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Sam Ling, Michael Pratte, Frank Tong; Precursors of orientation processing in the human LGN. Journal of Vision 2013;13(9):28. doi: https://doi.org/10.1167/13.9.28.
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© ARVO (1962-2015); The Authors (2016-present)
The lateral geniculate nucleus (LGN) is the first site in the brain to receive incoming signals from the retina, and is potentially well situated for early processing and active filtering of sensory information. Although most models of vision assume that orientation processing emerges in the primary visual cortex (V1), neurophysiological evidence suggests that predicates of orientation selectivity occur at earlier stages of processing – within the LGN and even the retina. Here, we used functional MRI in combination with multivariate pattern analysis to examine whether orientation selectivity, a visual feature commonly associated with visuocortical processing, exists in a more rudimentary form within the human LGN. We measured BOLD activity while participants viewed either oriented logarithmic spiral gratings at ±45° pitch, or linear gratings oriented ±45°. To ensure that fMRI decoding of the viewed orientation relied on orientation-selective information, rather than retinotopic luminance differences, the spatial phase of the grating was randomly determined on each presentation within each block. Our results revealed that reliable orientation information can be extracted from the activity patterns in the LGN, both for the spiral and linear gratings. Although modest in comparison to V1, orientation decoding in the LGN was statistically significant in all individual observers. These results suggest that orientation information may be processed to some extent before visual signals have entered the cortex, presenting an important variable to consider in models of orientation processing.
Meeting abstract presented at VSS 2013
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