Multi-channel EEG computer analysis from biofeedback epochs: a tool for studying the brain



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An EEG biofeedback study was performed in the cat to introduce an experimental design appropriate for biofeed-back research. The experiment was also intended to test the feasibility of using EEG biofeedback as a tool for studying interactions of various parts of the brain. The cats were trained to produce 8 Hz and 40 Hz EEG activity in the Center Median nucleus of the medial thalamus using an operant discrimination training paradigm where milk was used as reinforcement. Electrical activity was recorded simultaneously from other brain structures, including frontal cortex, dorsal hippocampus, visual cortex, mesencephalic reticular formation, and basal forebrain. EEG's were recorded on analog magnetic tape for later computer analysis with a sequence of programs written by the author to perform A/D conversion and to compute power, coherence, and phase spectra. Other data analyses were performed on latency to response, discrimination accuracy, and EEG amplitudes. Baseline EEG data consisted of recordings after training the animal to hold still. This holding still requirement was instituted to reduce movement artifact possibilities. Post-training EEG data consisted of recordings of the responses on both 8 Hz and 40 Hz schedules. The segments of data from magnetic tape were selected to obtain that portion of the record which contained the response which provided the animal with reinforcement. Computer analysis indicates that changes are introduced in various power, coherence, and phase spectra as a result of the biofeedback training. The 8 Hz condition appears to be a drowsy or light sleep state, while the 40 Hz condition appears to be an arousal state. The author believes that the techniques applied here with the modifications suggested, could be a very useful tool for studying the brain because it provides the experimenter with a normal preparation for study and with the ability to control that preparation within certain limits.