Afferent fibers and sensory ganglion cells within the oculomotor nerve in some mammals and man. II. Electrophysiological investigations.

The main aim of the present study was to localize with electrophysiological techniques the central projections and terminations of the aberrant trigeminal fibres contained in the oculomotor nerve of the lamb. After severing a trigeminal root, single-shock electrical stimulation of the trigeminal axons present in the central stump of the ipsilateral oculomotor nerve evoked field potentials in the area of, i) the subnucleus gelatinosus of the nucleus caudalis trigemini at the level of C1-C2; ii) the main sensory trigeminal nucleus; iii) the descending trigeminal nucleus and tract; iv) the adjacent reticular formation. Units whose discharge rate was influenced by such a stimulation were also found in the same territories. These regions actually exhibited degenerations after cutting an oculomotor nerve. We conclude, therefore, that the trigeminal fibres which leave the Vth nerve at the level of the cavernous sinus and enter the brain stem through the IIIrd nerve, end in the same structures which receive the terminations of the afferent fibres entering the brain stem through the sensory trigeminal root.