Visual motion modulates pattern sensitivity ahead, behind, and beside motion.
Retinal motion can modulate visual sensitivity. For instance, low contrast drifting waveforms (targets) can be easier to detect when abutting the leading edges of movement in adjacent high contrast waveforms (inducers), rather than the trailing edges. This target-inducer interaction is contingent on the adjacent waveforms being consistent with one another - in-phase as opposed to out-of-phase. It has been suggested that this happens because there is a perceptually explicit predictive signal at leading edges of motion that summates with low contrast physical input - a 'predictive summation'. Another possible explanation is a phase sensitive 'spatial summation', a summation of physical inputs spread across the retina (not predictive signals). This should be non-selective in terms of position - it should be evident at leading, adjacent, and at trailing edges of motion. To tease these possibilities apart, we examined target sensitivity at leading, adjacent, and trailing edges of motion. We also examined target sensitivity adjacent to flicker, and for a stimulus that is less susceptible to spatial summation, as it sums to grey across a small retinal expanse. We found evidence for spatial summation in all but the last condition. Finally, we examined sensitivity to an absence of signal at leading and trailing edges of motion, finding greater sensitivity at leading edges. These results are inconsistent with the existence of a perceptually explicit predictive signal in advance of drifting waveforms. Instead, we suggest that phase-contingent target-inducer modulations of sensitivity are explicable in terms of a directionally modulated spatial summation.
School of Psychology, The University of Queensland, St Lucia, Queensland 4072, Australia. Electronic address: d.arnold@psy.uq.edu.au.
Derek H
DH
Arnold
School of Psychology, The University of Queensland, St Lucia, Queensland 4072, Australia.
Welber
W
Marinovic
Department of Psychology, University of California, Berkeley, CA 94720, USA.
David
D
Whitney
D000328:Adult; D000704:Analysis of Variance; D015350:Contrast Sensitivity / Q000502:physiology*; D005425:Flicker Fusion / Q000502:physiology; D006801:Humans; D009039:Motion Perception / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D012684:Sensory Thresholds / Q000502:physiology
Motion; Predictive coding; Spatial coding; Spatial summation