An electroencephalographic signature predicts antidepressant response in major depression.

Antidepressants are widely prescribed, but their efficacy relative to placebo is modest, in part because the clinical diagnosis of major depression encompasses biologically heterogeneous conditions. Here, we sought to identify a neurobiological signature of response to antidepressant treatment as compared to placebo. We designed a latent-space machine-learning algorithm tailored for resting-state electroencephalography (EEG) and applied it to data from the largest imaging-coupled, placebo-controlled antidepressant study (n = 309). Symptom improvement was robustly predicted in a manner both specific for the antidepressant sertraline (versus placebo) and generalizable across different study sites and EEG equipment. This sertraline-predictive EEG signature generalized to two depression samples, wherein it reflected general antidepressant medication responsivity and related differentially to a repetitive transcranial magnetic stimulation treatment outcome. Furthermore, we found that the sertraline resting-state EEG signature indexed prefrontal neural responsivity, as measured by concurrent transcranial magnetic stimulation and EEG. Our findings advance the neurobiological understanding of antidepressant treatment through an EEG-tailored computational model and provide a clinical avenue for personalized treatment of depression.

Enhanced resilience towards ROADM-induced optical filtering using subcarrier multiplexing and optimized bit and power loading.

In flexible optical networks, lightpaths are routed from source to destination thanks to reconfigurable optical add-drop multiplexers (ROADMs) placed in every node connected by a line system. As ROADMs are based on wavelength selective switches (WSSs), which imply channel filtering, a non negligible performance reduction can be observed when lightpaths traverse many network nodes. Control plane software network controllers that base their decision on the quality of transmission of the physical layer must also take into account the impact of ROADMs cascading. The penalties caused by WSS cascading in single-carrier systems are mostly driven by uncompensated inter-symbol interference (ISI), and therefore their evaluation cannot be based on simple analytical solutions as required for real-time network control. In this paper, we consider a 200G optical system based on multi-subcarrier (MSC) modulation with hybrid modulation formats. Using a fully analytical framework, we show that it is possible to predict ROADM-induced penalties offline and accurately estimate the required settings for their transmitter-side mitigation through bit and/or power-loading. Moreover, resorting to both simulations and experiments, we also demonstrate that properly optimized MSC signals can provide an increased resilience to ROADM filtering with respect to standard single-carrier systems: applying analytically-driven bit-loading over 8×4 Gbaud and 16×2 Gbaud MSC signals after crossing 8 cascaded WSSs in a noise loading scenario, we experimentally found ∼2 dB gain in required SNR with respect to a traditional 32 Gbaud single-carrier signal.

Selective Effects of Psychotherapy on Frontopolar Cortical Function in PTSD.

OBJECTIVE: Exposure therapy is an effective treatment for posttraumatic stress disorder (PTSD), but a comprehensive, emotion-focused perspective on how psychotherapy affects brain function is lacking. The authors assessed changes in brain function after prolonged exposure therapy across three emotional reactivity and regulation paradigms. METHOD: Individuals with PTSD underwent functional MRI (fMRI) at rest and while completing three tasks assessing emotional reactivity and regulation. Individuals were then randomly assigned to immediate prolonged exposure treatment (N=36) or a waiting list condition (N=30) and underwent a second scan approximately 4 weeks after the last treatment session or a comparable waiting period, respectively. RESULTS: Treatment-specific changes were observed only during cognitive reappraisal of negative images. Psychotherapy increased lateral frontopolar cortex activity and connectivity with the ventromedial prefrontal cortex/ventral striatum. Greater increases in frontopolar activation were associated with improvement in hyperarousal symptoms and psychological well-being. The frontopolar cortex also displayed a greater variety of temporal resting-state signal pattern changes after treatment. Concurrent transcranial magnetic stimulation and fMRI in healthy participants demonstrated that the lateral frontopolar cortex exerts downstream influence on the ventromedial prefrontal cortex/ventral striatum. CONCLUSIONS: Changes in frontopolar function during deliberate regulation of negative affect is one key mechanism of adaptive psychotherapeutic change in PTSD. Given that frontopolar connectivity with ventromedial regions during emotion regulation is enhanced by psychotherapy and that the frontopolar cortex exerts downstream influence on ventromedial regions in healthy individuals, these findings inform a novel conceptualization of how psychotherapy works, and they identify a promising target for stimulation-based therapeutics.

Nonlinear mitigation on subcarrier-multiplexed PM-16QAM optical systems.

We report a comprehensive set of experimental, simulation and analytical results on the benefit of nonlinear mitigation strategies for multi-subcarrier (MSC) PM-16QAM transmission systems. First, we demonstrate ~9% maximum reach gain enabled by symbol-rate optimization (SRO) of MSC-PM-16QAM in a 31 channels WDM transmission experiment. Then, we demonstrate that, in the considered experimental scenario, the gain provided by digital backpropagation (DBP) over single-carrier (SC) transmission is similar to that achieved by SRO over MSC transmission. Furthermore, we show that the SRO phenomenon can be weakened after self-channel interference (SCI) removal through DBP. As a result, and due to DBP performance limitations in the experiment, the combined effect of SRO and DBP was found to enable only an additional 4% gain in maximum reach. Finally, we address the impact and symbol-rate dependence of nonlinear phase noise (NLPN) in MSC-PM-16QAM transmission, discussing on the NLPN mitigation capability of standard carrier phase estimation (CPE) and on respective gains that could be achieved through its enhanced mitigation.

1306-km 20x124.8-Gb/s PM-64QAM transmission over PSCF with net SEDP 11,300 (b ∙ km)/s/Hz using 1.15 samp/symb DAC.

We demonstrated the transmission of a Nyquist-WDM signal based on PM-64QAM modulation in an EDFA-only submarine configuration composed of 54.4 km-long fiber spans: 20 channels at 124.8-Gb/s were propagated over 1306 km of low-loss pure-silica-core fiber (PSCF). Thanks to an aggressive digital spectral shaping, we achieved a raw spectral efficiency (SE) of 10.4 b/s/Hz, corresponding to 8.67 b/s/Hz net SE when considering a 20% FEC overhead. Transmitter DACs are operated at a record-low 1.15 samples/symbol, enabled by the insertion of advanced anti-alias filters. The achieved SE-times-distance product was 11,327 (b ∙ km)/(s ∙ Hz), the highest reported so far for PM-64QAM. Combining the experimental results with the performance predictions obtained using an analytical model of nonlinear propagation in uncompensated coherent optical systems (the so-called "GN-model"), we show that PM-64QAM is a realistic option for ultra-high capacity systems in the 1,000 km range, carrying up 40 Tb/s in the C-band.

Analytical results on channel capacity in uncompensated optical links with coherent detection.

Based on a recently introduced model of non-linear propagation, we propose analytical formulas for the capacity limit of polarization-multiplexed ultra-dense WDM uncompensated coherent optical systems at the Nyquist limit, assuming both lumped and ideally distributed amplification. According to these formulas, capacity fundamentally depends on the transmitted power spectral density and on the total optical WDM bandwidth, whereas it does not depend on symbol-rate. Also, capacity approximately decreases by 2 [bit/s/Hz] for every doubling of link length. We show examples of capacity calculations for specific ultra-long-haul links with different polarization-multiplexed (PM) constellations, i.e. ideal PM-Gaussian, PM-QPSK (quadrature-phase shift keying) and PM-QAM (quadrature amplitude modulation). We show that the launch power maximizing capacity is independent of link length and modulation format. We also discuss the usable range of PM-QAM systems and validate analysis with simulations.

Experimental validation of an analytical model for nonlinear propagation in uncompensated optical links.

Link design for optical communication systems requires accurate modeling of nonlinear propagation in fibers. This topic has been widely analyzed in last decades with partial successes in special conditions, but without a comprehensive solution. Since the introduction of coherent detection with electronic signal processing the scenario completely changed because this category of systems shows better performances in links without in-line dispersion management. This change to uncompensated transmission allowed to modify the approach in the study of nonlinear fiber propagation and in recent years a series of promising analytical models have been proposed. In this paper, we present an experimental validation over different fiber types of an analytical model for nonlinear propagation over uncompensated optical transmission links. Considering an ultra-dense WDM system, we transmitted ten 120-Gb/s PM-QPSK signals over a multi-span system probing different fiber types: SSMF, PSCF and NZDSF. A good matching was found in all cases showing the potential of the analytical model for accurate performance estimation that could lead to powerful tools for link design.

Performance evaluation of coherent WDM PS-QPSK (HEXA) accounting for non-linear fiber propagation effects.

Coherent-detection (CoD) permits to fully exploit the four-dimensional (4D) signal space consisting of the in-phase and quadrature components of the two fiber polarizations. A well-known and successful format exploiting such 4D space is Polarization-multiplexed QPSK (PM-QPSK). Recently, new signal constellations specifically designed and optimized in 4D space have been proposed, among which polarization-switched QPSK (PS-QPSK), consisting of a 8-point constellation at the vertices of a 4D polychoron called hexadecachoron. We call it HEXA because of its geometrical features and to avoid acronym mix-up with PM-QPSK, as well as with other similar acronyms. In this paper we investigate the performance of HEXA in direct comparison with PM-QPSK, addressing non-linear propagation over realistic links made up of 20 spans of either standard single mode fiber (SSMF) or non-zero dispersion-shifted fiber (NZDSF). We show that HEXA not only confirms its theoretical sensitivity advantage over PM-QPSK in back-to-back, but also shows a greater resilience to non-linear effects, allowing for substantially increased span loss margins. As a consequence, HEXA appears as an interesting option for dual-format transceivers capable to switch on-the-fly between PM-QPSK and HEXA when channel propagation degrades. It also appears as a possible direct competitor of PM-QPSK, especially over NZDSF fiber and uncompensated links.

Evaluation of the computational effort for chromatic dispersion compensation in coherent optical PM-OFDM and PM-QAM systems.

Recently, coherent-detection (CoD) polarization multiplexed (PM) transmission has attracted considerable interest, specifically as a possible solution for next-generation systems transmitting 100 Gb/s per channel and beyond. In this context, enabled by progress in ultra-fast digital signal processing (DSP) electronics, both multilevel phase/amplitude modulated formats (such as QAM) and orthogonal-frequency-division multiplexed (OFDM) formats have been proposed. One specific feature of DSP-supported CoD is the possibility of dealing with fiber chromatic dispersion (CD) electronically, either by post-filtering (PM-QAM) or by appropriately introducing symbol-duration redundancy (PM-OFDM). In both cases, ultra-long-haul fully uncompensated links seem to be possible. In this paper we estimate the computational effort required by CD compensation, when using the PM-QAM or PM-OFDM formats. Such effort, when expressed as number of operations per received bit, was found to be logarithmic with respect to link length, bit rate and fiber dispersion, for both classes of systems. We also found that PM-OFDM may have some advantage over PM-QAM, depending mostly on the over-sampling needed by the two systems. Asymptotically, for large channel memory and small over-sampling, the two systems tend to require the same CD-compensation computational effort. We also showed that the effort required by the mitigation of polarization-related effects can in principle be made small as compared to that of CD over long uncompensated links.

Fundamental performance limits of optical duobinary.

We present a rigorous analysis defining the fundamental performance limits of duobinary line-coding for optical communications. First, we compare the back-to-back performance of duobinary and intensity modulation systems in an AWGN channel satisfying the Nyquist criterion, with both linear and quadratic receiver. We show that, also for duobinary and quadratic receiver, matched filtering is the best achievable condition. Then, we derive a detailed performance analysis of duobinary in an ASE-noise-limited direct-detection optical system considering noise on the entire space of polarizations. We show that for duobinary line-coding the expression of the bit error rate depends both on the shape of the transmitted pulse and on the receiver optical filter. Comparing duobinary coded and uncoded intensity modulation systems, we show the intrinsic advantages of using the duobinary line-coding in a system based on quadratic detection. Finally, some results for realistic setups are obtained through simulation and compared to the fundamental limits in order to show how close to those limits state-of-the-art systems can operate.

Performance evaluation and assessment of receiver impairments of a novel PolSK transceiver based on differential demodulation.

We present a novel transceiver setup for Polarization Shift Keying (PolSK) modulation using a simple transmitter and a receiver based on differential demodulation. The transmitter is made up of a LiNbO(3) phase modulator with the input fiber pigtailed at 45 degrees with respect to the principal axes of the modulator. The receiver is composed of an asymmetric Mach-Zehnder Interferometer (AMZI) and a couple of balanced photodetectors (BPD), as usually employed for receiving DPSK. To our knowledge, it is the first time such receiver structure is applied to PolSK. In order to fully assess the system performance of the proposed setup, we have carried out numerical simulations using a semi-analytical technique for bit-error-rate evaluation and performed experimental measurements at 10 Gbit/s. After having optimized transceiver performances, we evaluated the resilience to receiver impairments to verify the viability of a realistic implementation. Surprisingly, PolSK shows a better sensitivity using a single-end receiver (with the AMZI tuned at the minimum transmittance point) than using a balanced one. Another improvement has been obtained optimizing the driving voltage at the transmitter: this leads to a "non-ideal" PolSK modulation with non-orthogonal symbols, which shows an enhanced performance thanks to a synchronous phase modulation.

8B10B line coding to mitigate the non-uniform FM laser response of direct modulated CPFSK transmitter.

We propose to employ 8B10B line coding as a simple technique to mitigate the impact of non-uniform laser diode FM response on the system performance of directly-modulated CPFSK. Experimental results show its effectiveness in decreasing signal distortion and penalty.

Evaluation of a head mounted camera for clinical dental teaching.

OBJECTIVE: To evaluate the potential of a novel head mounted camera to both improve the level of detail observed by learners/teachers observing dental procedures being undertaken and to improve the level of feedback given to learners. DESIGN: Questionnaire. SUBJECTS AND METHODS: Qualified members of the dental team and those in training evaluated the usefulness of the application of a novel head mounted camera in their clinical teaching within Dundee Dental School and Hospital. RESULTS: A total of 210 questionnaires were issued and received for analysis. Although the device generally improved the level of detail observed by learners/teachers and improved the level of feedback given to learners, there was scope for improving upon image quality. The lighting of the environment in which the camera was used was a critical factor in optimising success. The different members of the dental team displayed different expectations of the device. This was attributed in part to their level of previous exposure to clinical work. In applying this technology it is therefore important to understand the needs of the user. CONCLUSIONS: The camera system did enhance the learning experience but required further refinement in relation to image quality.

Manifestaciones reumáticas asociadas al mieloma múltiple / Rheumatic manifestations associated with multiple myeloma

Se estudiaron 29 pacientes con discrasias de células plasmáticas, 28 con mieloma múltiple y 1 con plasmocitoma solitario. El propósito fue caracterizar las manifestaciones reumáticas para establecer: frecuencia, oportunidades en que el paciente consulta al reumatólogo antes del diagnóstico de la enfermedad de base, características clínicas, radiológicas y humorales de las mismas y formas de presentación inusual. 28/29 pacientes presentaron manifestaciones reumáticas, las cuales precedieron al diagnóstico en 19. En 14 pacientes motivaron la consulta inicial al reumatólogo. Manifestaciones reumáticas más frecuentes fueron: artralgias en 13, artritis en 5, en 1 de ellos con hallazgo de banda monoclonal en el líquido sinovial. 14 de los 29 pacientes presentados en este informe tuvieron hiperuricemia previa a todo tratamiento y ninguno con gota secundaria. Dos simularon artritis reumatoidea, en los cuales la necropsia reveló amiloide sinovial. 23 pacientes tuvieron dolor óseo, 14 lumbalgia y 3 periartritis de hombro; tumor óseo palpable en 4. Osteoporosis generalizada, lesiones líticas y aplastamiento vertebral en 21,16 y 10 pacientes, respectivamente. Uno simuló enfermedad de Paget ósea. Se destacan 5 casos como entidades reumáticas de presentación inusual de un MM (AU)

Manifestaciones reumáticas asociadas al mieloma múltiple / Rheumatic manifestations associated with multiple myeloma

Se estudiaron 29 pacientes con discrasias de células plasmáticas, 28 con mieloma múltiple y 1 con plasmocitoma solitario. El propósito fue caracterizar las manifestaciones reumáticas para establecer: frecuencia, oportunidades en que el paciente consulta al reumatólogo antes del diagnóstico de la enfermedad de base, características clínicas, radiológicas y humorales de las mismas y formas de presentación inusual. 28/29 pacientes presentaron manifestaciones reumáticas, las cuales precedieron al diagnóstico en 19. En 14 pacientes motivaron la consulta inicial al reumatólogo. Manifestaciones reumáticas más frecuentes fueron: artralgias en 13, artritis en 5, en 1 de ellos con hallazgo de banda monoclonal en el líquido sinovial. 14 de los 29 pacientes presentados en este informe tuvieron hiperuricemia previa a todo tratamiento y ninguno con gota secundaria. Dos simularon artritis reumatoidea, en los cuales la necropsia reveló amiloide sinovial. 23 pacientes tuvieron dolor óseo, 14 lumbalgia y 3 periartritis de hombro; tumor óseo palpable en 4. Osteoporosis generalizada, lesiones líticas y aplastamiento vertebral en 21,16 y 10 pacientes, respectivamente. Uno simuló enfermedad de Paget ósea. Se destacan 5 casos como entidades reumáticas de presentación inusual de un MM