An Electrophysiological Examination of the Insular Cortex and Its Role in Anxiety

Within the last three decades, psychological research surrounding brain-behavior relationships has become increasingly prevalent, as a better understanding of the brain structures and their functions can lead to more effective treatments for related psychological disorders. The focus of this study is the brain structure known as the insular cortex and its role in interoception and anxiety. Although the insula has been commonly referred to as an "enigma" by researchers, the structure and function have become increasingly better understood over time as neuroimaging techniques have improved. The insular cortices are functionally differentiated by hemisphere. The left hemispheric insular cortex is involved with parasympathetic processes and the insula within the right hemisphere with sympathetic processes. Both the right and left insular cortices are divided into anterior and posterior regions, which have differing functions. The focus of this paper is the right anterior insula, which has been associated with interoception, or the awareness of physiological processes (e.g. heartbeat). When considered in light of the James-Lange theory of emotion, it is plausible that an individual with greater activity in the right insula, and thus heightened interoceptive awareness, may attribute this interoceptive information as indicative of something harmful or maladaptive if they are sensitive to anxiety. Indeed, several studies have found that individuals with trait anxiety or anxiety sensitivity tend to be more sensitive to interoception and have overactivity in the insular cortex, supporting a relationship between these variables. This aligns with what is predicted by the James-Lange theory of emotion.;The aim of this study was to contribute to the body of research that links anxiety, interoception, and excess activity within the right insular cortex using archival EEG data. The study's hypothesis was that subjects who self-report anxiety as a presenting problem will likely have an elevated baseline of interoceptive attention and anxiety levels, which correspond to higher levels of right insular cortex activity than those subjects who did not report anxiety. Although the research to date has utilized fMRI and PET scans to measure activity in the insular cortex, this study employed EEG and LORETA, a tomography program, to measure excess activity within the right insula. Although there are limitations to using EEG, there are also benefits, including superior temporal resolution when compared to fMRI and PET scans, as well as greater availability and cost effectiveness. Brain waves recorded by EEG are separated in five categories of increasing hertz levels: delta, theta, alpha, beta, and gamma. Beta is associated with focused attention and with anxiety; therefore, excess activity in the beta hertz level was selected for study. Archival data used for this study was obtained from a database from patients seen at the psychiatric clinic Advanced Neurodiagnostics. Patients who had self-reported that anxiety was a presenting problem on an intake form, or patients who were receiving psychiatric treatment for anxiety, were selected for this study. All of these patients had undergone a resting state EEG, and their EEG results were calculated through LORETA, a tomography program capable of localizing activity from deep brain structures and compares brain activity to a normative database. Cases with excess beta activity greater than two standard deviations from the norm were selected for further analysis. Four categories were developed: self-reported anxiety, no self-reported anxiety, excess beta activity, and no excess beta activity. A Chi-Square Test of Independence was performed due to the dichotomous nature of the data, and a Fisher's Exact Test indicated that there was not a significant relationship between self-reported anxiety and excess beta activity in the right insula (Fisher's Exact Test = .189). Although the hypothesis was not supported, it is possible that the limitations of the study, including small N size, lack of formal anxiety measurement, and novel measurement method, masked a true relationship between anxiety and the insular cortex. If a relationship between anxiety, interoception and activity in the right insula had been supported in this study, clinical applications could include focusing on physiological aspects of anxiety for psychoeducation and treatment instead of other (e.g. cognitive) aspects of anxiety. Biofeedback techniques could be especially helpful for those patients whose anxiety is directly related to interoception. Using EEG to help determine the etiology of a client's anxiety symptoms could allow the patient to be treated more effectively more quickly. Future directions should include the establishment of excess activity in the insula using EEG/LORETA, establishing resting measurements of trait anxiety and insular cortex activity, further exploration of right versus left insular activity, and measurement of both state and trait anxiety as it relates to insular activity.