The Course of D I R E C T Projections from the Abducens Nucleus to the C

It seems clear, both from pathological material in humans t°,15 and experiments in monkeysS, 34, that the median longitudinal fasciculus (MLF) carries a stimulus to the medial rectus subnucleus of the oculomotor complex to effect the adductive portion of lateral gaze. The importance of this pathway was emphasized by Shanzer et al. 34, who showed that section of the MLF of the monkey blocked adduction to stimuli from the ipsilateral frontal cortex, ipsilateral fields of Forel or contralateral paramedian pontine reticular formation (PPRF). The essential nature of the ipsilateral paramedian pontine reticular formation in the generation of lateral gaze has had broad support for some time4, 27. This concept has been developed by others, who have contributed important data using neuroanatomic 2t and physiologic11,lz, z8 techniques showing that the region of the PPRF is indispensible t2 and temporally tightly linked z8 to lateral gaze. The anatomic link between the motor nuclei 0 I I and VI) and the supranuclear control center located in the ipsilateral PPRF has been more elusive. While there is