INDIANA U. (US) — Problems with balance may be a core component of bipolar disorder, signaling an increased risk of developing the condition.
Knowing that postural control is not just a random symptom could provide insight into both areas of the brain affected by psychiatric disorders like schizophrenia and neurological disorders like Huntington’s and Parkinson’s disease and point to new potential targets for treatment, according to a new study.
“For a number of psychological disorders, many different psychiatric treatments and therapies have been tried, with marginal effects over the long term. Researchers are really starting to look at new targets,” says Amanda Bolbecker, research scientist at Indiana University.
“Our study suggests that brain areas traditionally believed to be responsible for motor behavior might represent therapeutic targets for bipolar disorder.”
The study is published in the journal PLoS One.
Try as we might, humans cannot stand perfectly still, says S. Lee Hong, assistant professor of kinesiology and the study’s co-author. “Instead, we make small adjustments at our hips and ankles based on what our eyes, muscles, ligaments, tendons, and semi-circular canals tells us. The better these sensory sources are integrated, the less someone sways.”
Certain areas of the brain critical for motor control, mainly the cerebellum, basal ganglia, and brain stem, also aid in mood regulation and are areas where abnormalities often are found in people with bipolar disorder.
Postural sway—a measure of the degree of endless adjustments people make in an attempt to stand still—is considered a sensitive gauge of motor control that likely is affected by these abnormalities.
In the study, participants who had bipolar disorder displayed more postural sway, particularly when their eyes were closed, than study participants who had no psychological disorders. The troubles, which involved the participants’ ability to process non-visual sensory information related to balance, were not affected by their mood or the severity of their disorder.
“It appears that people with bipolar disorder process sensory information differently and this is seen in their inability to adapt their movement patterns to different conditions, such as eyes open versus eyes closed or feet together versus feet apart,” saysd Hong, whose research focuses on how humans control motion.
“The different conditions will cause people to use the information their senses provide differently, in order to allow them to maintain their balance.”
Bipolar disorder, formerly known as manic-depressive illness, is a severe psychiatric disorder characterized by extreme, debilitating mood swings and unusual shifts in a person’s energy and ability to function.
The study involved 16 people (seven women) with bipolar disorder and 16 age-matched people (nine women) who had no psychiatric disorders. They each stood barefoot and as still as possible on a piece of equipment called a force platform, which measured various aspects of postural sway as they stood with their eyes open and feet close together, eyes open and feet shoulder-width apart, eyes closed and feet together, and eyes closed and feet apart.
The measurements during each 2-minute pose included such factors as the area covered by a person’s circular sway, how quickly they revolved and the degrees by which the sway moved more front to back or side to side.
More findings include:
- The study does not suggest a “global motor deficit,” where people with bipolar disorder have movement problems all around. Instead, it suggests a specific problem adapting to changing sensory input—when people close their eyes, they rely on a different sources of sensory information, such as proprioception and the vestibular system.
- Participants with bipolar disorder displayed a large decline in postural control when their eyes were closed, regardless of the position of their feet.
- A significant difference between the study groups involved side-to-side postural control, which is largely a factor of the hips. The participants with bipolar disorder had less control. This difference was not seen in the front-to-back control, which relies on ankle adjustments. Participants with bipolar disorder might not have fully developed the control of posture using their hips, which is consistent with developmental factors contributing to bipolar disorder.
Research involving motor control, mood and psychiatric disorders is complicated because the primary treatment for them is medication, which can have severe side effects including motor control problems. A limitation of Hong and Bolbecker’s study is that they could not factor out the effects of the various kinds and combinations of medications taken by their study participants with bipolar disorder.
The study was supported by NARSAD: the Brain and Behavior Research Fund, formally called the National Alliance for Research on Schizophrenia and Depression.
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