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Specific Synonyms
Published in Terence R. Anthoney, Neuroanatomy and the Neurologic Exam, 2017
Pretectal area3 (C&S, p. 499 [Fig. 15–5]) Pretectal region1 (C&S, p. 424)Pretectum (ibid.)Kuhlenbeck and Miller (1949), however, recommended differentiating between “pretectal area” and “pretectal region” (see p. 393 of their article for details). See, also, D: Pretectal area.
ENTRIES A–Z
Published in Philip Winn, Dictionary of Biological Psychology, 2003
A GANGLION of the AUTO NOMIC NERVOUS SYSTEM: it has input from preganglionic neurons in the EDINGER-WESTPHAL NUCLEUS (via the OCULOMOTOR NERVE). The ciliary ganglion sends out fibres (the axons of postganglionic neurons) that innervate and control the muscles of the pupil of the eye. See also: cranial nerves; pretectum
Parallel Visual Pathways in a Dynamic System
Published in Jon H. Kaas, Christine E. Collins, The Primate Visual System, 2003
Vivien A. Casagrande, David W. Royal
If saccadic suppression does occur in LGN cells, what is the circuit responsible for the suppression? Intracellular recordings in rabbits87 helped identify and outline a potential circuit responsible for saccadic suppression in the LGN. This circuit involves a projection from the deep layers of the superior colliculus (SC) to thalamic reticular nucleus (TRN) via the central lateral (CL) nucleus of the thalamus. Furthermore, the overall time course of activation in the SC and suppression in the LGN fits with the time course of saccadic suppression. There are many other pathways that could provide for such suppression. The superior colliculus provides direct input to the LGN but only from the superficial layers that project, in primates, primarily to the K layers69 of the LGN. Thus far, however, too few K cells have been examined to determine if their responses to eye movements differ from the responses of P or M cells (Reference 85 and unpublished results). Other possible input sources include the midbrain reticular formation, pontine cholinergic cells, and the pretectum (see Reference 67). Regarding the pretectogeniculate pathway Schmidt88 has shown that pretectogeniculate cells are excited during saccades. Schmidt and colleagues8889× have argued that pretectogeniculate cells inhibit LGN interneurons, thus causing excita-tion of LGN relay cells. The latter circuit would be entirely appropriate to explain a postsaccadic enhancement of activity given the timing reported. However, others90 have provided evidence in cats that pretectal activity suppresses LGN activity and thus contributes directly to saccadic suppression.
Developing the theory of the extended amygdala with the use of the cupric-silver technique
Published in Journal of the History of the Neurosciences, 2023
Soledad de Olmos, Alfredo Lorenzo
Therefore, de Olmos decided to use his own skills with silver techniques by introducing variations from the Ramon y Cajal technique (Ramon y Cajal 1928). One of the versions he developed revealed the crystal-clear presence of degenerating fibers and terminal boutons in the pretectum two days after the transection of the optic tract. These degenerating fibers and axonal endings were heavily impregnated with dense, black silver grains that distinguished them from the normal argyrophilic elements reported by Knoche (1953, 1958). The characteristic features of these normal granular argyrophilic neurons were the impregnation of fine, dark-brown, dust-like silver grains in the perikaryon, which also extended through their axon and dendrites. Moreover, de Olmos realized that another difference that made his variant useful was that it demonstrated axonal fibers that formed the granular argyrophilic plexus along the medial eminence, the vascular organ of the lamina terminalis and the subfornical organ. None of the aforementioned techniques revealed this. de Olmos presented the advances of this work, titled “Modifications of the Nauta Gygax and Cajal Neurofibrillary Silver Staining Methods for the Study of Terminal Axonal Degeneration,” at a local meeting, with the ensuing article later printed in Spanish in the Neurology Bulletin of Cordoba (de Olmos 1960).
How sandbag-able are concussion sideline assessments? A close look at eye movements to uncover strategies
Published in Brain Injury, 2021
John-Ross Rizzo, Todd E. Hudson, John Martone, Weiwei Dai, Oluchi Ihionu, Yash Chaudhry, Ivan Selesnick, Laura J. Balcer, Steven L. Galetta, Janet C. Rucker
With regards to saccadic frequency, our results reveal that more saccades overall were deployed on sandbag trials compared to best effort trials. A logistic model incorporating these parameters with other eye movement metrics can detect sandbagged trials. The number of saccades for sandbag versus best effort trials yields saccade per object identified ratios of 1.43 and 1.15, respectively. While the latter is consistent with prior reports in healthy individuals (25), the former is grossly elevated. In fact, the numbers of saccades were not only greater in the sandbagged trials, but there was also a larger proportion of saccades made in the direction opposite reading flow. In previous work exploring concussion and the KD with objective eye movement characterization, participants post-concussion used on average 157 saccades to complete the KD test, with a saccade to object identified ratio of 1.31 (36). In concussion, the need for more saccades to complete a given task may stem from saccadic dysmetria and requisite corrective saccades to take gaze close to the targets of visual interest. Hypometria has been described in lesions involving the cortex, thalamus, pretectum, superior colliculus, and cerebellum, while hypermetria typically implicates the cerebellum (37–39). While further studies would allow a better understanding of how frequently these areas are involved in individuals with concussion, either looking off-target intentionally with over-corrections or completing staircase saccades in small increments are both potential avenues for sandbaggers to game their results.
Contrast Acuity and the King-Devick Test in Huntington’s Disease
Published in Neuro-Ophthalmology, 2020
Ali G. Hamedani, Tanya Bardakjian, Laura J. Balcer, Pedro Gonzalez-Alegre
The pupillary light reflex is a polysynaptic reflex arc that involves retinal photoreceptor activation and ganglion cell depolarisation; conduction through the optic nerve, chiasm, and tract; signalling across the pretectum to the Edinger-Westphal nucleus; and pupillary constriction via the third cranial nerve. Consequently, it can be affected by abnormalities at either the afferent or efferent level. In both symptomatic and presymptomatic patients with autosomal dominant Alzheimer’s disease, subtle differences in pupillary light reflex have been identified19, consistent with the cholinergic deficit observed in that disease. We did not observe any differences in pupillary function in HD, which may help to explain why the benefit from cholinesterase inhibitors for cognitive function or chorea in HD has been minimal.32 Because pupillometry was performed under scotopic (dark-adapted) conditions using mixed-wavelength white light, afferent activation was driven primarily by rod photoreceptors, and subtle cone or intrinsically photosensitive retinal ganglion cell dysfunction may not have been captured using this method. Future studies of pupillometry in HD would benefit from both photopic (light-adapted) and scotopic testing at different ranges of light wavelength.