Disinhibition of the superior colliculus restores orienting to visual stimuli in the hemianopic field of the cat

Following unilateral removal of all known visual cortical areas, a cat is rendered hemianopic in the contralateral visual field. Visual orientation can be restored to the blind hemifield by transection of the commissure of the superior colliculus or by destruction of the superior colliculus (SC) or...

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Bibliographic Details
Published in:Journal of comparative neurology (1911) 1997-11, Vol.387 (4), p.568-587
Main Authors: Ciaramitaro, Vivian M., Todd, Wendy E., Rosenquist, Alan C.
Format: Article
Language:English
Subjects:
Animals
Behavior, Animal - physiology
Bicuculline - analogs & derivatives
Bicuculline - pharmacology
Cats - physiology
cortical lesion
Functional Laterality - physiology
GABA Antagonists - pharmacology
gamma-aminobutyric
Injections
Male
neglect
Neural Inhibition - drug effects
Neural Inhibition - physiology
Orientation - physiology
Photic Stimulation
Remission Induction
sensorimotor integration
Superior Colliculi - drug effects
Superior Colliculi - pathology
Superior Colliculi - physiopathology
Vision Disorders - pathology
Vision Disorders - physiopathology
Visual Cortex - pathology
Visual Fields - physiology
visual orienting
Citations: Items that this one cites
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Summary:Following unilateral removal of all known visual cortical areas, a cat is rendered hemianopic in the contralateral visual field. Visual orientation can be restored to the blind hemifield by transection of the commissure of the superior colliculus or by destruction of the superior colliculus (SC) or the substantia nigra pars reticulata (SNpr) contralateral to the cortical lesion. It is hypothesized that a mechanism mediating recovery is disinhibition of the SC ipsilateral to the cortical lesion. The ipsilateral nigrotectal projection exerts a robust inhibitory tone onto cells in the SC. However, ibotenic acid destruction of SNpr neurons, which should decrease inhibition onto the SC, does not result in recovery. The failure of ipsilateral SNpr lesions to produce recovery puts into question the validity of SC disinhibition as a mechanism of recovery. We directly tested the disinhibition hypothesis by reversibly disinhibiting the SC ipsilateral to a visual cortical lesion with a gamma‐aminobutyric acid (GABA)A antagonist, bicuculline methiodide. In accordance with the hypothesis, transient disinhibition of the SC restored visual orienting for several hours in three of eight animals. Recovery was not a volume or pH effect and was distinct from the release of irrepressible motor effects (i.e., approach and avoidance behaviors) seen within the first hour after injection. Thus, in the absence of all visual cortical areas unilaterally, disinhibition of the SC can transiently restore the ability of the cat to orient to visual stimuli in the previously “blind” hemifield. J. Comp. Neurol. 387:568–587, 1997. © 1997 Wiley‐Liss, Inc.
ISSN:0021-9967
1096-9861
DOI:10.1002/(SICI)1096-9861(19971103)387:4<568::AID-CNE7>3.0.CO;2-0