Laboratory 6.2 Brain Waves

Electroencephalogram (EEG)

Machine that measures electrical activity of the brain by detecting electrical potential differences between different areas of the cerebral cortex; electrodes are placed on the scalp

Brain waves

Patterns in the electrical activity of the brain as measured by an EEG; each individual has unique brain waves, though there are 4 general groups based on frequency

Frequency (brain waves)

The number of wave peaks in 1 second (measured in Hz); used to classify the 4 types of brain waves

Amplitude (brain waves)

The height of a brain wave; produced by the number of synchronous neurons firing together, not the total amount of electrical activity

Factors that change brain waves

Aging, sensing different stimuli, pathological brain changes, and chemical imbalances in the body (e.g., hypoglycemia, anesthesia)

Alpha waves

Brain waves recorded when a subject is conscious and relaxed with eyes closed; opening the eyes or concentrating causes a decrease in amplitude and increase in frequency (alpha block); fear or excitement increases frequency further

Alpha block

The change in alpha waves when a relaxed subject opens their eyes or begins concentrating — amplitude decreases and frequency increases

Beta waves

Similar to alpha waves but with lower amplitude and higher frequency; recorded when the subject is mentally alert or concentrating on a problem or visual stimulus

Theta waves

Irregular wave pattern typically observed in children; uncommon in conscious adults but may appear during concentration

Delta waves

The slowest brain waves recorded in humans; typically observed in young children and infants when relaxed or sleeping

Clinical uses of EEG

Used to diagnose traumatic brain injuries, tumors, sleep disorders, strokes, and epilepsy; unconscious or comatose patients still show brain waves (though abnormal)

Flat EEG

An EEG showing no brain wave activity; one of the clinical signs of death