There are currently no reliable physical occurrences in the body that is a reflection of Bipolar Disorder, unlike schizophrenia with anatomic findings of ventricular enlargement during standard brain imaging (Psych, 2016). However, recent advances in technology have brought a range of possibilities for bipolar disorder, including advancements in neuroimaging providing insight to brain characteristics. Using the understanding that increases in blood flow equals increases in neural activity, imaging approaches such as single emission computed tomography (SPECT), positron emission tomography (PET) and functional MRI (fMRI) have been used to see which regions of the brain are more active than others (Psych, 2016). The approach using fMRI has shown consistent results in people with bipolar disorder. Phillips and Swartz were able to conclude that they observed abnormalities in neural circuits that involve emotional processing, emotional regulation, and reward processing (Phillips & Swartz, 2014).
Since Phillips’ and Swartz’s findings in 2014, efforts have been channeled into discovering a noninvasive test for comparing active brain regions to less active regions using fMRI. Phillips and a team of pediatric bipolar researchers developed and refined this technique for examining the neurobiological activity of emotion regulation in both bipolar spectrum disorders (BPSD) and attention deficit hyperactivity disorder (ADHD) as well as healthy controls to compare and contrast results. They focused primarily on assessing the functional connectivity of the amygdala-prefrontal activity and saw that “Amygdala-prefrontal cortical functional connectivity during implicit emotion processing differentiates youth with bipolar spectrum from youth with externalizing disorders” (Hafeman et. al. 2016). In other words, they saw that youth with bipolar spectrum disorders showed positive functional connectivity between the amygdala and regions in the ventral prefrontal cortex during emotional processing (Hafeman et. al. 2016). With closer analysis they saw that the functional connectivity between the amygdala and the left ventrolateral prefrontal cortex (VLPFC) in response to emotions versus shapes was a key finding when comparing the three groups. The healthy control and individuals with attention deficit hyperactivity disorder showed functional connectivity to shapes which is in contrast to individuals with bipolar spectrum disorders, who showed functional connectivity to emotions.
So what does all this mean? In the healthy control, it was observed that when amygdalae are more active, the left ventrolateral prefrontal cortex has a decrease in activity (Psych, 2016). However, with individuals with bipolar disorder, this relationship does not hold true, and in some cases goes in the opposite direction. It was observed that increased activity in the amygdala is mirrored with increased activity in the left ventrolateral prefrontal cortex.
Although this type of neuroimaging testing cannot be ordered currently, it is important to appreciate new findings that distinguish the differences between bipolar spectrum disorders (BPSD) and attention deficit hyperactivity disorder (ADHD) in its initial stages of discovery (Psych, 2016).
Future directions involve the inclusion of individuals at risk for bipolar disorder (Phillips & Swartz, 2014). Following these studies over time might prove useful to identifying relevant biomarkers which will guide better diagnosis and treatment. Increasing sample sizes would also prove beneficial and strengthen the replicability of the techniques and include variations of illnesses (Hafeman et. al. 2016). Research and findings like this bring us closer to being able to pinpoint differences in illnesses that can eventually lead to clear paths of better treatment.
Hafeman, D., Bebko, G., Bertocci, M. A., Fournier, J. C., Chase, H. W., Bonar, L., & … Phillips, M. L. (2016). Amygdala-prefrontal cortical functional connectivity during implicit emotion processing differentiates youth with bipolar spectrum from youth with externalizing disorders. Journal Of Affective Disorders, 20894-100. doi:10.1016/j.jad.2016.09.064
Phelps, J. (2016, November 8). A Lab Test for Bipolar Disorder? Retrieved November 24, 2016, from http://www.psychiatrictimes.com/bipolar-disorder/lab-test-bipolar-disorder
Phillips, M. L., & Swartz, H. A. (2014). A critical appraisal of neuroimaging studies of bipolar disorder: toward a new conceptualization of underlying neural circuitry and roadmap for future research. The American Journal of Psychiatry, 171(8), 829–843. http://doi.org/10.1176/appi.ajp.2014.13081008