www.imodel.org

GaborME.0.0

2007 Feb 11
Summary   This is an opponent motion energy model for direction selectivity. It consists of a two quadrature pairs of space-time oriented Gabor filters, one pair for the preferred and one for the antipreferred direction. The opponent output drives a Poisson spike generator. This basic model provides a rough approximation to macaque V1 complex DS cells.

GaborME.0.0.mod

Data

Results

The results here were obtained using this response file, which records spikes from a DS unit near the center of the stimulus grid.

Sine Tuning

• Direction - at TF 10 Hz, SF 1.2 cyc/deg
• Spatial frequency - in preferred and anti-preferred direction
• Temporal frequency - at SF 1.2 cyc/deg
• Static phase

Dynamic Random Stimuli

• Random direction vs. TF

Discussion

The temporal frequency tuning is narrower for this model than what is typical for V1 complex DS cells. The temporal Gaussian filter could be narrowed in the model to widen the TF tuning, but this will also further increase the phase-dependence of the model, turning the unit from complex to simple.

The STAs for the random direction stimulus show no systematic change in shape with speed (equivalent TFs). This is at odds with experimental results for DS simple and complex cells in V1, which tend to have wider STAs for slower motion. The STAs are narrower than the Gaussian model filter partly becuase of the squaring in the model.