title: Reduced thalamocortical functional connectivity in temporal lobe epilepsy.
abstract: OBJECTIVE
  In temporal lobe epilepsy (TLE), the thalamus is well known for its role in the propagation and spread of epileptiform activity. However, the integrity of thalamocortical functional connectivity (FC) in TLE and its relation to specific seizure patterns have not yet been determined. We address these issues with resting-state functional magnetic resonance imaging (fMRI).
  
  
  METHODS
  Resting-state fMRI was performed on two groups of unilateral TLE patients: those with focal seizures only (16 left TLE, 16 right TLE) and those with additional generalized seizures (16 left TLE, 10 right TLE), and 16 matched controls. A thalamic parcellation based on FC between five nonoverlapping cortical seeds (prefrontal, motor, somatosensory, parietal-occipital, and temporal) and the ipsilateral thalamus was carried out to parcel each thalamus into five corresponding segments. FCs between each segment and its ipsilateral cortical seed were extracted and compared across groups using analyses of variance (ANOVAs).
  
  
  RESULTS
  Compared to healthy controls, patients with TLE displayed decreased thalamocortical FC in multiple posterior and ventromedial thalamic segments of both the ictal and nonictal hemispheres. Our parcellation analysis revealed that these thalamic regions were functionally connected to the parietal/occipital and temporal lobes. In patients with TLE with focal seizures these regional thalamocortical FC decreases were limited to the ictal hemisphere. In contrast, TLE patients with both focal and generalized epileptiform activity displayed FC decreases in both the ictal and nonictal thalamus involving the dorsolateral pulvinar, a region preferentially connected to the parietal and occipital lobes.
  
  
  CONCLUSIONS
  Our data provide the first evidence of regional specific thalamocortical FC decreases in patients with unilateral TLE. Furthermore, our results demonstrate that patients with different seizure types present different thalamoparietal/occipital FC decrease patterns. While patients with focal seizures present thalamocortical FC decreases in the ictal hemisphere only, patients with additional generalized seizure activity also show thalamocortical FC decreases involving the thalamus in the nonictal hemisphere.
authors.affiliation: Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, U.S.A.
authors.forename: Xiaosong
authors.initials: X
authors.lastname: He
authors.affiliation: Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, U.S.A.
authors.forename: Gaelle E
authors.initials: GE
authors.lastname: Doucet
authors.affiliation: Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, U.S.A.
authors.forename: Michael
authors.initials: M
authors.lastname: Sperling
authors.affiliation: Department of Neurosurgery, Thomas Jefferson University, Philadelphia, Pennsylvania, U.S.A.
authors.forename: Ashwini
authors.initials: A
authors.lastname: Sharan
authors.affiliation: Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, U.S.A.
authors.forename: Joseph I
authors.initials: JI
authors.lastname: Tracy
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000098:blood supply / Q000473:pathology*; D004833:Epilepsy, Temporal Lobe / Q000473:pathology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009434:Neural Pathways / Q000098:blood supply / Q000473:pathology*; D010100:Oxygen / Q000097:blood; D012146:Rest; D013788:Thalamus / Q000098:blood supply / Q000473:pathology*
chemical_list: D010100:Oxygen
keywords: Functional connectivity; Resting-state functional MRI; Temporal lobe epilepsy; Thalamus