Xiaoli Li

Estimation of genuine and random synchronization in multivariate neural series

Synchronization is an important mechanism that helps in understanding information processing in a normal or abnormal brain. In this paper, we propose a new method to estimate the genuine and random synchronization indexes in multivariate neural series, denoted as GSI (genuine synchronization index) and RSI (random synchronization index), by means of a correlation matrix analysis and surrogate technique. The performance of the method is evaluated by using a multi-channel neural mass model (MNMM), including the effects of different coupling coefficients, signal to noise ratios (SNRs) and time-window widths on the estimation of the GSI and RSI. Results show that the GSI and the RSI are superior in description of the synchronization in multivariate neural series compared to the S-estimator. Furthermore, the proposed method is applied to analyze a 21-channel scalp electroencephalographic recording of a 35 year-old male who suffers from mesial temporal lobe epilepsy. The GSI and the RSI at different frequency bands during the epileptic seizure are estimated. The present results could be helpful for us to understand the synchronization mechanism of epileptic seizures.

Phase–amplitude coupling between theta and gamma oscillations during nociception in rat electroencephalography

In electroencephalography (EEG) study, gamma oscillations were reported to participate in pain processing; theta oscillations were also involved in pain processing. Moreover, theta always modulated gamma activity by phase-amplitude coupling in event-related oscillations. Whether theta modulate gamma by phase-amplitude coupling in pain processing is of interest. In the present study, using EEG of rats after laser nociceptive stimulation, we investigated gamma activity and phase-amplitude coupling between theta and gamma. It was found that induced gamma power increased starting 200 ms after nociceptive stimulation onset. Moreover, significant coupling between theta phase and gamma amplitude was found over frontal and parietal region after nociceptive stimulation. Our results for the first time suggest that coupling between theta and gamma is involved in nociception processing.

Modulation of Brain Electroencephalography Oscillations by Electroacupuncture in a Rat Model of Postincisional Pain

The present study aimed to investigate how ongoing brain rhythmical oscillations changed during the postoperative pain and whether electroacupuncture (EA) regulated these brain oscillations when it relieved pain. We established a postincisional pain model of rats with plantar incision to mimic the clinical pathological pain state, tested the analgesic effects of EA, and recorded electroencephalography (EEG) activities before and after the EA application. By analysis of power spectrum and bicoherence of EEG, we found that in rats with postincisional pain, ongoing activities at the delta-frequency band decreased, while activities at theta-, alpha-, and beta-frequency bands increased. EA treatment on these postincisional pain rats decreased the power at high-frequency bands especially at the beta-frequency band and reversed the enhancement of the cross-frequency coupling strength between the beta band and low-frequency bands. After searching for the PubMed, our study is the first time to describe that brain oscillations are correlated with the processing of spontaneous pain information in postincisional pain model of rats, and EA could regulate these brain rhythmical frequency oscillations, including the power and cross-frequency couplings.

Modulations on cortical oscillations by subthalamic deep brain stimulation in patients with Parkinson disease: A MEG study

OBJECTIVEnThe study aimed to explore the modification to cortical oscillations of Parkinson disease (PD) patients by subthalamic nucleus deep brain stimulation (STN DBS).nnnMETHODSnWith Magnetoencephalogram (MEG) detection, we examined the changes in absolute power spectrum of cortical oscillations in the PD patients with the treatment of STN DBS.nnnRESULTSnThe power analysis of PD patients showed a dominant over-synchronization of alpha and beta bands in temporal and occipital areas relative to the healthy control subjects. STN DBS on-state showed marked power increase in the gamma band of PD patients in the frontal and parietal relative to the DBS off-state. The alleviation of motor symptoms by STN DBS negatively correlated to the increase of high gamma oscillation in the right frontal cortex, and also correlated to the suppression of the alpha and beta oscillations in the right temporal cortex.nnnCONCLUSIONnThe treatment of STN DBS to PD patients might involve the augmentation of gamma activity and suppression of alpha and beta activities in cortical oscillations.

A Review of Resting-State Electroencephalography Analysis in Disorders of Consciousness

Recently, neuroimaging technologies have been developed as important methods for assessing the brain condition of patients with disorders of consciousness (DOC). Among these technologies, resting-state electroencephalography (EEG) recording and analysis has been widely applied by clinicians due to its relatively low cost and convenience. EEG reflects the electrical activity of the underlying neurons, and it contains information regarding neuronal population oscillations, the information flow pathway, and neural activity networks. Some features derived from EEG signal processing methods have been proposed to describe the electrical features of the brain with DOC. The computation of these features is challenging for clinicians working to comprehend the corresponding physiological meanings and then to put them into clinical applications. This paper reviews studies that analyze spontaneous EEG of DOC, with the purpose of diagnosis, prognosis, and evaluation of brain interventions. It is expected that this review will promote our understanding of the EEG characteristics in DOC.

Enhanced Gamma Oscillatory Activity in Rats with Chronic Inflammatory Pain

It has been reported that oscillatory gamma activity participates in brief acute pain and tonic ongoing pain. It is of great interest to determine whether the gamma activity is involved in chronic pain since chronic pain is a more severe pathological condition characterized by pain persistency. To investigate the oscillatory gamma activity in chronic pain, in the present study, we recorded spontaneous electrocorticogram (ECoG) signals during chronic pain development in rats with chronic inflammatory pain induced by monoarthritis. Power spectrum analysis of ECoG data showed that gamma power increased significantly at the late stage of chronic inflammatory pain. The increased gamma activity occurred mainly at electrodes over primary somatosensory cortices. In rats with chronic pain, the gamma power was positively correlated with the hyperalgesia measured by laser energy that elicited hindpaw withdrawal response. Furthermore, an increased coupling between the amplitude of gamma power and the phase of theta oscillations was observed in chronic inflammatory pain condition. These results indicate an enhanced spontaneous gamma activity in chronic pain and suggest a potential biomarker for the severity of chronic pain.

Effects of 10 Hz Repetitive Transcranial Magnetic Stimulation of the Left Dorsolateral Prefrontal Cortex in Disorders of Consciousness

Background While repetitive transcranial magnetic stimulation (rTMS) has been applied in treatment of patients with disorders of consciousness (DOC), a standardized stimulation protocol has not been proposed, and its therapeutic effects are inconsistently documented. Objectives To assess the efficacy of rTMS in improving consciousness in patients with persistent minimally conscious state (MCS) or unresponsive wakefulness syndrome (UWS), previously known as vegetative state (VS). Method A prospective single-blinded study, with selected subjects, was carried out. In total, 16 patients (5 MCS and 11 VS/UWS) with chronic DOC were included. All patients received active 10u2009Hz rTMS at the left dorsolateral prefrontal cortex (DLPFC), at one session per day, for 20 consecutive days. A single daily session of stimulation consisted of 1,000 pulses (10u2009s of 10u2009Hz trains; repeated 10 times with an inter-train interval of 60u2009s; and 11u2009min and 40u2009s for total session). The main outcome measures were changes in the total score on the JFK Coma Recovery Scale-Revised (CRS-R) scale. Additional measures were the impressions of caregivers after the conclusion of the interventions, which were assessed using the Clinical Global Impression-Improvement (CGI-I) scale. Results The CRS-R scores were increased in all 5 MCS patients and 4 of 11 VS/UWS patients, while a significant enhancement of CRS-R scores was observed compared to the baseline in all participants (pu2009=u20090.007). However, the improvement was more notable in MCS patients (pu2009=u20090.042) than their VS/UWS counterparts (pu2009=u20090.066). Based on the CGI-I scores, two patients improved considerably, two improved, six minimally improved, six experienced no change, and none deteriorated. Good concordance was seen between the CGI-I result and the increases in CRS-R scores. Conclusion Treatment of 10u2009Hz multisession rTMS applied to the left DLPFC is promising for the rehabilitation of DOC patients, especially those in MCS. Further validation with a cohort of a larger sample size is required.

Characterizing Heat-Sensitization Responses in Suspended Moxibustion with High-Density EEG

OBJECTIVEnWe have reported heat-sensitization responses during suspended moxibustion, whose occurrence is associated with significantly better therapeutic effects. The present study aimed to characterize the electrophysiological features of this interesting phenomenon with high-density electroencephalography (EEG).nnnMETHODSnWe performed EEG recording in a group of patients with chronic low back pain before, during, and after moxibustion treatment at DU3.nnnRESULTSn12 out of 25 subjects experienced strong heat-sensitization during moxibustion, which was accompanied by increased power spectral densities (PSDs) at the theta, alpha, and beta frequency bands. The scalp topographies of averaged power indicated that the theta and beta PSD changes were most obvious in fronto-central regions, whereas those of the alpha band were more global. In addition, nonsensitized and sensitized groups showed distinct activity patterns, with heat-sensitization inducing increased phase coherence at the theta and beta ranges.nnnCONCLUSIONSnThese data were the first objective evidence of heat-sensitization responses during suspended moxibustion, which were characterized by widespread oscillatory changes in scalp EEG.

Cortical activities of heat-sensitization responses in suspended moxibustion: an EEG source analysis with sLORETA

Moxibustion is under active research as a complementary and alternative treatment for various diseases such as pain. “Heat-sensitization” responses have been reported during suspended moxibustion, whose occurrence is associated with significantly better therapeutic effects. The present study aimed to investigate the cortical activities of this interesting phenomenon by a standardized low-resolution brain electromagnetic tomography. We performed electroencephalography recording in a group of patients with chronic low back pain before, during, and after moxibustion treatment at Yaoyangguan (DU3) areas. 11 out of 21 subjects experienced strong heat-sensitization during moxibustion, which were accompanied with significant decreases of current densities in the beta frequency bands in prefrontal, primary and second somatosensory, and cingulate cortices, as well as increased current densities in the alpha2 band in the left insula. No changes were detected in patients without sensitization responses, or in the post-moxibustion phase of either group. These data indicated widespread activity changes across different frequency bands during heat-sensitization. Cortical oscillatory activities could be used to evaluate the “heat-sensitization” responses during suspended moxibustion.

The Frontal Area with Higher Frequency Response Is the Principal Feature of Laser-Evoked Potentials in Rats with Chronic Inflammatory Pain: A Parallel Factor Analysis Study

Chronic pain is a pathological developing course of pain. In clinic, an objective indicator is needed for diagnosing and better controlling chronic pain. The abnormal neural responses in chronic pain are reflected by multiple event-related potentials (ERPs) in time, frequency, and location domain, respectively. However, multiple changes in ERPs are not applicable in clinic. So, the principal feature covered the most informative changes extracted from these three domains of ERP during the development of chronic pain is needed. In the present study, a parallel factor analysis method was employed to extract time–frequency–channel features of laser-evoked potential (LEP) simultaneously from rats with chronic inflammatory pain. Results showed that the main feature of LEP in channel domain locates in the frontal brain region in rats with chronic inflammatory pain while in the parietal brain region in control rats. In the frequency domain, the main frequency of LEP was significantly higher in chronic inflammatory pain rats than that in control rats. These findings indicate that the frontal region with higher frequency response to nociceptive information is the principal feature in the chronic pain state. Our study provided not only a principal feature of LEP but also a promising strategy for chronic pain, which is potential for clinic application.