*T. SIGURDSSON, C. K. CAIN, J. E. LEDOUX;
Ctr. for Neural Sci., New York Univ., New York, NY

Sensory adaptation is a form of short-term plasticity that plays a critical role in how information is processed by neural circuits. Here, we examined sensory adaptation in the lateral nucleus of the amygdala (LA), a region that is critically involved in attaching emotional significance to sensory cues in the environment. In urethane-anesthetized rats, we recorded single-unit responses of LA neurons while delivering pairs of auditory broadband stimuli (clicks and white noise pips) at interstimulus intervals of 100-2000 ms. LA neurons consistently displayed strong adaptation, as shown by a decrease in responsiveness to the second stimulus in a pair, that lasted up to at least 2 seconds. In order to examine whether adaptation of LA neurons is simply inherited from afferent structures, we recorded responses in the MGm/PIN, the primary source of auditory thalamic inputs to the LA. Although adaptation was observed in MGm/PIN neurons, it was not as pronounced as in neurons of the LA. We therefore considered whether synaptic depression at thalamic inputs might contribute to sensory adaptation in the LA. To test this possibility, we delivered paired pulses of electrical stimuli to the MGm/PIN and recorded single-unit responses in LA neurons. Consistent with the adaptation to auditory stimuli, LA neurons displayed strong paired-pulse depression in response to stimulation of MGm/PIN. Finally, for comparison we examined sensory adaption in neurons of the striatum (STR) immediately dorsal to the LA, which also receive auditory input from the MGm/PIN. Interestingly, STR neurons showed considerably less adaptation to auditory stimuli than neurons in LA. Furthermore, electrical stimulation of MGm/PIN caused less paired-pulse depression of STR neurons than LA neurons. These results suggest that sensory adaptation of LA neurons derives in part from depression at afferent synapses, which distinguishes the LA from its neighboring regions. The adaptive nature of LA sensory responses may enable it to perform important computational functions such as novelty detection.

Support Contributed By: R01 MH46516; R37 MH38774; K05 MH067048;P50 MH58911

Program No. 307.2/BBB15
Poster presentation:Sunday, Nov 04, 2007, 2:00 PM - 3:00 PM
Location: San Diego Convention Center: Halls B-H