MEO_Gabor

iModel

MEO_Gabor_Rot
... .010
... .s1tH
... .s1tH.tSD2
... .s1t2
... .sHt1
... .s2t1

MEO_Gabor_Rot
Opponent Motion Energy, Rotated Gabor Filter

Summary

This modification of the MEO_Gabor model has Gabor filters with Gaussian envelopes that are rotated in space-time to align with the orientation of the tilted sinusoidal grating, as depicted by McLean and Palmer (1994; their Fig 1A). The rotation in X-T results in a rotation in sensitivity in spatial and temporal frequency space that causes the SF-TF tuning to be inseparable. Inseparable tuning has been observed in some direction selective V1 neurons in macaque (Priebe et al. 2006), but rarely in cat (McLean and Palmer, 1994).

Results

Please get a Java compatible browser to see this.

References

McLean J, Palmer LA (1994) Organization of simple cell responses in the three-dimensional (3-D) frequency domain. Vis Neurosci 11:295-306.
Priebe NJ, Lisberger SG Movshon JA (2006) Tuning for spatiotemporal frequency and speed in directionally selective neurons of macaque striate cortex. J Neurosci 26:2941-2950.

The visual stimulus is processed (convolved) by four linear Gabor filters (two are shown; icons show x-t slices of 3D filters) to yield the signals fpe (filter preferred even), fpo (filter preferred odd), fae (anti-preferred even) and fao (anti-preferred odd). Each filter output is squared, and the signals are added for each quadrature pair to give the motion energy in the preferred direction, mep, and the anti-preferred direction, mea. These two oppositely tuned ME signals are subtracted to give the opponent motion energy, meopp.

The opponent signal (meopp) is then offset, scaled and half-wave rectified, and it is used to drive a Poisson spiking mechanism. The spikes are time shifted to simulate a neurobiological latency. See the model (.moo) files for the parameters that govern these computations.