POSTER PRESENTATION ABSTRACTS
Please note: All posters will be displayed in Salons 10-12.

FRIDAY, 10:15-11:00 AM

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Kanwal JS, Naumann RT, Washington SD.

Music, stress and emotions: responses of amygdalar neurons to complex sounds.

Georgetown University Medical Center kanwalj@georgetown.edu

PURPOSE: The amygdala is considered to be the seat of emotions whose sustained influence on hypothalamic activity may induce both short and long term stress leading to post-traumatic stress and anxiety disorders. Music helps us cope with stress on a daily basis protecting the mental health of the individual. How it does so remains a mystery. Musical sounds and music imagery are represented differently from speech in the auditory cortex (AC) of humans and can dramatically modify the activity induced by other tasks alone (Kanwal et al., 2000,Washington and Kanwal, 2002). Here we take an animal-model approach to explore sound processing in the amygdala. Since the amygdala is intimately involved in coordinating social and emotional behaviors and has widespread connections with both cortical and subcortical auditory structures, we postulated that neurons in the amygdala must respond selectively to species-specific sounds.

METHODS: To test this hypothesis, we presented different intensities of 91 variants of 14 simple syllabic calls to awake mustached bats, Pteronotus parnellii, a highly vocal and social species, and recorded single unit activity with tungsten microelectrodes from the basolateral nucleus of the amygdala.

RESULTS: In recordings from 7 locations in 4 bats, we obtained responses to tone bursts, frequency modulated sweeps and social calls. Contrary to our expectations, neurons responded well to all three types of stimuli. In this respect, neurons in the amygdala were similar in their responsiveness to those in the AC of the same species. Peak response latencies ranged from approximately 20 ms (short latency responses) to 100 ms (long latency responses). Whereas the short latencies overlap with those observed in the AC, the long latency responses were unique to neurons in the amygdala and matched more closely to those found in a frontal auditory field (Kanwal et al., 2000). Single unit activity in amygdalar neurons also showed tuning to FM sweeps and were highly selective to social calls. This is in contrast to neurons in various regions of the AC, which altogether respond to nearly the entire spectrum of call types (Kanwal, 2005). Local field potentials (bandpass filtered from 2 to 100 Hz) recorded in the amygdala showed significant responses to a large majority of the different call types. This suggests that the amygdala likely receives a wide spectrum of auditory inputs and imparts selectivity via local networks.

CONCLUSIONS: In the context of music perception in humans, our data show that the basolateral amygdala can be preferentially activated by the acoustic structure of sound and not solely by its emotional significance or meaning. This enables amygdalar neurons to be conditioned to many types of sounds based on experience. At the same time, the presence of call selectivity indicates that the amygdala is also preconditioned to respond best to certain meaningful sounds, which could underlie either a genetically determined or developmentally conditioned template for music perception.

 

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