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Yao Chen, Susana Martinez-Conde, Stephen Macknik, Harvey Swadlow, Jose-Manuel Alonso, Barry Lee; Input to cells in macaque V1 revealed with a novel grating stimulus. Journal of Vision 2007;7(15):57. doi: https://doi.org/10.1167/7.15.57.
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© ARVO (1962-2015); The Authors (2016-present)
We have recorded responses of cells in V1 of the awake macaque monkey to a novel grating stimulus drifting across their receptive fields which we call compound grating. It consists of equiluminant red and green bars separated by dark areas. The luminance component of this compound grating is twice the temporal (and spatial) frequency of the chromatic component. Retinal ganglion cells of the parvocellular (PC) and magnocellular (MC) pathways respond to compound gratings with distinct signatures. The ratios of the second harmonic (luminance) to the first harmonic (chromatic) response is bimodally distributed, with ratios less than one for PC cells and greater than one for MC cells. In contrast, the distribution of ratios for cortical cells is continuous. By comparing responses to conventional luminance, chromatic gratings and compound gratings, the input to many cortical cells could be identified as predominantly MC (62% of cells), a small group as predominantly PC (21% of cells), with some cells receiving combined input (17% of cells). These results confirm previous reports demonstrating a surprising amplification of the MC pathway at the cortical level (60% of cortical cells) and a significant group of luminance/chromatic cells (Johnson et al.). In addition, responses to chromatic gratings of cortical cells with MC input showed high 2nd/1st harmonic ratios, in a range found with MC ganglion cells (Lee et al.). This feature of MC cell responses thus appears to be manifest in V1, which may contribute to unsigned motion signals in MT.
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