Disturbances in sleep-waking pattern and cortical desynchronization after lateral hypothalamic damage: effect of the size of the lesion.

The effect of electrolytic lesions of varying size within the anterior part of the lateral hypothalamus (LH) on neocortical activity and quantitative sleep-waking relations was studied in male Wistar rats. It was found that extensive LH lesions caused simultaneously an abolishment of cortical desynchronizing reactions and an electroencephalographic insomnia. More restricted damage left the qualitative pattern of cortical EEG unchanged, but still produced substantial reduction in the amount of sleep. Pronounced EEG disturbances coexisted with relatively mild behavioral deficits. It is concluded that a constellation of the LH syndrome symptoms is critically dependent on the variations of lesion parameters.