title: Neural and vascular responses to fused binocular stimuli: a VEP and fNIRS study.
abstract: OBJECTIVE
  The aim of our study was to investigate the correlation between neural and hemodynamic responses to stereoscopic stimuli recorded over visual cortex.
  
  
  METHODS
  Test stimuli consisted of a static checkerboard (checks) and dichoptic static random dot (RD) presentations with no binocular disparity (ZD) or with horizontal disparity (HD). Hemodynamic responses were recorded from right and left occipital sites using functional near-infrared spectroscopy (fNIRS). Visual evoked potentials (VEPs) were recorded over three occipital sites to the onset of the same stimuli.
  
  
  RESULTS
  Early components, N1 and P2, were sensitive to HD, suggesting that an enhanced N1-reduced P2 complex could be an indicator of binocular disparity and stereopsis. VEPs to checks and ZD stimulation were similar. fNIRS recordings showed changes in hemodynamic activation from baseline levels in response to all stimuli. In general, HD elicited a larger vascular response than ZD. Oxyhemoglobin concentration (HbO) was correlated with the VEP amplitude during the checks and HD presentations.
  
  
  CONCLUSIONS
  We report an association between neural and hemodynamic activation in response to checks and HD. In addition, the results suggested that N1-P2 complex in the VEP could be a neural marker for stereopsis and fNIRS demonstrated differences in HbO. Specifically, checks and HD elicited larger hemodynamic responses than random dot patterns without binocular disparity.
authors.affiliation: Glasgow Caledonian University, Vision Sciences, Department of Life Sciences, Glasgow, United Kingdom. swijea11@gcal.ac.uk
authors.forename: Sobanawartiny
authors.initials: S
authors.lastname: Wijeakumar
authors.forename: Uma
authors.initials: U
authors.lastname: Shahani
authors.forename: Daphne L
authors.initials: DL
authors.lastname: McCulloch
authors.forename: William A
authors.initials: WA
authors.lastname: Simpson
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008297:Male; D010108:Oxyhemoglobins / Q000378:metabolism; D010775:Photic Stimulation / Q000379:methods; D019265:Spectroscopy, Near-Infrared / Q000379:methods; D015357:Vision Disparity / Q000502:physiology; D015348:Vision, Binocular / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology*; D055815:Young Adult
chemical_list: D010108:Oxyhemoglobins