I was really interested in researching Bipolar Disorder because while I know a lot about how it can manifest itself behaviorally, I knew very little to none about its neurological and biological background. I (incorrectly) assumed that I would stumble upon several articles leading to the same conclusion as to the biological basis of this disorder, and was disappointed and a little frustrated with the inconsistencies that I found. Every article title I saw seemed to focus on a different aspect of the disorder, ranging from tons of different treatments to different manipulations that people underwent during experiments. I just wanted to find out if, biologically, something in the brain caused bipolar disorder, or was at least correlated with the disorder. The first article, “The neural basis of mood dysregulation in bipolar disorder” I looked at was a review of MANY studies, (6 pages of references!) , and despite some neurological measures a lot of them seemed a bit subjective in their methodology. For example, many of the studies investigated people’s responses to emotionally salient stimuli such as human faces making happy, sad, fearful, or disgusted faces. Responses were often measured through neuroimaging techniques, and focused on certain regions of the brain such as the amygdala and prefrontal cortex. Several studies’ findings contradicted each other, but some results that seemed somewhat intuitive to me were that people in a manic state showed decreased amygdalar responses to sad facial expressions. It seems that they were, for whatever reason, not “in tune” with sad emotions, even those of other people.
The article progressed to discussing physical differences/abnormalities in people with bipolar disorder. Again, findings were extremely contradictory, but the most consensus was on increased gray matter in the thalamus and cortical regions, which are involved in response to emotional stimuli and mood generation. The author proposed that perhaps the mood instability of people with BD is due to increased activity in regions of mood generation as well as regions of decision about emotional material. So, the generation of moods is “abnormal” as is the interpretation of outside emotional material. In addition, reduced activity in regions that regulate responses would contribute to the person being unaware that his/her emotional perception is warped. A very interesting, seemingly out-of-the-blue suggestion the author offered was the perhaps depression in people with BD represents a relative normalization of abnormal pattern of emotional overreactivity in mania. Basically, the brain attempts to compensate and bring the person back from mania to a typical euthymic state, but goes too far. The alternation of states would then be viewed as failed attempts to normalize emotions… it’s like the pendulum got swinging too high and now it just can’t stop.
Another article, “Molecular neurobiology of bipolar disorder: A disease of ‘mood-stabilizing neurons’?” suggests that the neurons that typically stabilize people’s moods somehow become vulnerable or develop impaired resilience in people with BD. After enough neurons are lost, the mood-stabilizing effects are greatly reduced and the mood becomes very unstable, ranging largely and alternating between depression and mania. I would like to find out more about this theory, particularly what causes the neurons to become vulnerable in the first place, and how those mood-stabilizing neurons work in a healthy person.
One obstacle for studying people with bipolar disorder is that the disorder itself is characterized by two very different (as seen in the name, polar oppposite) mood states, and thus every study must include a control group, a bipolar currently depressed group, and a bipolar currently manic group. Many studies also included people with bipolar who were currently in neither category, but in a state of euthymia, somewhere right in the middle (where most people without depression/bipolar disorder usually are). Any study with 4 different group requires a lot of people, and bipolar disorder has high comorbidity rates, as do many other psychological disorders. I’ve been appreciating how difficult it can be to find and isolate one particular psychological disorder within someone…..nevermind within enough people for a legitimate study!