Current source density (sLORETA) in patients undergoing cognitive rehabilitation using dual task in the early postoperative period of coronary artery bypass grafting

Abstract

Highlights. For the first time, the method of standardized low resolution electromagnetic tomography – sLORETA was used to assess the neurophysiological correlates of the success of cognitive rehabilitation using dual task to recover the brain functions affected by ischemia during cardiac surgery.The patients who were successfully rehabilitated have demonstrated lower postoperative values of resting state theta activity within the right hemisphere, indicating the transfer effect, which is an important component of successful cognitive rehabilitation.Aim. Visualization and monitoring of brain ischemia is important for the diagnosis of cerebrovascular diseases. The aim of the study was to evaluate the possibilities and applicability of the method of standardized low resolution electromagnetic brain tomography – sLORETA for analyzing brain electrical activity in patients undergoing cognitive rehabilitation using dual tasks to recover impaired brain functions during ischemia associated with cardiac surgery.Methods. The study included 16 male patients (45–75 years old) who were admitted for planned coronary artery bypass grafting (CABG) to the Clinic at the Research Institute for Complex Issues of Cardiovascular Diseases. Clinical and neurophysiological examinations were performed 2–3 days before CABG and 1 week after surgery. All patients underwent cognitive rehabilitation that started at postoperative day 3 or 4 and lasted until discharge, the outcome was assessed as well. Monopolar EEG (62 channels) was recorded at rest in a sitting position with eyes closed in a light- and noise-insulated room using a Neuvo SynAmps2 Amplifier. Data processing of EEG background activity for sLORETA analysis was performed using the EEGLAB in MATLAB software (The MathWorks, Natick, MA, USA). The sLORETA algorithms were used to calculate dynamic cross spectrum and current source density within the analyzed frequency range (4–6 Hz). Statistical analysis of current source density indicators was carried out by using the method of statistical non-parametric mapping in the sLORETA software package, and the difference between the current source density in the pre- and postoperative period (after cognitive rehabilitation) was calculated as well.Results. Cognitive rehabilitation was successful in 44% (7 patients) of cases. The differences have been revealed between the groups with successful and unsuccessful cognitive rehabilitation by using sLORETA. The group with unsuccessful cognitive rehabilitation demonstrated higher current source density estimates in theta rhythm compared with the successful rehabilitation group, it was most pronounced (t>- 8.42; p<0.004) in the right hemisphere – Brodmann area 22, temporal lobe and superior temporal gyrus.Conclusion. The sLORETA method demonstrated the positive effect of cognitive training on changes in the spatial patterns of brain activity in patients undergoing onpump CABG. The successful cognitive rehabilitation was associated with lower postoperative resting state theta activity within the right hemisphere, indicating the transfer effect, which is an important component of successful cognitive rehabilitation.