Electrocorticography (ECoG) is a powerful tool for presurgical functional mapping. Power increase in the high gamma band has been observed from ECoG electrodes on the surface of the sensory motor cortex during the execution of body movements. In this study the authors aim to validate the clinical usage of high gamma activity in presurgical mapping by comparing ECoG mapping with traditional direct electrical cortical stimulation (ECS) and functional MRI (fMRI) mapping.
Seventeen patients with epilepsy participated in an ECoG motor mapping experiment. The patients executed a 5-minute hand/tongue movement task while the ECoG signal was recorded. All 17 patients also underwent extraoperative ECS mapping to localize the motor cortex. Eight patients also participated in a presurgical fMRI study. The high gamma activity on ECoG was modeled using the general linear model (GLM), and the regions showing significant gamma power increase during the task condition compared with the rest condition were localized. The maps derived from GLM-based ECoG mapping, ECS, and fMRI were then compared.
High gamma activity in the motor cortex can be reliably modulated by motor tasks. Localization of the motor regions achieved with GLM-based ECoG mapping was consistent with the localization determined by ECS. The maps also appeared to be highly localized compared with the fMRI activations. Using the ECS findings as the reference, GLM-based ECoG mapping showed a significantly higher sensitivity than fMRI (66.7% for ECoG, 52.6% for fMRI, p < 0.05), while the specificity was high for both techniques (> 97%). If the current-spreading effect in ECS is accounted for, ECoG mapping may produce maps almost identical to those produced by ECS mapping (100% sensitivity and 99.5% specificity).
General linear model–based ECoG mapping showed a superior performance compared to traditional ECS and fMRI mapping in terms of efficiency and accuracy. Using this method, motor functions can be reliably mapped in less than 5 minutes.
Abbreviations used in this paper:BOLD = blood oxygen level dependent; ECoG = electrocorticography; ECS = electrical cortical stimulation; fMRI = functional MRI; GLM = general linear model; TTL = transistor-transistor logic.
Address correspondence to: Bo Hong, Ph.D., Department of Biomedical Engineering, School of Medicine, Tsinghua University, Medical School Building B204, Qinghua Yuan 1, Beijing 100084, China. email: firstname.lastname@example.org.
Please include this information when citing this paper: published online April 19, 2013; DOI: 10.3171/2013.2.JNS12843.
BittarRGOlivierASadikotAFAndermannFPikeGBReutensDC: Presurgical motor and somatosensory cortex mapping with functional magnetic resonance imaging and positron emission tomography. J Neurosurg91:915–9211999
BrunnerPRitaccioALLynchTMEmrichJFWilsonJAWilliamsJC: A practical procedure for real-time functional mapping of eloquent cortex using electrocorticographic signals in humans. Epilepsy Behav15:278–2862009
CroneNEMigliorettiDLGordonBLesserRP: Functional mapping of human sensorimotor cortex with electrocorticographic spectral analysis. II. Event-related synchronization in the gamma band. Brain121:2301–23151998
CroneNEMigliorettiDLGordonBSierackiJMWilsonMTUematsuS: Functional mapping of human sensorimotor cortex with electrocorticographic spectral analysis. I. Alpha and beta event-related desynchronization. Brain121:2271–22991998
FandinoJKolliasSSWieserHGValavanisAYonekawaY: Intraoperative validation of functional magnetic resonance imaging and cortical reorganization patterns in patients with brain tumors involving the primary motor cortex. J Neurosurg91:238–2501999
HirschJRugeMIKimKHCorreaDDVictorJDRelkinNR: An integrated functional magnetic resonance imaging procedure for preoperative mapping of cortical areas associated with tactile, motor, language, and visual functions. Neurosurgery47:711–7222000
HolodnyAISchulderMLiuWCWolkoJMaldjianJAKalninAJ: The effect of brain tumors on BOLD functional MR imaging activation in the adjacent motor cortex: implications for image-guided neurosurgery. AJNR Am J Neuroradiol21:1415–14222000
PfurtschellerGGraimannBHugginsJELevineSPSchuhLA: Spatiotemporal patterns of beta desynchronization and gamma synchronization in corticographic data during self-paced movement. Clin Neurophysiol114:1226–12362003