Brain activity and how to measure it.

Our brain consists of billions of cells called neurons. They use electric impulses when communicating and therefore emitting continuous electrical activity inside the brain. Here is a single nerve cell from the cerebellum of the brain:

[image online] Available at: <; [Accessed 28 February 2012].

[image online] Available at: <; [Accessed 28 February 2012].

Guyton (1971, pp.511-512) states that  ‘both the intensity and patterns of this electrical activity are determined to a great extent by the overall excitation of the brain resulting from functions in the reticular activation system. … Much of the time, the brain waves are irregular and no general pattern can be discerned in the EEG. However, at other times, distinct patterns do appear. Some of these are characteristic of specific abnormalities of the brain, such as epilepsy. Others occur even in normal persons and can be classified into alpha, beta, theta, and delta waves.‘ Here is an image showing these waves:

[image online] Available at: <; [Accessed 28 February 2012].

Alpha waves are rhythmic waves which are found in the EEG’s of almost all normal persons when they are awake in a quiet, resting state of cerebration. During sleep the alpha waves disappear entirely, and when the awake person’s attention is directed to some specific type of mental activity, the alpha waves are replaced by asynchronous higher frequency but lower voltage waves.’ (Guyton, pp.512)
This image demonstrates it efficiently:


Beta waves usually would appear during activation of the central nervous system. Maximum mind power. All five external senses, logical mind, memory from the five senses & logical thinking.

Theta waves will occur during emotional stress such as disappointment and frustration. Also deep meditation. Deep inward thought. This is associated with life-like imagination. High state of mental concentration. A magical mind. Internal pictures / visualisation. Intuition, inner guidance. Access to unconscious material. Dreaming.

Delta waves will occur mainly in deep sleep, in infancy or in serious organic brain disease. Deep dreamless sleep. Deep relaxation. State of oneness, whole body feeling.

Apart from EEG method of displaying brain activity in form of waves there are several other technologies which allows people to measure and display the activity of human brain. Functional magnetic resonance imaging or functional MRI (fMRI) us another way to visualise activity of neurons inside the brain by detecting the blood changes. It uses a very complex method to measure oxygen levels in blood cells after being treated by noise. These changes are displayed by different colours:

[image online] Available at: <; [Accessed 28 February 2012].

This technique is used more in research rather than clinical treatments but it can also be used to investigate ill patients. ‘Physicians use fMRI to assess how risky brain surgery or similar invasive treatment is for a patient and to learn how a normal, diseased or injured brain is functioning. They map the brain with fMRI to identify regions linked to critical functions such as speaking, moving, sensing, or planning. This is useful to plan for surgery and radiation therapy of the brain. Clinicians also use fMRI to anatomically map the brain and detect the effects of tumors, stroke, head and brain injury, or diseases such as Alzheimer’s.’ (wikipedia article on fMRI)

Diffusion spectrum imaging (DSI)

[image online] Available at: <; [Accessed 28 February 2012].

[image online] Available at: <; [Accessed 28 February 2012].


Guyton, A. C., 1971. Basic Human Physiology: Normal Function and Mechanisms of Disease. London: W. B. Saunders Company.

Huddleston N., 2008. Brain Wave States & How To Access Them. [online] Available at: <; [Accessed 28 February 2012].

Wikipedia, 2012. Functional magnetic resonance imaging. [online] Available at: <; [Accessed 28 February 2012].



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