Despite years of research into bipolar disorder (manic depression), its underlying pathophysiology remains elusive. It is widely acknowledged that the disorder is strongly heritable, but the genetics are complex with less than full concordance in monozygotic twins and at least four susceptibility loci identified. We propose that bipolar disorder is the result of a genetic propensity for slow interhemispheric switching mechanisms that become `stuck' in one or the other state. Because slow switches are also `sticky' when compared with fast switches, the clinical manifestations of bipolar disorder may be explained by hemispheric activation being `stuck ' on the left (mania) or on the right (depression). Support for this `sticky ' interhemispheric switching hypothesis stems from our recent observation that the rate of perceptual alternation in binocular rivalry is slow in euthymic subjects with bipolar disorder (nˆ18, medianˆ0.27 Hz) compared with normal controls (nˆ49, medianˆ0.60 Hz, p50.0005). We have presented evidence elsewhere that binocular rivalry is itself an interhemispheric switching phenomenon. The rivalry alternation rate (putative interhemispheric switch rate) is robust in a given individual, with a test^retest correlation of more than 0.8, making it suitable for genetic studies. The interhemispheric switch rate may provide a trait-dependent biological marker for bipolar disorder.

Transcranial magnetic stimulation (TMS) has been widely used in studies of human motor and cognitive functions as well as in clinical treatment. Biophysical mechanism underlying its e!ect is, however, largely unknown. Here, we develop a theory to calculate the e!ect of magnetic stimulation on arbitrary neuronal structure. Then, we employ a computer simulation which combines a realistic multicompartmental model of neocortical neurons and the calculation of the induced electric "eld. The simulation shows that a single magnetic pulse applied to model cortical neurons can induce brief burst "ring followed by a silent period of duration comparable to experimental data of TMS. Our simulation o!ers a new clue to understand physiology of TMS by demonstrating that magnetic stimulation acts on biophysics of the dendrites in

Copyright © 2012 Patrick Callahan et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Introduction. Depression in adolescents and young people is associated with reduced social, occupational, and interpersonal functioning, increases in suicide and self-harm behaviours, and problematic substance use. Age-appropriate, evidence-based treatments are required to provide optimal care. Methods. “Evidence mapping ” methodology was used to quantify the nature and distribution of the extant high-quality research into the prevention and treatment of depression in young people across psychological, medical, and other treatment domains. Results. Prevention research is dominated by cognitive-behavioral- (CBT-)