Accession Number:

ADA265657

Title:

Locus Coeruleus, Vigilance and Stress: Brain Mechanisms of Adaptive Behavioral Responsiveness

Descriptive Note:

Final technical rept. 15 Dec 89-31 Dec 92,

Corporate Author:

HAHNEMANN UNIV PHILADELPHIA PA DEPT OF MENTAL HEALTH SCIENCES

Personal Author(s):

Report Date:

1993-05-13

Pagination or Media Count:

49.0

Abstract:

We have developed techniques for recording stable unit activity from individual monkey locus coeruleus LC neurons using microwire electrodes 25 micrometers diameter. A combination of improved electrode design, new microadvancer and methods to accurately localize the LC nucleus now permits stable recordings of high signalnoise better than 31 from single neurons in LC for several hours in the waking monkey performing a vigilance task. We have found that LC neurons vary activity phasically and tonically during vigilance performance. Phasic responses are selectively evoked by target cues, and follow new targets during acquisition of reversal in this task. Tonically, LC neurons vary activity levels in accordance with attentiveness to the task, as measured by the frequency of foveating a fix spot required to initiate each trial. Results indicate that the LC functions to regulate the lability of attention. In this view, performance on a task requiring focused attention varies with tonic LC activity in an inverted U relationship. Too little LC activity is associated with poor performance due to non-alertness, while high tonic LC activity corresponds to highly labile attention that prevents focusing attention for long time epochs. Together, these results indicate that optimal vigilance performance e.g., radar monitoring activity may require an intermediate level of LC activity and high phasic responsiveness of LC neurons.

Subject Categories:

  • Anatomy and Physiology
  • Medicine and Medical Research
  • Biomedical Instrumentation and Bioengineering
  • Human Factors Engineering and Man Machine Systems

Distribution Statement:

APPROVED FOR PUBLIC RELEASE