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Sonia Poltoratski, Devin McCormack, Frank Tong; Orientation-Tuned Surround Suppression in the Human LGN. Journal of Vision 2016;16(12):875. doi: 10.1167/16.12.875.
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© ARVO (1962-2015); The Authors (2016-present)
Surround suppression is a mechanism by which stimuli beyond a neuron's classical receptive field can modulate its response, and is critical for efficient natural vision. Studies have found suppression to be systematically dependent on the features of the surrounding stimulus, including its contrast, motion direction, and orientation; for instance, stimuli are most suppressed when the surround is iso-oriented, and least suppressed – or even enhanced – when the center and surround orientations are orthogonal. While surround suppression in the early visual system has typically been studied with single neuron recordings, more recent fMRI work has measured similar effects on a population level in early human visual cortex. Here, we report the first BOLD measures of surround suppression in the human lateral geniculate nucleus (LGN). We used high-resolution fMRI at 7 Tesla to investigate orientation-tuned surround suppression; our stimuli were large (4dva) annuli of sinusoidal gratings presented parafoveally. These center annuli were surrounded by a full-field grating that was either of the same or of an orthogonal orientation, while spatial phase was randomized. Surround suppression was defined as weaker responses at the center location when center/surround were iso-oriented than when their orientations were orthogonal. Across five observers, significant suppression was found in the LGN (t(4) = 4.153, p = 0.0142), as well as in cortical visual areas V1-V3. This stands in contrast with our prior findings that mean BOLD responses in the LGN are not modulated by orientation-defined salience when a particular grating and surrounding context are spatially separated (Poltoratski et al., VSS, 2015). Our results provide evidence of orientation-specific processing in the human LGN involving spatial interactions of surround suppression.
Meeting abstract presented at VSS 2016
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