Changes In Event Frequency Research Articles

Excitatory synaptic transmission in hippocampal area CA1 is enhanced then reduced as chronic epilepsy progresses

This study examines changes in synaptic transmission with progression of the chronic epileptic state. Male Sprague-Dawley rats (P40–45) were injected with either saline or pilocarpine. In rats injected with pilocarpine, status epilepticus ensued. Hippocampal slices were cut 20–60 days or 80–110 days post-treatment. Evoked and miniature EPSCs (mEPSCs) were recorded from CA1 pyramidal neurons using whole-cell voltage-clamp. Fiber volleys were also recorded from stratum radiatum. Evoked EPSCs from the pilocarpine-treated cohort showed enhanced amplitudes 20–60 days post-treatment compared to the saline-treated cohort, whereas mEPSCs recorded from the same age group showed no change in event frequency and a slight but significant decrease in mEPSC amplitude distribution. In contrast, comparing evoked EPSCs and mEPSCs recorded 80–110 days after treatment indicated reduced amplitudes from pilocarpine-treated animals compared to controls. mEPSC inter-event interval decreased. This could be explained by a partial depletion of the ready releasable pool of neurotransmitter vesicles in Schaffer collateral presynaptic terminals of the pilocarpine-treated rats. In both saline- and pilocarpine-treated cohorts, concomitant decreases in mEPSC amplitudes as time after treatment progressed suggest that age-related changes in CA1 circuitry may be partially responsible for changes in synaptic transmission that may influence the chronic epileptic state.

Short-term outcomes in pediatric and adolescent patients with psychogenic nonepileptic events seen by telemedicine during the COVID-19 pandemic

IntroductionPsychogenic nonepileptic events (PNEE) are a type of Functional Neurological Symptom Disorder that present with events that appear epileptic but are not associated with abnormal electrical activity in the brain. In response to the global COVID-19 pandemic, our PNEE clinic switched to a telemedicine format, and we present here our experience with providing care to children and adolescents with PNEE in this format. MethodsThe multidisciplinary clinic shifted to a telemedicine platform in March 2020 with the same joint provider format. Follow-up phone calls are completed at one and three months following the visit. Data are presented with descriptive statistics. Referral volume and outcomes data are compared to historical patients, including rates of diagnosis acceptance, linkage to counseling, and change in event frequency. ResultsTwenty-three patients were scheduled to be seen via telemedicine or hybrid visits from March through June, twenty completed their visits. Sixteen (70%) were reached for follow-up at one month. Of those reached, twelve (75%) accepted the diagnosis, eight (50%) were linked with counseling, and fourteen (88%) with improvement in event frequency. Of the sixteen reached at three months, eleven (69%) had accepted the diagnosis, ten (63%) were linked with counseling, and all but two reported improvement in event frequency. In comparison, the previously published results showed 3-month rates of 75% of patients accepting the diagnosis, 76% linked with counseling, and 75% with improvement in event frequency. ConclusionsVideo telemedicine visits are a feasible and effective way to provide care for children and adolescents with PNEE. At 3 months, patients seen by telemedicine had similar acceptance rates, decreased connection to counseling, and increased rate of improvement in event frequency. This study suggests telemedicine may have some benefits over traditional clinic visits, such as improved show rates and access to clinic; so should be considered a reasonable alternative to in-person visits.

Disentangling the Effects of Precipitation Amount and Frequency on the Performance of 14 Grassland Species.

Climate change is causing shifts in the amount and frequency of precipitation in many regions, which is expected to have implications for plant performance. Most research has examined the impacts of the amount of precipitation on plants rather than the effects of both the amount and frequency of precipitation. To understand how climate-driven changes in precipitation can affect grassland plants, we asked: (i) How does the amount and frequency of precipitation affect plant performance? (ii) Do plant functional groups vary in their response to variable precipitation? To answer these questions we grew 14 monocot and eudicot grassland species and conducted a factorial manipulation of the amount (70 vs 90mm/month) and frequency (every 3, 15, or 30 days) of precipitation under rainout shelters. Our results show that both the amount and frequency of precipitation impact plant performance, with larger effects on eudicots than monocots. Above- and below-ground biomass were affected by the amount of precipitation and/or the interaction between the amount and frequency of precipitation. Above-ground biomass increased by 21–30% when the amount of precipitation was increased. When event frequency was decreased from 3 to 15 or 30 days, below-ground biomass generally decreased by 18–34% in the 70 mm treatment, but increased by 33–40% in the 90 mm treatment. Changes in stomatal conductance were largely driven by changes in event frequency. Our results show that it is important to consider changes in both the amount and frequency of precipitation when predicting how plant communities will respond to variable precipitation.

Stakeholder Perspectives on the Attribution of Extreme Weather Events: An Explorative Enquiry

Abstract Recent extreme weather events and their impacts on societies have highlighted the need for timely adaptation to the changing odds of their occurrence. Such measures require appropriate information about likely changes in event frequency and magnitude on relevant spatiotemporal scales. However, to support robust climate information for decision-making, an effective communication between scientists and stakeholders is crucial. In this context, weather event attribution studies are increasingly raising attention beyond academic circles, although the understanding of how to take it beyond academia is still evolving. This paper presents the results of a study that involved in-depth interviews with stakeholders from a range of sectors about potential applications and the general usefulness of event attribution studies. A case study of the hot and dry summer 2012 in southeast Europe is used as a concrete example, with a focus on the applicability of attribution results across sectors. An analysis of the interviews reveals an abundant interest among the interviewed stakeholders and highlights the need for information on the causes and odds of extreme events, in particular on regional scales. From this data key aspects of stakeholder engagement are emerging, which could productively feed back into how probabilistic event attribution studies are designed and communicated to ensure practical relevance and usefulness for the stakeholder community.

Synaptic lability after experience-dependent plasticity is not mediated by calcium-permeable AMPARs

Activity- or experience-dependent plasticity has been associated with the trafficking of calcium-permeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (CP-AMPARs) in a number of experimental systems. In some cases it has been shown that CP-AMPARs are only transiently present and can be removed in an activity-dependent manner. Here we test the hypothesis that the presence of CP-AMPARs confers instability onto recently potentiated synapses. Previously we have shown that altered sensory input (single-whisker experience; SWE) strengthens layer 4-2/3 excitatory synapses in mouse primary somatosensory cortex, in part by the trafficking of CP-AMPARs. Both in vivo and in vitro, this potentiation is labile, and can be depressed by N-Methyl-D-aspartate receptor (NMDAR)-activation. In the present study, the role of CP-AMPARs in conferring this synaptic instability after in vivo potentiation was evaluated. We develop an assay to depress the strength of individual layer 4-2/3 excitatory synapses after SWE, using a strontium (Sr++)-replaced artificial cerebrospinal fluid (ACSF) solution (Sr-depression). This method allows disambiguation of changes in quantal amplitude (a post-synaptic measure) from changes in event frequency (typically a presynaptic phenomenon). Presynaptic stimulation paired with post-synaptic depolarization in Sr++ lead to a rapid and significant reduction in EPSC amplitude with no change in event frequency. Sr-depression at recently potentiated synapses required NMDARs, but could still occur when CP-AMPARs were not present. As a further dissociation between the presence of CP-AMPARs and Sr-depression, CP-AMPARs could be detected in some cells from control, whisker-intact animals, although Sr-depression was never observed. Taken together, our findings suggest that CP-AMPARs are neither sufficient nor necessary for synaptic depression after in vivo plasticity in somatosensory cortex. This article is part of a Special Issue entitled “Calcium permeable AMPARs in synaptic plasticity and disease.”

Diagnosing the Sensitivity of Binary Image Measures to Bias, Location, and Event Frequency within a Forecast Verification Framework

Abstract While the use of binary distance measures has a substantial history in the field of image processing, these techniques have only recently been applied in the area of forecast verification. Designed to quantify the distance between two images, these measures can easily be extended for use with paired forecast and observation fields. The behavior of traditional forecast verification metrics based on the dichotomous contingency table continues to be an area of active study, but the sensitivity of image metrics has not yet been analyzed within the framework of forecast verification. Four binary distance measures are presented and the response of each to changes in event frequency, bias, and displacement error is documented. The Hausdorff distance and its derivatives, the modified and partial Hausdorff distances, are shown only to be sensitive to changes in base rate, bias, and displacement between the forecast and observation. In addition to its sensitivity to these three parameters, the Baddeley image metric is also sensitive to additional aspects of the forecast situation. It is shown that the Baddeley metric is dependent not only on the spatial relationship between a forecast and observation but also the location of the events within the domain. This behavior may have considerable impact on the results obtained when using this measure for forecast verification. For ease of comparison, a hypothetical forecast event is presented to quantitatively analyze the various sensitivities of these distance measures.

Reply to comment by Jack Lewis et al. on “Forests and floods: A new paradigm sheds light on age‐old controversies”

Reply to comment by Jack Lewis et al. on “Forests and floods: A new paradigm sheds light on age‐old controversies”

The Changes in Ca2+ Sparks Associated with Measured Modifications of Intra-store Ca2+ Concentration in Skeletal Muscle

In cardiac muscle and amphibian skeletal muscle, the intracellular Ca2+ release that signals contractile activation proceeds by discrete local packets, which result in Ca2+ sparks. The remarkably stereotyped duration of these release events requires a robustly timed termination mechanism. In cardiac muscle the mechanism of spark termination appears to crucially involve depletion of Ca2+ in the lumen of the sarcoplasmic reticulum (SR), but in skeletal muscle, the mechanism is unknown. We used SEER (shifted excitation and emission ratioing of fluorescence) of SR-trapped mag-indo-1 and confocal imaging of fluorescence of cytosolic rhod-2 to image Ca2+ sparks while reversibly changing and measuring [Ca2+] in the SR ([Ca2+]SR) of membrane-permeabilized frog skeletal muscle cells. Sparks were collected in cells immersed in a solution promoting production of events at moderate frequency. Just after permeabilization, event frequency was zero, and in 10 minutes it reached close to a steady value. Controlled interventions modified [Ca2+]SR reversibly between a low value (299 μM on average in 10 experiments) and a high value (433 μM, a 45% average increase). This change increased sparks frequency by 93%, spatial width by 7%, rise time by 10%, and peak amplitude by 38% (provided that it was calculated in absolute terms, rather than normalized by resting fluorescence). The changes in event frequency and amplitude were statistically significant. The “strength” of the effect of [Ca2+]SR on frequency, quantified by decomposition of variance, was <6%. While the average change in [Ca2+]SR was limited, it reached up to 200% in individual fibers, without causing massive Ca2+ release or an increase of >3.5-fold in event frequency. Taken together with existing evidence that depletion is modest during Ca2+ sparks or release elicited by an action potential, the mild effects of [Ca2+]SR reported here do not support a major role of depletion in either the termination of sparks or the strong inactivation that terminates Ca2+ release at the global level in frog skeletal muscle.

Cancer Metastasis–Suppressing Peptide Metastin Upregulates Excitatory Synaptic Transmission in Hippocampal Dentate Granule Cells

Metastin is an antimetastatic peptide encoded by the KiSS-1 gene in cancer cells. Recent studies found that metastin is a ligand for the orphan G-protein-coupled receptor GPR54, which is highly expressed in specific brain regions such as the hypothalamus and parts of the hippocampus. This study shows that activation of GPR54 by submicromolar concentrations of metastin reversibly enhances excitatory synaptic transmission in hippocampal dentate granule cells in a mitogen-activated protein (MAP) kinase-dependent manner. Synaptic enhancement by metastin was suppressed by intracellular application of the G-protein inhibitor GDP-beta-S and the calcium chelator BAPTA. Analysis of miniature excitatory postsynaptic currents (mEPSCs) revealed an increase in the mean amplitude but no change in event frequency. This indicates that GPR54 and the mechanism responsible for the increase in EPSCs are postsynaptic. Metastin-induced synaptic potentiation was abolished by 50 microM PD98059 and 20 microM U0126, two inhibitors of the MAP kinases ERK1 and ERK2. The effect was also blocked by inhibitors of calcium/calmodulin-dependent kinases and tyrosine kinases. RT-PCR experiments showed that both KiSS-1 and GPR54 are expressed in the hippocampal dentate gyrus. Metastin is thus a novel endogenous factor that modulates synaptic excitability in the dentate gyrus through mechanisms involving MAP kinases, which in turn may be controlled upstream by calcium-activated kinases and tyrosine kinases.

Psychogenic nonepileptic seizures: acute change in event frequency after presentation of the diagnosis

Seizure frequency during inpatient video EEG monitoring was examined before and after the diagnosis of psychogenic nonepileptic seizures (PNES) was presented to patients ( N=22). A control group of 10 patients with epileptic seizures (ES) were also followed from pre- to postdiagnosis. The number of PNES or ES within the 24-hour period prior to diagnosis was compared with the number of events that occurred within the 24-hour period after presentation of the diagnosis. Findings indicate that patients with PNES had a significant decrease in the frequency of events after diagnosis, while those with ES showed no change in event frequency after diagnosis. Eighteen of twenty-two patients with PNES had no further events during an acute follow-up period. Results suggest that providing patients with a diagnosis of PNES appears to reduce the acute frequency of PNES and may be an important first step in the long-term remediation of PNES. Long-term follow-up is needed to determine if such feedback alters the course of the disorder.

Identifying the time scale of temporal association

Previously used methods of investigating the temporal association of behavioural events have tested sequences of events for temporal clumping; such an approach does not quantitatively indicate the time scale over which the association is significant. We present a novel method of analysis that specifically identifies this time scale, thereby allowing more ready elimination of competing causal hypotheses for the association observed. Our null hypothesis is that, following any event, the number of events in a given time interval is independent of the time elapsed since the initial event. The method is simple and robust against long-term changes in event frequency, and provides a more detailed quantitative description of the temporal association. We illustrate it using data on spawning in the blueheaded wrasse (Thalassoma bifasciatum). The analysis demonstrates that, after a spawning event, there is a 70% increase in mean spawning frequency which lasts for 30 s and then abruptly disappears. The effect of spawns appears to summate multiplicatively.

Prior probability information and changes in event frequency in three-choice learning.

In probabilistic situations known to be static, short-term alterations in event frequencies should have progressively less effect upon subjective probability as the number of trials increases. Assuming that expectation for a static environment would increase with increasing amount of prior information about the event probabilities, the amount of prior information and the location of alterations in event frequency were varied in a three-choice probability learning task. Both variables had large effects upon the observed choice patterns and, in general, the greater the amount of prior information, the less sensitive was choice behavior to changes in event frequency during later trials.