Unit activity of the medial wall of the rat prefrontal cortex was studied during delayed response in the U-shaped maze. Prefrontal units were shown to be polysensory. Rhythmical stimulation induced habituation of unit responses. Spatio-selective neurones were found which means that medial part of the prefrontal area is involved in short-term memory. The role of the area is discussed in relation to the goal-directed behaviour.