Physiological control systems can display reversible transitiions in behavior called bifurcations. These transitions can occur between steady state, periodic and chaotic dynamics. Chaotic behavior is deterministic in origin but highly disordered. Preliminary experimental evidence suggective of chaotic behavior in spontaneous cortical neural activity is described in the Progress Report. It has been suggested that these transitions constitute a common dynamical mechanism for several clinically observed failures of physiological regulation. A specific possibility has motivated this investigation: could a bifurcation be an early event in epileptogenesis? This investigaiton proposes to continue both theoretical and experimental investigations of bifurcations in neural behavior. A continued emphasis will be placed on theoretical work. However, the experimental work that has been initiated will continue and become increasingly important. A number of mathematical models of cellular processes display irregular behavior that qualitatively appears to be chaotic. A quantitative assessment of the models using the techniques of dynamical analysis (correlation dimension, Lyapounov exponents, Kolmogorov entropy) will be completed. Our preliminary studies of single unit recordings produced results that are consistent with chaotic behavior. However, the accuracy of these feasibility studies makes a conclusive characterization impossible. We propose to continue these studies using a more accurate experimental technique. A penicillin-induced acute epileptogenic focus will provide a means of investigating possible relationships between bifurcations and epileptogenic activity. In addition to measures of neural behavior derived from dynamical systems theory, we will include a battery of conventional neurophysiological analysis procedures. Correlations between these techniques will be investigated.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS019716-05
Application #
3399818
Study Section
(SSS)
Project Start
1983-07-01
Project End
1989-09-30
Budget Start
1988-04-01
Budget End
1989-09-30
Support Year
5
Fiscal Year
1988
Total Cost
Indirect Cost
Name
Allegheny University of Health Sciences
Department
Type
Schools of Medicine
DUNS #
City
Philadelphia
State
PA
Country
United States
Zip Code
19129
Rapp, P E; Schmah, T (1996) Complexity measures in molecular psychiatry. Mol Psychiatry 1:408-16
Theiler, J; Rapp, P E (1996) Re-examination of the evidence for low-dimensional, nonlinear structure in the human electroencephalogram. Electroencephalogr Clin Neurophysiol 98:213-22
Rapp, P E (1994) A guide to dynamical analysis. Integr Physiol Behav Sci 29:311-27
Farwell, L A; Martinerie, J M; Bashore, T R et al. (1993) Optimal digital filters for long-latency components of the event-related brain potential. Psychophysiology 30:306-15
Rapp, P E; Bashore, T R; Martinerie, J M et al. (1989) Dynamics of brain electrical activity. Brain Topogr 2:99-118
Zimmerman, I D; Rapp, P E (1989) Saltatory transitions are a naturally occurring property of evolving systems. Biol Cybern 62:167-75
Rapp, P E; Latta, R A; Mees, A I (1988) Parameter-dependent transitions and the optimal control of dynamical diseases. Bull Math Biol 50:227-53
Rapp, P E (1987) Why are so many biological systems periodic? Prog Neurobiol 29:261-73
Rapp, P E (1985) Communication and control in reproduction: the ubiquity of periodic phenomena. Biol Reprod 32:70-2