Yi Guosheng

Modulation of electroencephalograph activity by manual acupuncture stimulation in healthy subjects: An autoregressive spectral analysis

To investigate whether and how manual acupuncture (MA) modulates brain activities, we design an experiment where acupuncture at acupoint ST36 of the right leg is used to obtain electroencephalograph (EEG) signals in healthy subjects. We adopt the autoregressive (AR) Burg method to estimate the power spectrum of EEG signals and analyze the relative powers in delta (0 Hz–4 Hz), theta (4 Hz–8 Hz), alpha (8 Hz–13 Hz), and beta (13 Hz–30 Hz) bands. Our results show that MA at ST36 can significantly increase the EEG slow wave relative power (delta band) and reduce the fast wave relative powers (alpha and beta bands), while there are no statistical differences in theta band relative power between different acupuncture states. In order to quantify the ratio of slow to fast wave EEG activity, we compute the power ratio index. It is found that the MA can significantly increase the power ratio index, especially in frontal and central lobes. All the results highlight the modulation of brain activities with MA and may provide potential help for the clinical use of acupuncture. The proposed quantitative method of acupuncture signals may be further used to make MA more standardized.

Developments of neural effects inducedby noninvasive brain modulation

Noninvasive brain modulation (NBM) is such a stimulation technique that uses electric or magnetic fields to non-intrusively stimulate the central nervous system (CNS). Common NBM modalities include transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS). TMS usually uses pulsed fields of 1–4 Tesla in intensity with duration less than a millisecond to stimulate brain. Such strong field is sufficient to directly evoke action potentials in relevant neural tissue, which is referred as to suprathreshold field. Unlike TMS, tDCS delivers weak constant current of 0.5–2 mA in intensity to stimulate human cortex by means of a pair of electrode pads placed on the scalp. Such weak stimulus is unable to excite neural tissue to initiate action potentials, which is referred as to subthreshold fields. Nowadays, NBM has become a promising option for the treatment, diagnosis, and rehabilitation of a number of neurologic or psychiatric disorders in clinics, such as, epilepsy, schizophrenia, Alzheimer’s disease, depression, Parkinson’s disease, stroke, as well as pain syndromes. What is more, it is also a common tool used to study brain physiology and function, which has great potentials in exploring cognitive, emotion, memory, attention, learning, perception, language, and plasticity. As a noninvasive method of intervening brain activities, the NBM technique has significantly promoted the developments of cognitive science, neurophysiology, neurology and psychiatry in recent years. Although NBM has been widely and successfully applied in clinics and basic researches, it is still largely unknown how it interacts with CNS and modulates brain function. Such insufficient understanding of the potential mechanisms underlying NBM would delay the design of more effective stimulator as well as limit the development and optimization of stimulation protocols. One common principle for NBM techniques is that they modulate neural activity and ultimately behavior through the generation of extracellular electric fields around the interested brain tissue. According to this principle, two key problems should be considered when we are probing how NBM participates in brain activity and function. One is to determine the characteristics of extracellular fields generated in the brain tissue during stimulation. The common method for addressing this problem is finite element analysis. The other one is to investigate how this induced field modulates neural activity to alter brain function and ultimately behavior. The focus of recent researches associated with this problem is to identify the spiking behaviors of neural system stimulated by electric fields as well as to explore the biophysical basis for their generation. In this paper, we first introduce the application status of NBM in neuroscience and clinics. Then, we review the main findings on the neuromodulation effects of electric field, including electrophysiological experiment and computational modeling simulation. Finally, we raise several key issues that need to be addressed in the future.