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Kabilan Pitchaimuthu, Bao Nguyen, Allison McKendrick; Foveal centre surround contrast suppression reveals differential effect of ageing on binocular and interocular suppression . Journal of Vision 2016;16(12):783. doi: 10.1167/16.12.783.
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© ARVO (1962-2015); The Authors (2016-present)
Healthy ageing alters foveal surround suppression of apparent contrast (FSSAC). The neural basis of FSSAC is considered to reflect several V1 neuronal receptive field properties. Primate V1 neurons have distinct transient/sustained (Bair et al, 2003) and early/late (Webb et al, 2005) surround suppression mechanisms. Here, we tested whether similar properties are manifest for FSSAC and if so, are they altered by ageing? We measured the apparent contrast of a centre circular vertically oriented sinusoid (20% contrast, 4c/deg) alone or in the presence of an annular sinusoidal surround (40% contrast, 4c/deg) present foveally. Nineteen younger (aged 19-32) and 19 older (aged 61-78) adults were tested under two viewing conditions (binocular: centre and surround in both eyes; interocular: centre and surround in different eyes), two surround configurations (No/Parallel surround) and two stimulus durations (40ms/200ms). Suppression strength was calculated as Apparent ContrastNo Surround — Apparent ContrastParallel Surround. In both groups, using binocular viewing, stimulus durations of 40ms produced stronger suppression than 200ms, however, both stimulus durations produced similar amounts of suppression interocularly (stimulus duration X viewing condition: F(1,36)=7.19,P=0.01). This suggests that binocular FSSAC has increased surround adaptation for longer duration stimuli, but not the interocular FSSAC. For both stimulus durations, older adults showed increased binocular suppression relative to the younger group, however, interocular suppression was similar (age X viewing condition: F(1,36)=7.94,P< 0.01, age X stimulus duration: F(1,36)=0.04,P=0.84). Our data suggests that ageing alters surround suppression at a processing stage before binocular combination of visual signals, either prior to or including the input layers of V1.
Meeting abstract presented at VSS 2016
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