Insect stereopsis demonstrated using a 3D insect cinema by Nityananda V, Tarawneh G, Rosner R, Nicolas J, Crichton S, Read JCA, NityanandaTarawnehRosnerNicolasCrichtonRead2016.pdf (1.2 MiB) - Stereopsis - 3D vision – has become widely used as a model of perception. However, all our knowledge of possible underlying mechanisms comes almost exclusively from vertebrates. While stereopsis has been demonstrated for one invertebrate, the praying mantis, a lack of techniques to probe invertebrate stereopsis has prevented any further progress for three decades. We therefore developed a stereoscopic display system for insects, using miniature 3D glasses to present separate images to each eye, and tested our ability to deliver stereoscopic illusions to praying mantises. We find that while filtering by circular polarization failed due to excessive crosstalk, “anaglyph” filtering by spectral content clearly succeeded in giving the mantis the illusion of 3D depth. We thus definitively demonstrate stereopsis in mantises and also demonstrate that the anaglyph technique can be effectively used to deliver virtual 3D stimuli to insects. This method opens up broad avenues of research into the parallel evolution of stereoscopic computations and possible new algorithms for depth perception.
Viewing 3D TV over two months produces no discernible effects on balance, coordination or eyesight. by Read JCA, Godfrey A, Bohr I, SImonotto J, Galna B, Smulders TV, ReadGodfreyBohrSimonottoGalnaSmulders2016.pdf (2.2 MiB) - With the rise in stereoscopic 3D media, there has been concern that viewing stereoscopic 3D (S3D) content could have long-term adverse effects, but little data are available. In the first study to address this, 28 households who did not currently own a 3D TV were given a new TV set, either S3D or 2D. The 116 members of these households all underwent tests of balance, coordination and eyesight, both before they received their new TV set, and after they had owned it for 2 months. We did not detect any changes which appeared to be associated with viewing 3D TV. We conclude that viewing 3D TV does not produce detectable effects on balance, coordination or eyesight over the timescale studied. Practitioner Summary: Concern has been expressed over possible long-term effects of stereoscopic 3D (S3D). We looked for any changes in vision, balance and coordination associated with normal home S3D TV viewing in the 2 months after first acquiring a 3D TV. We find no evidence of any changes over this timescale.
Latitude and longitude vertical disparities by Read JCA, Phillipson GP, Glennerster A , ReadPhillipsonGlennerster09.pdf (5.2 MiB) - At around this time I'd been spending a lot of time thinking about vertical disparity, and had been awarded an MRC grant to study it. To begin with, I wasn't even entirely clear what vertical disparity was, and I had difficulty following some of the other papers on it. I realised that a lot of the confusion was occurring because there are actually several different definitions of "vertical disparity" in the literature -- I've identified at least four -- and to make matters worse, different papers aren't always clear about exactly which definition they have in mind. Unsurprisingly, this has caused a lot of confusion about what the properties of vertical disparity actually are. Part of the problem, I think, is that under some circumstances you obtain the same results regardless of whether you define the elevation coordinate as a latitude or a longitude on the retina, and this may have given the impression that it doesn't ever matter -- whereas in fact, under some circumstances, the two definitions give completely different results. So with my PhD student Graeme Phillipson and my old friend and colleague from back in Oxford, Andrew Glennerster, we decided to write a paper really getting into the nitty-gritty of vertical disparity, and laying out clearly what properties follow from different definitions. It may not be the most exciting paper ever, and like many of my papers, it has masses of Appendices filled with equations. But we hoped it would be a useful reference for anyone interested in vertical disparity -- and I did at least try hard to make the pictures pretty.
All Pulfrich-like illusions can be explained without joint encoding of motion and disparity. by Read JCA, Cumming BG , ReadCumming05c.pdf (2.8 MiB) - The final step was to build a neuronal model, and show that it experienced the illusion. We modelled a neuronal population constructed of neurons which either encoded motion, or depth (not both), and showed that a very simple way of "reading out" this activity, so as to convert it to a perception of depth, would be subject to the Pulfrich illusion. We also examined other evidence which had been put forward in support of the joint motion/depth idea, such as the illusion of swirling motion which occurs in dynamic noise with an interocular delay. We found that this, too, could be experienced by a brain which encoded motion and depth entirely separately. So, while there certainly are primate neurons which jointly encode motion and depth (notably in MT), there is no reason to suppose that these play a privileged role in supporting the Pulfrich effect and related illusions.
This series of three papers (Read & Cumming 2005abc) has recently attracted some criticism from Ning Qian and Ralph Freeman, in a paper entitled "Pulfrich phenomena are coded effectively by a joint motion-disparity process" (J Vis, 9(5): 1-16). My take on it is that we are all basically in agreement, but the situation is obscured by the lack of a clear agreed definition of "joint" vs "separate" encoding of motion and disparity. For example, we said that to be called a motion detector, a cell not only had to be tuned to speed, it also had to respond differently to opposite directions of motion, whereas Qian & Freeman required only speed tuning. I want to clear up one other point. Qian & Freeman say that our model is "non-causal", apparently because it responds to the disparity between a stimulus in one eye and a stimulus which arrives in the other eye at a later time. At the time that stimulus 1 occurs, stimulus 2 is still in the future. However, at the time the neuron responds to the disparity between the two stimuli, both stimuli have already occurred. Thus, the model is firmly causal. Indeed, our derivation of its properties explicitly sets the temporal kernel to zero for future times.
