[Electrical activity of the hippocampus during instrumental choice]

The power of theta-, delta-, alpha-, beta-low rhythms of the dorsal hippocampus telemetrically recorded was studied on four dogs after 24 and 48-hours water or food deprivation, after satisfaction of thirst and hunger as well as in choice between two different reinforcements (dried crust, water). A direct dependence between the strength of motivational state and the power of theta-rhythm has been found. In animals' behaviour two regimes of activity were singled out: stationary regime and transitory one. In the stationary regime, repetition of similar behavioural acts was attended by gradual increase in the power of theta-rhythm in the intervals between the signals. In case of changes from one behavioural form to the other (transitory regime) a selective sharp decline in the theta-rhythm power was observed.