Abstract
Glass patterns (GPs) have been widely employed to investigate the mechanisms underlying processing of global form from locally oriented cues. The current study aimed to psychophysically investigate the level at which global orientation is extracted from translational GPs using the tilt after-effect (TAE) and manipulating the spatiotemporal properties of the adapting pattern. We adapted participants to translational GPs and tested with sinewave gratings. In Experiment 1, we investigated whether orientation-selective units are sensitive to the temporal frequency of the adapting GP. We used static and dynamic translational GPs, with dynamic GPs refreshed at different temporal frequencies. In Experiment 2, we investigated the spatial frequency selectivity of orientation-selective units by manipulating the spatial frequency content of the adapting GPs. The results showed that the TAE peaked at a temporal frequency of ∼30 Hz, suggesting that orientation-selective units responding to translational GPs are sensitive to high temporal frequencies. In addition, TAE from translational GPs peaked at lower spatial frequencies than the dipoles’ spatial constant. These effects are consistent with form-motion integration at low and intermediate levels of visual processing.
Highlights
A critical problem in form vision concerns the neural mechanisms underlying the extraction of global form from local orientation cues encoded early in the visual system
In Experiment 1, we found that the temporal frequency manipulation produced quite noisy data, suggesting that tilt after-effect (TAE) from adaptation to translational dynamic translational Glass patterns (GPs) is weakly tuned to the adapting temporal frequency, peaking at 29.34 Hz
These results suggest that dynamic GPs produce stronger orientation adaptation than static GPs, but the effect drops when using very high temporal frequencies, possibly because these temporal frequencies (e.g., 84.75 Hz) do not allow optimal temporal summation, affecting the quality of the orientation signal generated by the adapting pattern
Summary
Two simple one-up/one-down staircases (Levitt, 1971) were used to estimate the point of subjective vertical (PSV) for each observer, that is, the orientation of the grating for which the observers were at chance in responding that the testing pattern was tilted either clockwise or counterclockwise from the vertical meridian. The staircase could start presenting the test grating tilted 20 deg either clockwise or counterclockwise from vertical and used the same step sizes as in the baseline condition. The perceptual bias introduced by GP adaptation was estimated from the PSV, while the variation of accuracy in discriminating whether the grating was tilted clockwise or counterclockwise from vertical was derived from the slope of the psychometric function. The mean of the slopes for the no-adaptation baseline condition were weighted by the SE values of the slope obtained from the curve fitting routine
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