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Konogan BARANTON, Thien Huong NGUYEN, Jean - Louis STIEVENART, Céline CAVEZIAN, Guillaume GIRAUDET; Brain of myopes dealing with blur. Journal of Vision 2013;13(9):503. doi: 10.1167/13.9.503.
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© ARVO (1962-2015); The Authors (2016-present)
Myopes and emmetropes present behavioural differences in presence of blur, whether in detection, tolerance and performance (Rosenfield and Abraham-Cohen, 1999). The purpose of our study was to compare the cortical response in myopes and in emmetropes when exposed to altered image resolution.
We explored 38 young adults aged from 18 to 35 years including 18 emmetropes and 20 corrected myopes through functional M.R.I. at 3 Tesla. Cortical response was registered while subjects observed boards of optotypes, made of isolated Sloan letters. We add a simulated blur of 2 diopters (3.5 cycle/deg cut-off) for at least 12 second, and then images became progressively sharp. To maintain subject’s attention, the task was to detect changes in blurriness. Reaction time was recorded. Data were analysed with SPM8 package. Functional series were coregistered with anatomic data acquisition, realigned, time corrected and normalized onto MNI. At group level, a random effect was performed using an individual t-contrast (p <0.001 uncorrected).
Behavioural data showed a quicker reaction for myopes than emmetropes (849ms vs. 1087ms, p=0.024). Global results showed similar responses in emmetropes and myopes in dorsal and ventral path with a predominance of the right hemisphere. Statistical comparison showed mild but significant differences between the two groups, the myopes presenting more activation in right middle temporal (BA21, 12 voxels, F=10.11), left putamen (5 voxels, F=8.57), right caudate nucleus (5 voxels, F=8.51) and right superior frontal area (5 voxels, F=8.09) when compared to emmetropes.
The predominance of right hemisphere might be linked with a specialisation for low spatial frequencies (Peyrin et al., 2010). Differences between two groups suggest a cortical adaptation in myopes in accordance with a fastest detection of blur variation, recruiting supplementary areas distant from occipital lobe to enhance altered image perception.
Meeting abstract presented at VSS 2013
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