Detrended fluctuation analysis of resting EEG in depressed outpatients and healthy controls.

OBJECTIVE: Recent findings have demonstrated that the EEG possesses long-range temporal (auto-) correlations (LRTC) in the dynamics of broad band oscillations. The analysis of LRTC provides a quantitative index of statistical dependencies in oscillations on different time scales. We analyzed LRTC in resting EEG signals in depressed outpatients and healthy controls. METHODS: The participants in this study were 11 non-depressed, age-matched controls, and 11 unmedicated unipolar depressed patients. EEG data were obtained from each participant during 5-min resting baseline periods with eyes closed and then analyzed with detrended fluctuation analysis (DFA), a scaling analysis method that quantifies a simple parameter to represent the correlation properties of a time series. The scaling exponent, the result of DFA, provides a quantitative measure of LRTC from the EEG. RESULTS: The present study demonstrates that all the scaling exponents in depressed patients and healthy controls were greater than 0.5 and less than 1.0, regardless of condition. Furthermore, the scaling exponents of depressed patients have relatively higher values in whole brain regions compared to healthy controls, with significant differences at F3, C3, T3, T4 and O1 channels (p<0.05). Finally, a significant linear correlation was observed between the severity of depression and the scaling exponent over most of the channels, except O2. CONCLUSIONS: These results suggest that the brain affected by a major depressive disorder shows slower decay of the LRTC, and that the persistence of the LRTC of EEG in depressed patients was associated with the severity of depression over most of the cortical areas. SIGNIFICANCE: The DFA method may broaden our understanding of the psychophysiological basis of depression.

Fractal analysis of EEG in hypnosis and its relationship with hypnotizability.

Fractal analysis was applied to study the trends of EEG signals in the hypnotic condition. The subjects were 19 psychiatric outpatients. Hypnotizability was measured with the Hypnotic Induction Profile (HIP). Fifty-four sets of EEG data were analyzed by detrended fluctuation analysis (DFA), a well-established fractal analysis technique. The scaling exponents, which are the results of fractal analysis, are reduced toward white noise during the hypnotic condition, which differentiates the hypnotic condition from the waking condition. Further, the decrease in the scaling exponents during hypnosis was solely associated with the eye-roll sign within specific cortical areas (F3, C4, and O1/2) closely related to eye movements and attention. In conclusion, the present study has found that the application of the fractal analysis technique can demonstrate the electrophysiological correlations with hypnotic influence on cerebral activity.

Neurofeedback training with virtual reality for inattention and impulsiveness.

In this research, the effectiveness of neurofeedback, along with virtual reality (VR), in reducing the level of inattention and impulsiveness was investigated. Twenty-eight male participants, aged 14-18, with social problems, took part in this study. They were separated into three groups: a control group, a VR group, and a non-VR group. The VR and non-VR groups underwent eight sessions of neurofeedback training over 2 weeks, while the control group just waited during the same period. The VR group used a head-mounted display (HMD) and a head tracker, which let them look around the virtual world. Conversely, the non-VR group used only a computer monitor with a fixed viewpoint. All participants performed a continuous performance task (CPT) before and after the complete training session. The results showed that both the VR and non-VR groups achieved better scores in the CPT after the training session, while the control group showed no significant difference. Compared with the other groups, the VR group presented a tendency to get better results, suggesting that immersive VR is applicable to neurofeedback for the rehabilitation of inattention and impulsiveness.

The effect of virtual reality cognitive training for attention enhancement.

Our main goal in this research was to validate the possibility of virtual reality (VR) for attention enhancement in cognitive training program. Then, we developed some cognitive training tasks using VR technology. Thirty subjects who had little behavioral problems and social problems were randomly assigned into three groups: VR group, non-VR group, and control group. Only the VR group used the head-mounted display (HMD) and position sensor. While the VR group and non-VR group performed cognitive training, the control group received no special treatment. All participants took their eight session tasks over 2 weeks. Participants executed a continuous performance task (CPT) before and after training sessions. We found that immersive VR with cognitive training is effective for attention enhancement. Also, we confirmed that our cognitive training can improve the attention span of children and adolescents with behavioral problems and help them learn to focus on some tasks.