Characterization of pretectal-nuclear-complex afferents to the pulvinar in the cat |
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Authors: | Schmidt M Sudkamp S Wahle P |
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Institution: | Allgemeine Zoologie and Neurobiologie, Ruhr-Universit?t Bochum, Germany. mschmidt@neurobiologie.ruhr-uni-bochum.de |
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Abstract: | We investigated anatomical and physiological properties of the projection from the pretectal nuclear complex (PNC) to the
ipsilateral lateral posterior–pulvinar complex in the cat. After Phaseolus vulgaris leucoagglutinin injections into the PNC, the majority (70%) of anterogradely labeled terminals was localized in the pulvinar
proper, the remaining 30% were scattered in the lateral and medial portions of the LP. No PNC neuron retrogradely labeled
from the pulvinar was found to also express glutamic acid decarboxylase (GAD) mRNA, although a large number of neurons carrying
the GAD label were found in close vicinity. In contrast, 69% of retrogradely labeled PNC cells also displayed glutamate-like
immunoreactivity. Twenty-six out of 96 (27%) visually responsive pulvinar neurons were orthodromically activated by electrical
stimulation of the ipsilateral PNC at latencies between 1 and 10 ms (median 1.9 ms). All orthodromically activated neurons
responded well to the onset and offset of large visual stimuli and to sudden stimulus shifts. Whenever a saccadic eye movement
was executed, these neurons were also activated, except during saccades in darkness. The comparison of saccade-evoked response
with responses to visual stimuli that elicit similar retinal image shifts revealed that pretectorecipient pulvinar neurons
also seem to receive a saccade-related non-visual input. All response properties correspond to those of a specific class of
pulvinar neurons that have been termed "SV" neurons because they respond to visual stimulation as well as during saccades.
They also closely resemble response properties of PNC neurons that project to the ipsilateral pulvinar. The results support
the proposal that PNC cells not only directly activate their postsynaptic target neurons in the pulvinar, but that they also
provide a visual input to these neurons that greatly contributes to their response characteristics.
Electronic Publication |
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Keywords: | Extrageniculate visual thalamus Pretectal nuclear complex Saccadic eye movements Visuomotor integration |
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