Retinal Model of the Dynamics of X and Y Pathways: A Neural Basis for Early Coarse-to-Fine Perception
W H A Beaudot, A Oliva *, J Hérault * (CSEM - Centre Suisse d'Électronique et de Microtechnique SA, Jaquet-Droz 1, CH 2007 Neuchâtel, Switzerland; * Laboratoire de Traitement d'Images et Reconnaissance de Formes Institut National Polytechnique de Grenoble, 46 avenue Félix Viallet, 38031 Grenoble Cedex, France)
Spatiotemporal inseparability was suggested to be a property of human vision by our retinal model of early visual perception (Beaudot and Hérault, 1994 Perception 23 Supplement, 25). We showed that the signal transmission in the outer plexiform layer acts as an inseparable spatiotemporal band-pass filter, and provides X and Y ganglion cells responses when convolved with transmission through the inner plexiform layer.
This leads to a time-dependent spatial transfer function, exhibiting an interesting property of Coarse-to-Fine perception. When stimulated by a new image, the response of the retina evolves over time from a low-pass to a band-pass function; low-frequencies in the spatial domain appear 14 ms after the onset of stimulation, while high-frequencies are extracted only after 30 ms. This Coarse-to-Fine property has been confirmed at a higher level by a series of psychophysical experiments on human observers.
Our retinal model suggests that: 1) high-spatial frequencies are carried by the X-cell pathway and appear 30 ms after stimulation, and that 2) low-spatial frequencies are carried by the Y-cell pathway and appear earlier than the high-spatial frequencies. We show that point 2 is because of the temporal high-pass and spatial low-pass filtering properties of the Y-type ganglion cells. This theoretical result suggests the nature of visual information sent from the retina to higher visual pathways such as the superior colliculus and the lateral geniculate nucleus.
© 1997 CSEM S.A.