Developmental Research
Preschool MMN
Processing Time and the Mismatch Negativity test (MMN)
Our brains are designed to recognize patterns in time, like the beat of a song or the hum of a motor. When patterns change, our brains recognize that something unexpected has happened and become more active. One of the ways to measure the ability of the brain to identify unexpected changes is called Mismatch Negativity or MMN. The MMN test is a recording of brainwaves, called an electroencephalogram or EEG. During this test a recording of pure tones are played through speakers at a volume of approximately 65dB, about the same volume as normal street traffic. These tones will occur every 500 milliseconds. Once in a while, the tone will occur before 500 milliseconds have passed. We record brain waves to determine if the brain noticed that the sound came a little bit early. We are interested in how well preschool age children sense a change in the time pattern of the sounds and what influences, such as genetics and exposure to tobacco, affect this ability.
The test begins with a thorough cleaning of the areas where we will be attaching the electrodes. In order to achieve a good connection, a gentle exfoliant is used to remove dead skin, followed by a scrubbing with an alcohol preparation pad that is designed to remove any excess exfoliant. Ten electrodes are placed on the child's face and head with a paste that helps pick up the brain's electrical activity. The child is asked to sit in a chair and relax and listen to the tones that are projected from the speakers. The cleaning of the child ’s skin and attaching the electrodes takes roughly 30-40 minutes, and each recording takes approximately 25 minutes. The entire session time lasts approximately 1 ½ to 2 hours in duration.
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