ME_Gabor

iModel

ME_Gabor_Rot
.moo

.s1tH .moo

.s1t2 .moo

ME_Gabor_Rot
Motion Energy, Rotated Gabor Filter

Summary

This modification of the ME_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 corresponds to a rotation in spatio-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), and has been associated with velocity, as opposed to SF and TF, tuning.

Results

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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 two linear Gabor filters (icons show x-t slices of 3D filters) to yield the signals fpe (filter preferred even) and fpo (filter preferred odd). The filter outputs are squared and the signals are added to give the motion energy in the preferred direction, mep.

The signal, which is non-negative, is then combined with an additive offset, scaled, and half-wave rectified, the latter having no effect unless the signal scaling or offset has created negative values). The result 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 the computations.