Why is Hubel and Wiesel's Description of the Classical Receptive Field Inadequate for an Understanding of Visual Perception?
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The ultimate goal for a system of visual perception is representing visual scenes. It is generally assumed that this requires an initial ‘break-down’ of complex visual stimuli into some kind of “discrete subunits” (De Valois & De Valois, 1980, p.316) which can then be passed on and further processed by the brain. The task thus arises of identifying these subunits as well as the means by which the visual system interprets and processes sensory input. An approach to visual scene analysis that prevailed for many years was that of individual cortical cells being ‘feature detectors’ with particular response-criteria. Though not self-proclaimed, Hubel and Wiesel’s theory of a hierarchical visual system employs a form of such feature detectors. I…show more content… Applying this notion to mammalian vision is however problematic; humans for example, are capable of visually perceiving greater detail and variety than a frog and would thus require considerably more of these uniquely coded feature detectors. The notion of a ‘grandmother cell’ was thus introduced to highlight the entailment of such a theory; if every unique stimulus requires its own feature-detector cell, an absurdly high number of neurons would be required for humans to represent the vast variety of visual scenes encountered in a lifetime.
Aware of this shortcoming, Hubel and Wiesel (1962,1965,1968) were cautious not refer to ‘feature detectors’ when examining the receptive fields of the mammalian visual cortex of live cats (Hubel & Wiesel, 1962) and monkeys (Hubel & Wiesel, 1968). Nonetheless, it is now widely accepted that Hubel and Wiesel’s theory of simple, complex and hyper-complex cells remains a form of the original feature-detector theory, albeit formulated into a more economical hierarchical structure. (Lennie, 2003; Martin, 1994) Hubel and Wiesel (962, 1965) concluded that vision involved a hierarchical process starting in the retina, continuing through the lateral geniculate body, the primary visual cortex and possibly even into areas V2 and V3. As sensory information travels further up the hierarchy, it passes through progressively higher-order cells that become increasingly