AVA Spring Meeting and AGM, University of Bradford, 26 March 2018

摘要

Binocular Summation: A Meta-Analysis of 65 Studies Daniel H. Baker and Freya A. Lygo Department of Psychology, University of York, York, UK Tim S. Meese and Mark A. Georgeson School of Life and Health Sciences, Aston University, Birmingham, UK Binocular summation is the advantage in contrast sensitivity when using two eyes versus one. It has been widely studied owing to its clinical importance as a measure of binocular function, and because the precise level of summation is determined by the magnitude of nonlinearities in the early visual system, before binocular combination. However, most studies have involved small sample sizes, making exact estimation problematic. We conducted a meta-analysis of 65 studies reporting psychophysical estimates of binocular summation in 716 observers. The lower bound of the 95% confidence interval on the mean summation ratio was consistently above the canonical value of 2 , regardless of how studies were weighted. We further explored how methodological factors affect summation estimates, both by using subsets of the meta-analysis data and also confirming with stand-alone studies. These analyses show that stimulus factors such as spatiotemporal frequency affect summation, and that the imbalance in sensitivity across the eyes can moderate summation estimates. We suggest that there is no single canonical value for binocular summation, but that instead it takes on a range of values between approximately 2 and 2, depending on stimulus properties. In addition, when the two eyes are not balanced, summation estimates are reduced when calculated relative to the threshold of the more sensitive eye, but can be slightly elevated when the mean monocular threshold is used. Future studies can obtain accurate summation estimates by normalising monocular contrasts to account for sensitivity differences or by modelling results using a simple two-parameter model of binocular combination. Ipsilateral Sensitivity to Visual Motion Is Restricted to V5/MT+ in the Right Cerebral Hemisphere Samantha L. Strong School of Optometry and Vision Science, University of Bradford, UK Edward H. Silson National Institute of Mental Health, Bethesda, USA André D. Gouws and Antony B. Morland York Neuroimaging Centre, York, UK Declan J. McKeefry School of Optometry and Vision Science, University of Bradford, UK Previous experiments have demonstrated that transcranial magnetic stimulation (TMS) of human V5/MT+ in the right cerebral hemisphere can induce deficits in visual motion perception in both the contra- and ipsi-lateral visual hemi-fields. However, when TMS is applied to left V5/MT+, motion deficits are restricted to the contra-lateral hemi-field (Thakral and Slotnick, 2011). One possible explanation for this may lie in differential stimulation of sub-divisions within V5/MT+ across the two hemispheres. V5/MT+ has two major sub-divisions: MT/TO-1 and MST/TO-2, and the latter sub-division contains neurons with large receptive fields (RFs) that extend much further into the ipsi-lateral hemi-field (up to 15°) than MT/TO-1. We wanted to re-examine this functional asymmetry between V5/MT+ across both hemispheres by using TMS. MT/TO-1 and MST/TO-2 were identified in six subjects using specialised fMRI localisers, and centre-of-mass co-ordinates were used as target points for the TMS experiment (70% strength; 25?Hz; 200?ms). Subjects identified the translational direction (up/down) of coherently moving dots presented in either the left or the right visual field whilst TMS pulses were applied synchronously with stimulus onset. Application of TMS to MT/TO-1 and MST/TO-2 in the right hemisphere affected ability to perceive direction of translational dots in both the contra-lateral and ipsi-lateral visual fields, whereas detrimental effects following application of TMS to MT/TO-1 and MST/TO-2 in the left hemisphere were restricted to the contra-lateral visual field. This result suggests an enhanced role for the right hemisphere in processing full-field translational motion, but contrary to our hypothesis, effects differ across hemispheres rather than within sub-divisions of V5/MT+. Reference Thakral, P. P., & Slotnick, S. D. (2011). Disruption of MT impairs motion processing. Neuroscience letters , 490 (3), 226–230 . Human S-Cone Electroretinograms Obtained by Silent Substitution Stimulation J. Maguire School of Optometry and Vision Science, University of Bradford, UK N. R. A. Parry School of Optometry and Vision Science, University of Bradford, UK; Vision Science Centre, Manchester Royal Eye Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK; Faculty of Biology, Medicine & Health, University of Manchester, UK J. Kremers School of Optometry and Vision Science, University of Bradford, UK; Department of Ophthalmology, University Hospital Erlangen, Germany I. J. Murray Faculty of Biology, Medicine & Health, University of Manchester, U