N1 Peak Research Articles

Cortical auditory potentials and cognitive potentials in individuals with and without vestibular dysfunction.

Background: Among individuals withvestibular dysfunction, the loss of vestibular sensory information is found to alter cognitive abilities that coordinate spatial and non-spatial information. P300 is an event-related potential commonly used to assess cognitive processing. The aim of the present study was to compare the latency and amplitude of cortical auditory evoked potential and P300 between individuals with vestibular dysfunction and individuals with no vestibular dysfunction. Methods: Forty adults with a mean age of 40.5 ± 13.07 participated in the study. Group I included 20 adults diagnosed with vestibular dysfunction and group II included 20 age-matched adults with no vestibular dysfunction. The P300 was recorded from the electrode site Cz and Pz. It was elicited using pure-tones in odd-ball paradigm. The latency and amplitude of peaks P1, N1, P2, and N2 of the cortical auditory evoked potential and the P300 were measured. Results: Significant amplitude difference was observed in cortical potentials at Cz and Pz. The P300 was present only in 70% of individuals with vestibular dysfunction compared to 100% among individuals with no vestibular dysfunction. The mean amplitude of the P300 was slightly larger in group 1 compared to group 2 and the mean latency of the P300 was similar in both groups. However, the difference in amplitude of the P300 between groups was not statistically significant. Conclusions: Knowing the cognitive function of individuals with vestibular dysfunction enables planning vestibular rehabilitation therapy, which enhances the quality of life in these individuals by improving their vestibular and cognitive functions.

Mingmu Xiaoyao granules regulate the PI3K/Akt/mTOR signaling pathway to reduce anxiety and depression and reverse retinal abnormalities in rats.

Objective: To investigate the effects of Mingmu Xiaoyao granules (MMXY) on the morphology and function of the retina and the mechanism of PI3K/Akt/mTOR pathway-related proteins in rats with anxiety and depression induced by chronic unpredictable mild stress (CUMS). Methods: Fifty-two male Sprague Dawley rats were randomly allocated to either a control (n = 14) or a simulated CUMS group (n = 38). The CUMS model was established successfully at 4 weeks. Six rats in each group were randomly selected to be sacrificed and their retinas isolated for histological examination. At 5 weeks, rats in the CUMS group were randomly allocated to the following groups: Model (CUMS + pure water), MMXY-H (CUMS + MMXY 7.2 g/kg/d), MMXY-L (CUMS + MMXY 3.6 g/kg/d), and CBZ (CUMS + Carbamazepine 20 mg/kg/d), with eight rats in each group. All rats were given the relevant intervention once a day. At 12 weeks, sucrose preference and open field tests were performed to evaluate the anxiety and depression status of rats. In live rats, optical coherence tomography angiography was used to measure retinal thickness and blood flow, while electroretinograms (ERGs) and visual evoked potentials (VEPs) were used to evaluate retinal function. The next day, the specimens were sacrificed for serological, histological, immunofluorescence, Western blot and transmission electron microscopy examinations to explore the mechanism of MMXY in CUMS rats. Results: MMXY improved the anxiety and depression-like behavior of rats. Results of optical coherence tomography angiography showed that MMXY improved retinal inner thickness and blood flow in CUMS rats. MMXY improved the amplitude of a- and b-waves in the scotopic and photopic ERG, as well as N2 and P2 peak time and amplitude in the flash-VEP in CUMS rats. Retinal histological staining and transmission electron microscopy showed that MMXY reversed retinal morphology and ultrastructure in CUMS rats. MMXY reduced the expression of Beclin1 and LC3I/II proteins, regulated the PI3K/Akt/mTOR pathway, inhibited autophagy, and had a protective effect on the retina in CUMS rats. Conclusion: MMXY may effectively improve retinal morphology and function as well as anxiety and depression-like behaviors in CUMS rats by regulating the PI3K/Akt/mTOR signaling pathway.

High-frequency oscillations-based precise temporal resolution of short latency afferent inhibition in the human brain

ObjectiveSensorimotor integration is a crucial process for adaptive behaviour and can be explored non-invasively with a conditioned transcranial magnetic stimulation (TMS) paradigm - i.e. short-latency afferent inhibition (SAI). To gain insight into the sensorimotor integration phenomenon, we used two different approaches to combine peripheral and cortical stimulation in the SAI paradigm, measuring not only the latency of low frequency somatosensory evoked potentials (SEPs) but also the peaks of high frequency oscillations (HFOs) underlying SEPs. MethodsThe interstimulus intervals (ISIs) between the electrical stimulation of the median nerve and the motor cortex magnetic stimulation were determined relative to the latency of the earliest SEPs cortical potential (N20) or the HFOs peaks. In particular, the first and last negative and positive peaks of HFOs were extracted through a custom-made MATLAB script. ResultsThirty-three healthy subjects participated in this study. We found out that muscle responses after TMS were suppressed when ISIs were comprised between –1 to +3 ms relative to the N20 peak and at all ISIs relative to HFOs peaks, except for the first negative peak. ConclusionsCoupling peripheral and cortical stimulation at early interstimulus intervals – before the SEPs N20 peak - may modulate muscle response. SignificanceOur findings confirm that afferent inhibition is produced both through a direct (thalamus-motor cortex) and indirect (thalamus-somatosensory-motor cortex) pathway.

Cortical auditory potentials and cognitive potentials in individuals with and without vestibular dysfunction

Background: Among individuals with vestibular dysfunction, the loss of vestibular sensory information is found to alter cognitive abilities that coordinate spatial and non-spatial information. P300 is an event-related potential commonly used to assess cognitive processing. The aim of the present study was to compare the latency and amplitude of cortical auditory evoked potential and P300 between individuals with vestibular dysfunction and individuals with no vestibular dysfunction. Methods: Forty adults with a mean age of 40.5 ± 13.07 participated in the study. Group I included 20 adults diagnosed with vestibular dysfunction and group II included 20 age-matched adults with no vestibular dysfunction. The P300 was recorded from the electrode site Cz and Pz. It was elicited using pure-tones in odd-ball paradigm. The latency and amplitude of peaks P1, N1, P2, and N2 of the cortical auditory evoked potential and the P300 were measured. Results: Significant amplitude difference was observed in cortical potentials at Cz and Pz. The P300 was present only in 70% of individuals with vestibular dysfunction compared to 100% among individuals with no vestibular dysfunction. The mean amplitude of the P300 was slightly larger in group 1 compared to group 2 and the mean latency of the P300 was similar in both groups. However, the difference in amplitude of the P300 between groups was not statistically significant. Conclusions: Knowing the cognitive function of individuals with vestibular dysfunction enables planning vestibular rehabilitation therapy, which enhances the quality of life in these individuals by improving their vestibular and cognitive functions.

Changes in somatosensory evoked potentials in rats following transient cerebral ischemia

Background. Cerebral ischemia induced by transient middle cerebral artery occlusion is one of the most popular ischemic stroke models used to evaluate drug candidates with neuroprotective properties. The possibilities of combining this model with neurophysiological techniques (e.g., electroencephalography, electrocorticography, evoked potential registration, etc.) to assess the effectiveness of novel pharmacotherapeutic strategies appear to be of great interest to current biomedical research.The aim. Identifying specific changes in somatosensory evoked potentials occurring after cerebral ischemia induced by middle cerebral artery occlusion in rats.Materials and methods. A total number of 18 white outbred male rats were randomized into 3 groups by 6 animals in each: 1) control (presumably healthy animals); 2) ischemia-30 (30-minute middle cerebral artery occlusion); 3) ischemia-45 (45-minute occlusion). At post-surgery day 7, cortical responses to sequential electrical stimulation of left and right n. ischiadicus were registered. N1, P2, N2, P3, and N3 peak latencies and amplitudes, peak-to-peak interval durations and amplitudes were calculated. Spearman’s rank correlation coefficients were used to assess the relationship between ischemia duration and evoked potential parameters, and the Chaddock scale was used to qualitatively evaluate the strength of correlations.Results. The rats subjected to cerebral ischemia demonstrated a decrease in some of the peak amplitudes of the ipsi- and contralateral somatosensory potentials evoked by n. ischiadicus stimulation. In the injured hemisphere, decreased P2 and N3 peak and P3–N3 interval amplitudes were registered ipsilaterally, and decreased P3 peak amplitudes and N2–P3 interval durations were observed contralaterally.Conclusions. The obtained data suggest that somatosensory evoked potential registration and analysis can be used to evaluate the functional state of central nerve tracts in rats subjected to cerebral ischemia.

Cortical Auditory Evoked Potentials in Children with Prenatal Exposure to Zika Virus.

Prenatal exposure to ZIKV can cause neurologic and auditory damage. The electrophysiological responses obtained by Cortical Auditory Evoked Potentials (CAEP) may provide an objective method to investigate the function of cortical auditory pathways in children exposed to ZIKV. This case series analyzed the findings of CAEP in prenatal-period ZIKV-exposed children with and without microcephaly. The CAEP was performed in a total of 24 children. Five magnetic resonance imaging (MRI) images of the inner ear and brain of microcephalic children were analyzed and compared with CAEP measurements. Ventriculomegaly (80%), cortical/subcortical calcification (80%), and brain reduction (60%) were the most common alterations in the MRI. The P1-N1-P2 complex of the CAEP was observed in all children evaluated. The peak N2 was absent in two children. In the comparison of the CAEP measurements between the groups, children with microcephaly presented a higher amplitude of P2 (p = 0.017), which may reflect immaturity of the auditory pathways. Microcephalic and normocephalic children with prenatal exposure to ZIKV presented with the mandatory components of the CAEPs, regardless of changes in the CNS, suggesting that this population has, to some extent, the cortical ability to process sound stimuli preserved.

Plasticity of visual evoked potentials in patients with neurofibromatosis type 1

ObjectiveThe inability to properly process visual information has been frequently associated with neurofibromatosis type 1 (NF1). Based on animal studies, the cause of cognitive disabilities in NF1 is hypothesized to arise from decreased synaptic plasticity. Visual cortical plasticity in humans can be investigated by studying visual evoked potentials (VEPs) in response to visual stimulation. MethodsVEP plasticity was assessed by measuring the increase of the peak amplitudes C1, P1, and N1 induced by 10-min modulation of checkerboard reversals in 22 adult NF1 patients and 30 controls. VEP signals were recorded pre-modulation, during modulation, and at 2, 7, 12, 17, 22, 27 min post-modulation. ResultsThe P1 amplitude increased significantly comparing post-modulation to pre-modulation in the control group. This potentiation was not observed in the NF1 group. ConclusionsVisual cortical plasticity could be measured using VEPs in response to visual stimulation in the control group. Individuals with NF1 may have reduced visual cortical plasticity, as indicated by their non-potentiated response to VEP induction. These findings should be interpreted with caution due to high inter-subject variability. SignificanceThe present study contributes to an improved assessment of the feasibility for using neurophysiological outcome measures in intervention studies of cognitive deficits among patients with NF1.

Auditory N100 amplitude deficits predict conversion to psychosis in the North American Prodrome Longitudinal Study (NAPLS-2) cohort

BackgroundThe auditory N100 is an event related potential (ERP) that is reduced in schizophrenia, but its status in individuals at clinical high risk for psychosis (CHR) and its ability to predict conversion to psychosis remains unclear. We examined whether N100 amplitudes are reduced in CHR subjects relative to healthy controls (HC), and this reduction predicts conversion to psychosis in CHR. MethodsSubjects included CHR individuals (n = 552) and demographically similar HC subjects (n = 236) from the North American Prodrome Longitudinal Study. Follow-up assessments identified CHR individuals who converted to psychosis (CHRC; n = 73) and those who did not (CHR-NC; n = 225) over 24 months. Electroencephalography data were collected during an auditory oddball task containing Standard, Novel, and Target stimuli. N100 peak amplitudes following each stimulus were measured at electrodes Cz and Fz. ResultsThe CHR subjects had smaller N100 absolute amplitudes than HC subjects at Fz (F(1,786) = 4.00, p 0.046). A model comparing three groups (CHRC, CHR-NC, HC) was significant for Group at the Cz electrode (F(2,531) = 3.58, p = 0.029). Both Standard (p = 0.019) and Novel (p = 0.017) stimuli showed N100 absolute amplitude reductions in CHR-C relative to HC. A smaller N100 amplitude at Cz predicted conversion to psychosis in the CHR cohort (Standard: p = 0.009; Novel: p = 0.001) and predicted shorter time to conversion (Standard: p = 0.013; Novel: p = 0.001). ConclusionN100 amplitudes are reduced in CHR individuals which precedes the onset of psychosis. N100 deficits in CHR individuals predict a greater likelihood of conversion to psychosis. Our results highlight N100's utility as a biomarker of psychosis risk.

Aging and sleep deprivation affect different neurocognitive stages of spatial information processing during a virtual driving task – An ERP study

We have previously shown that aging deteriorates detection of spatial visual and auditory stimuli and prolongs reaction times measured during a virtual driving task. Sleep deprivation affected the young more than the old. Here we determined the effects of age and sleep deprivation on ERPs elicited by spatial visual and auditory stimuli during virtual driving. Participants were 22 young (18–35 years) and 19 old (65–79) healthy males. Experiments were run in normal daytime condition and after a night of sleep deprivation. Aging shortened the peak latencies of the early P1 and N1 but increased the P3 latency. Sleep deprivation slowed down and diminished the N1 peaks of the young. General right-side preference was seen in latencies. Thus, the effects of aging could be seen in decision making and working memory related processes (P3), whereas those of sleep deprivation could be found in alerting and orienting functions (N1) in the young.

Comparison of the effect of sedation and general anesthesia on pattern and flash visual evoked potentials in normal dogs

BackgroundVisual evoked potentials (VEPs) can provide objective functional assessment of the post-retinal visual pathway. This study compared the effects of sedation (butorphanol and dexmedetomidine) and general anesthesia (propofol and sevoflurane) on pattern and flash VEPs. Dogs (n = 13) underwent sedation or anesthesia and VEPs were obtained from 3 subcutaneous recording electrodes placed on the head (O1, Oz, O2).ResultsPattern VEPs could only be recorded under sedation and a maximum of 3 peaks were identified (N75, P100, N135). Flash VEPs could be recorded under both sedation and anesthesia and a maximum of 5 peaks were identified (N1, P1, N2, P2, N3). The latency of the N1 peak and the baseline-N1 amplitude were significantly longer under general anesthesia.ConclusionVisual evoked potentials should be preferentially recorded in dogs sedated with dexmedetomidine and butorphanol, regardless of the stimulus.

Pain-Related Vertex Evoked Potentials. Comparison of Surface Electrical to Heat Stimulation.

Demonstration of nociceptive fiber abnormality is important for diagnosing neuropathic pain and small fiber neuropathies. This is usually assessed by brief heat pulses using lasers, contact heat, or special electrodes. We hypothesized that pain-related evoked potentials to conventional surface electrical stimulation (PREPse) can index Aδ afferences despite tactile Aß fibers coactivation. PREPse may be more readily used clinically than contact heat evoked potentials (CHEPS). Twenty-eight healthy subjects. Vertex (Cz-A1/A2) recordings. Electrical stimulation of middle finger and second toe with conventional ring, and forearm/leg skin with cup, electrodes. Contact heat stimulation to forearm and leg. Compression ischemic nerve blockade. PREPse peripheral velocities were within the midrange of Aδ fibers. N1-P1 amplitude increased with pain numerical rating scale graded (0-10) electrical stimulation (n = 25) and decreased with increasing stimulation frequency. Amplitudes were unchanged by different presentation orders of four stimulation intensities. PREPse N1 (∼130 milliseconds) and N2 (∼345 milliseconds) peaks were approximately 40 milliseconds earlier than that with CHEPS. PREPse and CHEPS N1-N2 interpeak latency (∼207 milliseconds) were similar. PREPse became unrecordable with nerve blockade of Aδ fibers. PREPse earlier N1 and N2 peaks, and similar interpeak N1-N2 latencies and central conduction velocities, or synaptic delays, to CHEPS are consistent with direct stimulation of Aδ fibers. The relation of vertex PREPse amplitude and pain, or the differential effects of frequency stimulation, is similar to pain-related evoked potential to laser, special electrodes, or contact heat stimulation. The relationship to Aδ was validated by conduction velocity and nerve block. Clinical utility of PREPse compared with CHEPS needs validation in somatosensory pathways lesions.

Enhanced Dichotic Listening and Temporal Sequencing Ability in Early-Blind Individuals.

Several studies have reported the better auditory performance of early-blind subjects over sighted subjects. However, few studies have compared the auditory functions of both hemispheres or evaluated interhemispheric transfer and binaural integration in blind individuals. Therefore, we evaluated whether there are differences in dichotic listening, auditory temporal sequencing ability, or speech perception in noise (all of which have been used to diagnose central auditory processing disorder) between early-blind subjects and sighted subjects. The study included 23 early-blind subjects and 22 age-matched sighted subjects. In the dichotic listening test (three-digit pair), the early-blind subjects achieved higher scores than the sighted subjects in the left ear (p = 0.003, Bonferroni’s corrected α = 0.05/6 = 0.008), but not in the right ear, indicating a right ear advantage in sighted subjects (p < 0.001) but not in early-blind subjects. In the frequency patterning test (five tones), the early-blind subjects performed better (both ears in the humming response, but the left ear only in the labeling response) than the sighted subjects (p < 0.008, Bonferroni’s corrected α = 0.05/6 = 0.008). Monosyllable perception in noise tended to be better in early-blind subjects than in sighted subjects at a signal-to-noise ratio of –8 (p = 0.054), the results at signal-to-noise ratios of –4, 0, +4, and +8 did not differ. Acoustic change complex responses to/ba/in babble noise, recorded with electroencephalography, showed a greater N1 peak amplitude at only FC5 electrode under a signal-to-noise ratio of –8 and –4 dB in the early-blind subjects than in the sighted subjects (p = 0.004 and p = 0.003, respectively, Bonferroni’s corrected α = 0.05/5 = 0.01). The results of this study revealed early-blind subjects exhibited some advantages in dichotic listening, and temporal sequencing ability compared to those shown in sighted subjects. These advantages may be attributable to the enhanced activity of the central auditory nervous system, especially the right hemisphere function, and the transfer of auditory information between the two hemispheres.

EEG theta and N400 responses to congruent versus incongruent brand logos

Neuroimaging and behavioral studies have shown that brands convey meaning to consumers. To investigate the immediate reactions of the brain to brand logos, followed either by congruent or incongruent pictorial brand-related cues, can deepen understanding of the semantic processing of brands, and perhaps how consolidated the logo is in consumers’ minds. Participants were exposed to different brand-related image sets, that were either congruent (a match between brand-related images and brand logo) or incongruent (a mismatch between brand-related images and brand logo) while having their brain signals recorded. Event-related potential and EEG time–frequency domain features were extracted from the signals of the target image (brand logo). The results showed significantly larger N400 peak and relative theta power increase for incongruent compared to congruent logos, which could be attributed to an error-monitoring process. Thus, we argue that brands are encoded deeply in consumers’ minds, and cognitive processing of mismatched (vs matched) brand logos is more difficult, leading to greater error monitoring. The results were mostly consistent with previous studies investigating semantic incongruences in the linguistic field. Therefore, the error-monitoring process could be extended beyond linguistic forms, for example to images and brands.

Relationship between Behavioral and Objective Measures of Sound Intensity in Normal-Hearing Listeners and Hearing-Aid Users: A Pilot Study.

Background: For hearing-impaired individuals, hearing aids are clinically fit according to subjective measures of threshold and loudness. The goal of this study was to evaluate objective measures of loudness perception that might benefit hearing aid fitting. Method: Seventeen adult hearing aid users and 17 normal-hearing adults participated in the study. Outcome measures including categorical loudness scaling, cortical auditory evoked potentials (CAEPs), and pupillometry. Stimuli were 1-kHz tone bursts presented at 40, 60, and 80 dBA. Results: Categorical loudness scaling showed that loudness significantly increased with intensity for all participants (p < 0.05). For CAEPs, high intensity was associated with greater P1, N1, and P2 peak amplitude for all listeners (p < 0.05); a significant but small effect of hearing aid amplification was observed. For all participants, pupillometry showed significant effects of high intensity on pupil dilation (p < 0.05); there was no significant effect of hearing aid amplification. A Focused Principal Component analysis revealed significant correlations between subjective loudness and some of the objective measures. Conclusion: The present data suggest that intensity had a significant impact on loudness perception, CAEPs, and pupil response. The correlations suggest that pupillometry and/or CAEPs may be useful in determining comfortable amplification for hearing aids.

EEG Evoked Potentials to Repetitive Transcranial Magnetic Stimulation in Normal Volunteers: Inhibitory TMS EEG Evoked Potentials.

The impact of repetitive magnetic stimulation (rTMS) on cortex varies with stimulation parameters, so it would be useful to develop a biomarker to rapidly judge effects on cortical activity, including regions other than motor cortex. This study evaluated rTMS-evoked EEG potentials (TEP) after 1 Hz of motor cortex stimulation. New features are controls for baseline amplitude and comparison to control groups of sham stimulation. We delivered 200 test pulses at 0.20 Hz before and after 1500 treatment pulses at 1 Hz. Sequences comprised AAA = active stimulation with the same coil for test–treat–test phases (n = 22); PPP = realistic placebo coil stimulation for all three phases (n = 10); and APA = active coil stimulation for tests and placebo coil stimulation for treatment (n = 15). Signal processing displayed the evoked EEG waveforms, and peaks were measured by software. ANCOVA was used to measure differences in TEP peak amplitudes in post-rTMS trials while controlling for pre-rTMS TEP peak amplitude. Post hoc analysis showed reduced P60 amplitude in the active (AAA) rTMS group versus the placebo (APA) group. The N100 peak showed a treatment effect compared to the placebo groups, but no pairwise post hoc differences. N40 showed a trend toward increase. Changes were seen in widespread EEG leads, mostly ipsilaterally. TMS-evoked EEG potentials showed reduction of the P60 peak and increase of the N100 peak, both possibly reflecting increased slow inhibition after 1 Hz of rTMS. TMS-EEG may be a useful biomarker to assay brain excitability at a seizure focus and elsewhere, but individual responses are highly variable, and the difficulty of distinguishing merged peaks complicates interpretation.

OC18: Transspinal direct current stimulation for pain treatment. Objective proof of concept, initial clinical findings and BDNF polymorphism

Introduction Transspinal Direct Current Stimulation (tsDCS) has been reported to block pain signaling. To approach clinical usage, two studies were performed. In both, the effect of BDNF polymorphism (Val/Met) was investigated. Materials and methods Study I Nineteen healthy controls, the anode over the tenth thoracic vertebra, the cathode over the shoulder. tsDCS: 2.5 A for 20 minutes, double blinded cross over design. Laser Evoked Potentials (LEPs): Stimulation of the dorsum of the hand and foot respectively, recordings at baseline, immediately after- and 30 minutes after the tsDCS stimulation. Amplitude and latency of the N2 peak was assessed and the subjects rated pain intensity. BDNF polymorphism was investigated in DNA from buccal mucosa cells. Study II Patients with neuropathic pain due to polyneuropathy are recruited. tsDCS is given at three days with one day between, BDNF polymorphism investigated as above. Results Study I Group level: LEP amplitudes successively reduced over time. Placebo; latencies unaffected from upper-, slightly increased from lower extremities. Verum; transiently increased from upper-, accumulatively increased from lower extremities in proportion to experienced pain. Individual level: Large variations. BDNF polymorphism influences the effect of stimulation with less pain reduction in those with less active BDNF (Val/Val). Study II Fourteen patients have been investigated. The results will be presented at the conference. Conclusions Short term, anodal thoracic tsDCS affects transspinal pain signaling with large inter-individual differences. Individualized tsDCS may be a treatment option for neuropathic pain. The type of BDNF one carries, seem to influence the effect of stimulation.

Cortical Sources of Respiratory Mechanosensation, Laterality, and Emotion: An MEG Study.

Airway obstruction activates mechanoreceptors that project to the cerebral cortices in humans, as evidenced by scalp encephalography recordings of cortical neuronal activation, i.e., respiratory-related evoked potential (RREP). However, neural evidence of both high spatial and temporal resolution of occlusion-elicited cortical activation in healthy individuals is lacking. In the present study, we tested our hypothesis that inspiratory mechanical stimuli elicit neural activation in cortical structures that can be recorded using magnetoencephalography (MEG). We further examined the relationship between depression and respiratory symptoms and hemispheric dominance in terms of emotional states. A total of 14 healthy nonsmoking participants completed a respiratory symptom questionnaire and a depression symptom questionnaire, followed by MEG and RREP recordings of inspiratory occlusion. Transient inspiratory occlusion of 300 ms was provided randomly every 2 to 4 breaths, and approximately 80 occlusions were collected in every study participant. Participants were required to press a button for detection when they sensed occlusion. Respiratory-related evoked fields (RREFs) and RREP peaks were identified in terms of latencies and amplitudes in the right and left hemispheres. The Wilcoxon signed-rank test was further used to examine differences in peak amplitudes between the right and left hemispheres. Our results showed that inspiratory occlusion elicited RREF M1 peaks between 80 and 100 ms after triggering. Corresponding neuromagnetic responses peaked in the sensorimotor cortex, insular cortex, lateral frontal cortex, and middle frontal cortex. Overall, the RREF M1 peak amplitude in the right insula was significantly higher than that in the left insula (p = 0.038). The RREP data also showed a trend of higher N1 peak amplitudes in the right hemisphere compared to the left (p = 0.064, one-tailed). Subgroup analysis revealed that the laterality index of sensorimotor cortex activation was significantly different between higher- and lower-depressed individuals (−0.33 vs. −0.02, respectively; p = 0.028). For subjective ratings, a significant relationship was found between an individual’s depression level and their respiratory symptoms (Spearman’s rho = 0.54, p = 0.028, one-tailed). In summary, our results demonstrated that the inspiratory occlusion paradigm is feasible to elicit an RREF M1 peak with MEG. Our imaging results showed that cortical neurons were activated in the sensorimotor, frontal, middle temporal, and insular cortices for the M1 peak. Respiratory occlusion elicited higher cortical neuronal activation in the right insula compared to the left, with a higher tendency for right laterality in the sensorimotor cortex for higher-depressed rather than lower-depressed individuals. Higher levels of depression were associated with higher levels of respiratory symptoms. Future research with a larger sample size is recommended to investigate the role of emotion and laterality in cerebral neural processing of respiratory sensation.

Seasonal and Spatial Variability of Biological N2 Fixation in a Cool Temperate Bog

AbstractNorthern peatlands are globally important carbon (C) and nitrogen (N) sinks due to slow decomposition rates resulting in long‐term organic matter accumulation. Despite their large N storage, peatlands depend on sources of bio‐available N to sustain their biomass production. Di‐nitrogen (N2) fixation represents an important biological N source in ombrotrophic bogs, but its environmental controls are still poorly understood. We examined seasonal and spatial variability of Sphagnum‐associated N2 fixation across a hydrological transect (hummock‐hollow‐beaver pond edge) in a temperate ombrotrophic bog. We measured N2 fixation in live Sphagnum plants by acetylene reduction assay calibrated with a 15N2 tracer method, bi‐weekly, from May to November over two growing seasons. We found that N2 fixation increased with soil temperature at 5 cm in the living Sphagnum mat explaining the seasonal variability in N2 fixation. Peak N2 fixation rates occur in mid‐August, when N2 fixation rates are about 10 times larger than during the shoulder seasons (May and November). Spatially, N2 fixation was larger in wetter Sphagnum with larger gravimetric water content in Sphagnum. This relationship was most pronounced in the peak growing season when N2 fixation rates were the highest. Finally, we estimated that the Mer Bleue bog receives around 0.3 g N m−2 annually through Sphagnum‐associated N2 fixation, which accounts for about a fourth of the N accumulated annually into Sphagnum. Future contributions from Sphagnum‐associated N2 fixation to N budgets in peatlands will depend on temperature and moisture changes which have contrasting effects on N2 fixation rates.

Third order nonlinear optical behavior and optical limiting properties of Ni2+ ions doped zinc nano-aluminates

Nanosized Zn1-xNixAl2O4(0 ≤ x ≤ 0.5) particles were synthesized using microwave assisted combustion process with metal nitrates as starting precursors. The crystalline behavior of the synthesized samples is confirmed through the powder XRD and TEM studies. XPS studies are employed to obtain the oxidation state and the chemical elements details. HR-SEM analysis shows the morphology of agglomerated coalescence behavior. The elemental composition of Zn, Ni, O and Al was qualitatively obtained from EDX analysis. UV-DRS spectra are used to evaluate the optical band gap which is in the range of ̴ 5.45 to 3.32 eV. In FTIR spectra, two essential peaks n1 and n2 are endorsed the existence of spinel structured Zn1-xNixAl2O4 (0 ≤ x ≤ 0.5). The exothermic transitions and weight loss of elements is obtained by TG-DTA analysis. The magnetic parameters are confirmed the super paramagnetic behavior for all nickel doped zinc aluminate nanoparticles. The nonlinear optical properties are determined by Z-scan technique. It is found that the optical threshold values are in the range of 5.98, 5.25, 4.85 and 3.73 mW respectively. All the samples are exhibited the defocusing effect at CW laser.

A Single Administration of Riluzole Applied Acutely After Spinal Cord Injury Attenuates Pro-inflammatory Activity and Improves Long-Term Functional Recovery in Rats.

After spinal cord injury (SCI), emergency treatment intervention can minimize tissue damage, which is closely related to the recovery of long-term function. Here, we examined whether the administration of a single dose of riluzole (6mg/kg) immediately after SCI was a critical window for the drug to exert its regulatory effect and limit long-term neurological deficits. The animals were sacrificed 1day after administration for investigation of neuronal survival and a potential neuroinflammatory response, and sacrificed in the 6th week for assessment of neurological function. Riluzole applied in a single dose immediately post-SCI decreased the mRNA level of interleukin-1β at 6h, reduced the destruction of neurons, and reduced the activation of microglia/macrophage M1 expression at day 1 post-SCI. Additionally, riluzole-treated rats showed higher expressions of interleukin-33 and its receptor ST2 in microglia/macrophages of the spinal cord than vehicle-treated rats, suggesting that this signaling pathway might be involved in microglia/macrophage-mediated inflammation. At 6weeks, riluzole-treated rats exhibited higher motor function scores than vehicle-treated controls. In addition, riluzole-treated rats exhibited higher expression of GAP43 protein and shorter N1 peak latency and larger N1-P1 amplitude in motor-evoked potentials, compared to vehicle-treated rats. Together, these data suggested that early application of riluzole after SCI could be crucial for long-term functional recovery, so it may represent a promising therapeutic candidate within the critical therapeutic window for acute SCI.