Limits...
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.

Show MeSH

Related in: MedlinePlus

Matrices of local and long-range functional connectivity in frontal and parietal/occipital clusters for the theta and upper alpha power bands.In FXS males, significant increased local functional connectivity was found in the parietal-occipital cluster for theta oscillations, whereas a decrease in local functional connectivity was found in this cluster for alpha oscillations. A significant increase in long-range (frontal-parietal/occipital) theta functional connectivity was found in FXS males. Asterisks represent significant differences at p<.05. Error bars represent standard error of the mean.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3921158&req=5

pone-0088451-g003: Matrices of local and long-range functional connectivity in frontal and parietal/occipital clusters for the theta and upper alpha power bands.In FXS males, significant increased local functional connectivity was found in the parietal-occipital cluster for theta oscillations, whereas a decrease in local functional connectivity was found in this cluster for alpha oscillations. A significant increase in long-range (frontal-parietal/occipital) theta functional connectivity was found in FXS males. Asterisks represent significant differences at p<.05. Error bars represent standard error of the mean.

Mentions: To investigate the integrity of short-range vs. long-range connections, a frontal and a posterior cluster were created by pooling of the FP1, PP2, F7, F3, Fz, F4, F8, and P3, Pz, P4, O1, Oz, O2 electrodes, respectively [27]. Short-range and long-range connections were analyzed for the theta, upper alpha, and beta band. Preliminary analyses confirmed the absence of laterality differences for the PLI values within the clusters. Laterality was therefore disregarded as a separate factor in the analyses. This analysis could shed further light on the putative discrepancies in short- vs. long-range connectivity in neurodevelopmental disorders [20], [46]. Results of this analysis are depicted in Figure 3. Lower short-range and long-range connectivity was observed for FXS individuals compared to controls for lower alpha oscillations in the short-range frontal, t(18) = −3.02, p = .007, ηp2 = .33, and posterior, t(18) = −4.20, p = .001, ηp2 = .50, clusters, as well as the long-range frontal-posterior cluster, t(18) = −2.98, p = .008, ηp2 = .33 (Figure 3, panel B). Also, posterior short-range connectivity was lower in FXS individuals than in controls for upper alpha connectivity in the posterior cluster, t(18) = 2.31, p = .033, ηp2 = .23 (Figure 3, panel C). In contrast, functional connectivity was higher in FXS individuals than in controls for theta oscillations in the short-range posterior, t(18) = 2.62, p = .017, ηp2 = .28, and long-range frontal-posterior cluster, t(18) = 2.62, p = .018, ηp2 = .28 (Figure 3, panel A). This impairment of long-range functional connectivity in FXS can be particularly ascribed to networks governing alpha oscillations at rest. In addition, the current data suggest that short-range frontal and posterior connectivity for alpha oscillations is also diminished in FXS individuals. However, increased long-range frontal-posterior and short-range posterior connectivity was observed in the theta spectral band in FXS, which may be a manifestation of the alleged immature cortical network characteristics reported in FXS [27].


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)

Matrices of local and long-range functional connectivity in frontal and parietal/occipital clusters for the theta and upper alpha power bands.In FXS males, significant increased local functional connectivity was found in the parietal-occipital cluster for theta oscillations, whereas a decrease in local functional connectivity was found in this cluster for alpha oscillations. A significant increase in long-range (frontal-parietal/occipital) theta functional connectivity was found in FXS males. Asterisks represent significant differences at p<.05. Error bars represent standard error of the mean.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0088451-g003: Matrices of local and long-range functional connectivity in frontal and parietal/occipital clusters for the theta and upper alpha power bands.In FXS males, significant increased local functional connectivity was found in the parietal-occipital cluster for theta oscillations, whereas a decrease in local functional connectivity was found in this cluster for alpha oscillations. A significant increase in long-range (frontal-parietal/occipital) theta functional connectivity was found in FXS males. Asterisks represent significant differences at p<.05. Error bars represent standard error of the mean.
Mentions: To investigate the integrity of short-range vs. long-range connections, a frontal and a posterior cluster were created by pooling of the FP1, PP2, F7, F3, Fz, F4, F8, and P3, Pz, P4, O1, Oz, O2 electrodes, respectively [27]. Short-range and long-range connections were analyzed for the theta, upper alpha, and beta band. Preliminary analyses confirmed the absence of laterality differences for the PLI values within the clusters. Laterality was therefore disregarded as a separate factor in the analyses. This analysis could shed further light on the putative discrepancies in short- vs. long-range connectivity in neurodevelopmental disorders [20], [46]. Results of this analysis are depicted in Figure 3. Lower short-range and long-range connectivity was observed for FXS individuals compared to controls for lower alpha oscillations in the short-range frontal, t(18) = −3.02, p = .007, ηp2 = .33, and posterior, t(18) = −4.20, p = .001, ηp2 = .50, clusters, as well as the long-range frontal-posterior cluster, t(18) = −2.98, p = .008, ηp2 = .33 (Figure 3, panel B). Also, posterior short-range connectivity was lower in FXS individuals than in controls for upper alpha connectivity in the posterior cluster, t(18) = 2.31, p = .033, ηp2 = .23 (Figure 3, panel C). In contrast, functional connectivity was higher in FXS individuals than in controls for theta oscillations in the short-range posterior, t(18) = 2.62, p = .017, ηp2 = .28, and long-range frontal-posterior cluster, t(18) = 2.62, p = .018, ηp2 = .28 (Figure 3, panel A). This impairment of long-range functional connectivity in FXS can be particularly ascribed to networks governing alpha oscillations at rest. In addition, the current data suggest that short-range frontal and posterior connectivity for alpha oscillations is also diminished in FXS individuals. However, increased long-range frontal-posterior and short-range posterior connectivity was observed in the theta spectral band in FXS, which may be a manifestation of the alleged immature cortical network characteristics reported in FXS [27].

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