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Pupillary light reflex circuits in the macaque monkey: the preganglionic Edinger-Westphal nucleus

May, Paul J., Sun, Wensi, Wright, Nicholas F. and Erichsen, Jonathan T. 2020. Pupillary light reflex circuits in the macaque monkey: the preganglionic Edinger-Westphal nucleus. Brain Structure and Function 225 (1) , pp. 403-425. 10.1007/s00429-019-02000-w

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Abstract

The motor outfow for the pupillary light refex originates in the preganglionic motoneuron subdivision of the Edinger– Westphal nucleus (EWpg), which also mediates lens accommodation. Despite their importance for vision, the morphology, ultrastructure and luminance-related inputs of these motoneurons have not been fully described in primates. In macaque monkeys, we labeled EWpg motoneurons from ciliary ganglion and orbital injections. Both approaches indicated preganglionic motoneurons occupy an EWpg organized as a unitary, ipsilateral cell column. When tracers were placed in the pretectal complex, labeled terminals targeted the ipsilateral EWpg and reached contralateral EWpg by crossing both above and below the cerebral aqueduct. They also terminated in the lateral visceral column, a ventrolateral periaqueductal gray region containing neurons projecting to the contralateral pretectum. Combining olivary pretectal and ciliary ganglion injections to determine whether a direct pupillary light refex projection is present revealed a labeled motoneuron subpopulation that displayed close associations with labeled pretectal terminal boutons. Ultrastructurally, this subpopulation received synaptic contacts from labeled pretectal terminals that contained numerous clear spherical vesicles, suggesting excitation, and scattered dense-core vesicles, suggesting peptidergic co-transmitters. A variety of axon terminal classes, some of which may serve the near response, synapsed on preganglionic motoneurons. Quantitative analysis indicated that pupillary motoneurons receive more inhibitory inputs than lens motoneurons. To summarize, the pupillary light refex circuit utilizes a monosynaptic, excitatory, bilateral pretectal projection to a distinct subpopulation of EWpg motoneurons. Furthermore, the interconnections between the lateral visceral column and olivary pretectal nucleus may provide pretectal cells with bilateral retinal felds.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Optometry and Vision Sciences
Additional Information: his article is licensed under a Creative Commons Attribution 4.0 International License
Publisher: Springer
ISSN: 1863-2653
Date of First Compliant Deposit: 14 May 2021
Date of Acceptance: 28 November 2019
Last Modified: 21 May 2021 11:00
URI: https://orca.cardiff.ac.uk/id/eprint/141323

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