superior colliculus(redirected from anterior quadrigeminal body)
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the paired, larger, rounded anterior eminence of the laminae of mesencephalic tectum; major afferent connections of the superficial layers are the retina and striate cortex; input to deep layers of the colliculus are polymodal. Its efferent connections are with the lower brainstem and spinal cord (tectobulbar tract and tectospinal tract) and with the pulvinar and other cell groups in the caudal part of the thalamus; it participates in the extrageniculate visual pathway. The layers of the superior colliculus from superficial to deep are: zonal layer (stratum zonale), superficial gray layer (stratum griseum superficial), optic layer (stratum opticum), intermediate gray layer (stratum griseum intermedium), intermediate white layer (stratum medullare intermedium), deep gray layer (stratum griseum profundum), and deep white layer (stratum medullare profundum).
Visual field loss in a quarter of the visual field of the eye. The defect is usually bilateral, as it is caused by a lesion past the optic chiasma. It may be homonymous (binasal, bitemporal, upper or lower), crossed (one upper and the other lower), congruous (equal size of the defects), or incongruous (unequal size of the defects) (Fig. Q1). Syn. quadrantanopsia; quadrantic anopsia; quadrantic hemianopia. See hemianopia.