Date of Award

Spring 2004

Document Type

Dissertation - Restricted

Degree Name

Doctor of Philosophy (PhD)


Biomedical Engineering

First Advisor

Ropella, Kristina M.

Second Advisor

Hudetz, Anthony G.

Third Advisor

Bosnjak, Zeljko


The overall goal of my research is to better understand the mechanism of general anesthesia on the central nervous system with a special reference to the loss of consciousness. Studying the effects of anesthesia on sensory perception and consciousness necessitates the examination of the spatio-temporal distribution of neural events in the primary sensory and association cortical brain regions. In this study, I applied non-parametric spectral and information-theoretic time-series analyses to quantify concentration-dependent effect of general anesthetics on spontaneous and visually evoked local field potentials in rat primary visual (Vl), parietal association (PTA), and frontal (FR) cortices. I focused on gamma (20-60 Hz) frequency components of the local field potentials as these oscillations have been suggested to play a role in the mechanism underlying consciousness [l]. The importance of the selected cortical regions in visual awareness, selective attention and working memory has been previously demonstrated [2]. The loss of righting reflex, a generally accepted behavioral index of loss of consciousness in rat [3], was assessed simultaneously with the electrophysiological recordings in rat in awake and steady state graded levels of anesthesia bracketing the point of loss of consciousness. In an attempt to reveal a unitary component of the anesthetic action producing unconsciousness, I used three general anesthetic agents halothane, isoflurane, and desflurane. These anesthetic agents belong to the family of inhalational anesthetics but have slightly different chemical structures and potencies.



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