Impact of volume-conducted potential in interpretation of cortico-cortical evoked potential: Detailed analysis of high-resolution electrocorticography using two mathematical approaches. Issue 4 (April 2017)

• Record Type: Journal Article
• Authors: Shimada, Seijiro; Kunii, Naoto; Kawai, Kensuke; Matsuo, Takeshi; Ishishita, Yohei; Ibayashi, Kenji; Saito, Nobuhito
• Is Part Of: Clinical neurophysiology. Volume 128:Issue 4(2017:Apr.)
• Page Start: 549
• Page End: 557
• Publication Date: 2017-04
• Subjects: DES direct electrical stimulation -- CCEP cortico-cortical evoked potential -- SPES single pulse electrical stimulation -- ALA anterior language area -- PLA posterior language area -- VCP volume-conducted potential -- PCA principal component analysis -- ECoG electrocorticography -- MRI magnetic resonance imaging -- CT computed tomography -- HGA high gamma activities -- EEG electroencephalography -- RMS root mean square; Cortico-cortical evoked potential -- Electrocorticography -- Epilepsy -- Principal component analysis -- Regression analysis -- Volume-conducted potential; Neurophysiology -- Periodicals; Electroencephalography -- Periodicals; Electromyography -- Periodicals; Neurology -- Periodicals; 612.8
• DOI: 10.1016/j.clinph.2017.01.012
• Languages: English
• ISSNs: 1388-2457

Abstract

Highlights: Impact of volume-conducted potential on cortico-cortical evoked potentials (CCEP) was evaluated with high-density grid electrodes. Volume-conducted potential accounted for the majority of the potential around the stimulation site. This study contributes to delineating the CCEP component which reflects true cortical connectivity. Abstract: Objective: Cortico-cortical evoked potential (CCEP) has been utilized to evaluate connectivity between cortices. However, previous reports have rarely referred to the impact of volume-conducted potential (VCP) which must be a confounding factor of large potential around the stimulation site. To address this issue, we challenged the null hypothesis that VCP accounts for the majority of the recorded potential, particularly around the stimulation site. Methods: CCEP was recorded with high-density intracranial electrodes in 8 patients with intractable epilepsy. First, we performed regression analysis for describing the relationship between the distance and potential of each electrode. Second, we performed principal component analysis (PCA) to reveal the temporal features of recorded waveforms. Results: The regression curve, declining by the inverse square of the distance, fitted tightly to the plots ( R 2 : 0.878–0.991) with outliers. PCA suggested the responses around the stimulation site had the same temporal features. We also observed the continuous declination over the anatomical gap and the phase reversal phenomena around the stimulation site. Conclusions: These results were consistent with the null hypothesis. Significance: This study highlighted the risk of misinterpreting CCEP mapping, and proposed mathematical removal of VCP, which could lead to more reliable mapping based on CCEP.