Medicine:Sprague effect

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The Sprague effect is the phenomenon where homonymous hemianopia, caused by damage to the visual cortex, gets slightly better when the contralesional superior colliculus is destroyed.[1][2] The effect is named for its discoverer, James Sprague, who observed this phenomenon in 1966 using a cat model.[3] Several reasons have been thought of for this happening, including mutual inhibition between the two brain hemispheres.[4] For similar reasons of inhibiting an inhibitory structure, damaging the substantia nigra, for instance by using ibotenic acid, can also cause the same improvement.[5]


  1. Weddell, Rodger A. (August 2004). "Subcortical modulation of spatial attention including evidence that the Sprague effect extends to man". Brain and Cognition 55 (3): 497–506. doi:10.1016/j.bandc.2004.02.075. PMID 15223196. 
  2. Lomber, Stephen G.; Malhotra, Shveta; Sprague, James M. (2007-02-01). "Restoration of Acoustic Orienting Into a Cortically Deaf Hemifield by Reversible Deactivation of the Contralesional Superior Colliculus: The Acoustic "Sprague Effect"". Journal of Neurophysiology (United States: Journal of Applied Physiology) 97 (2): 979–993. doi:10.1152/jn.00767.2006. PMID 17151228. 
  3. Sprague, James M. (1966-09-23). "Interaction of Cortex and Superior Colliculus in Mediation of Visually Guided Behavior in the Cat" (in en). Science 153 (3743): 1544–1547. doi:10.1126/science.153.3743.1544. PMID 5917786. 
  4. Hilgetag, Claus C. (2000-06-01). "Spatial neglect and paradoxical lesion effects in the cat — A model based on midbrain connectivity". Neurocomputing (ScienceDirect) 32-33: 793–799. doi:10.1016/S0925-2312(00)00246-0. 
  5. Wallace, Steven F.; Rosenquist, Alan C.; Sprague, James M. (1990). "Ibotenic acid lesions of the lateral substantia nigra restore visual orientation behavior in the hemianopic cat" (in en). The Journal of Comparative Neurology (Wiley-Blackwell) 296 (2): 222–252. doi:10.1002/cne.902960204.