| Nonlinear Dynamics, Psychology, and Life Sciences, Vol. 6, Iss. 4, Oct, 2002, pp. 323-334 @2002 Society for Chaos Theory in Psychology & Life Sciences Temporal Dynamics of Brain Activity in Human Memory Processes Abstract: We propose a line of study by which Functional Magnetic Resonance Imaging (FMRI) can be used together with nonlinear dynamics concepts as a medium for the study of brain organization. The concentration is on (a) the complex behavior of elementary neural circuits, and how they interact over brief spans of time to produce cognition and memory; and (b) the change in circuit patterns associated with aging. The method of orbital decomposition appears to be ideally suited for these objectives and for determining how they integrate into hierarchical processes. The adapted procedure begins with a 3-DFMRImatrix of metabolic activity. Recurring patterns within a matrix roware identified and matched across rows and across depth slices. These hierarchical patterns are then compared over time for further recurrences. The computational procedure identifies the optimal pattern length over time, the patterns, and the largest Lyapunov for the system of patterns. Computations are assisted by statistical tests for the extent to which the isolated patterns represent the underlying data. Keywords: FMRI, neural circuit, memory, topological entropy, Lyapunov exponent, symbolic dynamics |