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Resting-state EEG oscillatory dynamics in fragile X syndrome: abnormal functional connectivity and brain network organization.

van der Molen MJ, Stam CJ, van der Molen MW - PLoS ONE (2014)

Bottom Line: A decrease in global functional connectivity was observed in FXS males for upper alpha and beta frequency bands.For theta oscillations, we found increased connectivity in long-range (fronto-posterior) and short-range (frontal-frontal and posterior-posterior) clusters.These findings are discussed in terms of aberrant maturation of neuronal oscillatory dynamics, resulting in an imbalance in excitatory and inhibitory neuronal circuit activity.

View Article: PubMed Central - PubMed

Affiliation: Institute of Psychology, Developmental Psychology Unit, Leiden University, Leiden, the Netherlands ; Leiden Institute for Brain and Cognition. Leiden, the Netherlands.

ABSTRACT
Disruptions in functional connectivity and dysfunctional brain networks are considered to be a neurological hallmark of neurodevelopmental disorders. Despite the vast literature on functional brain connectivity in typical brain development, surprisingly few attempts have been made to characterize brain network integrity in neurodevelopmental disorders. Here we used resting-state EEG to characterize functional brain connectivity and brain network organization in eight males with fragile X syndrome (FXS) and 12 healthy male controls. Functional connectivity was calculated based on the phase lag index (PLI), a non-linear synchronization index that is less sensitive to the effects of volume conduction. Brain network organization was assessed with graph theoretical analysis. A decrease in global functional connectivity was observed in FXS males for upper alpha and beta frequency bands. For theta oscillations, we found increased connectivity in long-range (fronto-posterior) and short-range (frontal-frontal and posterior-posterior) clusters. Graph theoretical analysis yielded evidence of increased path length in the theta band, suggesting that information transfer between brain regions is particularly impaired for theta oscillations in FXS. These findings are discussed in terms of aberrant maturation of neuronal oscillatory dynamics, resulting in an imbalance in excitatory and inhibitory neuronal circuit activity.

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Global functional connectivity as indexed by the Phase Lag Index (PLI).(A) Functional connectivity matrices are presented for theta, alpha and beta bands, as group differences were largest for these spectral bands. (B) Group differences in PLI for the delta, theta, alpha, beta and gamma bands. As can be seen from these data, FXS males show significantly less functional connectivity in the upper alpha and beta frequency bands. Asterisks represent significant differences at p<.05. Error bars represent standard error of the mean.
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pone-0088451-g002: Global functional connectivity as indexed by the Phase Lag Index (PLI).(A) Functional connectivity matrices are presented for theta, alpha and beta bands, as group differences were largest for these spectral bands. (B) Group differences in PLI for the delta, theta, alpha, beta and gamma bands. As can be seen from these data, FXS males show significantly less functional connectivity in the upper alpha and beta frequency bands. Asterisks represent significant differences at p<.05. Error bars represent standard error of the mean.

Mentions: Figure 2 depicts an overview of the functional connectivity results for the various EEG spectral bands. A first step was to analyze group differences in overall PLI values (averaged over all pairs of EEG channels) per spectral band. In panel A of Figure 2, a clear difference can be observed in the PLI values between FXS and controls for the alpha spectral band. That is, functional connectivity was lower in FXS individuals for alpha oscillations, but these differences were only significant for the upper alpha spectral band (10–13 Hz), t(18) = −2.56, p = .020, ηp2 = .27. Since low spectral power could be an indication of confounded PLI estimation, we examined the correlations of the PLI per spectral band with their corresponding spectral power values. We only observed a negative correlation between PLI and spectral power of Beta oscillations (13–30 Hz), r = −.725, p = .04, which could possibly have underestimated the functional connectivity in the Beta band in FXS individuals. In addition, functional connectivity was lower in FXS individuals than in controls for beta oscillations (13–30 Hz), t(18) = −2.19, p = .042, ηp2 = .21. Higher functional connectivity was observed for FXS males in the theta band (4–8 Hz), but this difference was not significant. The overall functional connectivity results suggest differences in slow (theta) and faster (alpha and beta) oscillatory networks, which could be reflective of aberrant maturational processes, since functional connectivity in the alpha and beta bands are known to reach peak values at later stages during development [45].


Resting-state EEG oscillatory dynamics in fragile X syndrome: abnormal functional connectivity and brain network organization.

van der Molen MJ, Stam CJ, van der Molen MW - PLoS ONE (2014)

Global functional connectivity as indexed by the Phase Lag Index (PLI).(A) Functional connectivity matrices are presented for theta, alpha and beta bands, as group differences were largest for these spectral bands. (B) Group differences in PLI for the delta, theta, alpha, beta and gamma bands. As can be seen from these data, FXS males show significantly less functional connectivity in the upper alpha and beta frequency bands. Asterisks represent significant differences at p<.05. Error bars represent standard error of the mean.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3921158&req=5

pone-0088451-g002: Global functional connectivity as indexed by the Phase Lag Index (PLI).(A) Functional connectivity matrices are presented for theta, alpha and beta bands, as group differences were largest for these spectral bands. (B) Group differences in PLI for the delta, theta, alpha, beta and gamma bands. As can be seen from these data, FXS males show significantly less functional connectivity in the upper alpha and beta frequency bands. Asterisks represent significant differences at p<.05. Error bars represent standard error of the mean.
Mentions: Figure 2 depicts an overview of the functional connectivity results for the various EEG spectral bands. A first step was to analyze group differences in overall PLI values (averaged over all pairs of EEG channels) per spectral band. In panel A of Figure 2, a clear difference can be observed in the PLI values between FXS and controls for the alpha spectral band. That is, functional connectivity was lower in FXS individuals for alpha oscillations, but these differences were only significant for the upper alpha spectral band (10–13 Hz), t(18) = −2.56, p = .020, ηp2 = .27. Since low spectral power could be an indication of confounded PLI estimation, we examined the correlations of the PLI per spectral band with their corresponding spectral power values. We only observed a negative correlation between PLI and spectral power of Beta oscillations (13–30 Hz), r = −.725, p = .04, which could possibly have underestimated the functional connectivity in the Beta band in FXS individuals. In addition, functional connectivity was lower in FXS individuals than in controls for beta oscillations (13–30 Hz), t(18) = −2.19, p = .042, ηp2 = .21. Higher functional connectivity was observed for FXS males in the theta band (4–8 Hz), but this difference was not significant. The overall functional connectivity results suggest differences in slow (theta) and faster (alpha and beta) oscillatory networks, which could be reflective of aberrant maturational processes, since functional connectivity in the alpha and beta bands are known to reach peak values at later stages during development [45].

Bottom Line: A decrease in global functional connectivity was observed in FXS males for upper alpha and beta frequency bands.For theta oscillations, we found increased connectivity in long-range (fronto-posterior) and short-range (frontal-frontal and posterior-posterior) clusters.These findings are discussed in terms of aberrant maturation of neuronal oscillatory dynamics, resulting in an imbalance in excitatory and inhibitory neuronal circuit activity.

View Article: PubMed Central - PubMed

Affiliation: Institute of Psychology, Developmental Psychology Unit, Leiden University, Leiden, the Netherlands ; Leiden Institute for Brain and Cognition. Leiden, the Netherlands.

ABSTRACT
Disruptions in functional connectivity and dysfunctional brain networks are considered to be a neurological hallmark of neurodevelopmental disorders. Despite the vast literature on functional brain connectivity in typical brain development, surprisingly few attempts have been made to characterize brain network integrity in neurodevelopmental disorders. Here we used resting-state EEG to characterize functional brain connectivity and brain network organization in eight males with fragile X syndrome (FXS) and 12 healthy male controls. Functional connectivity was calculated based on the phase lag index (PLI), a non-linear synchronization index that is less sensitive to the effects of volume conduction. Brain network organization was assessed with graph theoretical analysis. A decrease in global functional connectivity was observed in FXS males for upper alpha and beta frequency bands. For theta oscillations, we found increased connectivity in long-range (fronto-posterior) and short-range (frontal-frontal and posterior-posterior) clusters. Graph theoretical analysis yielded evidence of increased path length in the theta band, suggesting that information transfer between brain regions is particularly impaired for theta oscillations in FXS. These findings are discussed in terms of aberrant maturation of neuronal oscillatory dynamics, resulting in an imbalance in excitatory and inhibitory neuronal circuit activity.

Show MeSH
Related in: MedlinePlus