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Global Motion Gabor

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Summary

A Gabor patch drifts briefly at one location by shifting the spatial phase of the sinusoid (short-range motion, or local motion), and it is then displaced to a new location (global motion, or long-range motion). A stimulus like this was used by Hedges et al. (2011, Curr Biol) to demonstrate that MT cells responded in a direction selective manner to local motion component and not to global motion.

Both monocular and binocular versions of this stimulus are implemented.

Examples

• globmo_gabor_opp.stm - 2017 Nov 13 - Movie (.mov) - Global motion to the right and local drift to the left.
• globmo_gabor_same.stm - 2017 Nov 13 - Movie (.mov) - Global motion to the right and local drift to the right.

Imperfections

None reported.

Parameters

• patch_n - The number of patches in the global motion sequence.

• patch_dur - (s) The duration that each patch remains at one location in the global sequence (local motion occurs during this time).

• patch_env - [Future] This will allow different envelopes for the onset and offset of each patch. Currently, the envelope is a boxcar, i.e., the patch appears at full contrast and remains that way until it is removed.

• glob_dir - (deg) The direction of global motion.

• glob_dx - (deg) The spatial shift between successive patches in the global sequence.

• glob_dt - (s) The temporal offset between patches.

• direction - (0..360) the direction of local motion created by phase-shifting in the Gabor. The Gabor orientation will be orthogonal to this direction.

• sf - (cyc/deg) spatial frequency of the sinewave component of the Gabor function.

• tf - (Hz) temporal frequency of the drifting sinewave component of the Gabor function.

• phase - (0..360) initial spatial phase of the drifting Gabor patches.

• sd_par - (deg) standard deviation of the Gaussian Gabor envelope running parallel to the orientation of the sinewave.

• sd_orth - (deg) standard deviation of the Gaussian Gabor envelope running orthogonal to the orientation of the sinewave.

• contrast - (0..1) contrast of the Gabor function.

• ...

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