Subcortical modulation of spatial attention including evidence that the Sprague effect extends to man

The Sprague effect is well-established–small tectal lesions restore visual orientation in the hemianopic field of animals with extensive unilateral geniculo-striate lesions. Studies of human midbrain visual functions are rare. This man with a midbrain tumour developed left-neglect through subsequent right frontal damage. Bilateral orientation returned after clear evidence of damage to the superior colliculus contralateral to the cortical lesion (showing the Sprague effect extends to man). Sustained right-neglect developed after probable additional damage to right superior colliculus. The regulation of spatial attention by tecto-pulvinar circuits is discussed, and it is argued that the reduced right tecto-pulvinar activity (consequent to the additional right collicular damage) was offset by over-compensatory increase in thalamic reticular nucleus (TRN) suppression of left pulvinar activity.