Journal of Neuroscience, Vol 14, 2933-2942, Copyright © 1994 by Society for Neuroscience
Hippocampal reflected optical patterns during sleep and waking states in the freely behaving cat
GR Poe, DM Rector and RM Harper
Brain Research Institute, University of California at Los Angeles 90024- 1763.
We examined reflected light as a measure of neural activity from a 2 mm2
area of dorsal hippocampus and surrounding neocortex in nine freely
behaving cats during sleep and waking states. Light reflectance at 660 or
700 nm was measured by a coherent fiber optic probe attached to a
charge-coupled device video camera that allowed acquisition of images from
subcortical structures. In the dorsal hippocampus, rapid eye movement sleep
(REMS) and active waking (AW) resulted in a significant decline (-0.9% +/-
0.3 and -2.0% +/- 0.5, respectively) in overall reflected light from the
dorsal hippocampus relative to quiet sleep (QS), while quiet waking (QW)
resulted in an overall increase (+2.0% +/- 0.4). In the neocortical probe
placement group, reflectance also decreased during AW (-1.6% +/- 0.5) and
increased during QW (+1.7 +/- 0.6) as compared to QS. In contrast to the
hippocampus, however, overall reflectance increased, rather than decreased,
in the neocortex during REMS (+2.7% +/- 1.3). We interpret a decline in
reflectance as representing increased activation of underlying neural
tissue. Thus, the cat dorsal hippocampus increased overall activity during
REMS as compared to QS, while neocortical structures decreased overall
activity during the same state. These results concur with expected activity
changes based on electrophysiologic and autoradiographic studies. The
imaging procedure provided a continuous assessment of spatially organized
neural activity changes in the freely behaving animal.
Previous Article | Next Article
