Aberrant Connectivity Between Key Regions of the Brain Responsible for Major Depressive Disorder
Feeling sad occasionally is normal, but if the sadness is prolonged with
additional symptoms of negative thinking, fatigue and withdrawal, it becomes a
matter of concern. These symptoms are characteristics of a serious mood
disorder called Major Depressive Disorder (MDD). MDD is associated with
cognitive and psychomotor dysfunction and people diagnosed with this disorder
often exhibit problems with executive functions such as difficulties in
concentrating and making decisions, and terminating the processing of negative
material.
Earlier studies found that people with depression had anomalies in the
structure and function of the frontal lobes of the brain. The frontal lobe,
that hosts the basal ganglia, controls activities such as reasoning, planning,
movement, as well as cognitive and emotional functions. Striatum is the main
component of basal ganglia (a mass of nerve cells in the cerebral hemispheres)
situated at the base of the forebrain. The striatum receives input from
the frontal cortex (or cerebral cortex) and sends output to other components of
the basal ganglia thus forming a 'circuit'. Some studies have implicated
anomalous functioning of the striatum in MDD, but these studies were
inconclusive.
So, Daniella Furman and her team conducted a study with the aim to
examine patterns of prefrontal cortex (PFC)-striatum connectivity [that
included the ventral striatum (VS), subgenual anterior cingulated cortex
(sACC), posterior cingulate
cortex (PCC), etc] in adults diagnosed with MDD. Twenty-one adults diagnosed
with MDD and 19 control participants with no history of psychiatric disorder
were included in this study. The subjects were all female and between 18 and 60
years of age.
The researchers obtained the Blood-oxygen-level dependent (BOLD) signal
data with 3 Tesla General Electric magnetic resonance imaging scanners. All
data preprocessing and analysis were carried out using Analysis of Functional
NeuroImages software. This study was published in the journal Biology of Mood
& Anxiety Disorders.
The results showed that women
with MDD had decreased connectivity between ventral striatum and other key
regions of the frontal cortex responsible for emotional behavior, learning,
memory and decision making.
However, there were certain limitations to this study.
• One of them was that all study
subjects were women, so these findings may or may not extend to men.
• Another limitation was that the
participants were receiving different psychoactive medications, and researchers
are not sure if they might selectively bear on a patient's 'frontostriatal
function'.
The authors concluded - 'Despite
these limitations, however, the results of the present study provide important
empirical support for the hypothesis that MDD is characterized, and even
maintained, by compromised frontostriatal function'.
Source: Furman, D. J., Hamilton, J. P., and Gotlib I. H.
Frontostriatal functional connectivity in Major Depressive Disorder. Biology of
Mood & Anxiety Disorders 2011, 1:11 doi:10.1186/2045-5380-1-11
http://www.biolmoodanxietydisord.com/content/pdf/2045-5380-1-11.pdf
Source: Medindia
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