3,032 research outputs found
Abnormal negative feedback processing in first episode schizophrenia: evidence from an oculomotor rule switching task
Background. Previous studies have shown that patients with schizophrenia are impaired on executive tasks,
where positive and negative feedbacks are used to update task rules or switch attention. However, research to date
using saccadic tasks has not revealed clear deficits in task switching in these patients. The present study used an
oculomotor ‘ rule switching ’ task to investigate the use of negative feedback when switching between task rules in
people with schizophrenia.
Method. A total of 50 patients with first episode schizophrenia and 25 healthy controls performed a task in which the association between a centrally presented visual cue and the direction of a saccade could change from trial to trial. Rule changes were heralded by an unexpected negative feedback, indicating that the cue-response mapping
had reversed.
Results. Schizophrenia patients were found to make increased errors following a rule switch, but these were almost entirely the result of executing saccades away from the location at which the negative feedback had been presented on the preceding trial. This impairment in negative feedback processing was independent of IQ.
Conclusions. The results not only confirm the existence of a basic deficit in stimulus–response rule switching in
schizophrenia, but also suggest that this arises from aberrant processing of response outcomes, resulting in a failure to appropriately update rules. The findings are discussed in the context of neurological and pharmacological
abnormalities in the conditions that may disrupt prediction error signalling in schizophrenia
Impact of Mass Azithromycin Treatment on the Prevalence of Active Trachoma and Ocular Chlamydia Trachomatis in the Gambia
Performance analysis a of solar driven organic Rankine cycle using multi-component working fluids
An electrooptical muscle contraction sensor
An electrooptical sensor for the detection of muscle contraction is described. Infrared light is injected into the muscle, the backscattering is observed, and the contraction is detected by measuring the change, that occurs during muscle contraction, between the light scattered in the direction parallel and perpendicular to the muscle cells. With respect to electromyography and to optical absorption-based sensors, our device has the advantage of lower invasiveness, of lower sensitivity to electromagnetic noise and to movement artifacts, and of being able to distinguish between isometric and isotonic contractions
Effects of Spatially Nonuniform Gain on Lasing Modes in Weakly Scattering Random Systems
A study on the effects of optical gain nonuniformly distributed in
one-dimensional random systems is presented. It is demonstrated numerically
that even without gain saturation and mode competition, the spatial
nonuniformity of gain can cause dramatic and complicated changes to lasing
modes. Lasing modes are decomposed in terms of the quasi modes of the passive
system to monitor the changes. As the gain distribution changes gradually from
uniform to nonuniform, the amount of mode mixing increases. Furthermore, we
investigate new lasing modes created by nonuniform gain distributions. We find
that new lasing modes may disappear together with existing lasing modes,
thereby causing fluctuations in the local density of lasing states.Comment: 26 pages, 10 figures (quality reduced for arXiv
FDTD Simulation of Thermal Noise in Open Cavities
A numerical model based on the finite-difference time-domain (FDTD) method is
developed to simulate thermal noise in open cavities owing to output coupling.
The absorbing boundary of the FDTD grid is treated as a blackbody, whose
thermal radiation penetrates the cavity in the grid. The calculated amount of
thermal noise in a one-dimensional dielectric cavity recovers the standard
result of the quantum Langevin equation in the Markovian regime. Our FDTD
simulation also demonstrates that in the non-Markovian regime the buildup of
the intracavity noise field depends on the ratio of the cavity photon lifetime
to the coherence time of thermal radiation. The advantage of our numerical
method is that the thermal noise is introduced in the time domain without prior
knowledge of cavity modes.Comment: 8 pages, 7 figure
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Novel mutation in CCBE 1 as a cause of recurrent hydrops fetalis from Hennekam lymphangiectasia-lymphedema syndrome-1.
Whole exome sequencing (WES) was used to determine the etiology of recurrent hydrops fetalis in this case of Hennekam lymphangiectasia-lymphedema syndrome-1. WES is a useful approach for diagnosing rare single-gene conditions with nonspecific phenotypes and should be considered early in the diagnostic process of investigating fetal abnormalities
Marginally Unstable Periodic Orbits in Semiclassical Mushroom Billiards
Optical mushroom shaped billiards offer a unique opportunity to isolate and
study non-dispersive, marginally unstable periodic orbits. Here we show that
the openness of the cavity to external fields presents unanticipated
consequences for the far-field distribution, including directional emission.
This is mediated by interactions of marginally unstable periodic orbits with
chaotic modes and is potentially relevant for the design of microcavity lasers.
We also show that such orbits are robust against perturbations to the shape of
the cavity, despite the non-generic character of the classical counterpart and
the lack of structural stability of the corresponding classical orbits.Comment: 10 pages, 6 figure
Regional trends in breast cancer incidence and mortality in Denmark prior to mammographic screening.
To provide a basis for the evaluation of mammographic screening programmes in Denmark, a study was undertaken of the regional differences in breast cancer incidence and mortality. All 16 regions were followed for the 20 year period, 1970-89, before the start of the first population-based mammographic screening programme in the Copenhagen municipality in 1991. Multiplicative Poisson models were used for the analysis. In general, the incidence increased during this period from 55 to 70 [per 100,000 standardised world standard population (WSP)], and the analysis shows this to be most pronounced among women below age 60. The mortality was more stable, changing only from 24 to 28 (per 100,000 standardised WSP), but a significant increase occurred in the late 1980s. The study showed regional differences in both incidence and mortality of breast cancer in Denmark. Both the incidence and the mortality varied between the regions, with maximum differences of 22%. The analysis showed no variation in the time trends in the different regions, and thus indicates that the use of a regional comparison group would be a valid basis for evaluation of the Copenhagen programme. Our study, however, underlies the difficulties inherent in the evaluation of screening programmes without internal control groups
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