Abstract
Adaptation to high temporal frequencies can induce a localised reduction in the apparent duration of dynamic tests (Johnston et al., 2006). This effect is dissociable from apparent speed changes (Ayhan et al., 2009), and the specificity of the effect for high temporal frequency adaptation, coupled with its insensitivity to stimulus orientation, suggests a causal locus at an early (pre-cortical) magnocellular stage of analysis (Johnston et al., 2006). The absence of adaptation-induced time compression for isoluminant tests supports this claim (Ayhan et al., 2009). Here we further examined the determinants of adaptation-induced time compression by investigating interactions between 1st-order luminance defined and 2nd- order luminance-contrast defined motion signals. We found that adaptation to an 8Hz first order stimulus markedly reduced the apparent durations of 1st and 2nd order 4Hz tests, whereas adaptation to a 2Hz 1st order signal had little impact on either test type. In contrast, adaptation to 8Hz 2nd order motion shortened the perceived duration of 4Hz 1st and 2nd order tests, but adaptation to a 2Hz 2nd order signal had a selective effect on 4Hz 2nd order tests, with little impact on 4Hz 1st order tests. We believe the efficacy of both 1st order luminance and 2nd order luminance-contrast adaptation further implicates an early magnocellular locus as the critical site for time-compression adaptation.
Meeting abstract presented at VSS 2014