The organization of motivation at the thalamic level of the cat

Abstract Three different behavioral tests in combination with recording of the electrical activities of different parts of the brain have been used to study the motivational effects elicited from different parts of the nonspecific thalamic system by electrical stimulation. Stimulation of the anterior region (anterior and dorsomedial group of nuclei) produced different forms of arrest reactions sometimes mixed with phasic movements and exerted a suppressing effect on conditional reflexes. In the case of low frequency stimulation a strict correlation was found between the suppressing effect and a late surface negative wave in the neocortical leads. In the case of high frequency stimulation a correlation between the hemispherical localization of high amplitude slow wave spindles and the direction of movements was obtained. In striking contrast to the anterior thalamus stimulation of the posterior thalamic (including the pretectal) region produced marked activating effects in a conditional environment. Self-stimulation could only be obtained from the anterior region. The effects are interpreted as the result of interactions of an internal negative feed-back and reciprocal inhibitory mechanisms showing increasing complexities as one ascends in a caudo-anterior direction through the thalamic nonspecific system.