NONSTANDARD MODELS FOR STUDY OF COGNITIVE ERPS

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DESCRIPTION (Investigator's Abstract): Certain brain potentials can be seen or averaged out of the brain waves, time-locked to events which in humans are associated with a thought, a question, an expectation met or not met. a surprise or-a recognition; these will be called cognitive event-related potentials (ERPs). The long- term objective is to understand these relatively high level Ems in the light of comparative studies and evolution. The specific aims are to find such ElRPs in selected species of non- mammalian vertebrates (elasmobranchs, bony fish) and invertebrates (crustaceans and cephalopods), using various stimulus paradigms adapted to them, to determine their dynamic properties with permutations of the temporal patterns of rare and common stimuli of greater or lesser ethological valence, to estimate the dependence on exogenous variables (physical aspects of stimuli) vs endogenous factors (brain state variables), and-to discover the brain regions involved. The research design is to employ multiple electrodes on and in the brain in behaving subjects, wideband amplifiers to record both spike and low wave activity, single sweep and averaged sweep display, and old and new methods of analysis of data. The latter includes, firstly, distribution of coherence between all possible pairs of loci, in space and time, at new levels of resolution, millimeters and fractions of a second. Secondly, the higher moments of nonlinear cooperativity will be measured by computing the bispectrum and bicoherence, revealing quadratic phase coupling between frequency components both within the same channel and between channels.