Learn more about the childhood P50!
When our brains process stimuli, such as sound, the cells
communicate by producing small electrical impulses. An
EEG, or electroencephalogram, is a recording of that
electrical activity which is displayed in the form of waves
(brain waves). The p50 test that we do is a recording of
your brain waves in response to a particular sound, or in
other words, an auditory evoked potential recording. We
record your response to a pair of clicks that sound like
someone snapping his/her fingers. For most people the
recordings show that their brain responds to the first click
and has a much lower response to the second click. This
occurs because the brain is wired to assume that repeated
sounds are background noises and can generally be
ignored.
Individuals with schizophrenia and other mental
disorders, usually respond similarly to both clicks which
is evident in their brain wave recordings. When the brain
screens out the second sound, we say they “gate,” and
when the person does not screen out the second sound we
call this as “non-gating”. In other words, people that
“gate” seem to be able to drown out background noise
better then people that “do not gate.” “Gating” is not
diagnostic, meaning you cannot tell if the person has
schizophrenia or not by looking at the results. In fact,
many people respond equally to both sounds and yet have
do not have a psychiatric illness. What we look at with
the p50 recordings are group differences between the
individuals with mental illness and other groups of
individuals either with a different disorder, without any
diagnosis, or with family members of the affected
individual so that we can say with more certainty that
“gating” is impaired in individuals with schizophrenia.
By noting these differences we can then look at the areas
in the brain and the genes that are associated with
auditory gating. This will help us get closer to
discovering better treatment options and potentially
finding a way to reduce the incidence of major mental
illnesses like schizophrenia and bipolar disorder in the
general population.
What to expect when doing the p50:
First we will clean your child’s skin with alcohol pads
and a scrubbing gel to remove oils from your skin. We
will place five electrodes on your child’s face and head
using a conductive paste and some cloth tape. Two of the
electrodes will be on his/her ears, two will be around one
of the eyes, and the other will be on the top of the head.
Nothing comes through these wires to your child’s head;
these electrodes only record your brain waves. We will
place headphones on your child and test your hearing
when listening to the clicks. While listening to the clicks,
you will be asked to stare at a particular spot on the wall
or ceiling so that you do not move around as much. A
p50 recording generally takes between 30 and 60
minutes.