Aberrant Connectivity Between Key Regions of the Brain Responsible for Major Depressive Disorder

Patients suffering from Major Depressive Disorder are most likely to have decreased or disruptive connectivity between the striatum and the frontal cortex of the brain, according to Daniella Furman and colleagues from the Department of Psychology, Stanford University.

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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