In particular, noninvasive brain stimulation offers a convenient tool to directly target the network level by altering the temporal structure of neuronal activity. With the exception of a few novel and rather poorly understood brain stimulation approaches such as ultrasound4,5 and laser,6 the vast majority of noninvasive brain stimulation is based on the activator Calcitriol application of electric and magnetic fields to modulate neuronal activity. Yet, since the development of the Inhibitors,research,lifescience,medical electroencephalogram (EEG) early in the 20th century,7 we know that network activity in brains also generates its own, endogenous, electric fields.8 In this review,

we will discuss both endogenous and exogenous electric fields and will highlight the promising opportunities for the rational design of noninvasive brain stimulation approaches for the treatment Inhibitors,research,lifescience,medical of psychiatric disorders. In particular, there will be a focus on the modulation of cortical oscillations, a hallmark of physiological and pathological

brain function.9,10 Ubiquitous neuronal network signal as a convenient epiphenomenon? Neuronal signaling relies on the generation and transmission of transient electric impulses that represent the fundamental information unit in the brain.11,12 The canonical model of neural information processing is based on the notion that changes of the electric potential inside neurons relative Inhibitors,research,lifescience,medical to the constant electric potential Inhibitors,research,lifescience,medical outside of the neuron determines the membrane voltage, and therefore the functional state of individual neurons.13 Yet, the vast majority of selleck kinase inhibitor neurophysiology studies are based on measurements of changes in the extracellular voltage such as the classical EEG, broadly used in both clinical and basic science settings, and the local field potential (LFP), an invasive recording of the extracellular voltage routinely performed in neuroscience animal studies.14 These fluctuations of extracellular voltage represent the endogenous electric field and reflect the activity of a large number of (synchronized) neurons; they have provided the basis for numerous discoveries Inhibitors,research,lifescience,medical AV-951 about physiological

and pathological states in the brain. These electric signals have routinely been considered an epiphenomenon in neuroscience, in the sense that the endogenous electric field plays no functional (”active“) role per se, but rather, represents a convenient side product of neuronal network activity to the benefit of the researcher or clinician who wants to measure brain activity. This view was supported by the realization that endogenous electric fields were comparably low in magnitude (around 1 V/m) and therefore unlikely to be powerful enough to directly modulate neuronal signaling. Studies which demonstrated that such weak electric fields change the membrane voltage only by an amount much smaller (typically about 0.