Brain-stem and cortical interactions in the interhemispheric delayed response.

Acute experiments on cats under chloralose anesthesia were designed to study the role of the brain stem in the transmission of the interhemispheric delayed response (IDR). Experiments on interaction of potentials recorded in brain stem and at cortex led to the conclusion that the IDR is relayed to the contra-lateral hemisphere via routes which pass through the general area of the mesencephalic reticular formation. Other brain-stem areas, not directly in the pathway, also have access to the cortical fields discharging the IDR. During passage through the mesencephalon and elaboration at the cortex the IDR comes under the influence of afferent activity. To a more or less considerable extent, depending on the time relationships, this interaction is reciprocal. Characteristics of the IDR were investigated and the findings confirmed in preparations with brains radically split longitudinally in the mid-line. An integrative function based upon cortical-brain-stem-cortical and afferent activity is suggested for the IDR system.