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nilsu atilgan, Sheng He; Visual crowding effect in the Parvocellular and Magnocellular visual pathways. Journal of Vision 2018;18(10):847. doi: https://doi.org/10.1167/18.10.847.
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A key function of the human visual system is to recognize objects, and often in the visual periphery. However, an object that is easily recognized on its own could become unrecognizable if surrounded by other objects, especially in peripheral vision. This detrimental effect of nearby objects on visual discrimination of a target object is known as crowding. Even though there have been numerous studies that have investigated crowding phenomenon, its neural substrates remain unclear. Previous studies have primarily focused on finding the stage(s) in the visual hierarchy where crowding starts to limit target processing, with little attention directed to potential differences of the crowding effect in different visual pathways. The current study investigated the nature of crowding with stimuli designed to separately engage the Parvocellular (P) or Magnocellular (M) pathway, by tuning stimulus features for the targeted pathway and using background to saturate the other pathway. The critical spacing of crowding, that is the minimal distance between target and flanking objects that allows identification of the target object, was measured. The smaller critical spacing indicates weaker crowding effect. Participants completed an orientation detection task at 8° eccentricity in the P and M pathway conditions while inter-stimulus spacing was varied (ranged 0.9°- 4.4°). Results show, consistent among all subjects, that the critical spacing of crowding is smaller in the P pathway than that in the M pathway, suggesting that the crowding effect is more severe in the M than in the P pathway. This result may reflect the fact that at the same eccentricity, neurons in the P pathway tend to have smaller receptive fields than that in the M pathway.
Meeting abstract presented at VSS 2018
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