Projections from the superior colliculus motor map to omnipause neurons in monkey

Jean A. Büttner-Ennever, Anja K.E. Horn, V. Henn, B. Cohen

Research output: Contribution to journalArticlepeer-review

101 Scopus citations

Abstract

Descending projections from the superior colliculus (SC) motor map to the saccadic omnipause neurons (OPNs) were examined in monkeys by using anterograde transport of tritiated leucine. The SC was divided into three zones: the rostral pole of the motor map, a small horizontal saccade zone in central SC, and a large horizontal saccade zone in caudal SC. Tracer injections into the intermediate layers of the three zones led to different patterns of silver grain deposits in and around nucleus raphe interpositus (RIP), which contains the OPNs: 1) From the rostral pole of the motor map, coarse axon branches of the crossed predorsal bundle spread medially into the RIP, branched, and terminated predominantly unilaterally over cells on the same side. 2) From the small horizontal saccade zone, the axon branches were of a finer caliber and terminated diffusely in the RIP, mainly on the same side. 3) From the large horizontal saccade zone, no terminal labeling was found within the RIP. 4) From the rostral pole of the motor map and small horizontal saccade zone, fiber branches from the ipsilateral descending pathway terminated diffusely over RIP. 5) In addition, terminal labeling in reticulospinal areas of the pons and medulla increased in parallel with the size of the saccade according to the SC motor map. The results suggest that there are multiple projections directly onto OPNs from the rostral SC but not from the caudal SC associated with large gaze shifts. The efferents from the rostral pole of the motor map may subserve the suppression of saccades during visual fixation, and those from the small horizontal saccade zone could inhibit anatagonist premotor circuits.

Original languageEnglish
Pages (from-to)55-67
Number of pages13
JournalJournal of Comparative Neurology
Volume413
Issue number1
DOIs
StatePublished - 11 Oct 1999
Externally publishedYes

Keywords

  • Gaze fixation
  • Nucleus raphe interpositus
  • Predorsal bundle
  • Rostral pole of the superior colliculus motor map
  • Saccade generator
  • Superior colliculus ipsilateral descending pathway

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