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Locus Coeruleus, Vigilance and Stress: Brain Mechanism of Adaptive Behavioral Responsiveness
Annual rept. 15 Dec 1989-14 Dec 1990
HAHNEMANN UNIV PHILADELPHIA PA DEPT OF MENTAL HEALTH SCIENCES
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Methods were developed for recording from locus coeruleus LC neurons in behaving monkeys using a microwire electrode holder allowing easy electrode repositioning in vivo. These techniques have vastly improved our data collection, so that we now routinely record from over 100 LC neurons per animal. Recordings of individual neurons are stable for periods of 30 min to 4 h. Methods were also developed for computer presentation of stimuli and task control in an oddball visual discrimination task. Other development included computer methods for data acquisition and analysis on a separate machine during this task. Results indicated that most LC neurons are activated selectively for target stimuli during this task they are not activated appreciably by nontarget stimuli. In addition, preliminary results suggest that tonic LC activity varies closely with the animals attentiveness to the task. These results indicate that very small changes in the tonic discharge rate of LC neurons may produce marked changes in attentiveness, and that focused, attentive behavior may demand an intermediate level of LC discharge combined with robust phasic responses to meaningful sensory stimuli.
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