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Jens Christiansen, Anthony D'Antona, Steven Shevell; Neural pathways of induced steady color shifts caused by temporally varying context. Journal of Vision 2008;8(6):570. doi: 10.1167/8.6.570.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose & Method: When a field surrounding a physically steady central region is slowly modulated in chromaticity over time ( ∼3 Hz), modulation of the surround remains visible but the central region appears steady (De Valois et al., 1986). Further, modulation between ∼3 – 20 Hz along the l or s axis of the MacLeod-Boynton color space (time-average chromaticity metameric to equal energy white) shifts the steady appearance of the central region toward redness or yellowness, respectively (D'Antona & Shevell, 2006). This study examined whether the induced steady color shifts occur independently in l and s pathways. If so, induced color shifts with modulation along only l or only s can determine (by vector summation) induced color shifts with simultaneous modulation along both the l and s directions. Further, changing the relative phase of simultaneous l and s temporal modulation by 180°, should not influence the color shift. These predictions were investigated by square-wave modulation of surrounds at 6.25 Hz along the l axis alone, the s axis alone, or along intermediate axes. Induced colors were measured using achromatic cancellation. Results & Conclusion: Shifting the relative phase of simultaneous l and s modulation caused sharply different induced steady color shifts. Further, color shifts from simultaneous modulation along l and s axes were not a simple combination of the shifts from modulation along only the l or s axis. Independent neural responses in l and s pathways cannot explain these findings. The measurements indicate a contribution from a cortical mechanism sensitive to the specific chromatic axis of modulation.
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