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To the Editor We applaud McGrath and colleagues1 for exploring the use of brain state as a way to predict differential outcomes from either psychotherapy or medication as treatment for depression. Hypometabolism in the right anterior insula correlated with symptom reduction through cognitive behavioral therapy, whereas hypermetabolism in the right anterior insula correlated with symptom reduction through escitalopram. In their discussion, the authors pointed out roles of the anterior insula for interoception, self-awareness, and cognitive control. We wish to highlight additionally that the insulae are loci for lateralized management of autonomic functioning. In particular, the right anterior insula regulates sympathetic activity, and the left insula appears to be responsible for parasympathetic activity.2 It may be that depressed individuals with greater right anterior insular activity have higher sympathetic arousal and are thus relatively impaired in their capacity to successfully apply cognitive-behavioral strategies. These individuals may preferentially benefit from psychopharmacological agents, which are known to have effects on autonomic tone.3 In our own work, we have found that hemispheric lateralization of autonomic management may be discerned through surface brain electrical activity recordings, with clinical implications. We recently reported a relationship between temporal high-frequency brain electrical asymmetry, calculated from 2-channel, 1-minute bilateral recordings, and peripheral measures of cardiovascular autonomic regulation. Rightward temporal asymmetry correlated with higher heart rate and lower heart rate variability.4 Furthermore, in a clinical trial, we found that autocalibration of right-dominant high-frequency temporal activity toward greater symmetry appeared to correlate with insomnia symptom reduction for individuals with insomnia and depressive symptoms.5 We are thus excited that data from positron-emission tomography and surface brain electrical activity recordings may be converging on a unitary conclusion about the role of lateralized activity in temporal lobe–region structures for mental health intervention.
Tegeler CH, Lee SW, Shaltout HA. Significance of Right Anterior Insula Activity for Mental Health Intervention. JAMA Psychiatry. 2014;71(3):336. doi:10.1001/jamapsychiatry.2013.3507