Researchers measured brain responses to acupuncture with magnetoencephalography (MEG) and concluded that acupuncture induces specific responses to brain Regions of Interest (ROIs). Researchers took MEG measurements of the frontal, central, temporal, parietal and occipital regions of the brain while study participants were needled at acupuncture point ST36 (Zusanli). The control group received acupuncture needle stimulation at a nearby non-acupuncture point. The researchers discovered that, "Significantly increased delta power and decreased alpha as well as beta power in bilateral frontal ROIs were observed following stimulation at ST36."

MEG and Brain Waves
MEG maps brain activity by measuring naturally occurring magnetic fields in the brain, which are produced by electric currents produced by the brain. Alpha waves are neural oscillations in the 8-12 Hz range. These brain waves occur during wakeful relaxation with the eyes closed.

Alpha Waves
Alpha waves diminish with the eyes open, during drowsiness and sleep. Alpha waves are thought to be related to visual cortex activity and to play a role in network coordination and communication. Alpha wave intrusion is the appearance of alpha waves during non-REM sleep, a time when delta wave activity is normally dominant. Alpha wave intrusion is commonly found in patients with chronic fatigue and may be associated with fibromyalgia.

Beta Waves
Beta waves are between 12 – 30 Hz. Beta waves occur during waking consciousness. Beta waves occur in conjunction with muscle contractions during isotonic movements.

Delta Waves
Delta waves are between 0 – 4 Hz. Delta waves have the highest amplitude of the brain waves. Delta waves appear in stage three sleep and are predominant in stage four of sleep. Delta waves stimulate the release of growth hormone releasing hormone (GHRH) and prolactin (PRL). Delta waves inhibit thyroid stimulating hormone (TSH). Disruption of delta wave sleep contributes to type II diabetes. Delta wave disruption by alpha waves is connected with fibromyalgia and poor quality of sleep.

References:
Differential spectral power alteration following acupuncture at different designated places revealed by magnetoencephalography (Proceedings Paper). Youbo You; Lijun Bai; Ruwei Dai; Ting Xue; Chongguang Zhong; Zhenyu Liu; Hu Wang; Yuanyuan Feng; Wenjuan Wei; Jie Tian. 14 April 2012.

Proceedings Vol. 8317. Medical Imaging 2012: Biomedical Applications in Molecular, Structural, and Functional Imaging, Robert C. Molthen; John B. Weaver, Editors.