Correlations in low-frequency BOLD fluctuations reflect cortico-cortical connections

Cross-correlation of low-frequency temporal fluctuations (<0.08 Hz) was use d to correlate widely separated anatomic regions during continuous performa nce of a spatial working memory task. The regions of highest correlation to right-hemisphere dorsolateral prefrontal cortex correspond to the regions of largest baseline signal change in a conventional block-style functional MRI paradigm. Additionally, it is shown that the correlations between eleme nts of the functional network increase during performance of a task that ac tivates the network when compared to a task that does not directly stimulat e the functionally connected network. (C) 2000 Academic Press.