Far field somatosensory evoked potentials in the cat.

Averaged somatosensory evoked potentials (SEP) after forepaw stimulation were recorded from skull electrodes in the cat. The cortical component of the SEP was preceded by four far-field potentials (Component I, II, III, IV). A study of these components suggests that: (1) Component I originates in the cervical spinal cord; (2) Component II is generated in the nucleus cuneatus and/or medial lemniscus; (3) Component III-A recorded widely over the skull probably reflects activity in the cerebellum and/or cerebellar pathways; (4) Component III-B seen over the somato-sensory area results from superposition of component III-A and activity in the ventral posterior nucleus of the thalamus and (5) Component IV orginates in the sensory radiation with some contribution from the thalamus.