Topographic Analysis of Contact Heat Evoked Potentials
Date Issued
2016
Date
2016
Author(s)
Chen, Wei-Che
Abstract
Background: Contact heat evoked potentials (CHEPs) can be used to study pain phenomenon because contact heat does not cause local tissue damage and therefore the skin can be repeatedly stimulated. EEG recording using single vertex channel at Cz has demonstrated that it is an objective marker to document pain and peripheral nerve injury. Previous studies using EEG or functional MRI have shown activation of various brain areas. This study is designed to further study brain activation when healthy subjects or patients of peripheral neuropathy are stimulated with contact heat. Methods: Healthy subjects and patients of peripheral neuropathy are stimulated in the right leg with contact heat pulses of 51°C and multiple channel EEG signals are recorded by using the Neuroscan Quik-Cap System. After the signals are preprocessed by MATLAB and EEGLAB, standardized low-resolution electromagnetic tomography(sLORETA) is used to localize areas of activation in each subject group. Group independent component analysis (ICA) is also performed in each group to find independent components with significant activation after heat stimuli. sLORETA analyses are then applied to those significant independent component for localization of brain activation. After reviewing the above results and references, several regions of interests (ROIs) are chosen and correlation of sLORETA current density in each ROI with pain score are performed. Results: Seventeen healthy subjects and 17 patients of various peripheral neuropathies are recruited to the current study. Brain localization using event-related potential and sLORETA reveals the activation of the anterior cingulate gyri in the healthy subjects and of the left temporooccipital junction in the patients. Brain activation after group ICA analysis also concurs with the previous findings and common activation in the left (contralateral) posterior parietal cortex is found. Participation and/or responses of multiple brain areas after contact heat stimuli are found. Regions of interest analyses not only reveal correlation of the activation in the bilateral cingulate gyri and left operculoinsular cortex with numerical rating scales of pain, but also activation in the dorsolateral prefrontal cortices is also positively correlated with scales of pain. Conclusion: In this study, common activation in the anterior cingulate gyri, dorsolateral prefrontal cortices, contralateral postcentral gyrus and contralateral posterior parietal cortex is found in both healthy subjects and patients of peripheral neuropathy. Specific activation of the left temporooccipital junction in patients is also found and needs further study.
Subjects
contact heat evoked potential (CHEP)
brain localization
multi-channel electroencephalograph
low-resolution electromagnetic tomography (LORETA)
independent component analysis (ICA)
Type
thesis
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