Abstract
Complex nerve remodeling occurs in the injured brain area during functional rehabilitation after a brain injury; however, its mechanism has not been thoroughly elucidated. Neural remodeling can lead to changes in the electrophysiological activity, which can be detected in an electroencephalogram (EEG). In this paper, we used EEG band energy, approximate entropy (ApEn), sample entropy (SampEn), and Lempel–Ziv complexity (LZC) features to characterize the intrinsic rehabilitation dynamics of the injured brain area, thus providing a means of detecting and exploring the mechanism of neurological remodeling during the recovery process after brain injury. The rats in the injury group (n = 12) and sham group (n = 12) were used to record the bilateral symmetrical EEG on days 1, 4, and 7 after a unilateral brain injury in awake model rats. The open field test (OFT) experiments were performed in the following three groups: an injury group, a sham group, and a control group (n = 10). An analysis of the EEG data using the energy, ApEn, SampEn, and LZC features demonstrated that the increase in SampEn was associated with the functional recovery. After the brain injury, the energy values of the delta1 bands on day 4; the delta2 bands on days 4 and 7; the theta, alpha, and beta bands and the values of ApEn, SampEn, and LZC of the cortical EEG signal on days 1, 4 and 7 were significantly lower in the injured brain area than in the non-injured area. During the process of recovery for the injured brain area, the values of the beta bands, ApEn, and SampEn of the injury group increased significantly, and gradually became equal to the value of the sham group. The improvement in the motor function of the model rats significantly correlated with the increase in SampEn. This study provides a method based on EEG nonlinear features for measuring neural remodeling in injured brain areas during brain function recovery. The results may aid in the study of neural remodeling mechanisms.
Highlights
Brain injury is one of the main causes of death and disability worldwide [1,2]
The results indicated that the values of the beta bands, approximate entropy (ApEn), and sample entropy (SampEn) of the EEG signal in the injured area showed an increasing trend during the recovery process
Studies have shown that changes in neuroplasticity are the basis for the recovery of motor function after brain injury [34]. These results suggest that the changes in the EEG features caused by neuronal activity during nerve remodeling in injured brain areas might be a good indicator of brain function recovery
Summary
Brain injury is one of the main causes of death and disability worldwide [1,2]. Functional rehabilitation occurs to some extent during the recovery period after a brain injury, and the mechanism of rehabilitation has long been a major issue in clinical settings and brain science. The current research indicates that blood vessel and nerve remodeling occur during the brain function recovery period [3]. Many reports have described vascular remodeling, such as through optical coherence tomography (OCT), which has shown morphological changes in different types of blood vessels during photothrombotic occlusion and later recovery [4]. Because the process of nerve remodeling is very complex, it has been studied in few reports to date.
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