Dynamics of fronto-parietal synchrony during working memory.
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1
Montana State University , United States
The fronto-parietal cortical network plays a key role in controlling working memory. These processes are thought to involve the temporal coordination of activity within and between areas of the prefrontal (PFC) and posterior parietal (PPC) cortical regions. Previously, we reported task-dependent fronto-parietal coherence, in the beta (12-25 Hz) and gamma range (26-40 Hz) frequency range of the local field potential (LFP). Here we characterize the time-dependent dynamics of these interactions across single trials. We recorded the LFP from 2-6 sites simultaneously in both the PFC and PPC of a macaque monkey performing a rule-based, delayed match-tosample task in which the monkey was required to remember either the location or the identity of the sample object. The LFP was bandpass filtered (10-50 Hz) and a moving window correlation analysis (200 ms window, ± 50 ms time lag) was performed on all pairs of signals on each trial. The peak correlation coefficients were compared to shuffled surrogate distributions from the same data (p<.05). Significant correlation coefficients, and their time lags, were evaluated with respect to their probability and variance across trials. During stable performance (>80%correct responses), the probability and magnitude of correlation within and between the PFC and PPC was transiently suppressed during the sample stimulus, increased monotonically during the delay period (slope of the linear regression different from zero at p<.05), and dropped again following the match stimulus. These changes were accompanied by a decrease in the variance of the correlation phase lag during the delay that reached a minimum at the time of the earliest match onset. These effects occurred in 31.8/30.6%(n=85) of PFC pairs, 64.7/60.8%(n=102) of PPC pairs, and 48.6/45.7%(n=243) of PFC-PPC pairs during the location/identity rule. In a subset of the pairs, correlation probability was observed to differ across the set of 9 sample stimuli during the delay period. These results demonstrate a time-dependent increase in the magnitude and precision of LFP synchrony within and between the PFC and PPC that is task and stimulus specific and peaks just prior to the match stimulus. In conclusion, working memory processes modulate the probability of neuronal synchrony.
Conference:
Computational and Systems Neuroscience 2010, Salt Lake City, UT, United States, 25 Feb - 2 Mar, 2010.
Presentation Type:
Poster Presentation
Topic:
Poster session I
Citation:
Dotson
NM,
Salazar
RF and
Gray
CM
(2010). Dynamics of fronto-parietal synchrony during working memory..
Front. Neurosci.
Conference Abstract:
Computational and Systems Neuroscience 2010.
doi: 10.3389/conf.fnins.2010.03.00017
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Received:
17 Feb 2010;
Published Online:
17 Feb 2010.
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Correspondence:
Nicholas M Dotson, Montana State University, Bozeman, United States, ndotson@cns.montana.edu