title: Spatiotemporal dynamics of low frequency fluctuations in BOLD fMRI of the rat.
abstract: OBJECTIVE
  To examine spatiotemporal dynamics of low frequency fluctuations in rat cortex.
  
  
  METHODS
  Gradient-echo echo-planar imaging images were acquired from anesthetized rats (repetition time = 100 ms). Power spectral analysis was performed to detect different frequency peaks. Functional connectivity maps were obtained for the frequency peaks of interest. The images in the filtered time-series were displayed as a movie to study spatiotemporal patterns in the data for frequency bands of interest.
  
  
  RESULTS
  High temporal and spectral resolution allowed separation of primary components of physiological noise and visualization of spectral details. Two low frequency peaks with distinct characteristics were observed. Selective visualization of the second low frequency peak revealed waves of activity that typically began in the secondary somatosensory cortex and propagated to the primary motor cortex.
  
  
  CONCLUSIONS
  To date, analysis of these fluctuations has focused on the detection of functional networks assuming steady state conditions. These results suggest that detailed examination of the spatiotemporal dynamics of the low frequency fluctuations may provide more insight into brain function, and add a new perspective to the analysis of resting state fMRI data.
authors.affiliation: Georgia Institute of Technology and Emory University, Biomedical Engineering, Atlanta, Georgia, USA.
authors.forename: Waqas
authors.initials: W
authors.lastname: Majeed
authors.forename: Matthew
authors.initials: M
authors.lastname: Magnuson
authors.forename: Shella D
authors.initials: SD
authors.lastname: Keilholz
mesh_terms: D000818:Animals; D001931:Brain Mapping / Q000379:methods*; D002540:Cerebral Cortex / Q000033:anatomy & histology*; D017352:Echo-Planar Imaging / Q000379:methods*; D007091:Image Processing, Computer-Assisted; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors