Magdalena Wlad: Exploring the ACC as a predictive and regulatory structure in relation to psychiatric symptoms

Abstract

The anterior cingulate cortex (ACC) is a brain structure involved in emotion and cognitive processing. Previous research has suggested that the ACC is implicated in psychiatric disorders, although its role is not fully understood.

This thesis explores the role of the ACC in psychiatric symptoms using functional magnetic resonance imaging. Study I investigated dorsal ACC (dACC) activity during cognitive challenge in social anxiety disorder (SAD). Studies II-III investigated behavioral, neural (including ACC) and peripheral (skin conductance response, SCR) reactivity to emotion anticipation and processing in depression; study II by comparing patients with healthy controls and study III by investigating effects of repetitive transcranial magnetic stimulation (rTMS) treatment on these measures. Study IV extended findings from studies I-III by investigating brain function, including dACC activity during cognitive challenge, in a longitudinal follow-up study of cardiac arrest survivors, a group with increased risk of developing psychiatric symptoms. 

Results showed that depression affects emotion anticipation and processing at the behavioral, neural and peripheral level (study II). ACC and right insula activity was increased, and SCRs decreased, during positive anticipation in patients, suggesting that sensory integration and interoception are disrupted in depression. No effect on reactivity was seen with rTMS treatment; however, decreased anhedonia symptoms were correlated with increased ACC activity with treatment (study III). Increased ACC activity in depression (study II) might therefore reflect a compensatory mechanism strengthened by rTMS (study III). dACC activity during cognitive challenge was unaffected in SAD (study I), which, although dACC activity has previously been shown to predict treatment response in SAD, suggests that its predictive properties do not reflect pre-treatment differences in activity. Cognitive deficits were present in cardiac arrest survivors, but cognitive function improved over time and dACC activity was unaffected (study IV).

Results from this thesis support the notion that the ACC is involved in emotion processing in depression and plays a role in rTMS treatment. Dorsal ACC activity during cognitive challenge seems unaffected in cardiac arrest survivors and SAD, shedding light on its predictive properties. Taken together, these findings contribute to a deepened understanding of the ACC and its relation to psychiatric symptoms.