Significant Decrease In Amplitude Research Articles

ELEKTROFIZJOLOGICZNE POMIARY UPOŚLEDZENIA SŁUCHU U NARAŻONYCH NA HAŁAS ŻOŁNIERZY ZE SŁUCHEM W NORMIE

IntroductionSome electrophysiological changes can occur in the auditory system in response to noise exposure with or without any permanent auditory threshold shift. The purpose of this study was to identify and measure cochlear function after noise exposure in individuals with normal hearing according to standard audiometric thresholds.Material and methodsPure tone audiometry (PTA) over the standard 0.250–8 kHz range and at 12 kHz, as well as distortion product otoacoustic emission (DPOAE) and auditory brainstem response (ABR) testing, were performed on 42 soldiers who had participated in combat. A control group of 40 participants underwent the same tests.ResultsIn the noise-exposed group, significantly poorer PTA thresholds were recorded at 12 kHz. DPOAE levels were significantly low only at 4 kHz. On ABR testing, both wave I and wave V demonstrated a significant decrease in amplitude and a significant increase in latency for the noise-exposed group.ConclusionsOur findings reveal that high levels of noise can not only damage outer hair cells but also cause changes at the level of the synapses (synaptopathy) which are not evident using standard PTA tests. However, electrophysiological methods can detect some changes in cochlear function.

Shoulder Dysfunction and Quality of Life Following Modified Radical and Selective Neck Dissection: A Prospective Comparative Study.

Head and neck cancers are fairly common in India due to the widespread consumption of tobacco and neck dissection is a major component in the surgical management. The objective of this study is to analyze the effect of MRND and SND on shoulder function and quality of life in patients of head and neck cancer. Our study is a prospective comparative study on 65 head and neck cancer patients divided into 2 groups-33 in group A (MRND group) and 32 in group B (SND group). Clinical evaluation of shoulder function was done pre-operatively, 1week, 1month, 3month and 6month post-operatively using arm abduction scores (AAS) and shoulder pain and disability index (SPADI). Nerve-conduction study (NCS) was done pre-operatively and 3months post-operatively for assessment of SAN. Neck dissection quality of life questionnaire (NDQOL) was used as a quality-of-life measure. A total of 65 neck dissections were included in the analysis (33 in group A and 32 in group B) out of which 53 were males and 12 were females. The mean AAS on the 6th post-operative month in group A was significantly lower than that of group B (p = 0.01). The mean SPADI scores on the 6th post-operative month was significantly worse in group A than group B (p value 0.01). On NCS, a significant decrease in amplitude was seen in group A (p = 0.02) and a significant increase in latency was noted in group B (p = 0.005). Quality of life score on 6th post-operative month showed no significant difference between both the groups (p > 0.05). Level V dissection in MRND is associated with higher incidence and greater severity of shoulder dysfunction. AAS and SPADI score are useful tools in post operative follow up of shoulder dysfunction. NCS helps in the detection of neuropathy and to determine its severity. Early rehabilitation promotes long term recovery.

A Prospective, Monocentric Case-Control Study on Uncontrolled Psoriasis as Independent Risk Factor for a Hypercoagulable State.

Chronic inflammatory diseases, including psoriasis, are associated with development of venous thromboembolism (VTE). The clot lysis profile (CLP) provides information on both the clotting tendency and fibrinolysis activity. We hypothesized that CLP in uncontrolled psoriasis patients is disturbed towards more clotting/less lysis compared to healthy controls (HC) and that successful psoriasis treatment could normalize the CLP. In this project, we aim to compare the CLP in patients with uncontrolled psoriasis with age- and sex-matched HC and investigate the effect of anti-inflammatory treatment on CLP. Patients with uncontrolled psoriasis [psoriasis area severity index (PASI) or body surface area (BSA) > 10] (n = 87) and HC (n = 87) were recruited at a tertiary dermatology department. Samples from patients were obtained before treatment and when disease control was obtained (PASI < 3). Amplitude, area under the curve (AUC) and 50% clot lysis time were determined. At baseline, psoriasis patients had higher median amplitude and AUC compared with HC (p < 0.0001). After correction for possible confounders (BMI, smoking behavior, psoriatic arthritis, arterial hypertension, diabetes and coronary artery disease), the increased amplitude in psoriasis patients compared to HC remained significant. Successful anti-inflammatory treatment resulted in a significant decrease in amplitude (p = 0.0365). This is the first prospective study comparing the CLP of psoriasis patients with that of HC. A significant increase in both amplitude and area under the curve, indicative of a hypercoagulable CLP, was observed in psoriasis patients compared to HC. After successful anti-inflammatory treatment, amplitude significantly decreased.

Motor-evoked potential monitoring from urinary sphincter muscle during pediatric untethering surgery: a case series.

Postoperative urinary dysfunction following untethering surgery for spinal lipoma is devastating. To assess urinary function, we invented a pediatric urinary catheter equipped with electrodes for the direct transurethral recording of myogenic potential from the external urethral sphincter (EUS). This paper presents two cases in which urinary function was monitored intraoperatively by recording of motor-evoked potential (MEP) from EUS during untethering surgery in children. Two children (aged 2 and 6years) were included in this study. One patient had no preoperative neurological dysfunction, while the other had frequent urination and urinary incontinence. A pair of surface electrodes was attached to a silicone rubber urethral catheter (6 or 8 Fr; diameter, 2 or 2.6mm). The MEP from the EUS was recorded to assess the function of the centrifugal tract from the motor cortex to the pudendal nerve. Baseline MEP waveforms from the EUS were successfully recorded with latency and amplitude of 39.5ms and 66µV in patient 1 and 39.0ms and 113µV in patient 2, respectively. A significant decrease in amplitude was not observed during surgery in the two cases. No new urinary dysfunction and complications associated with the urinary catheter-equipped electrodes developed postoperatively. Using an electrode-equipped urinary catheter, monitoring of MEP from the EUS could be applicable during untethering surgery in pediatric patients.

Seismic amplitude response to internal heterogeneity of mass-transport deposits

Abstract. Compared to unfailed sediments, mass-transport deposits are often characterised by a low-amplitude response in single-channel seismic reflection images. This “acoustic transparency” amplitude signature is widely used to delineate mass-transport deposits and is conventionally interpreted as a lack of coherent internal reflectivity due to a loss of preserved internal structure caused by mass-transport processes. In this study we examine the variation in the single-channel seismic response with changing heterogeneity using synthetic 2-D elastic seismic modelling. We model the internal structure of mass-transport deposits as a two-component random medium, using the lateral correlation length (ax) as a proxy for the degree of internal deformation. The average internal reflectivity is held approximately constant with increasing deformation by fixing the two component sediment lithologies to have realistic P-wave velocity and density based on sediment core measurements from the study area. For a controlled single-source synthetic model a reduction in observed amplitude with reduced ax is consistently observed across a range of vertical correlation lengths (az). For typical autonomous underwater vehicle (AUV) sub-bottom profiler acquisition parameters, in a simulated mass-transport deposit with realistic geostatistical properties, we find that when ax≈1 m, recorded seismic amplitudes are, on average, reduced by ∼25 % relative to unfailed sediments (ax≫103 m). We also observe that deformation significantly larger than core scale (ax&gt;0.1 m) can generate a significant amplitude decrease. These synthetic modelling results should discourage interpretation of the internal structure of mass-transport deposits based on seismic amplitudes alone, as acoustically transparent mass-transport deposits may still preserve coherent, metre-scale internal structure. In addition, the minimum scale of heterogeneity required to produce a significant reduction in seismic amplitudes is likely much larger than the typical diameter of sediment cores, meaning that acoustically transparent mass-transport deposits may still appear well stratified and undeformed at core scale.

Visual pathway function in untreated individuals with major depression.

Major depression (MD) is the one of the most debilitating diseases, affecting millions of people all around the world. To establish visual pathway function in untreated individuals with MD. In 29 untreated, newly diagnosed, ophthalmologically asymptomatic individuals (58 eyes) with MD (mean age: 47.3 years) and in 29 (58 eyes) of age-, sexand refractive error-matched healthy controls (mean age: 46.8 years), the following examinations were performed: 1) best corrected distance visual acuity (BCDVA); 2) intraocular pressure (IOP); 3) and 4) biomicroscopy of anterior and posterior segment of eye; 5) macular structure (SD-OCT-Zeiss); and 6) pattern visual evoked potentials (PVEPs) measurements according to the International Society for Clinical Electrophysiology of Vision (ISCEV) standard (ISCEV-standard PVEPs). An analysis of correlation between the parameters of PVEPs and the depression severity (Hamilton Depression Rating Scale (HAMD)) was performed. To estimate the diagnostic power of PVEPs test, a receiver operating characteristics (ROC) curve was used. Data were analyzed with the significance level of p < 0.05. In the study group and in healthy control, the clinical results and macular structure were normal and not different. In the MD group, in PVEPs test (check size: 1°4'and 0°16'), a significant decrease of amplitudes of P100 (AP100), associated with prolonged P100 peak time (PTP100; check size: 0°16', p < 0.004) were detected. The most frequent abnormality in PVEPs examination in the MD group was AP100 reduction (in 69% of individuals) detected using stimulation check size 0°16'. The statistically significant positive correlation between PTP100 (check size: 0°16') and HAMD score was found in severe MD (p = 0.03). The analysis of ROC curve revealed the highest sensitivity of 0.759 and specificity of 1.0 for AP100 (0°16'). The area under the curve (AUC) was 0.841 (p < 0.001). In individuals with newly diagnosed, ophthalmologically asymptomatic and untreated MD, a dysfunction of visual pathway is present without other signs of ocular pathology. The visual pathway dysfunction measured with ISCEV PVEPs has a potential value to be an objective biomarker of MD.

Introducing a noninvasive, non-surgical, and reversible animal model for fecal incontinence using abobotulinumtoxinA in dogs.

The aim of this study was to introduce a new animal model of fecal incontinence (FI) by injecting abobotulinumtoxinA in the external anal sphincter (EAS) muscle of dogs which replaces models based on anal sphincter destructions that are invasive, mostly require surgical procedures, expensive, permanent, and painful to the animals. 4 healthy mongrel dogs were used in this study. First, they were received NaCl 0.09% (as control) injections in EAS muscle and effects were assessed by means of Electromyography (EMG) and clinically evaluated by sphincter pinch test and presence of leakage of feces for 2 weeks. Then, they received abobotulinumtoxinA in EAS muscle and reevaluated for 6 weeks to see short-term and medium-term effects of abobotulinumtoxinA injection. Saline had no significant changes in results obtained from EMG, however, there were significant decreases in amplitudes of action potentials after receiving abobotulinumtoxinA in comparison with no injection or saline injection in EAS muscle. Pinch tests were normal after saline injection assessment period, however, then started to be negative, ranging from two days after abobotulinumtoxinA injection to seven days after receiving abobotulinumtoxinA. Animals also had significant presentations of fecal incontinence (leakage of feces and cage contamination with feces) from the 1st week after receiving abobotulinumtoxinA until the 6th week after receiving abobotulinumtoxinA. AbobotulinumtoxinA caused paralysis in the EAS and producd FI conditions in dogs. This animal model was an appropriate substitute to the various invasive, expensive and also complicated procedures with an easy, feasible, noninvasive and non-painful single-stage abobotulinumtoxinA injection.

The Auditory Afferent Pathway as a Clinical Marker of Alzheimer's Disease.

Brain stem neural tracts and nuclei may be disturbed prior to observable neuronal atrophy in AD. In this perspective, we discuss the notion of functional deficits presenting prior to structural abnormalities in Alzheimer's disease (AD). Imaging of inferior colliculi using magnetic resonance spectroscopy (MRS) shows significant decrease in the neuronal markers, N acetyl aspartate/creatine ratio and increase in the glial marker myo-Inositol, in subjects with Mini-Mental State Examination scores greater than 24 and with no signs of atrophy in their MRI of the medial temporal lobe. Abnormalities in components of the auditory event-related potentials (ERPs) are described in cognitive impairment including AD. We observed a significant decrease in amplitude and increase in latency during the first 10 ms of auditory evoked potentials measured on electroencephalography (EEG) indicating slow auditory response of the brainstem. EEG spectral power recorded at the cortex is also associated with neural activity at the level of the inferior colliculi. We postulate that a functional examination of auditory afferent pathways, using non-invasive techniques, such as MRS, brain stem auditory evoked potentials (BAEPs) and ERPs may improve diagnostic accuracy of AD. Functional changes precede structural changes and it is important to further understand the relationship between biochemical and electrophysiological measures such as MRS, BAEPs and EEG.

Neurophysiological biomarkers of peripheral nervous system affection in patients with stable chronic obstructive pulmonary disease (COPD)

BackgroundChronic obstructive pulmonary disease (COPD) is accompanied by substantial systemic dysregulations that comprise systemic inflammation and neurohormonal activation in addition to many neurological involvements, such as cerebrovascular diseases, polyneuropathies, motor neuron diseases, and cognitive impairment has been described in COPD patients. The aim of the current work was to detect the subclinical affection of the peripheral nervous system in patients with stable COPD.ResultsForty COPD patients and 30 subjects as healthy control were enrolled. All included subjects were submitted to complete medical history, clinical evaluations, investigations in the form of; arterial blood gases, spirometry, in addition to nerve conduction study. The patients with COPD were classified according to GOLD criteria for severity in grade I in 7.5% grade II in 62.5%, grade III in 20%, and grade IV in 10%. The results show a statistically significant increase in distal latency and a statistically significant decrease of amplitude and conduction velocity in patients with COPD when compared to the examined nerves of control group. The demyelinating nerve affection was the most common.ConclusionIn COPD patients the peripheral nervous system could be affected subclinically once the severity of COPD increased and the patient should be neurophysiologically observed for early recognition of peripheral nervous system affection.

Functional alterations of retinal neurons and vascular involvement progress simultaneously in the Psammomys obesus model of diabetic retinopathy.

To investigate the progression of diabetic retinopathy (DR) in a new diurnal animal model, we monitored clinically the DR in Psammomys obesus (P. obesus) during 7 months using electroretinography (ERG) and imaging techniques. After the onset of DR, all ERG components decreased progressively. In scotopic conditions, by 3-months of disease progression, the diabetic P. obesus displayed a significant decrease in amplitude of b-max, b-wave responses, and mixed b-waves. While mixed a-wave decreased between 4 and 7 months. Significant differences of OP2 appeared following 1 month of disease. In photopic conditions, we noticed a decrease in the a-wave at 2 months, while it took more than 5 months in b-wave amplitude. The photopic negative response (PhNR) and the i-wave amplitudes decreased following 4 and 5 months. OP1 and OP2 were the first to be altered and a significant decrease in the amplitude started after 3 months. Finally, 30 Hz-flicker and photopic S-cone were impaired after 2 and 3 months, respectively. The assessment of the eye fundus of the retina revealed an abnormal vascular architecture appeared at Months 6 and 7. In addition, we noticed exudates in the superior periphery of the retina at the same stage. The retina thickness showed a significant reduction at Month 7. Our results indicate that the clinical correlates of human DR are present in diabetic P. obesus. The depressed of ERGs, disruption of retinal architecture, and the appearance of exudates may reflect vascular and neuronal damage throughout the retina as are seen in the advanced stages of human DR.

Electromyographic Evaluation of Early Stage Results of Exoscopic Microdecompressive Spinal Surgery in Dogs

Background: Spinal surgical interventions are generally used in the treatment of various spinal pathologies such as vertebral fracture, luxation-subluxation, congenital vertebral deformities, discal hernia, infection and tumor. Minimally invasive spinal surgery contributes to rapid recovery by reducing iatrogenic muscle damage and postoperative pain. In minimally invasive spinal surgery, a new hybrid imaging technique, the exoscope, has been developed in the last decade The purpose of this study was to report efficacy of the exoscopic microdecompressive spinal surgery (MDSS) and its early postoperative electromyography (EMG) results in dogs.Materials, Methods &amp; Results:The material of this study consisted of the owned 10 dogs with spinal cord injury resulted from the different etiologies. On the basis of examinations, medical support (fluid therapy, corticosteroid, etc.) was applied to the required dogs. Exoscopic MDSS was performed under general anesthesia in dogs. The neurologic, radiologic and EMG examination were completed at pre- and postoperative periods. EMG results at postoperative 1st week showed increased conduction velocity and amplitudes in 3 cases. There was no significant change in a case. And, there was a slight slowdown in conduction velocity and significant decrease in amplitudes in a case. At postoperative 4th week, ther was increased conduction velocity and amplitudes in 8 cases and needle EMG showed that spontan muscle activity was normal in 5 cases, mild in 2 cases, moderate a case and severe in a case. But spontan muscle activity was unfollowed in a case. Postoperative outcomes were poor in 3 cases, fair in 3 cases, good in 3 cases and unfollowed in a case. Discussion: Spinal cord injuries encountered in veterinary medicine have significant morbidity and mortality. In spinal patients, in addition to neurological examination, lesion localization can be determined using imaging techniques such as radiology, computed tomography, and MRI. EMG and somatosensory evoked potentials examinations are used to evaluate quantitative functional recovery, especially in spinal cord injuries. EMG also provides an opportunity to evaluate muscle activation patterns during recovery. Exoscopic spinal surgery is the newest hybrid imaging technique. Exoscopic MDSS facilitated manipulation by providing adequate illumination and vision at the exploration site. Exoscopic MDSS has the advantages of microscopic surgery and is a new technique that can be applied in dogs with spinal pathology.

Influence of Heat Transfer on Decreasing Intensity of a Spherical Explosion in Aqueous Foam

The two-phase model of aqueous foam behavior under strong spherical shock wave (SW) impact, is developed using equations of mixture conservation of momentum, mass and internal energy for each phase in Lagrange variables, taking into account bulk viscosity and interphase heat transfer. The numerical implementation of the model was carried out by the counting method, using the Neu-mann-Richtmyer viscosity and the Courant stability condition. The spherical explosion was modeled in the form of a SW, which has the same energy of charge of explosives, as used in experiments. A satisfactory agreement was obtained between the numerical solution, received by the proposed model, the analytical self-similar L.I. Sedov’s solution on a point spherical explosion in a gas and a new experimental data on the spherical explosion in aqueous foam. The causes, which lead to a significant decrease in amplitude and SW velocity in the studied media, are investigated in detail.

Evaluation of the Effects of Chronic Injection of D-Galactose on Auditory Brainstem Responses as a Model for Studying Age-Related Hearing Loss

The D-galactose induced mimetic aging rat model has been widely used in studies of age-associated diseases recently. Evidence indicates that D-GAL could also play a key role in age-related hearing loss. However, there is conflicting data about the relationship between the D-GAL injection and tone-burst auditory brainstem responses (ABRs). The present study aimed to compare ABRs in D-GAL injected rats compared with young and naturally aged rats. Tone-burst ABR was recorded and analyzed at the frequencies of 4,6,8,12 and 16 kHz in male young (3-month-old, n=10), naturally aging (18-month-old, n=10) and D-GAL injected (3-month-old, 500 mg/kg D-GAL injection for 8 weeks, n=10) Wistar rats. When the ABRs thresholds obtained in the D-GAL group and the natural aging group were compared with the thresholds in the young group, we observed a significant increase in thresholds, which affected all of the frequencies (P&lt;0.05). A statistically significant decrease in amplitude of wave PI at 4 and 8 kHz, PII at 4,8 kHz, PIV at 4,6,8,12 and 16 kHz was also observed in naturally aging group compared with young group. However, in D-GAL group, a significant difference was exclusively detected in amplitude of PIII at 4 kHz. Latency did not reveal any significant difference between the groups (P&gt;0.05). The present study confirmed that experimental injection of 500 mg/kg/day D-GAL for 8 weeks to Wistar rats could lead to ABRs threshold shifts but not latency. Because there are several types of presbycusis, further studies are needed to determine what type of presbycusis is induced by D-GAL and where is the first region affected by it to provide the best treatment and prevention methods. © 2019 Tehran University of Medical Sciences. All rights reserved. Acta Med Iran 2019;57(5):281-288.

Bitter Taste Receptors as Regulators of Abdominal Muscles Contraction.

Bitter taste receptors (TAS2R) are expressed in many non-sensor tissues including skeletal muscles but their function remains unexplored. The aim of this study is to investigate the role of TAS2R in rat abdominal skeletal muscles contractions using denatonium, a TAS2R agonist. Low concentration of denatonium (0.01 mmol/l) caused a significant decrease of amplitudes of the electrical field stimulation (EFS)-induced contractions in abdominal skeletal muscles preparations in vitro. This inhibitory effect was significantly reduced when the preparations were pre-incubated with gentamicin (0.02 mmol/l) used as a non-specific inhibitor of IP3 formation or with BaCl(2) (0.03 mmol/l) applied to block the inward-rectifier potassium current. All experiments were performed in the presence of pipecuronium in order to block the nerve stimulation of the contractions. The data obtained suggest that denatonium decreases the force of rat abdominal muscles contractions mainly via activation of TAS2R, phosphatidylinositol 4,5-biphosphate and its downstream signal metabolites.

The Effect of Recording Montage and Tone Burst Duration on Cervical and Ocular Vestibular Evoked Myogenic Potential Latency and Amplitude.

Objectives The objectives of this study were (a) to investigate the optimal tone burst duration when recording the cervical vestibular evoked myogenic potential (cVEMP) and the ocular vestibular evoked myogenic potential (oVEMP) and (b) to determine whether monopolar recording influences the latency or amplitude of the cVEMP or the oVEMP. Method Fifteen subjects ( M = 27.7 years, SD = 6.73 years) participated in this study. The participants had no prior history of otological or neurological disease. Both oVEMPs and cVEMPs were recorded at a fixed stimulus level for stimulus durations of 2, 5, 10, and 25 ms. For both cVEMP and oVEMP, responses were obtained using a traditional differential recording montage and a monopolar recording montage. Results The cVEMP and the oVEMP had the greatest amplitude in the 2-ms stimulus condition. There was a statistically significant decrease in amplitude for durations greater than 2 ms. Monopolar and bipolar cVEMP and oVEMP latencies and amplitudes were not significantly different. Conclusion As stimulus duration increased beyond 2 ms, the amplitude of the response decreased for both the cVEMP and the oVEMP. There was no significant change in latency with increasing stimulus duration for either response. These results suggested the optimal stimulus duration for both the oVEMP and cVEMP is 2 ms, and there is no apparent advantage of using a bipolar recording technique.

Electromagnetic Fields at Very Close Range From a Tower Struck by Lightning in Presence of a Horizontally Stratified Ground

In this paper, we present an analysis of electromagnetic fields generated by a lightning return stroke to a tall tower in presence of a horizontally stratified two-layer ground. The electromagnetic fields are evaluated at a distance of 50 m from the tower for two observation points above and below the ground surface, by using the finite-difference time-domain method. The developed numerical model is validated using available experimental data obtained at the CN Tower in Toronto. To illustrate and discuss the effect of the soil stratification on the electromagnetic fields, we adopt two different cases characterized, respectively, by an upper layer less conductive than the lower level, and vice versa. The obtained results show, for the considered distance range (50 m), that the electromagnetic fields above ground at such close distance are nearly insensitive to the ground stratification. However, the underground electromagnetic fields are markedly affected by the properties of the soil layers. In the presence of a lower layer of higher conductivity, the horizontal electric field is characterized by a faster rise time, a significant decrease in amplitude and a bipolar wave-shape compared to that in the case of a homogeneous ground with the upper-layer characteristics. On the other hand, the presence of a lower layer with lower conductivity results in an increase of the peak value of the underground horizontal electric field.

Age Related Decline in Cortical Multifocal Flash VEP: Latency Increases Shown to Be Predominately Magnocellular.

As the visual system ages, flicker sensitivity decreases and the latencies of cortical visual evoked potentials (VEP) increase. However, the extent to which these effects reflect age-related changes in the magnocellular (M) and or parvocellular (P) pathways remain unclear. Here, we investigated the relation between flicker fusion frequencies and VEP non-linearities induced by rapid stimulation, as a function of age over 6 decades. The approach, using Wiener kernel analysis of multifocal flash (mf)VEP, allows the extraction of signatures of both M and P processing and hence establishing a neural basis of the known decline in flicker fusion threshold. We predicted that, in a sample of 86 participants, age would be associated with a latency increase in early mfVEP response components and that flicker fusion thresholds, for both low and high contrast stimuli, would relate to the temporal efficiency of the M-generated VEP component amplitudes. As expected, flicker fusion frequency reduced with age, while latencies of early second order peaks of the mfVEP increased with age, but M temporal efficiency (amplitude ratio of first to second order peaks) was not strongly age-related. The steepest increases in latency were associated with the M dominated K2.1 (second order first slice) N70 components recorded at low and high contrast (6.7 and 5.9 ms/decade, respectively). Interestingly, significant age-related latency shifts were not observed in the first order responses. Significant decreases in amplitude were found in multiple first and second order components up to 30 years of age, after which they remained relatively constant. Thus, aging and decline in visual function appears to be most closely related to the response latencies of non-linearities generated by the M pathway.

Cosinor Analysis Reveals Non‐dipping Hypertension in Mixed Background Strain Mice Lacking the Circadian Clock Protein PER1

Cardiovascular disease is the leading cause of death among Americans. Hypertension is the leading risk factor for cardiovascular disease, thus blood pressure (BP) regulation is imperative for maintaining cardiovascular health. BP exhibits a circadian rhythm that is regulated through many mechanisms. Humans experience a BP rhythm resulting in a 10–20% dip in BP during their resting period. Individuals who fail to maintain this dip, termed non‐dippers, are associated with worse cardiovascular outcomes. The circadian clock mechanism, which includes the transcription factors PERIOD, BMAL1, CLOCK, and CRYPTOCHROME, is necessary to maintain this rhythm. Past studies in our lab have shown that global loss of PER1 leads to non‐dipping hypertension in male C57BL/6 mice in response to high salt diet plus an aldosterone analogue desoxycorticosterone pivalate‐salt (DOCP) (Solocinski et al. 2017). The goal of this study was to determine the BP phenotype of Per1 knockout (KO) mice on a salt‐sensitive 129/sv/s1s4 background strain. 129/sv/s1s4 mice were implanted with radiotelemetry devices and maintained in a normal 12‐hour light/dark period. BP was monitored continuously while the mice were subjected to a control diet, a high salt (HS) diet, or a HS diet plus treatment with an aldosterone analogue DOCP. BP rhythms were analyzed through the program Cosinor (www.circadian.org) to determine the mesor, amplitude, and acrophase. When evaluating a cosine wave, the mesor is the midline between the peak and the trough, the amplitude is the measure of the mesor to the peak, and the acrophase is the time point of the peak. These values were then used to discern whether the mice maintained a BP rhythm. The 129/sv/s1s4 Per1 KO experienced a 9‐mmHg increase in BP in response to HS/DOCP (P&lt;0.01, n=8). In contrast, the wild type (WT) mice (n=5) did not experience a significant increase in BP after HS/DOCP. Furthermore, the KO mice had a 2.4‐mmHg decrease in amplitude (P=0.01), whereas the WT mice did not exhibit a significant decrease in amplitude. The WT mice on control diet exhibited a 12.8% dip in BP during their inactive period compared to their active period, which insignificantly decreased to an 11.5% dip on HS/DOCP diet. However, the KO mice on control diet had an 11% dip, which decreased to 5.4% dip on HS/DOCP diet (P&lt;0.05, n=5–8). These data demonstrate that loss of Per1 in male 129/sv/s1s4 mice leads to a non‐dipping phenotype in response to HS/DOCP treatment. Importantly, these findings represent the reproducibility of the non‐dipping hypertension phenotype we previously observed in C57BL/6 mice in a distinct strain on a mixed background.Support or Funding InformationAmerican Physiological Society Undergraduate Summer Fellowship Program; American Society of Nephrology Foundation for Kidney ResearchThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

P 52 Amplitude modulation of the somatosensory alpha rhythm by transcranial alternating current stimulation applied at the individual endogenous frequency

Background/research question In a recent study we could demonstrate, that transcranial alternating current stimulation (tACS), applied at the individual somatosensory mu-alpha-frequency (mu-tACS), modulated somatosensory perception phasically. From other studies it is also known, that tACS, applied over visual areas may increase the amplitude of ongoing visual alpha oscillations. We therefore wanted to examine whether our behaviorally relevant mu-tACS protocol may also modulate somatosensory mu-alpha oscillations. Method For this purpose 23 participants (mean age: 27; 11 female) were tested in a combined tACS/EEG experiment with a randomized, single-blinded crossover design. Initially, each participant’s individual mu-alpha peak frequency was identified in a pre-experiment. Subsequently we applied two blocks of tACS (verum and sham, duration: 5 min) bilaterally over somatosensory areas, with a stimulation-free interval of five minutes between both blocks, while participants were watching a movie in silence and their EEG was recorded. For data analysis mu-alpha amplitudes two minutes before and two minutes after each stimulation block were extracted and compared between mu-tACS and sham. Results When comparing amplitude modulations of mu-alpha oscillations we found a significant difference between mu-tACS and sham with a significant decrease in amplitude after stimulation for the mu-tACS block but not for sham. This decrease in mu-alpha amplitude had a bilateral, central topography. Furthermore this modulation was specific for somatosensory mu-alpha-oscillations and not seen for visual alpha-oscillations. Discussion/Conclusion We here present electrophysiological evidence for a specific interaction between mu-tACS and somatosensory mu-alpha oscillations, supporting the functional specificity of tACS as an intervention method. However, the direction of modulation (amplitude decrease) was somehow unexpected, as an increase in amplitude of visual alpha oscillations during and after tACS over visual areas was reported in other studies. The difference may be related to potentially different characteristics of the modulated brain rhythm or the stimulation protocol and should be addressed in additional future studies.

Abnormal Cortical Plasticity in Youth with Autism Spectrum Disorder: A Transcranial Magnetic Stimulation Case-Control Pilot Study.

Objective: This case–control study investigated the use of a low-intensity repetitive transcranial magnetic stimulation (rTMS) protocol to measure motor cortex (M1) plasticity in youth with autism spectrum disorder (ASD) compared with typically developing children (TDC). We hypothesized that impairments in long-term potentiation-like properties represent a neurophysiological biomarker of abnormal cortical function in ASD.Methods: We studied youth with ASD aged 11–18 years and matched controls (TDC). Intermittent theta burst stimulation (iTBS) was delivered to the dominant M1 at an intensity of 70% of resting motor threshold. Suprathreshold single-pulse TMS was performed to compare amplitudes of motor-evoked potentials (MEP) measured from surface electromyography electrodes on a target muscle before (20 pulses) and after (10 pulses/time point) iTBS at predefined timepoints (up to 30 minutes) to measure any potentiation effects. A linear mixed model was used to examine group differences in MEP amplitudes over time following iTBS.Results: Nine youth with ASD (mean age 15.6; 7 males; 6 right-hand dominant) and 9 TDC (mean age 14.5; 5 males; 9 right-hand dominant) participated. All subjects tolerated the procedure well. Both groups had a mean increase in excitability after iTBS for 30 minutes; however, the time course of excitability changes differed (F9,144 = 2.05; p = 0.038). Post-hoc testing identified a significant decrease in amplitude of the ASD group at 20 minutes following iTBS compared with the TDC after correcting for multiple comparisons.Conclusion: In this study, we demonstrate early evidence for a potential physiological biomarker of cortical plasticity in youth with ASD using a rapid low-intensity rTMS protocol with a discriminate measure at 20 minutes following stimulation. The procedure was well tolerated by all 18 participants. Future work will include modification of the protocol to improve the ability to distinguish subtypes of ASD based on behavioral and cognitive testing.