Regional Variation in Interhemispheric Coordination of Intrinsic Hemodynamic Fluctuations

Phyllis Green and Randolph Cōwen Institute for Pediatric Neuroscience at the New York University Child Study Center, New York, New York 10016, USA.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.34). 01/2009; 28(51):13754-64. DOI: 10.1523/JNEUROSCI.4544-08.2008
Source: PubMed


Electrophysiological studies have long demonstrated a high degree of correlated activity between the left and right hemispheres, however little is known about regional variation in this interhemispheric coordination. Whereas cognitive models and neuroanatomical evidence suggest differences in coordination across primary sensory-motor cortices versus higher-order association areas, these have not been characterized. Here, we used resting-state functional magnetic resonance imaging data acquired from 62 healthy volunteers to examine interregional correlation in spontaneous low-frequency hemodynamic fluctuations. Using a probabilistic atlas, we correlated probability-weighted time series from 112 regions comprising the entire cerebrum. We then examined regional variation in correlated activity between homotopic regions, contrasting primary sensory-motor cortices, unimodal association areas, and heteromodal association areas. Consistent with previous studies, robustly correlated spontaneous activity was noted between all homotopic regions, which was significantly higher than that between nonhomotopic (heterotopic and intrahemispheric) regions. We further demonstrated substantial regional variation in homotopic interhemispheric correlations that was highly consistent across subjects. Specifically, there was a gradient of interhemispheric correlation, with highest correlations across primary sensory-motor cortices (0.758, SD=0.152), significantly lower correlations across unimodal association areas (0.597, SD=0.230) and still lower correlations across heteromodal association areas (0.517, SD=0.226). These results demonstrate functional differences in interhemispheric coordination related to the brain's hierarchical subdivisions. Synchrony across primary cortices may reflect networks engaged in bilateral sensory integration and motor coordination, whereas lower coordination across heteromodal association areas is consistent with functional lateralization of these regions. This novel method of examining interhemispheric coordination may yield insights regarding diverse disease processes as well as healthy development.

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Available from: Dylan G. Gee, Oct 08, 2015
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    • "Differences in ReHo across participants may indicate variation in the biological processes that subtend local functional connectivity fALFF ALFF is the standard deviation of the bandpass filtered (0.01–0.1 Hz) fMRI signal of a given voxel. fALFF is the ratio of ALFF to the average amplitudes of the entire frequency range (Zou et al., 2008) Measures power of a brain area's spontaneous activity that falls within the frequencies typically associated with resting state functional connectivity VMHC Pearson's correlation coefficient between the time series of a given voxel and that of its symmetrical interhemispheric counterpart (Zuo et al., 2010) Measures the strength of interhemispheric connectivity, which is thought to reflect hemispheric functional specialization (Stark et al., 2008) MDMR The computation of this multivariate approach included three steps (Shehzad et al., 2014). For details, see Section 2.4.3 "
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    08/2015; DOI:10.1016/j.dcn.2015.07.007
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    • "Prior to conducting the whole-brain connectivity analysis, we evaluated the degree of correlation between the two ACC and two HF time series. Strong correlation between homologous seed time series (as previously documented for resting state data, e.g., Stark et al., 2008) would obviate independent analyses for each seed region. For bilateral ACC, the mean correlation (Pearson's r) across participants exceeded 0.8 in all conditions (mean/SD in the four conditions: "
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    • "The following analysis was thus based on the assumption that pure cerebellar signals are more correlated across hemispheres than with adjacent cerebral signals. A higher correlation between time series of cerebellar homologs as compared to nonhomologs provides support for a similar interhemispheric synchrony in the cerebellum as previously observed in the cerebrum (Stark et al., 2008). Supplementary Fig. 1 demonstrates the mean intracerebellar correlation. "
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