Functional brain connectivity in electrical status epilepticus in sleep.

Electrical status epilepticus in sleep (ESES) is an age-related, self-limited epileptic encephalopathy. The syndrome is characterized by cognitive and behavioral abnormalities and a specific EEG pattern of continuous spikes and waves during slow-wave sleep. While spikes and sharp waves are known to result in transient cognitive impairment during learning and memory tasks performed during the waking state, the effect of epileptiform discharges during sleep on cognition and behavior is unclear. There is increasing evidence that abnormalities of coherence, a measure of the consistency of the phase difference between two EEG signals when compared over time, is an important feature of brain oscillations and plays a role in cognition and behavior. The objective of this study was to determine whether coherence of EEG activity is altered during slow-wave sleep in children with ESES when compared to typically developing children. We examined coherence during epochs of ESES versus epochs when ESES was not present. In addition, we compared coherence during slow-wave sleep between typically developing children and children with ESES. ESES was associated with remarkably high coherences at all bandwidths and most electrode pairs. While the high coherence was largely attributed to the spikes and spike-and-wave discharge, activity between spikes and spike-and-wave discharge also demonstrated high coherence. This study indicates that EEG coherence during ESES is relatively high. Whether these increases in coherence correlate with the cognitive and behavioral abnormalities seen in children with this EEG pattern remains to be determined.

Solution processes for ultrabroadband and omnidirectional graded-index glass lenses with near-zero reflectivity in high concentration photovoltaics.

Concentrator photovoltaic (CPV) systems, where incident direct solar radiation is tightly concentrated onto high-efficiency multi-junction solar cells by geometric optical elements, exhibit the highest efficiencies in converting the sun's energy into electric power. Their energy conversion efficiencies are greatly limited, however, due to Fresnel reflection losses occurring at three air/optics interfaces in the most sophisticated dual-stage CPV platforms. This paper describes a facile one-step wet-etching process to create a nanoporous surface with a graded-index profile on both flat and curved glasses, with capabilities of achieving ~99% average transmission efficiency in a wide wavelength range from 380 nm to 1.3 µm and for a wide range of incident angles up to ±40° regardless of the polarization state of incident sunlight. The simplicity of the etching process remarkably increases their versatility in various optical elements that require unconventional form factors such as Fresnel lenses and microlens arrays, and/or demanding curvatures along with much reduced dimensions such as ball lenses. Etched glass surfaces on two-stage optical concentrating systems yield enhancements in total optical transmission efficiencies by 13.8% and in the photocurrent by 14.3%, as experimentally determined by measurements on microscale triple-junction solar cells. The presented strategy can be widely adapted in a variety of applications such as image sensors, display systems, and other optoelectronic devices.

Concentrator photovoltaic module architectures with capabilities for capture and conversion of full global solar radiation.

Emerging classes of concentrator photovoltaic (CPV) modules reach efficiencies that are far greater than those of even the highest performance flat-plate PV technologies, with architectures that have the potential to provide the lowest cost of energy in locations with high direct normal irradiance (DNI). A disadvantage is their inability to effectively use diffuse sunlight, thereby constraining widespread geographic deployment and limiting performance even under the most favorable DNI conditions. This study introduces a module design that integrates capabilities in flat-plate PV directly with the most sophisticated CPV technologies, for capture of both direct and diffuse sunlight, thereby achieving efficiency in PV conversion of the global solar radiation. Specific examples of this scheme exploit commodity silicon (Si) cells integrated with two different CPV module designs, where they capture light that is not efficiently directed by the concentrator optics onto large-scale arrays of miniature multijunction (MJ) solar cells that use advanced III-V semiconductor technologies. In this CPV+ scheme ("+" denotes the addition of diffuse collector), the Si and MJ cells operate independently on indirect and direct solar radiation, respectively. On-sun experimental studies of CPV+ modules at latitudes of 35.9886° N (Durham, NC), 40.1125° N (Bondville, IL), and 38.9072° N (Washington, DC) show improvements in absolute module efficiencies of between 1.02% and 8.45% over values obtained using otherwise similar CPV modules, depending on weather conditions. These concepts have the potential to expand the geographic reach and improve the cost-effectiveness of the highest efficiency forms of PV power generation.

State-Dependent Differences in Functional Connectivity in Young Children With Autism Spectrum Disorder.

BACKGROUND: While there is increasing evidence of altered brain connectivity in autism, the degree and direction of these alterations in connectivity and their uniqueness to autism has not been established. The aim of the present study was to compare connectivity in children with autism to that of typically developing controls and children with developmental delay without autism. METHODS: We assessed EEG spectral power, coherence, phase lag, Pearson and partial correlations, and epileptiform activity during the awake, slow wave sleep, and REM sleep states in 137 children aged 2 to 6 years with autism (n = 87), developmental delay without autism (n = 21), or typical development (n = 29). FINDINGS: We found that brain connectivity, as measured by coherence, phase lag, and Pearson and partial correlations distinguished children with autism from both neurotypical and developmentally delayed children. In general, children with autism had increased coherence which was most prominent during slow wave sleep. INTERPRETATION: Functional connectivity is distinctly different in children with autism compared to samples with typical development and developmental delay without autism. Differences in connectivity in autism are state and region related. In this study, children with autism were characterized by a dynamically evolving pattern of altered connectivity.

Brain connectivity in West syndrome.

PURPOSE: Hypsarrhythmia, the pathognomonic EEG pattern of West syndrome, is typically characterized by a high amplitude, arrhythmic, and asynchronous pattern. While this severely aberrant pattern would suggest severe abnormalities in connectivity, coherence has not yet been systematically assessed in hypsarrhythmia. METHODS: We evaluated the EEGs of 28 infants, 12 with infantile spasms with hypsarrhythmia and 16 similarly age control infants for coherence and spectral power. RESULTS: Children with infantile spasms and hypsarrhythmia EEGs had marked abnormalities in coherence and spectral power compared to normal children of similar ages. During sleep increases in delta, theta, alpha and beta coherences were seen, particularly at long inter-electrode distances while at short inter-electrode distances coherences were decreased in the theta and beta range, particularly in the frontal region. The enhanced coherences at long inter-electrode distances suggest that during sleep in children with infantile spasms widely spread cortical region do not have functional differentiation whereas in the frontal lobe there is reduced functional connectivity and integration of local cortical regions. Children with continued seizures and developmental delay showed persistent abnormalities in coherence. CONCLUSION: This study demonstrates that hypsarrhythmic EEGs have marked abnormalities in coherence spectral power and such abnormalities may be related to cognitive impairment.

Printing-based assembly of quadruple-junction four-terminal microscale solar cells and their use in high-efficiency modules.

Expenses associated with shipping, installation, land, regulatory compliance and on-going maintenance and operations of utility-scale photovoltaics can be significantly reduced by increasing the power conversion efficiency of solar modules through improved materials, device designs and strategies for light management. Single-junction cells have performance constraints defined by their Shockley-Queisser limits. Multi-junction cells can achieve higher efficiencies, but epitaxial and current matching requirements between the single junctions in the devices hinder progress. Mechanical stacking of independent multi-junction cells circumvents these disadvantages. Here we present a fabrication approach for the realization of mechanically assembled multi-junction cells using materials and techniques compatible with large-scale manufacturing. The strategy involves printing-based stacking of microscale solar cells, sol-gel processes for interlayers with advanced optical, electrical and thermal properties, together with unusual packaging techniques, electrical matching networks, and compact ultrahigh-concentration optics. We demonstrate quadruple-junction, four-terminal solar cells with measured efficiencies of 43.9% at concentrations exceeding 1,000 suns, and modules with efficiencies of 36.5%.

Transitory effect of spike and spike-and-wave discharges on EEG power in children.

BACKGROUND: Spikes and spike-and-wave discharges on the EEG of children are a strong biomarker of epilepsy. There is increasing evidence that these EEG abnormalities also impair brain function and result in transitory cognitive impairment. Studies in animal models have shown that EEG spikes alters single cell firing and that such impairment in firing may extend beyond the duration of the spike-and-wave discharge. Whether interictal epileptiform discharges have lasting effects on EEG activity in humans is not known. METHODS AND RESULTS: The EEGs of 60 consecutive children with focal or interictal spike-and-wave discharges were evaluated using power spectral analysis to determine if there were any changes in power spectra from before to after the interictal abnormalities. Neither focal spike-and-wave nor generalized spike-and-wave discharges had any effect on the EEG frequency or spectral power following the discharge. CONCLUSION: While interictal EEG discharges temporarily alter neural activity during the duration of the spike-and-wave discharge, there is no evidence that alterations of spectral power continue beyond the duration of the interictal discharge. The effects of interictal activity on EEG rhythms therefore appear to be quite transient and confined to the duration of the interictal discharge.

The association between psychosis proneness and sensory gating in cocaine-dependent patients and healthy controls.

This was a naturalistic study of 23 abstinent cocaine-dependent patients and 38 controls who were studied using a paired-stimulus paradigm to elicit three mid-latency auditory evoked responses (MLAERs), namely, the P50, N100, and P200. Sensory gating was defined as the ratio of the S2 amplitude to the S1 amplitude. Psychosis-proneness was assessed using four Chapman psychosis proneness scales measuring perceptual aberration, magical ideation, social anhedonia, and physical anhedonia. Omnibus correlations based upon the entire sample revealed significant and differential relationships between the MLAER components and psychosis-proneness. Social Anhedonia scale scores accounted for the largest proportion of variance in the P50 gating ratio, while Perceptual Aberration scores accounted for the largest proportion of variance in P200 gating. Psychosis proneness and sensory gating appear to be associated. In particular, poorer P50 gating is related to higher scores on the Social Anhedonia scale in healthy controls and across mixed samples of cocainede-pendent patients and controls. These findings hold significance for the further understanding of the relationship between deficient sensory gating ability and the propensity to developing psychotic symptoms in a vulnerable population like cocaine-dependent individuals.

Relevance of attention in auditory sensory gating paradigms in schizophrenia A pilot study.

The paired-click paradigm (PCP) is widely used to study sensory habituation or gating in a number of psychiatric and neurological conditions. The classic paradigm does not control for attentional factors. In order to assess the influences of incorporating attentional control measures we administered the auditory PCP (S1-S2) in three different attention (passive, auditory attention to S2, visual attention to a concurrent continuous performance task [CPT]) conditions to a group of chronic, medicated schizophrenia patients (N=12) and a group of healthy subjects (N=15) to evaluate the effects of attention on sensory gating measures. A significant effect of attention on S1 amplitudes was shown for P50 in both groups, and N100 or P200 in schizophrenia patients. Attention status had a significant effect on S2 amplitudes for N100 and P200, and N100 and P200 gating ratios. Despite the effect of attention on S1 P50 amplitudes there was no effect on the gating ratio. In terms of group differences, visual attention to the concurrent CPT during the paired-click sensory gating task significantly enhanced the detection of deficient gating of the N100 and P200 components in schizophrenia patients. The data support the continued utilization of the passive gating paradigm for examining P50 gating but strongly suggest that for studies examining gating of the N100 or P200 components, a visual distraction paradigm may enhance the detection of abnormal gating in schizophrenia patients.

P50, N100, and P200 sensory gating: relationships with behavioral inhibition, attention, and working memory.

P50, N100, and P200 auditory sensory gating could reflect mechanisms involved in protecting higher-order cognitive functions, suggesting relationships between sensory gating and cognition. This hypothesis was tested in 56 healthy adults who were administered the paired-click paradigm and two adaptations of the continuous performance test (Immediate/Delayed Memory Task, IMT/DMT). Stronger P50 gating correlated with fewer commission errors and prolonged reaction times on the DMT. Stronger N100 and P200 gating correlated with better discriminability on the DMT. Finally, prolonged P200 latency related to better discriminability on the IMT. These findings suggest that P50, N100, and P200 gating could be involved in protecting cognition by affecting response bias, behavioral inhibition, working memory, or attention.

Sensory-gating deficit of the N100 mid-latency auditory evoked potential in medicated schizophrenia patients.

The clinical and neuro-cognitive correlates of the P50 and N100 auditory evoked responses gating deficits in schizophrenia have thus far eluded identification. Based on our prior results, we hypothesized that, in addition to the P50, gating of the N100 is significantly decreased in schizophrenia and that this deficit correlates with the negative symptoms dimension of schizophrenia. Amplitudes and gating measures of the P50 and N100 were compared between stable out-patients (N=45) (mainly on atypical antipsychotics) with chronic schizophrenia and age- and gender-matched healthy controls (N=49) and the clinical correlates examined. All subjects underwent the paired-stimulus paradigm in 3 or 4 different days. Data from day one and the mean of all days (MOAD) were examined. P50 and N100 amplitudes and gating measures were correlated with PANSS and Wisconsin Card Sorting Test data. Utilizing day one data, no amplitude or gating measures were significantly different between the groups. Utilizing MOAD data, both P50 and N100 gating were significantly decreased in schizophrenia patients. The N100 gating deficit correlated with the negative-symptoms cluster and measures of frontal lobe dysfunction. The data suggest a correlation between N100 gating deficit and the negative-cognitive deficits dimensions of schizophrenia. Data also suggest that improving the signal to noise ratio (MOAD data) increases the sensitivity for detecting gating abnormalities and assessing their clinical correlates.

The Role of Age, Gender, Education, and Intelligence in P50, N100, and P200 Auditory Sensory Gating.

P50, N100, and P200 auditory sensory gating reflect distinct mechanisms involved in protecting the integrity of higher-order functions. They have been implicated in multiple psychiatric disorders. Recent studies showed the (limited) effects of age and gender on sensory gating in control subjects, suggesting there may be other sources of variance. Two potential sources may be education and intelligence (intellectual capability), variables that frequently differ across studies and across experimental groups. We explored potential effects of age, gender, education, and intelligence (Shipley intelligence scale) on P50, N100, and P200 sensory gating measured with the paired-click paradigm in 60 healthy subjects recruited from the general population. Increased intellectual capability related to stronger N100 and P200 gating and more pronounced N100 and P200 amplitudes. In addition, increased age related to weaker P200 gating and smaller P200 amplitudes. Gender had negligible effects. Intellectual capability or age could contribute to variation in N100 or P200 auditory sensory gating and should be controlled for when studying sensory gating in clinical and control groups.

Attentional deficits in cocaine-dependent patients: converging behavioral and electrophysiological evidence.

Although there are several reports of patients with cocaine dependence displaying cognitive deficits, the nature of their information processing deficits is not well characterized. In the present study, the attentional performance of cocaine-dependent patients (n=14) was examined and compared with that of healthy control individuals (n=15). Attention was assessed using an auditory oddball event-related task as well as the Continuous Performance Test (CPT, Identical Pairs version). The cocaine-dependent group displayed P300 amplitude reduction compared to controls. The group difference in P300 response latency did not reach significance. On the CPT, the cocaine-dependent patients displayed significantly poorer discriminability and greater errors of commission than the controls. There was a positive correlation between performance on the oddball event-related task and performance on the CPT. This investigation provides converging behavioral and electrophysiological evidence of attentional deficits in cocaine-dependent patients.

Cocaine-dependence and cocaine-induced paranoia and mid-latency auditory evoked responses and sensory gating.

Cocaine-dependence has been shown to affect the amplitudes of the P50 mid-latency auditory evoked response (MLAER) as well as P50 sensory gating. The effects on subsequent MLAERs (N100 and P200) have not been examined. The objective of the current study was to further assess the effects of chronic cocaine use on the P50, N100, and P200 components. Thirty-four, at least three weeks abstinent, cocaine-dependent individuals and 34 age and gender matched healthy controls were examined. The amplitudes, latencies and gating measures were calculated and compared between the groups. The N100 and P200 were significantly smaller in patients as compared to control subjects. Sensory gating of the P50, the N100, and the P200 were deficient in cocaine-dependent subjects. Latencies of all measured components were prolonged in subjects who reported developing paranoia while intoxicated. Finally, a positive correlation was found between length of abstinence and evoked response amplitudes. We conclude that the effects of cocaine on sensory gating extend beyond the P50 to the N100 and the P200 components. The data also suggest that prolonged latency of the evoked potentials may be a correlate of cocaine-induced psychosis. Finally, the data suggest that some recovery of amplitude and gating occurs with abstinence.

Effect of valacyclovir on viral shedding in immunocompetent patients with recurrent herpes simplex virus 2 genital herpes: a US-based randomized, double-blind, placebo-controlled clinical trial.

OBJECTIVE: To determine the efficacy of daily suppressive therapy with a 1-g dose of valacyclovir in reducing total (clinical and subclinical) herpes simplex virus 2 (HSV-2) shedding compared with placebo in Immunocompetent patients diagnosed as having recurrent HSV-2 genital herpes. PATIENTS AND METHODS: From June 18, 2004, to December 17, 2004, patients from 27 US sites with a history of 6 or more genital herpes recurrences per year were randomized in a 3:1 ratio to receive 1 g/d of valacyclovir or placebo. During the double-blind suppressive therapy, patients were provided with the study drug (500-mg valacyclovir caplets or matching placebo) and Instructed to take 2 caplets once daily without regard to meals for 60 days. Daily genital and anal or rectal swabs were self-collected during the 60-day study period for evaluation of HSV-2 viral shedding as determined by quantitative type-specific polymerase chain reaction assay. RESULTS: One hundred fifty-two patients were randomized into this study, 43 to placebo and 109 to 1 g/d of valacyclovir. A total of 134 completed the study (40 placebo [93%], 94 valacyclovir [86%]), and 18 prematurely withdrew (3 placebo [7%], 15 valacyclovir [14%]). Valacyclovir significantly reduced the percentage of days with total (clinical and subclinical) HSV-2 shedding throughout 60 days compared with placebo. In the intent-to-treat population, a 71% reduction in total shedding (P < .001), a 58% reduction in subclinical shedding (P < .001), and a 64% reduction in clinical shedding (P = .01) were observed. Valacyclovir was not associated with any significant toxic effects compared with placebo. CONCLUSION: This study demonstrated that 1 g/d of valacyclovir administered for 60 days was generally well tolerated and was an effective suppressive therapy that significantly reduced total (clinical and subclinical) HSV-2 shedding compared with placebo in immunocompetent patients diagnosed as having recurrent HSV-2 genital herpes.

Mid-latency auditory-evoked responses and sensory gating in focal epilepsy: a preliminary exploration.

The relationship between epilepsy and psychosis is not well defined. Sensory gating is a possible endophenotype for psychosis, and has not been fully examined in epileptic patients. The authors examined 29 patients with focal epilepsy who were on antiepileptic medications, and 29 age-matched healthy comparison subjects, using a paired-stimulus (S1-S2) paradigm. P50 and N100 amplitudes or gating did not differ between the groups. The P200 was significantly smaller and did not gate as well in epileptic patients. Though alteration of sensory gating can be demonstrated in epileptic patients, it seems to be qualitatively different from alterations reported in association with schizophrenia.