title: Superior colliculi involvement in poststroke unilateral spatial neglect: a pilot study.
abstract: OBJECTIVE
  The neural mechanisms underlying unilateral spatial neglect (USN) are unclear. The superior colliculi (SC) may be involved in USN expression, and the spatial summation effect (SSE), where reaction times to bilateral stimuli are faster than to unilateral, may be a behavioral index of SC function. We determined the feasibility of investigating SC contribution to poststroke USN using the SSE in 3 groups.
  
  
  METHODS
  Seven participants with left near-extrapersonal space USN (USN+) following right hemisphere stroke, 10 without (USN-), and 10 controls were tested under binocular/monocular (right eye patched) conditions while responding to unilateral/bilateral stimuli. Control and USN- groups completed the SSE paradigm.
  
  
  RESULTS
  Most USN+ participants were unable to initiate the SSE paradigm due to poor visual fi xation and demonstrated higher contrast sensitivity for left-sided stimuli. Controls showed an SSE (under both viewing conditions) while the USN- showed an abnormal SSE whereby reaction times to bilateral stimuli were faster than to unilateral-left but not to unilateral-right stimuli (under both binocular/monocular conditions).
  
  
  CONCLUSIONS
  This study is the fi rst to investigate SC contribution in poststroke USN using the SSE; we identifi ed higher contrast sensitivity to left-sided stimuli and poor fi xation in the USN+ group. These fi ndings suggest avenues for research that may lead to novel rehabilitation interventions.
authors.affiliation: School of Physical and Occupational Therapy, McGill University, Montreal, Quebec, Canada.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Ogourtsova
authors.forename: Nicol
authors.initials: N
authors.lastname: Korner-Bitensky
authors.forename: Sandra E
authors.initials: SE
authors.lastname: Leh
authors.forename: Gail
authors.initials: G
authors.lastname: Eskes
authors.forename: Alain
authors.initials: A
authors.lastname: Ptito
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015350:Contrast Sensitivity; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010468:Perceptual Disorders / Q000209:etiology / Q000473:pathology*; D010775:Photic Stimulation; D010865:Pilot Projects; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time; D013028:Space Perception / Q000502:physiology*; D020521:Stroke / Q000150:complications; D013477:Superior Colliculi / Q000503:physiopathology*