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Adhira Sunkara, Gregory DeAngelis, Dora Angelaki; Compensation of heading tuning for eye pursuit in Macaque area VIP: Retinal and extra-retinal contributions. Journal of Vision 2013;13(9):113. doi: 10.1167/13.9.113.
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© ARVO (1962-2015); The Authors (2016-present)
Moving in a 3D environment results in a projected vector field on the retina termed optic flow. For linear translations, this pattern is radially symmetric around a ‘Focus of Expansion’ (FOE) corresponding to the heading direction. Eye movements introduce rotations which disrupt the FOE, obscuring the true heading. Psychophysical studies show that humans are capable of perceiving their true heading despite pursuit eye movements. Two strategies that the brain can use to recover heading in the presence of rotations include (i) Subtracting extra-retinal velocity signals from optic flow (ii) Using visual information present in retinal cues to separate translation from rotation based on the differences in their flow properties. To evaluate the contributions of each strategy, we introduce rotations to translational flow fields using eye pursuit (real pursuit, RP) or add rotation to the stimulus, simulating eye pursuit during fixation (simulated pursuit, SP). RP and SP produce the same retinal stimulation, but SP lacks extra-retinal signals. Heading stimuli (3D dot cloud) is presented for both conditions while recording extracellularly from macaque ventral intraparietal area (VIP), which has both heading direction tuning and eye pursuit responses. We compared the full tuning curve for translations in the horizontal plane to the tuning during RP/SP. We observe slightly larger shifts in tuning (indicating incomplete compensation) for SP than RP, but much smaller than a purely extra-retinal strategy suggests. This study presents neural evidence in support of a combination of retinal and extra-retinal cues for pursuit compensation. We also observe larger gain fields during RP compared to SP, suggesting that gain fields can encode the presence of eye rotations. These gain fields can potentially be useful for identifying whether the rotation present in retinal cues is a result of eye movements or another source such as head movements, or moving on a curved path.
Meeting abstract presented at VSS 2013
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