title: Cluster analysis detection of functional MRI activity in temporal lobe epilepsy.
abstract: OBJECTIVE
  The objective of this pilot study was to evaluate the ability of a novel method of cluster analysis, 2dTCA, for identifying and characterizing peak fluctuations in fMRI BOLD signals in the temporal lobes and the default-mode network in temporal lobe epilepsy (TLE) without EEG.
  
  
  METHODS
  BOLD fMRI images were acquired in 17 TLE patients and compared to EEG. The timing of significant transient BOLD peaks was estimated by 2dTCA, and activation maps were determined.
  
  
  RESULTS
  Sixteen subjects (94%) showed apparent temporal lobe activation. Mesial temporal activation was present in 76.4% (13 patients). Temporal lobe or insula activations were detected ipsilateral to the EEG focus in 64.7% (11 patients), bilaterally with no predominance in 29.4% (5 patients), and exclusively contralateral to the EEG focus in none. Eleven subjects showed activation in the so-called default-mode network including posterior cingulate, bilateral posterior parietal cortex, and sometimes anterior cingulate cortex.
  
  
  CONCLUSIONS
  These results demonstrate significant positive BOLD fluctuations in the temporal lobes and default-mode regions in a higher percentage of TLE patients than previously reported using other methods. These fluctuations appear physiologically relevant and suggest increased neural activity which may not be detected on scalp EEG, but which may be important in understanding the mechanisms and origins of epileptic discharges.
authors.affiliation: Vanderbilt University Institute for Imaging Science, Department of Radiology and Radiological Sciences, Vanderbilt University, 1161 21st Avenue South, Nashville, TN 37232-2310, USA. victoria.morgan@vanderbilt.edu
authors.forename: Victoria L
authors.initials: VL
authors.lastname: Morgan
authors.forename: John C
authors.initials: JC
authors.lastname: Gore
authors.forename: Bassel
authors.initials: B
authors.lastname: Abou-Khalil
mesh_terms: D000328:Adult; D001931:Brain Mapping; D016000:Cluster Analysis; D004569:Electroencephalography / Q000379:methods; D004833:Epilepsy, Temporal Lobe / Q000473:pathology* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010865:Pilot Projects; D013057:Spectrum Analysis; D013702:Temporal Lobe / Q000098:blood supply*
chemical_list: D010100:Oxygen