Section_6_Notes

Section_6_Notes - Cognitive Neuroscience Lecture 6 The...

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Cognitive Neuroscience Lecture 6 The single most characteristic feature of attention is its selectivity . It selects one item for perception to the exclusion of others, or selects one motor act to the exclusion of others. This selectivity has been explained in neural terms as being necessary to conserve certain limited “resources”. Such resources could be critical neuronal populations in the cortex that would be overwhelmed with processing tasks if attentional mechanisms did not allocate them to one specific task at a time. Recast in terms of cognit activation, the explanation might be that the activation of multiple cognits at the same could cause massive interference by activation of associated cognits. Attention would then be necessary to select only a limited number of cognits for activation at a time. As Fuster states, “The role of attention is to select one of those networks at a time and to keep it active for as long as it serves a cognitive function or the attainment of a behavioral goal.”
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Biological roots of attention Any organism must process a continuous flow of sensory information and produce a continuous stream of motor output in order to adapt to the environment in a way that is conducive to its survival. In lower organisms the only feedback from effector systems to sensory systems is external, i.e. through the external environment. Hence, their behavior consists of simple reactions to sensory stimuli. Higher organisms also have internal feedback mechanisms from effector to sensory systems, allowing a greater degree of behavioral control. Internal feedback provides a means for effector systems to regulate sensory systems to “set” them for improved receptivity and analysis of sensory input. Here, “improved” means more consistent with adaptive behavior.
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Internal feedback is a form of corollary discharge which allows “tuning” of sensory systems to produce more adaptive behavior through enhanced sensory analysis. For example, a visual stimulus is initially processed hierarchically in a feedforward manner, activating multiple sensory and frontal executive areas. The executive areas may initiate movements that enhance sensory processing, e.g. moving the eyes to foveate the stimulus for improved acuity. They also may send internal feedback signals to the visual system to directly enhance sensory processing. This represents a kind of attentional control that provides the sensory system with information from the frontal hierarchy concerning the behavioral relevance of the stimulus. Attentional feedback does not need to come all the way from the prefrontal cortex. It may originate at various levels of the same or different perceptual hierarchies.
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Attentional control operates to both facilitate and attenuate sensory and motor processes. This control may operate by a combination of excitation and inhibition. Excitation and inhibition interact at all levels of the central nervous system. Sensory example: lateral inhibition (on-center; off-surround) enhances spatial
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This note was uploaded on 10/21/2011 for the course ISC 5465 taught by Professor Bressler during the Fall '11 term at FAU.

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Section_6_Notes - Cognitive Neuroscience Lecture 6 The...

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