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Brain Scans John McManamy Your Depression Pre-order my book and Bipolar
Carol Tamminga MD, of the University of Texas Southwestern Medical Center at
on Amazon Disorder Source
Dallas, told a seminar at the 2003 NAMI convention how she and her colleagues eagerly waited outside the door in anticipation of viewing their first brain scans of a patient with schizophrenia. Much to their dismay, the images looked normal, Knowledge is
which was their first lesson in the art of subtlety. Necessity
A study by Ahmad Hariri PhD et al of the NIMH appearing in the July 19, 2002
Research may lead
Science divided 28 subjects into two groups, those who had a short form (allele)
of the serotonin transporter gene SLC6A4, and those with the long allele. Cellswith the long variant express nearly double the serotonin reuptake as those withthe short allele. The subjects were placed in an MRI machine and completed a
simple exercise involving processing the images of three different faces. The brain
used before and
scans revealed that those with the short allele displayed a significantly greater
after PET scans to
response in the right amygdala while engaged in the task. The amygdala is a tiny,
track Haldol and
almond-shaped part of the brain which governs fear. When the subjects were
Clozaril at work."
given a thinking task not involving emotions, no variants were seen. Newsletter
In the authors’ words: "Our results directly implicate a genetically determined link
Your online source for issues that matter to you. Main articles page.
between serotonin transporter function and the response of brain regions criticalfor emotion processing."
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This may very well be the first study linking genes to emotions in humans, and it
the heading and your email address in the
certainly won’t be the last, thanks to our increasing ability to literally peer inside
the skull and view what is taking place. Find out more. Brain Science 101
Perhaps the number one question about brain scans concerns whether it will be possible to use the technology to diagnose depression or bipolar disorder. The
short answer is maybe. In early 2002, a possible taste of the future occurred in a
Washington DC courtroom when plaintiff Jane Fitts successfully used brain scans
showing an atrophied parietal lobe and other abnormalities to convince a federal
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judge that her bipolar disorder was "physical" in nature, thus allowing her to
accrue extended disability according to the terms of her health plan (see article).
The technology we have may already be sufficient to make a diagnosis. What islacking is our knowledge of what makes a particular brain abnormality unique to a
certain illness. But that may change, with researchers increasingly turning to brainscans to discover how we tick. Positron emission tomography (PET) involves the subject inhaling or being
injected with radioactive tracers, which are absorbed into the brain tissue. A
positively-charged particle (positron) collides with an electron in the tissue,
destroying both and resulting in two photons that are detected by the PETscanners. Increases or decreases in cerebral blood flows to and from regions of
the brain are measured by radiation counts.
Dr Tamminga is the author of a classic 1992 study involving PET scans on 12
patients with schizophrenia, which identified functional abnormalities in their limbiccircuits compared with normal controls. In a study published in 2003, Dr
Tamminga used before and after PET scans to track Haldol and Clozaril at work,finding both similarities and differences in blood flows to certain regions of the
brain that could account for their clinical benefits and side effects.
A pioneering study by Baxter et al using PET to measure resting glucose
metabolism in patients with unipolar, bipolar, and secondary depression found low
metabolism in the dorsal anterior prefrontal cortex, which increased when theirdepression was treated (March 1989 Archives of General Psychiatry, Vol 46 No
3). Succeeding studies have implicated abnormal activity in other areas of thefrontal cortex and the amygdala.
A 1997 study by Helen Mayberg MD of the University of Texas Health Center, San
Antonio et al used PET scans to find that the rate of metabolism in the anteriorcingulate accurately predicted treatment response or nonresponse in depressed
patients (March 1997 NeuroReport). In a study published in the May 2002
American Journal of Psychiatry, using the same technology, Dr Mayberg foundthat both antidepressant and placebo responders experienced the same reactions
in the cortex and limbic regions of the brain, but those taking antidepressants alsoexperienced unique changes in the brainstem, striatum, and hippocampus. Other Science
A study published in the October 2000 AJP used PET scans to find that peoplewith bipolar I have 30 percent more monoamine releasing cells, which send the
neurotransmitters serotonin, dopamine, and norepinephrine into the brain. "To putit simply," explained the study’s lead author Jon-Kar Zubieta MD, PhD in a press
release, "these patients' brains are wired differently, in a way that we mightexpect to predispose them to bouts of mania and depression."
Progress or Regress?
Through PET scans, we have learned that the therapeutic dose for anantipsychotic medication occurs when approximately 65 percent of the brain’s
dopamine D2 receptors are occupied and that their notorious side effects begin tohappen when the 80 percent threshold is crossed, thus giving physicians a clear
picture of how to accurately dose their patients. We are also learning about how
experimental drugs bind to their intended targets. Merck used PET scans to itsbenefit in determining that its substance P antagonist (on the market as Emend for
chemo-induced nausea but which failed clinical trials for depression) achieved 90
Advancing to 1948
percent occupancy on the brain's NK1 receptors. Single photon emission computed tomography (SPECT) is similar to PET in that it is sensitive to radioactive tracers absorbed into the brain, this time coming from the emission of photon gamma rays. It is the older technology and is seldom used today. Both PET and SPECT allow the brain to be viewed as it is actually functioning - thinking, remembering, experiencing pain or pleasure, and so on. This functioning is interpreted by PET in brilliant hues that psychiatrists can show to their patients to dramatize mental illness at work.
Gunnar Heuser MD, PhD of UCLA has been using a hyperbaric chamber on thoseexposed to neurotoxins, including several who manifested ADD. Of 10 patients hetreated for toxic encephalopathy (which results in cognitive and memoryimpairment), eight showed significant improvement and two marginal improvementon cognitive tests. Before and after SPECT imaging revealed marked reduction inblue and violet areas - signifying a return of more normal blood flow - in the brain. Magnetic resonance imaging (MRI) essentially takes pictures of the brain's water. As opposed to PET scans, MRIs do not require radioactive tracers and thus can be used repeatedly on subjects. Instead, these scanners are sensitive to oxygen, which is released from hemoglobin when blood flow to various parts of the brain is increased. MR spectroscopy measures the chemistry of the brain while fMRI (functional MRI) measures activity (with subjects performing tasks during the scan). The standard strength of an MRI is 1.5 Tesla, with newer machines capable of achieving much higher resolution at three, four, seven, and 9.4 Tesla. At four Tesla, for instance, an MRI can separate glutamate from glutamine.
Kevin Lim MD of the University of Minnesota is using a novel MR method, diffusiontensor imaging (DTI) to produce images of white matter in the brains of subjectswith schizophrenia and geriatric depression. The white matter takes the shape offine fibers that run like wiring beneath the cortex. Lesions in white matter havebeen identified in age-related illnesses such as dementia, and are the increasing
focus of investigation in mental illnesses.
Gerard Sanacara MD, PhD of Yale has used magnetic resonance spectroscopyto measure the neurotransmitter GABA in the brain, finding that those withmelancholic depression show low GABA concentrations in the occipital cortex,while the depletion is not as pronounced for those with atypical depression,indicating a diagnostic potential for subtypes of depression (March, 2003 AJP). Before and after scans of eight patients who had ECT found a doubling of GABA,and similar scans of patients on SSRIs showed a slow rise in GABA levels in nineof 11 of them. Conclusion
The next time you encounter a skeptic who tells you your illness is all in your head,you may want to download and print brain scans and keep them handy for futureencounters. At the very least, these images eloquently portray in a way thatwords cannot that our illness is demonstrably real.
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