Behavioral transitions modulate hippocampal electroencephalogram correlates of open field behavior in the rat: support for a sensorimotor function of hippocampal rhythmical synchronous activity.

A clear relationship exists between moment-to-moment behavioral elements and hippocampal rhythmical synchronous activity (RSA) (theta rhythm). However, behavioral elements are not isolated events but are part of behavioral sequences in a context of behavioral activity. By concurrently monitoring open field behavior and hippocampal EEG, EEG correlates of open field behavior in relation to preceding and following behavior were studied in Sprague Dawley rats to determine whether the behavioral context influences EEG correlates of behavior. Results show that preceding and subsequent behavioral patterns influenced the spectral power correlates of behavior. RSA power was increased when a "type 1 behavior" (voluntary movement) preceded the behavior compared with when a "type 2 behavior" (automatic movement, awake immobility) preceded it. The modulating effect of behavioral transitions was shown for several types of behaviors, and systematic modulation of hippocampal EEG correlates of behavior was demonstrated. The present report shows that the strong and systematic relationship between hippocampal RSA and behavior is modulated by the behavioral-sequential context. Thus, in addition to the well established relationship between RSA and motor activity, a second nonmotor process seems to contribute to hippocampal RSA. A likely candidate is a sensory process, which is in accordance with theories on the sensorimotor function of hippocampal RSA.