Visual recognition: From retina to inferotemporal cortex

Neurophysiological data indicate that the visual system is capable of performing sophisticated visual processing tasks in 100 to 150 ms. This rapidity, together with knowledge concerning the anatomical organisation of the visual system and the physiological properties of its neurones impose serious constraints which need to be taken into account by models of visual processing. In particular, it would seem that a great deal of processing can be done on the basis of pupety ''feed-forward'' processing mechanisms involving ten or so layers of processing, where each neurone only has time to emit a very small number of action potentials. We suggest that one of the keys to understanding the remarkable efficiency of the visual system lies in the use of asynchronous processing - the earliest neurones to fire at any given level of the visual system are those which can provide the most information about the stimulus to be identified.