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Richard Sylvester, John-Dylan Haynes, Geraint Rees; Saccadic modulation of activity in human LGN and V1. Journal of Vision 2005;5(8):577. doi: 10.1167/5.8.577.
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© ARVO (1962-2015); The Authors (2016-present)
During saccades the visual image moves across the retina at high velocity, yet no blurring of the visual scene is perceived. Suppression of visual sensitivity at the time of saccades has been shown in many studies of human visual perception and may contribute to maintaining perceptual continuity across saccades. However, the neural mechanisms underlying this saccadic suppression are unclear. We used functional MRI in combination with retinotopic mapping to examine responses in cortical and sub-cortical visual areas during saccades in seven normal subjects. We found that activity in both primary visual cortex (V1) and the lateral geniculate nucleus (LGN) was strongly modulated by saccades. Furthermore, this modulation depended on the strength of concurrent visual stimulation. In complete darkness and in the presence of visual stimuli that evoked weak activation of V1 and LGN, saccades led to reliable signal increases in V1 and LGN (corollary discharge). However, in the presence of strong visual stimulation, saccades led to suppression of visually-evoked responses in V1 and LGN (saccadic suppression). This pattern of modulation of activity by saccades supports a model of saccadic suppression where corollary discharge has a suppressive effect on visually evoked responses at the earliest stages of visual processing.
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