Functional MRI (fMRI) can be applied to study the functional connectivity of the human brain. It has been suggested that fluctuations in the blood oxygenation level-dependent (BOLD) signal during rest reflect the neuronal baseline activity of the brain, representing the state of the human brain in the absence of goal-directed neuronal action and external input, and that these slow fluctuations correspond to functionally relevant resting-state networks. Several studies on resting fMRI have been conducted, reporting an apparent similarity between the identified patterns. The spatial consistency of these resting patterns, however, has not yet been evaluated and quantified. In this study, we apply a data analysis approach called tensor probabilistic independent component analysis to resting-state fMRI data to find coherencies that are consistent across subjects and sessions. We characterize and quantify the consistency of these effects by using a bootstrapping approach, and we estimate the BOLD amplitude modulation as well as the voxel-wise cross-subject variation. The analysis found 10 patterns with potential functional relevance, consisting of regions known to be involved in motor function, visual processing, executive functioning, auditory processing, memory, and the socalled default-mode network, each with BOLD signal changes up to 3%. In general, areas with a high mean percentage BOLD signal are consistent and show the least variation around the mean. These findings show that the baseline activity of the brain is consistent across subjects exhibiting significant temporal dynamics, with percentage BOLD signal change comparable with the signal changes found in task-related experiments.functional connectivity ͉ functional MRI ͉ resting fluctuations T ypical functional MRI (fMRI) research focuses on the change in blood oxygenation level-dependent (BOLD) signal caused by the neural response to an externally controlled stimulus͞task. The fMRI signal during ''on'' periods is contrasted with recordings during a baseline or control condition, resulting in the relative signal change because of the specific process being studied. Recently, increased attention has been directed at investigating the features of the baseline state of the brain. Of particular interest are low-frequency fluctuations (Ϸ0.01-0.1 Hz) observed in the BOLD signal, which have been found to display spatial structure comparable to task-related activation (1-3). There is an ongoing discussion as to whether these fluctuations in the BOLD signal predominantly reflect changes of the underlying brain physiology independent of neuronal function (4-6), or instead reflect the neuronal baseline activity of the brain when goal-directed neuronal action and external input are absent (7,8). The view that coherencies in resting fluctuations represent functional resting-state networks linked to underlying neuronal modulations is consistent with the appearance of these coherencies within cortical gray matter areas of known functional relevance. For example, one of th...