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Neural mechanisms for detecting and remembering novel events

Neural mechanisms for detecting and remembering novel events Novel or unexpected events or stimuli draw our attention and are more easily remembered than predictable or familiar ones. Evidence from a variety of sources is beginning to clarify the neural mechanisms that contribute to this response to novelty. When a stimulus is repeated, the neuronal response to it (in many parts of the brain) often decreases rapidly. The response is highest when the stimulus is novel. Behavioural responses also depend on stimulus novelty: the initial presentation seems to produce 'priming' so that repeated stimuli are processed more efficiently. Repetition suppression of neuronal responses occurs over short timescales and is stimulus-specific. Stimulus repetition can also cause suppression of responses over longer time periods, including over weeks of training on a task. This effect seems to rely on synaptic plasticity mediated by NMDA (N-methyl-D-aspartate) receptors. It has been proposed that the reduction in population activity represents a sparsening of the response to a stimulus that leaves a more robust response carried by fewer neurons. Reductions in responses in early visual areas might result from decreased feedback from higher visual areas of cortex. Another type of novelty that has been studied is contextual novelty. This arises when an unexpected stimulus or event occurs, for example a dog's bark amidst a string of birdsong. Stimuli that are contextually novel produce characteristic event-related potentials in human electroencephalograms. These potentials seem to be generated by frontal and temporal areas of cortex. Evidence from functional imaging studies supports the idea that a network of brain areas responds to contextual novelty. This network probably produces the enhanced memory that is seen for contextually novel stimuli. The neurotransmitter acetylcholine and the neuromodulator noradrenaline seem to be important for the generation of this response. An integrated view of novelty processing could see the release of acetylcholine and noradrenaline being increased in response to a novel stimulus, and modulating the activity of the cortical areas to which they project. This in turn would lead to the production of novelty-related potentials and the modulation of synaptic plasticity. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Nature Reviews Neuroscience Springer Journals

Neural mechanisms for detecting and remembering novel events

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References (152)

Publisher
Springer Journals
Copyright
Copyright © 2003 by Nature Publishing Group
Subject
Biomedicine; Biomedicine, general; Neurosciences; Behavioral Sciences; Biological Techniques; Neurobiology; Animal Genetics and Genomics
ISSN
1471-003X
eISSN
1471-0048
DOI
10.1038/nrn1052
Publisher site
See Article on Publisher Site

Abstract

Novel or unexpected events or stimuli draw our attention and are more easily remembered than predictable or familiar ones. Evidence from a variety of sources is beginning to clarify the neural mechanisms that contribute to this response to novelty. When a stimulus is repeated, the neuronal response to it (in many parts of the brain) often decreases rapidly. The response is highest when the stimulus is novel. Behavioural responses also depend on stimulus novelty: the initial presentation seems to produce 'priming' so that repeated stimuli are processed more efficiently. Repetition suppression of neuronal responses occurs over short timescales and is stimulus-specific. Stimulus repetition can also cause suppression of responses over longer time periods, including over weeks of training on a task. This effect seems to rely on synaptic plasticity mediated by NMDA (N-methyl-D-aspartate) receptors. It has been proposed that the reduction in population activity represents a sparsening of the response to a stimulus that leaves a more robust response carried by fewer neurons. Reductions in responses in early visual areas might result from decreased feedback from higher visual areas of cortex. Another type of novelty that has been studied is contextual novelty. This arises when an unexpected stimulus or event occurs, for example a dog's bark amidst a string of birdsong. Stimuli that are contextually novel produce characteristic event-related potentials in human electroencephalograms. These potentials seem to be generated by frontal and temporal areas of cortex. Evidence from functional imaging studies supports the idea that a network of brain areas responds to contextual novelty. This network probably produces the enhanced memory that is seen for contextually novel stimuli. The neurotransmitter acetylcholine and the neuromodulator noradrenaline seem to be important for the generation of this response. An integrated view of novelty processing could see the release of acetylcholine and noradrenaline being increased in response to a novel stimulus, and modulating the activity of the cortical areas to which they project. This in turn would lead to the production of novelty-related potentials and the modulation of synaptic plasticity.

Journal

Nature Reviews NeuroscienceSpringer Journals

Published: Mar 1, 2003

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