The neuropsychologist Stephen Kosslyn has commented, in relation to metamorphopsia: "[The] dissociation between experience and function is fascinating, suggesting that experience is produced by a collateral process...outside the 'chain of command' that results in recognition. If so, then this collateral path can be disrupted while the main one is left unimpaired."
Kosslyn's suggestion is, I think, right on. The only reasonable inference is that sensation (which is clearly what he means here by "experience") is indeed "outside the chain of command" that leads to perceptual recognition. However, [no one who has] thought about these strange phenomena [has] as yet been ready to follow where, to me, they seem obviously to lead.
If sensation can be side-lined, then doesn't this mean that sensation is in reality some kind of side show? It might be going too far to suggest that sensation plays no part in perception. But I think the weight of evidence really does suggest that sensation and perception, although they are triggered by the same event, are essentially independent takes on this event, occurring not in series but in parallel, and only interacting, if they ever do, much further down the line.-- Nicholas Humphrey (2006)
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