The projection from the nucleus reticularis tegmenti pontis to the cerebellum in the rhesus monkey

SummaryFollowing injections of horseradish peroxidase in various parts of the monkey cerebellum, the distribution of labelled cells in the nucleus reticularis tegmenti pontis (NRT) has been studied. As a rule, labelled cells are found at all rostrocaudal levels of the NRT regardless of the injection size and site. The densest projection from NRT seems to reach the vermal visual area (lobulus VII), a less dense projection supplies the anterior lobe while the paramedian lobule receives a more sparse projection than the anterior lobe. Very few labelled cells were found in the NRT after injections of crus I and II. The projection is topographically organized so that the dorsomedial part of the NRT supplies lobulus VII, a large central region sends fibres to the anterior lobe (and the cerebellar hemispheres), while the lateral extension of NRT (processus tegmentosus lateralis) is connected with the paramedian lobule.The results of the present study are compared with those of a preceding one of cortical afferents to NRT. It is concluded that the cortical areas projecting to the NRT seem likely to exert their influences on largely different parts of the cerebellum via the NRT. The present results are also discussed inrelation to termination of other afferent contingents in the NRT, and it is concluded that the NRT is not homogenous anatomically, and consequently different parts of the nucleus would be expected to play somewhat different functional roles.

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