A new neuroimaging study in Spain compared brain activity of persons suffering from bipolar disorder and of healthy individuals. It reported that poor psychosocial functioning in persons suffering from bipolar disorder is associated with lower activation levels in multiple regions of the brain cortex that include the fronto-parietal memory network and inferior temporo-occipital regions. The study was published in Psychiatry Research.
Bipolar disorder is a mental illness that causes unusual shifts in mood, energy, activity levels, concentration, and the ability to carry out everyday tasks. It was formerly known as the manic-depressive illness or the manic depression. Only one out of every four persons suffering from bipolar disorder manages to achieve remission of the symptoms and regain normal functioning. Due to this, bipolar disorder has great implications both for the quality of life of people suffering from it and for public health.
Scientists have extensively studied factors that are important for long-term functioning of persons with the bipolar disorder. They found that impaired cognition is one of the most important contributors to the poor overall functioning of these individuals. It is not known whether the impairment of psychological and social functioning of individuals with bipolar disorder is related to abnormalities in brain functioning.
Studies using functional magnetic resonance imaging found abnormal activation changes in fronto-limbic regions that might be relevant to the emotional dysregulation and cognitive symptoms present in the disorder. Other studies pointed to the possible importance of the default mode network (DMN).
The default mode network is a large network of brain cells that increases its activity when the person is not focused on the outside world and is at rest while being awake. It consists of brain cells located in the dorsal medial prefrontal cortex, posterior cingulate cortex/precuneus, and angular gyrus regions of the brain.
Study authors Norma Verdolini and her colleagues wanted to further examine the relationship between changes in functioning of the brain in persons suffering from bipolar disorder and psychosocial functioning. They recorded activities of the brain while the person was performing cognitive tasks.
Participants were 31 adults meeting criteria for bipolar disorder, who were at the time in a tranquil, stable mental state (so-called euthymia), not having had an episode of illness for at least 3 months before inclusion in the study. They were also required to have low scores on assessments of depression (Hamilton Rating Scale for Depression) and manic symptoms (the Young Mania Rating Scale) at the time of the study. The study also included 31 healthy participants who were matched with participants in the bipolar disorder group on age, self-reported gender and intelligence.
Participants with bipolar disorder additionally completed an assessment of psychosocial functioning using the Functional Assessment Short Test – FAST, an interviewer-administered instrument developed by the Bipolar and Depressive Disorders Program of the Hospital Clínic in Barcelona to assess functional impairment in bipolar disorder.
All study participants underwent functional magnetic resonance imaging scans. During scanning they completed working memory and cognition tasks that were known to produce activations and deactivations of brain cells in healthy individuals that are clearly visible on the images of the brain.
Results showed that participants with bipolar disorder performed more poorly on cognitive tasks they were asked to perform during scanning compared to healthy participants. Participants suffering from bipolar disorder who had less psychosocial impairment (as assessed by FAST) performed better in these tasks.
Functional magnetic resonance images captured while the participants were performing cognitive tasks showed that patterns of activation and deactivation of brain areas were similar in participants with bipolar disorder and healthy participants. However, activations in participants with bipolar disorder were less extensive with smaller activations in the cerebellum and inferior middle occipital cortex regions of the brain. Deactivations were also less extensive than in the group of healthy participants, particularly in the medial prefrontal cortex.
Analysis of the whole brain showed differences in overall activation between two groups of participants and also a failure of deactivation in the medial frontal cortex region of the brain in participants with the bipolar disorder. Researchers identified six clusters of activations in the brain whose differences in activity between individuals were linked to levels of psychosocial impairment.
These clusters of neural cells were located in dorsolateral prefrontal cortex, the superior parietal cortex, and temporo-occipital regions of the brain on both sides, but also in the inferior frontal cortex regions on the left side of the brain. Cognitive and occupational functioning were domains most strongly associated with brain activations in these clusters.
“The results suggest that poor psychosocial functioning in BD [bipolar disorder] individuals is associated with hypoactivation in a range of cortical regions, including the fronto-parietal working memory network and inferior temporo-occipital regions,” the researchers concluded.
The study sheds light on neural underpinnings of bipolar disorder. However, it also has limitations that need to be taken into account. Notably, the number of participants included in the study was small and researchers did not take into account the fact that participants with bipolar disorder were taking medications that might have affected the brain activity. Additionally, participants with bipolar disorder included in the study exhibited on average only mild to moderate levels of psychosocial impairment.
The study, “The relationship between cognition and functioning in Bipolar Disorder: An investigation using functional imaging during working memory performance”, was authored by Norma Verdolini, Silvia Alonso-Lana, Pilar Salgado-Pineda, Salvador Sarro, Raymond Salvador, Teresa Maristany, Jose M. Goikolea, Caterina M. Bonnin, Ines Martín, Laura Salo, Ana Romaguera, Elena Rodriguez-Cano, Adriane R. Rosa, Eduard Vieta, and Edith Pomarol-Clotet.
