Neural activity of nucleus reticularis tegmenti pontis--the origin of visual mossy fiber afferents to the cerebellar flocculus of rabbits.

Activities of 55 neurons were extra- and intracellularly recorded in the nucleus reticularis tegmenti pontis (Nrt) of anesthetized rabbits. The cells were antidromically activated from the flocculus as well as orthodromically from the optic tracts. They were antidromically activated from either the ipsilateral or contralateral flocculus (latency, 0.94 msec) but not from the flocculi on both sides. There was no preference for projection to either the ipsilateral or contralateral flocculus. Twenty out of 55 neurons were orthodromically activated from the ipsilateral and 15 neurons from the contralateral optic tract. The remaining 20 neurons were excited from the optic tract on both sides. The orthodromic latencies were all in the same range with a mean of 4.7 msec. These findings demonstrate the existence of neurons in the Nrt that transfer visual signals to the flocculus through mossy fiber afferents. They indicate that Nrt neurons may contribute to controlling eye movements through the flocculus.