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Medical Definition of Gray layer of superior colliculus
1. Term applied to any one of the three major layers of gray matter of the superior colliculus that alternate with layers composed chiefly of nerve fibres: 1) the superficial gray layer of superior colliculus, above the largely white layer of the incoming fibres of the optic tract (optic layer); 2) the middle gray layer of superior colliculus, placed between the optic layer and a more deeply located layer of fibres, the stratum lemnisci; 3) the deep gray layer of superior colliculus, between the stratum lemnisci and the central gray substance surrounding the cerebral aqueduct, and containing the large nerve cells from which most of the colliculus descending connections (tectobulbar, tectopontine, and tectospinal tract) originate. Synonym: stratum griseum colliculi superioris, stratum cinereum colliculi superioris. (05 Mar 2000)