24 research outputs found
Constitutive spectral EEG peaks in the gamma range: suppressed by sleep, reduced by mental activity and resistant to sensory stimulation
This Document is Protected by copyright and was first published by Frontiers. All rights reserved. it is reproduced with permission.
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.Objective: In a systematic study of gamma activity in neuro-psychiatric disease, we unexpectedly observed distinctive, apparently persistent, electroencephalogram (EEG) spectral peaks in the gamma range (25–100 Hz). Our objective, therefore, was to examine the incidence, distribution and some of the characteristics of these peaks.
Methods: High sample-rate, 128-channel, EEG was recorded in 603 volunteers (510 with neuropsychiatric disorders, 93 controls), whilst performing cognitive tasks, and converted to power spectra. Peaks of spectral power, including in the gamma range, were determined algorithmically for all electrodes. To determine if peaks were stable, 24-h ambulatory recordings were obtained from 16 subjects with peaks. In 10 subjects, steady-state responses to stimuli at peak frequency were compared with off-peak-frequency stimulation to determine if peaks were a feature of underlying network resonances and peaks were evaluated with easy and hard versions of oddball tasks to determine if peaks might be influenced by mental effort.
Results: 57% of 603 subjects exhibited peaks >2 dB above trough power at or above 25 Hz. Larger peaks (>5 dB) were present in 13% of subjects. Peaks were distributed widely over the scalp, more frequent centrally. Peaks were present through the day and were suppressed by slow-wave-sleep. Steady-state responses were the same with on- or off-peak sensory stimulation. In contrast, mental effort resulted in reductions in power and frequency of gamma peaks, although the suppression did not correlate with level of effort.
Conclusions: Gamma EEG can be expressed constitutively as concentrations of power in narrow or wide frequency bands that play an, as yet, unknown role in cognitive activity.
Significance: These findings expand the described range of rhythmic EEG phenomena. In particular, in addition to evoked, induced and sustained gamma band activity, gamma activity can be present constitutively in spectral peaks
Surface Laplacian of Central Scalp Electrical Signals is Insensitive to Muscle Contamination
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any copyrighted components of this work in other works."Abstract—Objective: To investigate the effects of surface
Laplacian processing on gross and persistent electromyographic
(EMG) contamination of electroencephalographic (EEG) signals
in electrical scalp recordings.
Methods: We made scalp recordings during passive and active
tasks, on awake subjects in the absence and in the presence of
complete neuromuscular blockade. Three scalp surface
Laplacian estimators were compared to left ear and common
average reference (CAR). Contamination was quantified by
comparing power after paralysis (brain signal, B) with power
before paralysis (brain plus muscle signal, B+M). Brain:Muscle
(B:M) ratios for the methods were calculated using B and
differences in power after paralysis to represent muscle (M).
Results: There were very small power differences after
paralysis up to 600 Hz using surface Laplacian transforms (B:M>
6 above 30 Hz in central scalp leads).
Conclusions: Scalp surface Laplacian transforms reduce
muscle power in central and peri-central leads to less than one
sixth of the brain signal, 2-3 times better signal detection than
CAR.
Significance: Scalp surface Laplacian transformations provide
robust estimates for detecting high frequency (gamma) activity,
for assessing electrophysiological correlates of disease, and also
for providing a measure of brain electrical activity for use as a
‘standard’ in the development of brain/muscle signal separation
methods
Exercise training improves long-term memory in obese mice
Obesity has been linked to a range of pathologies, including dementia. In contrast, regular physical activity is associated with the prevention or reduced progression of neurodegeneration. Specifically, physical activity can improve memory and spatial cognition, reduce age-related cognitive decline, and preserve brain volume, but the mechanisms are not fully understood. Accordingly, we investigated whether any detrimental effects of high-fat diet (HFD)-induced obesity on cognition, motor behavior, adult hippocampal neurogenesis, and brain-derived neurotrophic factor (BDNF) could be mitigated by voluntary exercise training in male C57Bl/6 mice. HFD-induced impairment of motor function was not reversed by exercise. Importantly, voluntary wheel running improved long-term memory and increased hippocampal neurogenesis, suggesting that regular physical activity may prevent cognitive decline in obesity
Visual Experiences during Paralysis
Rationale: Paralyzed human volunteers (n = 6) participated in several studies the primary one of which required full neuromuscular paralysis while awake. After the primary experiment, while still paralyzed and awake, subjects undertook studies of humor and of attempted eye-movement. The attempted eye-movements tested a central, intentional component to one’s internal visual model and are the subject of this report. Methods: Subjects reclined in a supportive chair and were ventilated after paralysis (cisatracurium, 20 mg intravenously). In illumination, subjects were requested to focus alternately on the faces of investigators standing on the left and the right within peripheral vision. In darkness, subjects were instructed to look away from a point source of light. Subjects were to report their experiences after reversal of paralysis. Results: During attempted eye-movement in illumination, one subject had an illusion of environmental movement but four subjects perceived faces as clearly as if they were in central vision. In darkness, four subjects reported movement of the target light in the direction of attempted eye-movements and three could control the movement of the light at will. Conclusion: The hypothesis that internal visual models receive intended ocular-movement-information directly from oculomotor centers is strengthened by this evidence
Visual Experiences during Paralysis
Rationale: Paralyzed human volunteers (n = 6) participated in several studies the primary one of which required full neuromuscular paralysis while awake. After the primary experiment, while still paralyzed and awake, subjects undertook studies of humor and of attempted eye-movement. The attempted eye-movements tested a central, intentional component to one’s internal visual model and are the subject of this report. Methods: Subjects reclined in a supportive chair and were ventilated after paralysis (cisatracurium, 20 mg intravenously). In illumination, subjects were requested to focus alternately on the faces of investigators standing on the left and the right within peripheral vision. In darkness, subjects were instructed to look away from a point source of light. Subjects were to report their experiences after reversal of paralysis. Results: During attempted eye-movement in illumination, one subject had an illusion of environmental movement but four subjects perceived faces as clearly as if they were in central vision. In darkness, four subjects reported movement of the target light in the direction of attempted eye-movements and three could control the movement of the light at will. Conclusion: The hypothesis that internal visual models receive intended ocular-movement-information directly from oculomotor centers is strengthened by this evidence
Assessing Africa-Wide Pangolin Exploitation by Scaling Local Data
Overexploitation is one of the main pressures driving wildlife closer to extinction, yet broad-scale data to evaluate species' declines are limited. Using African pangolins (Family: Pholidota) as a case study, we demonstrate that collating local-scale data can provide crucial information on regional trends in exploitation of threatened species to inform conservation actions and policy. We estimate that 0.4-2.7 million pangolins are hunted annually in Central African forests. The number of pangolins hunted has increased by ∼150% and the proportion of pangolins of all vertebrates hunted increased from 0.04% to 1.83% over the past four decades. However, there were no trends in pangolins observed at markets, suggesting use of alternative supply chains. The price of giant (Smutsia gigantea) and arboreal (Phataginus sp.) pangolins in urban markets has increased 5.8 and 2.3 times respectively, mirroring trends in Asian pangolins. Efforts and resources are needed to increase law enforcement and population monitoring, and investigate linkages between subsistence hunting and illegal wildlife trade
EpiNet as a way of involving more physicians and patients in epilepsy research: validation study and accreditation process
Objective
EpiNet was established to encourage epilepsy research. EpiNet is used for multicenter cohort studies and investigator‐led trials. Physicians must be accredited to recruit patients into trials. Here, we describe the accreditation process for the EpiNet‐First trials.
Methods
Physicians with an interest in epilepsy were invited to assess 30 case scenarios to determine the following: whether patients have epilepsy; the nature of the seizures (generalized, focal); and the etiology. Information was presented in two steps for 23 cases. The EpiNet steering committee determined that 21 cases had epilepsy. The steering committee determined by consensus which responses were acceptable for each case. We chose a subset of 18 cases to accredit investigators for the EpiNet‐First trials. We initially focused on 12 cases; to be accredited, investigators could not diagnose epilepsy in any case that the steering committee determined did not have epilepsy. If investigators were not accredited after assessing 12 cases, 6 further cases were considered. When assessing the 18 cases, investigators could be accredited if they diagnosed one of six nonepilepsy patients as having possible epilepsy but could make no other false‐positive errors and could make only one error regarding seizure classification.
Results
Between December 2013 and December 2014, 189 physicians assessed the 30 cases. Agreement with the steering committee regarding the diagnosis at step 1 ranged from 47% to 100%, and improved when information regarding tests was provided at step 2. One hundred five of the 189 physicians (55%) were accredited for the EpiNet‐First trials. The kappa value for diagnosis of epilepsy across all 30 cases for accredited physicians was 0.70.
Significance
We have established criteria for accrediting physicians using EpiNet. New investigators can be accredited by assessing 18 case scenarios. We encourage physicians with an interest in epilepsy to become EpiNet‐accredited and to participate in these investigator‐led clinical trials
Clinical outcomes and response to treatment of patients receiving topical treatments for pyoderma gangrenosum: a prospective cohort study
Background: pyoderma gangrenosum (PG) is an uncommon dermatosis with a limited evidence base for treatment.
Objective: to estimate the effectiveness of topical therapies in the treatment of PG.
Methods: prospective cohort study of UK secondary care patients with a clinical diagnosis of PG suitable for topical treatment (recruited July 2009 to June 2012). Participants received topical therapy following normal clinical practice (mainly Class I-III topical corticosteroids, tacrolimus 0.03% or 0.1%). Primary outcome: speed of healing at 6 weeks. Secondary outcomes: proportion healed by 6 months; time to healing; global assessment; inflammation; pain; quality-of-life; treatment failure and recurrence.
Results: Sixty-six patients (22 to 85 years) were enrolled. Clobetasol propionate 0.05% was the most commonly prescribed therapy. Overall, 28/66 (43.8%) of ulcers healed by 6 months. Median time-to-healing was 145 days (95% CI: 96 days, ∞). Initial ulcer size was a significant predictor of time-to-healing (hazard ratio 0.94 (0.88;80 1.00); p = 0.043). Four patients (15%) had a recurrence.
Limitations: No randomised comparator
Conclusion: Topical therapy is potentially an effective first-line treatment for PG that avoids possible side effects associated with systemic therapy. It remains unclear whether more severe disease will respond adequately to topical therapy alone
Receptor-mediated phosphoinositide metabolism in the rat cerebellar granule cell.
Cerebellar granule cells in culture have recently become a widely used neuronal preparation, because of their receptor integrity and ability to release the neurotransmitter, glutamate. The basis of this thesis was the detailed investigation of receptor-mediated phosphoinositide signalling and its role in intracellular Ca2+ in this cell type. The muscarinic activated accumulation of 3H-InsPx in this cell is the most potent reported, stimulating some 20 fold over basal and was selected as the agonist of choice for further study. Pharmacological determination of antagonist inhibition of 3H-NMS binding and 3H-InsPx production, identified the muscarinic receptor coupled to PI hydrolysis as of the M3 receptor subtype. Carbachol induced 3H-InsPx was demonstrated, at least in part, to originate from the hydrolysis of PtdInsP2, due to the capacity of the cell to produce Ins(1,4,5)P3, the intracellular Ca2+-mobilising second-messenger. The calcium mobilising properties now well established for Ins(1,4,5)P3, were confirmed in the cerebellar granule cell. 45Ca2+ release by Ins(1,4,5)P3 was stereospecific, heparin sensitive. Displacement of 32P-Ins(1,4,5)P3 confirmed the presence of Ins(1,4,5)P3 sites, that had previously gone undetected in this cell type. Fluorescent Ca2+ indicators, like fura-2, have recently been developed and enable the detailed analysis of intracellular [Ca2+] changes to be performed in intact cells, both in population and at the single cell level. Single cell studies in fura-2 loaded cerebellar granule cells, showed considerable heterogeneity in their responsiveness to carbachol. Very few cells demonstrated a classical receptor mediated Ins(1,4,5)P3-type increase in [Ca2+]i, the majority being dependent on extracellular Ca2+. Most cells exhibited a muscarinic-mediated Ca2+ entry phenomenon, that was only visible in the absence of extracellular Mg2+, suggesting some added complexity that needs further investigation. The possibility of a role of Ins(1,4,5)P3 in neurotransmitter release in this cell type is considered