title: Cortical connectivity in fronto-temporal focal epilepsy from EEG analysis: A study via graph theory.
abstract: OBJECTIVE
  It is believed that effective connectivity and optimal network structure are essential for proper information processing in the brain. Indeed, functional abnormalities of the brain are found to be associated with pathological changes in connectivity and network structures. The aim of the present study was to explore the interictal network properties of EEG signals from temporal lobe structures in the context of fronto-temporal lobe epilepsy.
  
  
  METHODS
  To complete this aim, the graph characteristics of the EEG data of 17 patients suffering from focal epilepsy of the fronto-temporal type, recorded during interictal periods, were examined and compared in terms of the affected versus the unaffected hemispheres. EEG connectivity analysis was performed using eLORETA software in 15 fronto-temporal regions (Brodmann Areas BAs 8, 9, 10, 11, 20, 21, 22, 37, 38, 41, 42, 44, 45, 46, 47) on both affected and unaffected hemispheres.
  
  
  RESULTS
  The evaluation of the graph analysis parameters, such as 'global' (characteristic path length) and 'local' connectivity (clustering coefficient) showed a statistically significant interaction among side (affected and unaffected hemisphere) and Band (delta, theta, alpha, beta, gamma). Duncan post hoc testing showed an increase of the path length in the alpha band in the affected hemisphere with respect to the unaffected one, as evaluated by an inter-hemispheric marker. The affected hemisphere also showed higher values of local connectivity in the alpha band. In general, an increase of local and global graph theory parameters in the alpha band was found in the affected hemisphere. It was also demonstrated that these effects were more evident in drug-free patients than in those undergoing pharmacological therapy.
  
  
  CONCLUSIONS
  The increased measures in the affected hemisphere of both functional local segregation and global integration could result from the combination of overlapping mechanisms, including reactive neuroplastic changes seeking to maintain constant integration and segregation properties.
  
  
  CONCLUSIONS
  This reactive neuroplastic mechanism seeking to maintain constant integration and segregation properties seems to be more evident in the absence of antiepileptic treatment.
authors.affiliation: Brain Connectivity Laboratory, IRCCS San Raffaele Pisana, Rome, Italy. Electronic address: fabrizio.vecchio@uniroma1.it.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Vecchio
authors.affiliation: Brain Connectivity Laboratory, IRCCS San Raffaele Pisana, Rome, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Miraglia
authors.affiliation: Department of Life, Health and Environmental Sciences, L'Aquila, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Curcio
authors.affiliation: Institute of Neurology, Department of Geriatrics, Neuroscience and Orthopedics, Catholic University, Policlinic A. Gemelli, Rome, Italy.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Della Marca
authors.affiliation: Institute of Neurology, Department of Geriatrics, Neuroscience and Orthopedics, Catholic University, Policlinic A. Gemelli, Rome, Italy.
authors.forename: Catello
authors.initials: C
authors.lastname: Vollono
authors.affiliation: Institute of Neurology, Department of Geriatrics, Neuroscience and Orthopedics, Catholic University, Policlinic A. Gemelli, Rome, Italy.
authors.forename: Edoardo
authors.initials: E
authors.lastname: Mazzucchi
authors.affiliation: IRCCS Centro Neurolesi Bonino-Pulejo, Messina, Italy.
authors.forename: Placido
authors.initials: P
authors.lastname: Bramanti
authors.affiliation: Brain Connectivity Laboratory, IRCCS San Raffaele Pisana, Rome, Italy; Institute of Neurology, Department of Geriatrics, Neuroscience and Orthopedics, Catholic University, Policlinic A. Gemelli, Rome, Italy.
authors.forename: Paolo Maria
authors.initials: PM
authors.lastname: Rossini
mesh_terms: D000328:Adult; D000368:Aged; D001931:Brain Mapping / Q000379:methods; D002540:Cerebral Cortex / Q000503:physiopathology*; D004569:Electroencephalography / Q000379:methods*; D017034:Epilepsy, Frontal Lobe / Q000175:diagnosis / Q000503:physiopathology*; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000503:physiopathology*; D055815:Young Adult
keywords: Alpha band; EEG; Fronto-temporal epilepsy; Functional connectivity; Graph theory; eLORETA