Functional Organization and Information Processing Within the Suprachiasmatic Nucleus Assessed by Multiunit Recording in Vitro
Tcheng, Thomas Kim
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https://hdl.handle.net/2142/82538
Description
Title
Functional Organization and Information Processing Within the Suprachiasmatic Nucleus Assessed by Multiunit Recording in Vitro
Author(s)
Tcheng, Thomas Kim
Issue Date
1999
Doctoral Committee Chair(s)
Gillette, Martha U.
Department of Study
Neuroscience
Discipline
Neuroscience
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Animal Physiology
Language
eng
Abstract
The rat suprachiasmatic nucleus (SCN) contains a network of interconnected cellular circadian pacemakers. The functional organization of circadian pacemaker activity, and information processing in the SCN were examined using electrophysiological methods in vitro. A novel carbon fiber bundle (CFB) multiunit electrode was developed for use in recording the activity of local populations of SCN neurons. Multiunit activity (MUA) recording and single-unit activity (SUA) recording techniques were used to examine circadian rhythms of SCN neuronal activity, and several quantitative methods for estimating the time-of-peak (TOP) of the SCN circadian rhythm were evaluated. Mid-day peaks of both SUA and MUA indicated that the circadian phases of individual cellular circadian pacemakers in the SCN were coupled with each other within both local and distributed populations. The redundant distribution of pacemaker activity within the SCN was demonstrated by surgically isolating small areas of the SCN and recording a mid-day peak from them. Acute responses to neurochemical treatments were recorded using the CFB multiunit electrode to examine information-processing mechanisms in the SCN. A variety of drugs was used to test several of the classical neurotransmitter systems present in the SCN. Most treatments elicited both excitatory and inhibitory responses (during separate trials). The majority of MUA responses to pharmacological treatments were consistent with the expected direct effects of the drugs used. A common response was spontaneous reversal of an initial response, even during the application of the treatment, suggesting the operation of a homeostatic mechanism. Multiunit activity responses to drug treatments varied depending on the time of day they were applied. Inhibitory responses were more common during the day, when neuronal activity was the highest, and excitatory responses were more common during the early night, when neuronal activity is decreasing. Overall, these studies show that the SCN is a redundant, distributed network of individual cellular circadian pacemakers capable of coordinating their behavior during complex information processing activities.
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