LOCUS-COERULEUS ACTIVITY IN MONKEY - PHASIC AND TONIC CHANGES ARE ASSOCIATED WITH ALTERED VIGILANCE

Citation
J. Rajkowski et al., LOCUS-COERULEUS ACTIVITY IN MONKEY - PHASIC AND TONIC CHANGES ARE ASSOCIATED WITH ALTERED VIGILANCE, Brain research bulletin, 35(5-6), 1994, pp. 607-616
Citations number
50
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Neurosciences
Journal title
ISSN journal
0361-9230
Volume
35
Issue
5-6
Year of publication
1994
Pages
607 - 616
Database
ISI
SICI code
0361-9230(1994)35:5-6<607:LAIM-P>2.0.ZU;2-C
Abstract
Impulse activity of individual neurons in the nucleus locus coeruleus (LC) was recorded from chair-restrained, unanesthetized cynomolgus mon keys. LC activity was closely related to the behavioral state of the a nimal. In alert waking, LC neurons displayed continuous, moderately ir regular activity. In contrast, prolonged pauses in activity accompanie d drowsiness. These pauses preceded eye closure and occurred 1-3 s bef ore the onset of slow-wave EEG. At awakening, LC activation preceded b y up to 3 s desynchronized EEG and eye opening. LC activity during ale rtness varied tonically. During behavioral agitation LC activity was h igher than during goal-directed task behavior (described below). In ad dition to these changes in tonic activity, LC neurons were also phasic ally responsive to certain sensory stimuli. These cells responded sele ctively to unexpected, meaningful sounds. LC neurons were also recorde d during a visual oddball discrimination task in which the monkey was required to selectively release a lever in response to an infrequent v isual cue (target cue; CS+) to receive juice reward. LC neurons were s electively activated by CS+ cues in this task; no other task events ev oked LC activity. The mean latency of CS+ response was 108 ms (90 ms f or multicell recordings), more than 150 ms prior to the behavioral res ponse (lever release). These responses became smaller in later epochs during the session, along with deteriorating task performance. It is p roposed that these short-lasting stimulus-evoked LC responses may help optimize behavioral responses and increase vigilance to subsequent se nsory stimuli. Together, LC may contribute both to maintaining tonic l evels of vigilance and to phasically modulating the current vigilance level in a stimulus-dependent made.