The AFC and event-related power spectra describe the brain system’s transfer properties, eg, excitability and susceptibility to respond, by revealing resonant as well as salient frequencies. The AFC does not simply represent the spectral power density characterizing the transient signal in the frequency domain but the predicted behavior of the system (brain) assuming sinusoidal modulated input signals of defined frequencies were applied as stimulation. Since it reflects amplification in a given frequency channel, the Inhibitors,research,lifescience,medical AFC is expressed in relative units. Hence, the presence

of a peak in the AFC or post-stimulus spectra reveals the resonant frequencies interpreted as the most preferred oscillations of the system during the Inhibitors,research,lifescience,medical response to a stimulus. In order to calculate the AFC, ERP are first averaged and then transformed to the frequency domain using a one-sided Fourier transform (Laplace transform).15,24 Brain oscillations in response to stimulation have helped to advance the analysis. First of all, in order to perform Fourier analysis of brain responses, an averaging procedure is applied to the data of healthy buy Stattic subjects and patients. Following artifact rejection, selective averaging is performed. The averaged potentials (EP and/or ERP) are then analyzed using a fast Fourier transform (FFT) and single Inhibitors,research,lifescience,medical epochs are digitally filtered based on the cut-off

frequencies of the evoked power spectra. Lastly the

data are averaged across subjects to produce a grand average. Another option is power spectral analysis Inhibitors,research,lifescience,medical of the grand average with adaptive digital filtering. Examples of changes in the electroencephalogram and event-related oscillations Power spectral analysis of the spontaneous electroencephalogram Power spectral analysis of spontaneous EEG activity is one of the most successfully applied methods Inhibitors,research,lifescience,medical for identifying biomarkers. (Figure 1). shows the grand averages of power spectra in 18 bipolar euthymic subjects (red) and 18 healthy controls (black) in the alpha frequency range for the eyes closed recording session from occipital locations (O1, Oz, and O2): the power spectrum in the euthymic subjects ranged up to 1 μV2 across all electrodes but up to 4.8 μV2 for O1, 4 μV2 for Oz, and 4.5 μV2 for O2 Montelukast Sodium in the controls. Figure 1. Eyes closed mean power values for occipital (O) electrodes. Modified from ref 25: Basar E, Güntekin B, Atagün Mi, Turp Gölbasi B, Tülay E, Özerdem A. Brain’s alpha activity is highly reduced in euthymic bipolar … Event-related spectra in the alpha frequency range are also drastically reduced in BD.25 Only the marked decrease in alpha power shown in (Figure 1). could possibly serve as a neurophysiologic marker in BD. Phase locking in the gamma band in healthy subjects In inter-trial coherence plots of EROs (Figure 2), the general time course and frequency composition are completely changed. Figure 2.