PS275 Lecture Notes - Overdiagnosis, Indigenous Peoples Of The Americas, Criterion Validity

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1 Feb 2013

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Biological Assessment Measures Of Brain Structure and Function:
The clinical utility of biological assessment measures was clearly illustrated in a study by Hentschel et Al, that was
conducted with 100 patients referred to a university clinic because of memory difficulties (see figure 4.4, page 119).
In port-mortem studies , the brains of deceased patients are removed and the amount of specific neurotransmitters in
particular brain areas can then be directly measured. Different brain areas can then be directly measured.
Different brain areas can be infused with substances that bind to receptors and the amount of binding can then be
quantified; more binding indicates more receptors.
Another common method of neuro-chemical assessment involves analysing the metabolites of neurotransmitters that
have been broken down by enzymes.
A metabolite, typically an acid, is produced when a neurotransmitter is deactivated. The metabolites can be detected
in urine, blood, and cerebrospinal fluid (the fluid in the spinal column and in the brain’s ventricles.
A high level of a particular metabolite indicates a high level of the transmitter, and a low level indicates a low level of
the transmitter. People with depression have low levels of the main metabolite of serotonin.
neurologist: a physician who specialises in medical diseases that affect the nervous system, such as muscular
dystrophy, cerebral palsy, or Alzheimer’s.
Neuropsychologist: a psychologist who studies how dysfunctions of the brain affect the way we think, feel and behave.
The goals of neuropsychological testing:
(1) To measure as reliably, validly, and completely as possible the behavioural correlates of brain functions.
(2) To identify the characteristic profile associated with a neuro-behavioural syndrome (differential diagnosis).
(3) To establish possible localization, lateralization, and etiology of a brain legion.
(4) To determine whether neurpsychological deficits are present (ie perceptual, cognitive, motor) regardless of
(5) To describe neuropsychological strengths, weaknesses and strategy of problem solving.
(6) To assess the patient’s feelings about his or her syndrome.
(7) To provide treatment recommendations to patient, family, school...
Neuropsychologists have developed tests to asses behavioural disturbances caused by brain dysfunctions.
Neuropsychological tests: all are based on the idea that different psychological functions (eg motor speed, memory,
language) are localized in different areas of the brain. Thus, finding a deficit on a particular test can provide clues about
where in the brain some damage may exist.
One neuropsychological test is Reitan’s modification of a battery of group tests previously developed by Halstead.
the following are four of the tests included in ther Halstead-Reitan battery.
1- Tactile performance test time: while blindfolded, the patient tries to fit variously shaped blocks int spaces
of a form board, first using the preffered hand, then the other, and finally both.
2- Tactile performance test memory: After completing the times test, the participant is asked to draw the
form board from memory, showing the blocks in their proper location.
a. Both this and the timed test are sensitive to damage in the right parietal lobe
3- Category test. The patient, seeing an image on a screen that suggest one of the numbers from one to four,
presses a button to show which number he thinks it is. The patient must keep track of these images and
signals in order to figure out the rules for making the correct choices.
a. This test measures problem solving, in particular the ability to abstract a principle from a non-verbal
array of events. (Poor performance is a good indicator of brain damage).
4- Speech Sounds Perception Test. Participants listen to a series of nonsense words, each comprising two
consonants with a long “e” sound in the middle. They then select the “word” they heard from a set of
a. This test measures left-hemisphere function, especially temporal and parietal areas.
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