Pizzagalli , Diego A, et al. “Euthymic Patients with Bipolar Disorder Show Decreased Reward Learning in a Probabilistic Reward Task.” Euthymic Patients with Bipolar Disorder Show Decreased Reward Learning in a Probabilistic Reward Task, Elsevier, 1 Feb. 2008, https://www.sciencedirect.com/science/article/pii/S000632230701205X?ref=pdf_download&fr=RR-2&rr=80612919bf6819ef
People with Bipolar Disorder display recurrent episodes of depression, mania, and hypomania. When people are in a manic state, they show hyperhedonia, which means they display increased pleasure-seeking behavior and goal-directed behavior. On the other hand, when people are in a depressive episode, they show anhedonia which means they do not have pleasure-seeking behavior or goal-directed behavior, those reactions are decreased. During these manic states, they experience very high highs and very low lows.
Strakowski, Stephen M, et al. “A Preliminary fMRI Study of Sustained Attention in Euthymic, Unmedicated Bipolar Disorder.” Nature News, Nature Publishing Group, 2 June 2004, www.nature.com/articles/1300492.
Assessments were done on patients diagnosing them with bipolar disorder or assessing that they do not have it. Patients with bipolar were also assessed for euthymia. Both patients with BP and patients without BP were given the Young Mania Rating Scale (YMRS) and Hamilton Depression Rating Scale (HDRS). Bipolar patients and healthy patients were then asked to perform a task. They were each given a series of 4 digits and were asked to respond by pressing a button whenever the same digit would appear twice. Then a control was performed, both bipolar patients and patients without bipolar were asked to watch a presentation with the number 1234 on it and not respond. Afterward, they were taken to an MRI where they had to wear goggles that mimicked a presentation on a computer screen, brain responses were recorded. After this, all patients participated in an fMRI, and during the fMRI, patients who did not have bipolar disorder participated in Continuous Performance Task-Identical Pairs (CPT-IP) and alternative box car designs. After these results were analyzed, it showed that for patients with bipolar disorder and patients who did not have bipolar disorder, the results between demographic and clinical variables were equal. The mean and the range of values were low, which the article says makes it clinically meaningless.
Cotovio, Gonçalo, and Albino J Oliveira-Maia. “Functional Neuroanatomy of Mania.” Translational Psychiatry, U.S. National Library of Medicine, 24 Jan. 2022, www.ncbi.nlm.nih.gov/pmc/articles/PMC8786958/.
Mania is episodes of mood disturbance, sleep, behavior, and perception. It often occurs that when people experience a manic episode they experience irritable mood, increased energy, grandiose thoughts, impaired thinking, etc. When this study was conducted, the neuroanatomy of bipolar mania was obtained from images via fMRI or PET (positron emission tomography). Imaging from patients with mania and patients who were considered healthy but had euthymia or other neuropsychiatric disorders were compared. Results showed that patients with mania showed decreased activity in key limbic regions such as the inferior frontal gyrus, and right medial frontal gyrus, but showed increased activity in the right insula and bilateral basal ganglia. fMRI scans also showed that patients who had mania showed decreased activity in the amygdala when responding to emotional cues.
Allen, J.J., et al. “Effect of Bipolar Disorder on Left Frontal Cortical Responses to Goals Differing in Valence and Task Difficulty.” Biological Psychiatry, Elsevier, 24 Oct. 2007, www.sciencedirect.com/science/article/pii/S0006322307007524.
The behavioral activation system (BAS) regulates approach behavior in response to reward, and the behavioral inhibition system inhibits behavior in response to threat. Bipolar patients exhibit an increase in BAS activity in response to rewards. Lesion studies show that the left frontal cortical regions are the regions involved in bipolar disorder in patients with secondary mood disorder. The proximity of the lesions from the left hemisphere to the frontal regions is strongly related to depression symptoms. It is similar to the right hemisphere lesions, lesions in the reward systems (thalamus, caudate, etc.) are related to secondary mania.
Young, Jared W., et al. “Mice with Reduced DAT Levels Recreate Seasonal-Induced Switching between States in Bipolar Disorder.” Nature News, Nature Publishing Group, 27 Feb. 2018, www.nature.com/articles/s41386-018-0031-y.
There are many things that can trigger manic depressive states, but in this article, it is hypothesized that the change in seasons can trigger manic depressive states. In mice, Dopamine transporter (DAT) polymorphisms have been linked to bipolar disorder. This experiment compared behaviors in long active photoperiods and short active photoperiods. All the mice in this experiment were housed in climate-controlled photoperiod chambers. The chambers were set to either a short active photoperiod, a normal active photoperiod, or a long active photoperiod. After housing these mice in these climate-controlled photoperiod chambers for 2 weeks, short active photoperiod and long active photoperiod chambers drove the mice to depression-like and risk-taking-like behavior. Compared to the mice housed in the normal active photoperiod chambers, mice in “extreme photoperiod lengths” changed their behavior to depression-like or mania-like behavior.