STATE-DEPENDENT ASPECTS OF COGNITION

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Such cognitive functions as perception, memory and orientation change markedly when we first fall asleep and then change even more dramatically when we begin to dream. Proceeding from the philosophical assumption that the brain-mind is an integrated system, we believe that state-dependent aspects of cognition may best be understood in terms of the now well- documented changes in brain state that differentiate waking, non-REM (NREM) and REM sleep. Our basic concept is that the state-dependent changes In cognition may be related to the shift in the balance of brainstem neuromodulatory system - a shift from aminergic dominance in waking to cholinergic dominance in REM sleep. We plan to study the effect of this modulatory shift by analyzing cognitive functioning in the immediate post-awakening period, when the brain still evinces characteristics of the preceding sleep state. We propose a series of studies designed to better characterize and model the state-dependent nature of both behavioral and subjective aspects of cognition. We will measure state-dependent aspects of performance on two behavioral tests: semantic priming which measures associative memory and perceptual cuing which measures the orienting of attention. We have shown that both are sensitive to changes in brain-mind state. Building on previous observations documenting the discontinuities of the subjects' orientation to time, place and person during dreaming, we plan to quantify the intensity of orientational instability using a new approach based on graph theory. We will also explore the validity of the concept of dream plot coherence using a novel "spliced dream" technique. One unique feature of the proposed research is the longitudinal, repeated measures design which has an extended home-based data collection segment interposed between standard laboratory assessments. To achieve this goal, we will use a newly developed state assessment technique, called the "Nightcap," along with a portable computer-based cognition assessment system. Because we will be able to collect data in a home setting, we expect to eliminate many of the disadvantages of standard sleep laboratory experimentation, and obtain more reliably naturalistic data.