Manic-depressive psychosis: hyperactive brain activity, even in remission
Molecular Psychiatry 2007
Journal of Psychiatry 2007
A joint CEA-Inserm study conducted at the Joliot Hospital Service has revealed that even in remission phase, patients with bipolar disorder, a mood disorder formerly known as manic-depressive psychosis, still present hyper-reactivity to emotional stimuli. A follow-on study conducted in these patients highlighted a higher density of white matter, which acts as the cabling that relays information between the two hemispheres of the brain. Both these studies have just been published, the first in the April 2007 issue of the American Journal of Psychiatry, the second in the May 2007 issue of Molecular Psychiatry.
Manic-depressive psychosis (MDP), now known as bipolar disorder, is a common psychiatric disorder that in its most acute form, affects between 0.4 and 1.6% of the population, with onset often occurring during or soon after adolescence. The illness often has debilitating effects in terms of social life and career possibilities. It involves manic episodes typically characterised by hyperactivity and 'highs' that alternate with regular bouts of one or more major depressive episodes.
The two studies led at SHFJ were focused on patients in remission phase no longer presenting symptoms of the disorder. The research teams used magnetic resonance imaging (MRI) to highlight that despite remission, anatomical and functional specificities continue to persist.
The first study measured levels of brain activity in the regions involved in processing emotional information in seventeen patients (receiving psychiatric treatment at Henri Mondor hospital and Albert-Chenevier hospital in Créteil, Greater Paris) and seventeen controls. The subjects were shown six series of emotionless faces interspersed with images of faces showing either joy or fear. Each series combined a pair of expressions (joy/fear; fear/no emotion; joy/no emotion), where one of the expressions served as the 'odd one out'. In each series, the subjects were asked to make a reflex decision to select one of the two emotional states and reject the other.
The results of the test showed that patients in remission phase gave similar performances to the control group, with the scores being essentially the same. However, functional magnetic resonance imaging (fMRI) revealed that in order to perform these different tasks, where it was assumed that emotion-related information would be interfering with inhibition thresholds, the bipolar disorder subjects used the brain regions involved in processing emotion more than the controls[1]. In addition to this over-activation of the brain areas involved (i.e. the frontal regions and parts of the deep grey matter nuclei), the bipolar disorder patients further differentiated themselves from the control group by activating other brain structures located in the temporal cortex.
The second study, which included sixteen patients and sixteen controls, analysed the density of the white matter that channels nerve impulses into the grey matter2. Diffusion MRI, which is implemented to get a detailed architectural map of the neuronal tissues, enabled the research team to highlight a significant increase in white matter fibers in these same bipolar disorder patients in remission phase. This regional increase in white matter may change how information is transmitted in certain areas of the brain, which could help explain the results of the first study conducted on the very same patients. Could this be what drives the over-activation of the areas related to processing emotional information, or is it the result of a way the brain adapts its processes in response to this stress? Either way, this specificity, which persists long after the patient no longer shows symptoms, could be an example of the brain making persistent readjustments in its emotion processing-related regions.
Text: Marie Vandermersch
[1] The subjects went through a control exercise built around the same principle, where they were asked to select or reject either a male or a female face. When the emotional process was not triggered, there was no difference in how the information was being processed between the bipolar disorder group and the control group.
2 The human brain is essentially built from 3 components: grey matter, white matter, and cerebrospinal fluid. Grey matter, which contains the nerve cell nuclei, is found at the brain surface (the gyri and sulci of the cerebral cortex) and the deep grey matter nuclei (thalamus, caudate nucleus, etc.). The grey matter is where all our actions, thoughts and feelings are processed. The white matter is formed of axons, the nerve cell extensions. These fibers are like our information superhighways. They are wrapped in a layer of myelin, which is a fatty substance that promotes information transmission. The cerebrospinal fluid circulating in and around the brain provides a liquid-based protection that is also able to transport certain substances.
