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.

Glass patterns (GPs) consist of randomly distributed dot pairs (dipoles) whose orientations are determined by specific geometric transforms. We investigated the role of visuospatial attention in the processing of global form from GPs by measuring the effect of distraction on adaptation to GPs. In the nondistracted condition, observers were adapted to coherent GPs. After the adaptation period, they were presented with a test GP divided in two halves along the vertical and were required to judge which side of the test GP was more coherent. In the attention-distracted condition, a high-load rapid serial visual presentation task was performed during the adapting period. The magnitude of the form after-effect was measured using a technique that measures the coherence level at which the test GP appears random. The rationale was that if attention has a modulatory effect on the spatial summation of dipoles, in the attention-distracted condition, we should expect a weaker form after-effect. However, the results showed stronger form after-effect in the attention-distracted condition than in the nondistracted condition, suggesting that distraction during adaptation increases the strength of form adaptation. Additional experiments suggested that distraction may reduce the spatial suppression from large-scale textures, strengthening the spatial summation of local-oriented signals.

Models of human cortex propose the existence of neuroanatomical pathways specialised for different behavioural functions. These pathways include a ventral pathway for object recognition, a dorsal pathway for performing visually guided physical actions and a recently proposed third pathway for social perception. In the current study we tested the hypothesis that different categories of moving stimuli are differentially processed across the dorsal and third pathways according to their behavioural implications. Human participants (N=30) were scanned with functional magnetic resonance imaging (fMRI) while viewing moving and static stimuli from five categories (faces, bodies, scenes, objects, and scrambled objects). Whole brain group analyses showed that moving bodies and moving objects increased neural responses in bilateral V5/MT+ and intraparietal sulcus (IPS), parts of the dorsal pathway. In addition, moving faces and moving bodies increased neural responses in bilateral V5/MT+ and the right posterior superior temporal sulcus (rpSTS), parts of the third pathway. This pattern of results was also supported by a separate region of interest (ROI) analysis showing that moving stimuli produced more robust neural responses for all visual object categories, particularly in lateral and dorsal brain areas. Our results suggest that dynamic naturalistic stimuli from different categories are routed along specific visual pathways that process their unique behavioural implications.

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