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Precise spike synchronization in monkey motor cortex:
from time estimation processes to the selection of movement direction| old_uid | 3526 |
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| title | Precise spike synchronization in monkey motor cortex:
from time estimation processes to the selection of movement direction |
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| start_date | 2007/11/26 |
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| schedule | 16h |
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| online | no |
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| summary | It is commonly accepted that perceptually and behaviorally relevant events are reflected in changes in firing rate in widely distributed populations of neurons. Another concept, the temporal coding hypothesis, suggests that not only changes in firing rate but also precise spike timing constitutes an important part of the representational substrate for perception and action, such as spike synchronization or other precise spatio-temporal patterns of spike occurrences among neurons organized in functional groups, commonly called cell assemblies.
The accurate estimation of time intervals or the temporal prediction of forthcoming events is essential for optimizing motor performance. During preparation and execution of a planned movement, motor cortical neurons change their activity not only in relation to the features of the forthcoming movement (such as its direction [1]) but also in relation to higher cognitive events linked to time estimation processes [2], e.g. signal expectancy. Using a delayed pointing task, it as been shown that, at the moment when a GO signal was expected but did not appear, some neurons changed phasically their activity [3] and transient synchronization among two or more neurons occurred [4,5].
To explore spike synchronization patterns in pairs of neurons in relation to expectancy and/or to prior information about movement direction, we recorded simultaneously the activities of multiple neurons in monkey primary motor cortex during the performance of various motor tasks including an instructed delay. To investigate the dynamics of spike synchrony, the unitary events method [7] and the classical tool of cross correlation analysis were used.
We found (i) consistent patterns of spike synchronizations linked to signal expectancy, and to
time estimation processes. Surprisingly, we observed (ii) an effect of learning new durations,
with a shift in time of the transient occurrence of synchrony from the old expected signal to a
new one. And finally, we found (iii) directionally selective patterns of spike synchronizations
during movement preparation which presented reciprocal patterns related to the two opposite
movement directions.
[1] Riehle A (2005) In: Riehle A, Vaadia E (eds) Motor cortex in voluntary movements: a distributed
system for distributed functions. CRC-Press, Boca Raton, FL, pp 213-240
[2] Roux S, Coulmance M, Riehle A (2003) Europ J Neurosci 18:1011-1016
[3] Renoult L, Roux S, Riehle A (2006) Europ J Neurosci 23: 3098-3108
[4] Riehle A, Grün S, Diesmann M, Aersten A. Science (1997) 278:1950-1953
[5] Grammont F, Riehle A (2003) Biol Cybern 88: 360-373
[7] Grün S, Diesmann M, Aersten A. Neural Comput (2002) 14:43-80, 81-119 |
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| responsibles | van Vreeswijk, Hansel |
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