Low Band Power Research Articles

0094 Oscillatory Theta-Band Activity as a Sleep Stage Independent Measure of REM-like Activity throughout Sleep

Abstract Introduction The importance of human cortical theta-band power during REM is suggested by its association with aspects of emotional processing. Currently, this is measured first by visual-inspection of polysomnography to define REM-sleep (scored-REM) and then summing the total theta power within. However, activity attributed to scored-REM has been hypothesized to occur during some scored-NREM (“covert REM”) and total theta conflates different theta-band sources. Oscillatory theta-band activity (OTA) in the hippocampus and associated regions is the hallmark of REM-like sleep in invasive animal studies. We posit that an EEG assessment specifically targeting all-night OTA is a more accurate biomarker of theta-dependent REM functions than current methods. As a first step towards testing this hypothesis, we developed a sleep stage independent approach to isolate REM-like OTA from scalp-EEG. For validation, we compared this measure to conventional-staging and high-frequency activity. Methods Our method uses Irregular-Resampling Auto-Spectral Analysis to remove the aperiodic spectrum (a major source of theta-band power), followed by low-band power normalization to derive the relative oscillatory-theta activity (OTA). Covert REM-containing epochs were calculated based on OTA exceeding a threshold. We combined data from two in-laboratory studies resulting in a sample size of 42 healthy young adult subjects. Analyses used non-sleep restricted overnight EEG recordings from a frontal channel. Results A clear oscillatory-theta peak was observed after processing. Using all sleep stages, we found separation of OTA from total theta-band power evidenced by conventional staging (OTA: scored-REM>scored-NREM, p=0.003 vs total theta: scored-REM<scored-NREM, p<0.001) and correlation with beta-band activity (OTA: r=0.2, p<0.001 vs total theta: p=0.4). Supporting “covert REM”, OTA was present during scored-NREM (p<0.001). On average during a single sleep episode, covert REM was found in 28% of scored- NREM epochs (range=2-85%). Conclusion We developed a novel automated method for measuring REM-like oscillatory-theta activity, independent of conventional sleep staging methods. This method was used to measure REM-like activity across all sleep stages and, as reported in a companion abstract, test the hypothesis that this constitutes a better predictor of REM-dependent behavioral effects than current conventions. Support (If Any) This effort was fully supported by the Department of Defense Military Operational Medicine Research Program (MOMRP).

Dorsomedial prefrontal rTMS for depression in borderline personality disorder: A pilot randomized crossover trial

Recently, a small literature has emerged suggesting that repetitive transcranial magnetic stimulation (rTMS) may offer benefit for MDD even in BPD patients, perhaps by enhancing cognitive control, and/or disrupting excessive 'non-reward' activity in right orbitofrontal regions. This study aimed primarily to assess the therapeutic effects of dorsomedial prefrontal cortex (DMPFC)-rTMS against MDD symptoms in BPD patients, and secondarily to assess whether the therapeutic effects ensued via mechanisms of reduced impulsivity and core BPD pathology on clinical scales (BIS-11, ZAN-BPD) or of reduced alpha- and theta-band activity on EEG recordings of right orbitofrontal cortex.. In a crossover-design trial, 20 BPD patients with MDD underwent 2×30 session/15 day blocks of either active-then-sham or sham-then-active bilateral 20Hz DMPFC-rTMS. Sixteen out of 20 patients completed treatment. A significant (p=0.00764) crossover effect was detected, with overall reductions in HamD17 score from 23.1±SD3.1 to 10.75±SD5.8. Nine out of 16 (56.3%) treatment completers achieved response (>50% improvement) and 6/16 (37.5%) achieved remission (HamD≤7), maintained at 1 month followup. BIS-11 scores remained unchanged, and ZAN-BPD scores improved similarly in both groups with no significant crossover effect. Change in low-band power over right orbitofrontal regions correlated with clinical improvement. This was a crossover study with a small sample size. A randomized controlled trial with larger sample size will be needed to establish the efficacy more definitively. The results suggest efficacy for DMPFC-rTMS in treating MDD in BPD, and provide a foundation for a larger future trial.

Design of MICS Band Low Power Transmitter for Implantable Medical Applications

The cyborg can control robotic arm by means of the brain implant. The design of implantable node is critical because the surgically implanted node should consume very low power. In this paper, an efficient CMOS Transmitter in terms of low power is presented for Implantable Medical Devices in the MICS band. The RF front-end transmitter consists of up-conversion mixer and a power amplifier. The designs have been done using Cadence RF Spectre tools with 180 nm technology and the transmitter front-end consumes 900μW for the MICS band.

A Wide Gain Control Range V-Band CMOS Variable-Gain Amplifier With Built-In Linearizer

In this paper, the design and analysis of a CMOS variable gain amplifier (VGA) with the built-in linearizers and noise reduction technique are presented. A <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> -band low power and miniature VGA is designed and fabricated. To maximize the gain control range and to improve the linearity, an auxiliary nMOS transistor is added in the cascode structure as a built-in linearizer. Moreover, to reduce the noise figure (NF), an inductor is placed between the transistors in the cascode structure. At the high gain state, the VGA offers a maximum gain of 22 dB with a minimum NF of 4.8 dB at 62 GHz. Due to the built-in linearizers, the VGA demonstrates 40-dB gain control range with a third-order input intercept point (IIP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) of -19 dBm at 60 GHz. At the low gain state, the VGA has 3 dBm of IIP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> . In both states, the power consumption is 26 mW from a 2-V voltage supply. The chip size is 0.91 × 0.69 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , including pads. To the authors' knowledge, this VGA demonstrates largest gain control range, the lowest power consumption, and the lowest NF at the high gain state for reported 90-nm CMOS millimeter-wave VGAs.

A low power UWB low noise amplifier using current reused and feedback techniques

AbstractThis letter presents a full band low power low noise amplifier design in 0.18‐μm complementary metal‐oxide‐semiconductor FET (CMOS) technology.The proposed circuit adopts current reused technique to achieve low power consumption, and shunt resistive feedback for wide‐band operation. An excellent wide and flat gain, low noise figure, are achieved by composes of these techniques. The implemented ultra‐wideband (UWB) low noise amplifier (LNA) exhibits a flat gain of 18 dB with total power consumption of 5.2 mA from 1.8 V power supply. The noise figure is 3.1 dB within the entire bandwidth. The input and output return loss is less than −10 dB in the specified bandwidth. The proposed technique exhibits 0.8 dBm of IIP3. The active die area of UWB LNA occupies 0.72 mm2. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 54:471–474, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26550

Pre-stimulus alpha power affects vertex N2–P2 potentials evoked by noxious stimuli

It is well known that scalp potentials evoked by nonpainful visual and auditory stimuli are enhanced in amplitude when preceded by pre-stimulus low-amplitude alpha rhythms. This study tested the hypothesis that the same holds for the amplitude of vertex N2-P2 potentials evoked by brief noxious laser stimuli, an issue of interest for clinical perspective. EEG data were recorded in 10 subjects from 30 electrodes during laser noxious stimulation. The artifact-free vertex N2-P2 complex was spatially enhanced by surface Laplacian transformation. Pre-stimulus alpha power was computed at three alpha sub-bands according to subject's individual alpha frequency peak (i.e. about 6-8Hz for alpha 1, 8-10Hz for alpha 2 and 10-12Hz for alpha 3 sub-band). Individual EEG single trials were divided in two sub-groups. The strong-alpha sub-group (high band power) included halfway of all EEG single trials, namely those having the highest pre-stimulus alpha power. Weak-alpha sub-group (low band power) included the remaining trials. Averaging procedure provided laser evoked potentials for both trial sub-groups. No significant effect was found for alpha 1 and alpha 2 sub-bands. Conversely, compared to strong-alpha 3 sub-group, weak-alpha 3 sub-group showed vertex N2-P2 potentials having significantly higher amplitude (p<0.05). These results extend to the later phases of pain processing systems the notion that generation mechanisms of pre-stimulus alpha rhythms and (laser) evoked potentials are intrinsically related and subjected to fluctuating "noise". That "noise" could explain the trial-by-trial variability of laser evoked potentials and perception.