Differential effect of side of temporal lobe epilepsy on lateralization of hippocampal, temporolateral, and inferior frontal activation patterns during a verbal episodic memory task

The encoding of verbal stimuli elicits left-lateralized activation patterns within the medial temporal lobes in healthy adults. In our study, patients with left- and right-sided temporal lobe epilepsy (LTLE, RTLE) were investigated during the encoding and retrieval of word-pair associates using functional magnetic resonance imaging. Functional asymmetry of activation patterns in hippocampal, inferior frontal, and temporolateral neocortical areas associated with language functions was analyzed. Hippocampal activation patterns in patients with LTLE were more right-lateralized than those in patients with RTLE (P<0.05). There were no group differences with respect to lateralization in frontal or temporolateral regions of interest (ROIs). For both groups, frontal cortical activation patterns were significantly more left-lateralized than hippocampal patterns (P<0.05). For patients with LTLE, there was a strong trend toward a difference in functional asymmetry between the temporolateral and hippocampal ROIs (P=0.059). A graded effect of epileptic activity on laterality of the different regional activation patterns is discussed.

[1]  G. Jackson,et al.  Functional connectivity networks are disrupted in left temporal lobe epilepsy , 2006, Annals of neurology.

[2]  D. Gadian,et al.  Language reorganization in children with early-onset lesions of the left hemisphere: an fMRI study. , 2004, Brain : a journal of neurology.

[3]  J. Desmond,et al.  Material-specific lateralization in the medial temporal lobe and prefrontal cortex during memory encoding. , 2001, Brain : a journal of neurology.

[4]  C. Elger,et al.  Memory reorganization in adult brain: observations in three patients with temporal lobe epilepsy , 2002, Epilepsy Research.

[5]  Friedrich G. Woermann,et al.  Memory fMRI lateralizes temporal lobe epilepsy , 2001, Neurology.

[6]  Frank Kügler,et al.  Comparison of implicit memory encoding paradigms for the activation of mediotemporal structures , 2007, Epilepsy & Behavior.

[7]  R. C. Oldfield.  The assessment and analysis of handedness: the Edinburgh inventory. , 1971, Neuropsychologia.

[8]  John S. Duncan,et al.  Material-specific lateralization of memory encoding in the medial temporal lobe: Blocked versus event-related design , 2005, NeuroImage.

[9]  John S Duncan,et al.  Reorganization of Verbal and Nonverbal Memory in Temporal Lobe Epilepsy Due to Unilateral Hippocampal Sclerosis , 2007, Epilepsia.

[10]  M. Jones-Gotman,et al.  Localization of lesions by neuropsychological testing. , 1991, Epilepsia.

[11]  W H Theodore,et al.  Seizure focus affects regional language networks assessed by fMRI , 2005, Neurology.

[12]  Arthur W. Toga,et al.  A Probabilistic Atlas of the Human Brain: Theory and Rationale for Its Development The International Consortium for Brain Mapping (ICBM) , 1995, NeuroImage.

[13]  Guillén Fernández,et al.  Left hippocampal pathology is associated with atypical language lateralization in patients with focal epilepsy. , 2006, Brain : a journal of neurology.

[14]  J. Desmond,et al.  Material‐specific lateralization of prefrontal activation during episodic encoding and retrieval , 1998, Neuroreport.

[15]  C. Elger,et al.  Shift-back of right into left hemisphere language dominance after control of epileptic seizures: Evidence for epilepsy driven functional cerebral organization , 2006, Epilepsy Research.

[16]  S. Petersen,et al.  Hemispheric Specialization in Human Dorsal Frontal Cortex and Medial Temporal Lobe for Verbal and Nonverbal Memory Encoding , 1998, Neuron.

[17]  F. Woermann,et al.  Epileptic activity influences the lateralization of mesiotemporal fMRI activity , 2004, Neurology.

[18]  C. Helmstaedter,et al.  Cognitive Outcomes in Patients with Chronic Temporal Lobe Epilepsy , 2006, Epilepsia.

[19]  Judy Illes,et al.  Memory Lateralization in Medial Temporal Lobe Epilepsy Assessed by Functional MRI , 2002, Epilepsia.

[20]  G. Jackson,et al.  Reorganization of verbal memory and language: A case of dissociation , 1999, Journal of the International Neuropsychological Society.

[21]  M. Cheung,et al.  Effects of Illness Duration on Memory Processing of Patients with Temporal Lobe Epilepsy , 2006, Epilepsia.

[22]  Andreas Schulze-Bonhage,et al.  The reliability of fMRI activations in the medial temporal lobes in a verbal episodic memory task , 2005, NeuroImage.

[23]  M. D’Esposito,et al.  Functional MRI lateralization of memory in temporal lobe epilepsy , 1998, Neurology.

[24]  J B Poline,et al.  Episodic memory in left temporal lobe epilepsy: a functional MRI study. , 2000, Brain : a journal of neurology.

[25]  J. Fell,et al.  Intrasubject reproducibility of presurgical language lateralization and mapping using fMRI , 2003, Neurology.

[26]  Paul J. Laurienti,et al.  An automated method for neuroanatomic and cytoarchitectonic atlas-based interrogation of fMRI data sets , 2003, NeuroImage.

[27]  A. Wyler,et al.  Reorganization of Verbal Memory Function in Early Onset Left Temporal Lobe Epilepsy , 1997, Brain and Cognition.

[28]  J. A. Frost,et al.  Side of seizure focus predicts left medial temporal lobe activation during verbal encoding , 1998, Neurology.