Abstract
Background: Jain et al. [VSS 2008] showed that attending to one of two competing motion signals with different frequency components can modulate within-modality Motion Aftereffects (MAE). The auditory MAE duration was strongly modulated, while there was only a weak modulation of visual static MAE duration and no modulation of visual dynamic MAE duration.
Goals: In the current study we examined whether a more sensitive measure would reveal a modulation of dynamic visual MAE. Further, we developed neurophysiologically relevant computational models to explore possible mechanisms for the observed effects.
Methods: The adaptation stimulus comprised two sinusoidal gratings moving in opposite directions; the test stimulus was a fixed-duration counter-phase flickering grating at an intermediate frequency. On each trial, subjects attended to the motion signal carried by low/high frequencies during adaptation and continuously reported their perceived motion direction during both adaptation and test phase. The percentage direction dominance during test phase was taken as a measure of MAE. The computational model was based on the biased-competition model used by Reynolds et al. [J. of Neuroscience 1999]. The effects of attention were modeled by biasing the weights of neuronal connections in favor of the attended spectral features. The same model structure was used to explain results within both modalities with the spatial frequency tuning in the visual modality replaced with temporal frequency tuning in the auditory modality.
Results and Conclusions: We observed significant modulation of dynamic MAE when we used a more sensitive measure. Overall, the effects were strongest for auditory MAE, moderate for static MAE and weakest for dynamic MAE, which is in decreasing order of spectral specificity. The model had an excellent correlation (99.63%) with the behavioral data and was also able to incorporate the frequency contingency of the visual MAE as observed by Shioiri and Matsumiya [VSS 2006].