The two key parameters of evolution A Glennerster |
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School of Psychology and CLS, University of Reading, United Kingdom
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| David Marr (Marr, 1982, Vision: A computational investigation into the human representation and processing of visual information, New York, Freeman) urged neuroscientists to consider the computational theory underlying visual processes but this has rarely been attempted for vision as a whole. From an evolutionary or developmental perspective, two important things change as organisms develop more complex behaviours: (i) the dimensionality of the space describing sensory+motivational contexts for action and (ii) the length of the path through that space before a reward is achieved. For example, the behaviour of a single-celled organism could be described using only two stored contexts defined in a three-dimensional space (signalling, say, the concentration gradients of two chemicals in the environment and the mass of the organism) while the equivalent sensory+motivational contexts for a human might be 10^10 in length with a concomitantly larger number of stored contexts. The analysis of retinal flow, visual stability, multi-sensory integration and other processes can be viewed quite differently in this framework. The output of the cortex is a point that moves through a high dimensional space. This truism may be a helpful concept if the paths it follows through the space are shaped by evolution and development. |
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