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Evelina Tapia, Bruno G. Breitmeyer; Magno- and Parvo-pathway contributions to masked priming by form: Effects of contrast and wavelength. Journal of Vision 2009;9(8):809. doi: 10.1167/9.8.809.
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© ARVO (1962-2015); The Authors (2016-present)
Masked response priming relies on the influence of nonconsciously processed information on the response to a visible probe stimulus. The question we address is to what extents the magno- (M) and parvo- (P) cellular pathways contribute to masked priming by form. To address this issue, we exploited the facts that 1) M contrast sensitivity is higher at low contrasts and saturates at contrasts of 0.2–0.3, while P contrast sensitivity increases monotonically up to 1.0; and 2) long-wavelength backgrounds suppress the M response. We used a metacontrast paradigm to render the target, acting as the prime, invisible, while the following mask served as the probe. Choice reaction times to the shape of the probe, whose form could either be congruent or incongruent relative to that of the prime, were used to assess priming effects. In Experiment 1, using dark on white stimuli, we varied the contrast of the prime from 0.05 to 1.0, while the mask's contrast was set at 1.0. In Experiment 2, for the same contrasts, prime and probe stimuli consisted of luminance increments on either equiluminant red or green backgrounds. Our results showed 1) that the strength of the priming effect was a nonmonotonic function of prime contrast, however, in a direction opposite to that predicted by M-pathway contribution and 2) that wavelength had no overall effect on priming effects. Although the M pathway has been implicated in nonconscious processing of visual information, our results indicate that it does not contribute to the nonconscious priming by form.
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