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Richard Heitz, Geoffrey Woodman, Pierre Pouget, Jeremiah Cohen, Jeffrey Schall; Effects of luminance contrast on visual responses in frontal eye field. Journal of Vision 2008;8(6):295. doi: https://doi.org/10.1167/8.6.295.
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© ARVO (1962-2015); The Authors (2016-present)
The division of the early visual system into rapid, more sensitive magnocellular and slower, more selective parvocellular divisions is well established. Cells in the magnocellular division exhibit high contrast sensitivity while cells in the parvocellular division exhibit more graded responses to changes in contrast. How far this division extends in the visual pathway is unknown. One likely candidate for integration of the two processing streams is frontal eye field (FEF), a region of frontal cortex which plays a critical role in saccade target selection and eye movement initiation. Anatomical evidence confirms that FEF receives afferents converging from dorsal and ventral stream areas (Schall, Morel, King, & Bullier, 1995). We investigated the extent to which FEF visual neurons show the functional distinction between parvo- and magnocellular divisions. Single-units were recorded in FEF of two macaque monkeys performing a memory-guided saccade task with target stimuli of variable luminance contrast. Two populations of visual responses were observed: one population exhibited a strong modulation in onset latency with luminance contrast. The other population demonstrated very little modulation with contrast. The data suggest that FEF not only receives distinct input from different cortical streams, but maintains this distinction in its output.
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