIH MH00956;NIH MH58911;NIH MH46516;NIH MH38774

Program No. 370.9/KK27
Poster presentation:Monday, Oct 16, 2006, 8:00 AM - 9:00 AM
Location: Georgia World Congress Center: Halls B3-B5