This paper represents the first major project I did after coming to work with Bruce. Here, we set out to test some more predictions of the energy model, and compare them with the predictions of the model proposed in Read et al. (2002). One prediction of the energy model is that the Fourier power spectrum of the disparity tuning curve is simply the product of the spatial frequency tuning measured in each of the two eyes. We showed that this isn't true in real cells. Real disparity tuning curves do not tend to have as strong oscillations as you would expect from the band-pass spatial frequency tuning in V1. You might think this could be explained by a relatively trivial modification of the energy-model -- suppose real cells receive input from several subunits with some jitter in their preferred disparity. This could smear out side-lobes which would otherwise have been observed. However, we were able to show that this simple generalisation of the energy-model could not explain the data either. It seems you need a more serious modification.

We showed that the model we'd proposed previously, Read et al. 2002, does seem to be able to account for the data. The key feature which makes this possible is that it allows non-linearities before binocular combination, whereas the energy model is linear up to binocular combination. (Unfortunately, it's this very linearity which makes the energy model so easy to handle mathematically!) We also pointed out that a non-linearity before binocular combination seems necessary in order to explain the behaviour of cells in which one eye always has a suppressive effect.