A rational, multispectral mapping algorithm for primary motor cortex: A primary step before cortical stimulation

Abstract

Summary Objective For future artificial intelligence–based brain mapping, development of a rational and safe scoring system for a brain motor mapping algorithm using electrocorticography (ECoG score), which contains various spectral, purely intrinsic brain activities, is necessary for either before or in the absence of electrical cortical stimulation (ECS). Methods We evaluated 1114 electrodes of 10 consecutive focal epilepsy patients who underwent subdural electrode implantation before epilepsy surgery at Kyoto University Hospital during 2011‐2017. Data from ECoG‐based mapping (bandpass filter of 0.016‐300/600 Hz) to define the primary motor area (M1) localization were used to create an ECoG score (range = 0‐4) by assigning 1 point each for the occurrence of ECoG components: very slow movement‐related cortical potentials (<0.5‐1.0 Hz), event‐related synchronization (76‐100 Hz or 100‐200 Hz), and event‐related desynchronization (8‐12 Hz or 12‐24 Hz). The ECoG score was assessed by calculating the sensitivity, specificity, and cutoff values of the score for localization concordance with M1 defined using only ECS as a reference. Results With an area under the receiver operating characteristic curve (AUC) of 0.76, cutoffs of scores of 4 and 1 showed high specificity (94%) and sensitivity (98%) in concordance with ECS‐based mapping, respectively. The ECoG score for mapping M1 of the upper limb achieved greater accuracy (AUC = 0.85) compared to that of the face (AUC = 0.64). Significance The ECoG score proposed in the present study is rational, simple, and useful to define M1, and it is spatially concordant with ECS. Although ECS is still widely employed for presurgical examination, our proposed application of the ECoG score may be suitable for future brain M1 mapping, and possibly beyond M1 mapping, independently of ECS.

A score to map the lateral nonprimary motor area: Multispectrum intrinsic brain activity versus cortical stimulation

“…For each electrode, we assessed the significance of ECoG components: BP (<1 Hz), ERD (proportional power decrease in the 8‐24–Hz band), and ERS (proportional power increase in the 40‐80–Hz band). Combined analysis using BP/ERS/ERD is rational and accurate, because analysis of multiple ECoG components involving every spectrum on various spatiotemporal scales allows exhaustive probing of the brain. Different ECoG components in their frequency ranges (BP/ERS/ERD) could have appeared independently to some extent .…”

“…Combined analysis using BP/ERS/ERD is rational and accurate, because analysis of multiple ECoG components involving every spectrum on various spatiotemporal scales allows exhaustive probing of the brain. Different ECoG components in their frequency ranges (BP/ERS/ERD) could have appeared independently to some extent . The locations of implanted electrodes with representative waveforms are shown in Figure A,B.…”

“…Using linear regression, we defined the significance of BP/ERS/ERD (Figure ) . The thresholds for BP/ERS/ERD differed substantially, because higher thresholds such as mean ± 3 SD at baseline may limit BP occurrence; we recently reported that using different thresholds for BP/ERS/ERD allows highly specific/sensitive brain mapping …”

“…To propose an NPMA score specific to the lateral frontal convexity, this study selectively assessed electrodes located in the PrCG, SFG, MFG, POp, PTr, and L‐PrF based on MRI. Data on electrodes located on the medial and basal frontal areas and extrafrontal lobes were not used to derive the score because our non–task‐specific ECoG components were presumably not applicable to those regions …”

“…Electrocorticography (ECoG)‐based mapping, which reflects multispectrum intrinsic activities related to the NPMA (eg, slow cortical potentials and spectrum changes accompanied by self‐initiated movements regardless of the site of movement), might provide an alternative. We have recently proposed an ECoG‐based scoring system for M1 mapping . As the next step, this study aimed to develop scoring for the NPMA (NPMA score) that will investigate the physiological roles or the networks of NPMA, as an alternative to ECS.…”