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Monday, December 20, 2010

THEORIES OF PERCEPTION

The serial model
It is natural to assume that sensory processing proceeds through a series of stages. Obviously, the sense organs first transduce the stimulus. In the case of vision, further processing then occurs in the retina before the results of the analysis are sent up the optic nerve, to the thalamus, and then to the primary visual cortex. In other sensory modalities, the signals pass to their own ‘primary’ sensory areas of cerebral cortex for interpretation. For all sensory modalities, there are then several further stages of processing which occur within the cortex itself. Indeed, as much as one half of the cortex is involved purely in perceptual analysis (mostly in vision). At each stage, further work takes place to analyse what is happening in the environment. Because several such steps are involved, this way of understanding perception as a sequence of processes is known as the serial model. [serial model the assumption that perception takes place in a series of discrete stages, and that information passes from one stage to the next in one direction only] But the serial model is now known to be inadequate, or at least incomplete. So it has been replaced, or at least modified, firstly by the parallel processing model and then, [parallel processing perceptual processing in which it is assumed that different aspects of perception occur simultaneously and independently (e.g. the processing of colour by one set of neural mechanisms at the same time as luminance is being processed by another set)] most recently, by the recurrent processing model. [recurrent processing occurs when the later stages of sensory processing influence the earlier stages (top-down), as the output of a processing operation is fed back into the processing mechanism itself to alter how that mechanism subsequently processes its next input]

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