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Mark Greenlee, Maka Malania, Maja Traurig, Tina Plank; Effect of perceptual training on neural correlates of radial-tangential anisotropy in visual crowding. Journal of Vision 2018;18(10):757. doi: 10.1167/18.10.757.
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One of the characteristic features of visual crowding is radial-tangential anisotropy, i.e. the crowding area has an ellipsoid shape that is elongated along the radial axis connecting target with the fovea. Kwon et al (2014) explored the neural correlates of this anisotropy in early visual cortex. They found a reduction of BOLD signal in V1 while the target was presented together with radially arranged flankers compared to the condition when only radial flankers were presented. The opposite finding holds for tangentially arranged flankers. There is further evidence (Chung et al., 2010) that the spatial extent of crowding can be altered by training. Here we asked whether such an alteration of the crowding area would be reflected in the BOLD responses in early visual cortex after training on a crowding task. Six healthy volunteers participated (mean age 23.5 years). A Landolt-C optoype was used as a target surrounded by same-sized circles as flankers (0.75°, target-to-flankers spacing = 0.94°) presented at 6.5° eccentricity in the upper-right visual quadrant. High-resolution T1-weighted anatomical images and T2*-weighted functional images were obtained by 3-Tesla MRI scanner (Prisma, Siemens). Three of the participants were trained over three consecutive days (total number of trials = 2568) on the same gap-detection task. Post-training fMRI images were then acquired. Prior to training, all participants showed the radial-tangential anisotropy in BOLD signal in early visual areas, i.e. a strong reduction in BOLD signal in the condition with target plus radial flankers, thereby replicating the results of Kwon et al (2014). After training the BOLD signal increased in the target-plus-radial-flanker condition. Our results suggest that changes in BOLD responses after training reflect training-induced plasticity in early visual cortex.
Meeting abstract presented at VSS 2018
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