Periods of rest in fMRI contain individual spontaneous events which are related to slowly fluctuating spontaneous activity
Article first published online: 14 FEB 2012
Copyright © 2011 Wiley Periodicals, Inc.
Human Brain Mapping
Volume 34, Issue 6, pages 1319–1329, June 2013
How to Cite
Petridou, N., Gaudes, C. C., Dryden, I. L., Francis, S. T. and Gowland, P. A. (2013), Periods of rest in fMRI contain individual spontaneous events which are related to slowly fluctuating spontaneous activity. Hum. Brain Mapp., 34: 1319–1329. doi: 10.1002/hbm.21513
- Issue published online: 15 APR 2013
- Article first published online: 14 FEB 2012
- Manuscript Accepted: 14 OCT 2011
- Manuscript Revised: 29 AUG 2011
- Manuscript Received: 18 MAY 2011
- Wellcome Trust (7T programme)
- nonstationary spontaneous activity;
- brain mapping
fMRI studies of brain activity at rest study slow (<0.1 Hz) intrinsic fluctuations in the blood-oxygenation-level-dependent (BOLD) signal that are observed in a temporal scale of several minutes. The origin of these fluctuations is not clear but has previously been associated with slow changes in rhythmic neuronal activity resulting from changes in cortical excitability or neuronal synchronization. In this work, we show that individual spontaneous BOLD events occur during rest, in addition to slow fluctuations. Individual spontaneous BOLD events were identified by deconvolving the hemodynamic impulse response function for each time point in the fMRI time series, thus requiring no information on timing or a-priori spatial information of events. The patterns of activation detected were related to the motor, visual, default-mode, and dorsal attention networks. The correspondence between spontaneous events and slow fluctuations in these networks was assessed using a sliding window, seed-correlation analysis, where seed regions were selected based on the individual spontaneous event BOLD activity maps. We showed that the correlation varied considerably over time, peaking at the time of spontaneous events in these networks. By regressing spontaneous events out of the fMRI signal, we showed that both the correlation strength and the power in spectral frequencies <0.1 Hz decreased, indicating that spontaneous activation events contribute to low-frequency fluctuations observed in resting state networks with fMRI. This work provides new insights into the origin of signals detected in fMRI studies of functional connectivity. Hum Brain Mapp, 2013. © 2012 Wiley Periodicals, Inc.