TY - JOUR
T1 - Undirected graphs of frequency-dependent functional connectivity in whole brain networks
JF - Philosophical Transactions of the Royal Society B: Biological Sciences
JO - Philos Trans R Soc Lond B Biol Sci
SP - 937
LP - 946
M3 - 10.1098/rstb.2005.1645
VL - 360
IS - 1457
AU - Salvador, Raymond
AU - Suckling, John
AU - Schwarzbauer, Christian
AU - Bullmore, Ed
Y1 - 2005/05/29
UR - http://rstb.royalsocietypublishing.org/content/360/1457/937.abstract
N2 - We explored properties of whole brain networks based on multivariate spectral analysis of human functional magnetic resonance imaging (fMRI) time-series measured in 90 cortical and subcortical subregions in each of five healthy volunteers studied in the (no-task) resting state. We note that undirected graphs representing conditional independence between multivariate time-series can be more readily approached in the frequency domain than the time domain. Estimators of partial coherency and normalized partial mutual information ϕ, an integrated measure of partial coherence over an arbitrary frequency band, are applied. Using these tools, we replicate the prior observations that bilaterally homologous brain regions tend to be strongly connected and functional connectivity is generally greater at low frequencies [0.0004, 0.1518 Hz]. We also show that long-distance intrahemispheric connections between regions of prefrontal and parietal cortex were more salient at low frequencies than at frequencies greater than 0.3 Hz, whereas many local or short-distance connections, such as those comprising segregated dorsal and ventral paths in posterior cortex, were also represented in the graph of high-frequency connectivity. We conclude that the partial coherency spectrum between a pair of human brain regional fMRI time-series depends on the anatomical distance between regions: long-distance (greater than 7 cm) edges represent conditional dependence between bilaterally symmetric neocortical regions, and between regions of prefrontal and parietal association cortex in the same hemisphere, are predominantly subtended by low-frequency components.
ER -