Peak Amplitude Of Response Research Articles

Characterization of Crack Geometry Parameters Based on Three-dimensional Transient Magnetic Field of Rectangular Pulsed Eddy Current

Eddy current testing plays an important role in assessing the surface quality of metal structures. Based on pulsed eddy current (PEC) testing, a new magnetic field characterization technique for surface cracks is proposed in this paper. The three-dimensional transient magnetic field is studied, revealing its distribution characteristics and transient response in the presence of cracks. The results show that the transient magnetic field contains valuable information. Specifically, the distributions of the magnetic field components Bx and Bz at the initial time are effective in evaluating crack length and depth. The time response of Bx provides characteristic information about defect length, emphasizing the importance of selecting the appropriate detection location. Additionally, the peak position and response amplitude of Bz can characterize crack depth. The effects of the pulse rising time and coil liftoff on the transient magnetic field are also studied. The study shows that the pulse rising time should be as short as possible, and the characteristics of rectangular PEC help mitigate the effects of liftoff. The rich features extracted from the transient magnetic field provide a new means to evaluate crack geometry, improving testing capabilities and detection accuracy.

Task-dependent contribution to edge-based versus region-based texture perception

Texture segregation studies indicate that some types of textures are processed by edge-based and others by region-based mechanisms. However, studies employing nominally edge-based textures have found evidence for region-based processing mechanisms when the task was to detect rather than segregate the textures. Here we investigate directly whether the nature of the task determines if region-based or edge-based mechanisms are involved in texture perception. Stimuli consisted of randomly positioned Gabor micropattern texture arrays with five types of modulation: orientation modulation, orientation variance modulation, luminance modulation, contrast modulation and contrast variance modulation (CVM). There were four modulation frequencies: 0.1, 0.2, 0.4 and 0.8 cpd. Each modulation type was defined by three types of waveforms: sinewave (SN) with its smooth variations, square-wave (SQ) and cusp-wave (CS) with its sharp texture edges. The CS waveform was constructed by removing a sinewave from an equal amplitude square-wave. Participants performed two tasks: detection in which participants selected which of two stimuli contained the modulation and discrimination in which participants indicated which of two textures had a different modulation orientation. Our results indicate that threshold amplitudes in the detection task followed the ordering SQ < SN < CS across all spatial frequencies, consistent with detection being mediated by the overall energy in the stimulus and hence region based. With the discrimination task at low texture spatial frequencies and with CVM textures at all spatial frequencies the order was CS ≤ SQ with both < SN, consistent with being edge-based. We modeled the data by estimating the spatial frequency of a Difference of Gaussian filter that gave the largest peak amplitude response to the data. We found that the peak amplitude was lower for detection than discrimination across all texture types except for the CVM texture. We conclude that task requirements are critical to whether edges or regions underpin texture processing.

Evaluating Diffusion Models for the Automation of Ultrasonic Nondestructive Evaluation Data Analysis

We develop decision support and automation for the task of ultrasonic non-destructive evaluation data analysis. First, we develop a probabilistic model for the task and then implement the model as a series of neural networks based on Conditional Score-Based Diffusion and Denoising Diffusion Probabilistic Model architectures. We use the neural networks to generate estimates for peak amplitude response time of flight and perform a series of tests probing their behavior, capacity, and characteristics in terms of the probabilistic model. We train the neural networks on a series of datasets constructed from ultrasonic non-destructive evaluation data acquired during an inspection at a nuclear power generation facility. We modulate the partition classifying nominal and anomalous data in the dataset and observe that the probabilistic model predicts trends in neural network model performance, thereby demonstrating a principled basis for explainability. We improve on previous related work as our methods are self-supervised and require no data annotation or pre-processing, and we train on a per-dataset basis, meaning we do not rely on out-of-distribution generalization. The capacity of the probabilistic model to predict trends in neural network performance, as well as the quality of the estimates sampled from the neural networks, support the development of a technical justification for usage of the method in safety-critical contexts such as nuclear applications. The method may provide a basis or template for extension into similar non-destructive evaluation tasks in other industrial contexts.

Correlation and modal analysis techniques for the study of the VIV response of a twin-box deck based on 3D LES simulations

AbstractTwin-box decks are prone to vortex-induced vibration (VIV) at moderate wind speeds, and previous studies have shown a complex interplay between the flow and the two parallel box girders. OpenFOAM is used to model the aerodynamic and aeroelastic responses of the twin-box deck of the Stonecutters Bridge by means of 3D LES simulations. Two cases are thoroughly analysed under smooth incoming flow: (i) static deck and ii) heave peak amplitude response at VIV excitation. The computational data provided by the CFD simulations have been exploited aiming at better understanding the complex aerodynamic and aeroelastic phenomena taking place. First, spanwise correlation analyses are applied to understand the level of organisation of the forcing flow actions, and identify the regions of the deck affected by different flow structures. Second, three different mode decomposition techniques (POD, SPOD and DMD) are applied to the time-dependent pressure distributions, revealing the pivotal role played by the leeward box in the twin-box deck response under wind action. The modal analyses are of utmost interest in the development of Reduced Order Models (ROM) for the VIV response of twin-box long-span bridges.

Perinatal ethanol exposure alters respiratory chemoreflex responses in anesthetized rats

In the USA 10-15% of pregnant women drink alcohol (ethanol) leading to a variable compilation of developmental abnormalities, including deficits in critical homeostatic functions such as poor coordination of suckling, breathing, and swallowing. Here, we test the hypothesis that perinatal ethanol exposure alters respiratory chemoreflex responses in neonatal rats. Pregnant rats were exposed to 5% ethanol through their drinking water starting on embryonic day 5, which exposes the fetuses to ethanol during gestation and then after birth through the breast milk. Pups of both sexes were studied in the first week of life (postnatal days (P) 1-5). First, in awake pups, we used head-out plethysmography to assess the effects of ethanol exposure on the respiratory response to a brief, 5- minute episode of hypoxic hypercapnia (12% O2/5% CO2, balance N2, delivered through a nose cone). We found no significant differences in the frequency (P = 0.6667), tidal volume (P = 0.3627), or minute ventilation (P = 0.1582) responses to the challenge between control and ethanol exposed pups (2-way ANOVA, n = 6 control and 6 ethanol pups). In a second experiment, we used electromyography in anesthetized pups to study the diaphragm and tongue muscle responses to nasal occlusion, which results in strong muscle efforts but an absence of lung inflation, as well as hypoxia, hypercapnia, and acidosis. Here, we found that both diaphragm and tongue muscle EMG responses were significantly blunted in ethanol exposed animals compared to control. This included a decrease in the peak amplitude responses of both muscles (2-way ANOVA: diaphragm, P = 0.0175; tongue, P= 0.0317, n = 8 control and 8 ethanol pups), as well as a delay in the onset of the tongue muscle activation (Student’s unpaired T-test, P = 0.0219, n = 8 control and 8 ethanol pups). Together, these data indicate that perinatal ethanol exposure causes impairments in respiratory chemoreflex control, which appear to be highly dependent on level of arousal. NIH 5R01HD071302-08 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Temporal Dynamics of Neural Responses in Human Visual Cortex.

Neural responses to visual stimuli exhibit complex temporal dynamics, including subadditive temporal summation, response reduction with repeated or sustained stimuli (adaptation), and slower dynamics at low contrast. These phenomena are often studied independently. Here, we demonstrate these phenomena within the same experiment and model the underlying neural computations with a single computational model. We extracted time-varying responses from electrocorticographic recordings from patients presented with stimuli that varied in duration, interstimulus interval (ISI) and contrast. Aggregating data across patients from both sexes yielded 98 electrodes with robust visual responses, covering both earlier (V1-V3) and higher-order (V3a/b, LO, TO, IPS) retinotopic maps. In all regions, the temporal dynamics of neural responses exhibit several nonlinear features. Peak response amplitude saturates with high contrast and longer stimulus durations, the response to a second stimulus is suppressed for short ISIs and recovers for longer ISIs, and response latency decreases with increasing contrast. These features are accurately captured by a computational model composed of a small set of canonical neuronal operations, that is, linear filtering, rectification, exponentiation, and a delayed divisive normalization. We find that an increased normalization term captures both contrast- and adaptation-related response reductions, suggesting potentially shared underlying mechanisms. We additionally demonstrate both changes and invariance in temporal response dynamics between earlier and higher-order visual areas. Together, our results reveal the presence of a wide range of temporal and contrast-dependent neuronal dynamics in the human visual cortex and demonstrate that a simple model captures these dynamics at millisecond resolution.SIGNIFICANCE STATEMENT Sensory inputs and neural responses change continuously over time. It is especially challenging to understand a system that has both dynamic inputs and outputs. Here, we use a computational modeling approach that specifies computations to convert a time-varying input stimulus to a neural response time course, and we use this to predict neural activity measured in the human visual cortex. We show that this computational model predicts a wide variety of complex neural response shapes, which we induced experimentally by manipulating the duration, repetition, and contrast of visual stimuli. By comparing data and model predictions, we uncover systematic properties of temporal dynamics of neural signals, allowing us to better understand how the brain processes dynamic sensory information.

Experimental study on dynamic responses of a deep-sea mining system

The global demand for minerals has raised interest in the design and study of Deep-Sea Mining (DSM) systems for minerals. In this study, the global dynamic responses of a DSM system are investigated using a scaled model test in an ocean basin. Vessel movements, loads of rigid pipe, and buffer accelerations were recorded when the system is exposed to different excitation. The peak response amplitude operator of the roll motion of a vessel under a 90∘ incident wave is found to decrease by 26% due to the underwater structures of the DSM system. Under excitation containing irregular waves, the maximum response value occurs at 0.4 Hz in the y-axis moments under current only excitation and at 0.11 Hz in the axial force. The experiments give insight into the vessel-motion-induced vortex-induced vibration (VIV) on the rigid pipe, and find that the interaction of irregular waves and currents on the DSM system resulting in 48%, 25% and 37.8% increase of the buffer’s displacements in x-, y- and z-direction compared with the linear combination of results under current only and wave only case. These results can be used to develop general guidelines for the design of DSM systems in the industry.

Novel geometries of serrated helical strakes to suppress vortex-induced vibrations and reduce drag

We present an experimental investigation on the effectiveness of unconventional geometries of serrated helical strakes to suppress the cross-flow vortex-induced vibrations (VIV) of a circular cylinder with low mass and structural damping. The VIV responses of five models of strakes are compared with that of a bare cylinder at moderate Reynolds numbers: one continuous helical strake, two serrated strakes and two inverted strakes. While the conventional strake suppressed 88% of the peak amplitude of response with a 48% drag reduction, the most efficient serrated strake reduced the peak amplitude of vibration by 95% producing 54% less drag than a bare cylinder. When the models were not allowed to respond to VIV they all increased drag in relation to that of bare cylinder. We verified that simply inverting the local angle of attack of the individual blades in relation to the helical pitch of the strake did not produce a favourable result in terms of VIV suppression, but reduced drag and fluctuating lift on a fixed body. Visualization of the flow around the blades helped to clarify the hydrodynamic mechanisms governing flow separation in the near wake, disrupting the formation of coherent vortices and reducing VIV.

Preattentive processing of visually guided self-motion in humans and monkeys.

The visually-based control of self-motion is a challenging task, requiring - if needed - immediate adjustments to keep on track. Accordingly, it would appear advantageous if the processing of self-motion direction (heading) was predictive, thereby accelerating the encoding of unexpected changes, and un-impaired by attentional load. We tested this hypothesis by recording EEG in humans and macaque monkeys with similar experimental protocols. Subjects viewed a random dot pattern simulating self-motion across a ground plane in an oddball EEG paradigm. Standard and deviant trials differed only in their simulated heading direction (forward-left vs. forward-right). Event-related potentials (ERPs) were compared in order to test for the occurrence of a visual mismatch negativity (vMMN), a component that reflects preattentive and likely also predictive processing of sensory stimuli. Analysis of the ERPs revealed signatures of a prediction mismatch for deviant stimuli in both humans and monkeys. In humans, a MMN was observed starting 110 ms after self-motion onset. In monkeys, peak response amplitudes following deviant stimuli were enhanced compared to the standard already 100 ms after self-motion onset. We consider our results strong evidence for a preattentive processing of visual self-motion information in humans and monkeys, allowing for ultrafast adjustments of their heading direction.

Speech evoked potentials in cochlear implant recipients with auditory neuropathy spectrum disorder

Purpose Cochlear implantation (CI) is now recognised as the most possible approach to help ANSD patients in improving their capability in hearing and speech communication. Because there are no reliable methods in clinical practice to identify the exact lesion site and mechanisms for a certain ANSD patient, the efficacy of CI is difficult to predict before surgery. This study was done to study speech ABR and CAEP P1 in ANSD subjects fitted with CIs and to compare results of both tests in ANSD versus SNHL subjects fitted with unilateral CIs, then correlate between both tests in both types of hearing loss. Method The current study was a case-control study, conducted on a total number of 45 subjects who were classified into three groups (one control and two study groups). The control group comprised 16 subjects with normal peripheral hearing sensitivity (NH group) who were age matched to both study groups. The study group comprised 29 children who underwent cochlear implantation. The study group were subdivided according to preoperative diagnosis of the type of their hearing loss into two groups (a group of children with sensorineural hearing loss; SNHL-CI) and (a group of children with Auditory neuropathy spectrum disorder; ANSD-CI). Both study groups were subjected to detailed history taking, aided warble-tone sound field audiometry, Speech-evoked potentials (P1 & ABR) and Questionnaire. Results There were statistically significant differences between the control group and both study subgroups regarding the P1 latencies. While; there were no statistically significant differences between {SNHL-CI group &ANSD-CI}. S-ABR waves were detected in 100% of control group, 75% of SNHL-CI group and 53.8% of ANSD-CI group. Sound-field S-ABR measured in the CI recipients indicated statistically significant delayed latencies than in the NH group. In addition, these results demonstrated that the frequency following response peak amplitude was significantly higher in CI recipients, than in the NH counterparts. Finally, the neural phase locking was significantly higher in CI recipients. Conclusion The findings of sound-field S-ABR demonstrated that CI recipients have neural encoding deficits in temporal and spectral domains at the brainstem level; therefore, the sound-field S-ABR can be considered an efficient clinical procedure to assess the speech processing in CI recipients.

Resonance in vortex-induced in-line vibration at low Reynolds numbers

Abstract

Modeling the temporal dynamics of neural responses in human visual cortex

Cortical responses to visual stimuli exhibit complex temporal dynamics, including sub-additive temporal summation, response reduction with repeated or sustained stimuli (adaptation), and slower dynamics at low contrast. Multiple computational models have been proposed to account for these dynamics in several measurement domains, including single-cell recordings, psychophysics, and fMRI. It is challenging to compare these models because there are differences in model form, test stimuli, and instrument. Here we present a new dataset that is well-suited to compare models of neural temporal dynamics. The dataset is from electrocorticographic (ECoG) recordings of human visual cortex, which measures cortical neural population responses with high spatial and temporal precision. The stimuli were large, static contrast patterns and varied systematically in contrast, duration, and inter-stimulus interval (ISI). Time-varying broadband responses were computed using the power envelope of the band-pass filtered voltage time course (50-170 Hz) recorded from a total of 126 electrodes in ten epilepsy patients, covering earlier (V1-V4) and higher-order (LO, TO, IPS) retinotopic maps. In all visual regions, the ECoG broadband responses show several non-linear features: peak response amplitude saturates with high contrast and long stimulus durations; response latency decreases with increasing contrast; and the response to a second stimulus is suppressed for short ISIs and recovers for longer ISIs. These features were well predicted by a computational model (Zhou, Benson, Kay and Winawer, 2019) comprised of a small set of canonical neuronal operations: linear filtering, rectification, exponentiation, and a delayed divisive gain control. These results demonstrate that a simple computational model comprised of canonical neuronal computations captures a wide range of temporal and contrast-dependent neuronal dynamics at millisecond resolution. Finally, we present a software repository that implements models of temporal dynamics in a modular fashion, enabling the comparison of many models fit to the same data and analyzed with the same methods.

Explaining individual differences in infant visual sensory seeking.

Individual differences in infants’ engagement with their environment manifest early in development and are noticed by parents. Three views have been advanced to explain differences in seeking novel stimulation. The optimal stimulation hypothesis suggests that individuals seek further stimulation when they are under‐responsive to current sensory input. The processing speed hypothesis proposes that those capable of processing information faster are driven to seek stimulation more frequently. The information prioritization hypothesis suggests the differences in stimulation seeking index variation in the prioritization of incoming relative to ongoing information processing. Ten‐month‐old infants saw 10 repetitions of a video clip and changes in frontal theta oscillatory amplitude were measured as an index of information processing speed. Stimulus‐locked P1 peak amplitude in response to checkerboards briefly overlaid on the video at random points during its presentation indexed processing of incoming stimulation. Parental report of higher visual seeking did not relate to reduced P1 peak amplitude or to a stronger decrease in frontal theta amplitude with repetition, thus not supporting either the optimal stimulation or the processing speed hypotheses. Higher visual seeking occurred in those infants whose P1 peak amplitude was greater than expected based on their theta amplitude. These findings indicate that visual sensory seeking in infancy is explained by a bias toward novel stimulation, thus supporting the information prioritization hypothesis.

A Normative Study of Objective Measures of Disparity Vergence and Saccades in Children 9 to 17 Years Old

This study establishes normative data for objective outcome measures of vergence and saccade eye movements for the pediatric population. These data should facilitate future clinical trial design. This study was designed to establish normative data for objective measures of disparity vergence and saccades in children between the ages 9 and 17 years using an objective binocular eye movement tracking system. Participants (aged 9 to 17 years) had a vision examination including refraction, accommodative, and binocular vision testing. Eligibility criteria included 20/25 visual acuity with best correction, normal accommodation, and binocular vision. The ISCAN RK-826PCI binocular tracking system (ISCAN, Woburn, MA) was used to objectively record horizontal, symmetrical disparity vergence, and saccadic eye movements. Parameters assessed included peak velocity, time to peak velocity, latency, and response amplitude for both disparity vergence and saccades. One hundred eighteen participants were recruited (54.94% female; mean age, 13.5 years), and 77.1% (91/118) of the participants completed the assessment with usable data. A sample of the normative data included peak velocity (°/s), which had a mean ± standard deviation of 25.4 ± 2.9, 22.0 ± 3.0, 225 ± 16.7, and 332.5 ± 20.5 for 4° convergence, 4° divergence, 5° saccades, and 10° saccades, respectively. The mean ± standard deviation for the latency (seconds) measures were 0.28 ± 0.1, 0.28 ± 0.16, 0.23 ± 0.05, and 0.23 ± 0.05 for 4° convergence, 4° divergence, 5° saccades, and 10° saccades, respectively. Normative data enable researchers to have benchmark results for comparison with patient populations with binocular dysfunction. These objective disparity vergence measures can serve as outcome measures in future clinical trials to assess the effectiveness of therapeutic interventions by determining whether post-treatment results are similar to normal data.

Dynamic Analysis of Carrier Structure of a Marine Underwater Mechanical Arm

In this paper, the support structure of a certain type of marine underwater manipulator is taken as the object to carry out solid modeling and mechanical properties analysis. At sea level 5, the maximum stress and displacement of the carrier structure are obtained through static analysis, and the first six frequency modes, peak response frequency and amplitude of the carrier structure are obtained through modal analysis and harmonious response analysis. The results show that the safety can be guaranteed under 5-level sea conditions, and the influence of cyclic loads on the structure is significant. The influence of cyclic loads on the structure should be taken into account when analyzing the structure. The research results have engineering application value and guiding significance for optimum design and safety strength checking of underwater manipulator carrier structure.

Type 1 Diabetes Results in Significant Purinergic Receptor Remodeling in Podocytes

P2 (purinergic) receptors have been proposed to be potential viable targets for the treatment of various cardiovascular and renal disorders. Previous studies in our lab have demonstrated that the predominant purinergic signaling pathway in healthy podocytes is through P2Y1 metabotropic receptors. It was also reported that expression of purinergic receptors in different tissues, including kidney, is dynamic and might be changed under pathological conditions such as diabetic nephropathy. We hypothesized that prolonged type 1 diabetes (T1D) would result in substantial changes to podocyte purinergic calcium signaling and result in a transition from predominantly metabotropic signaling through P2Y1 to increased ionotropic signaling through P2X receptors. To do this we utilized the established T1D model of streptozocin‐injected Dahl Salt Sensitive (SS) rats, and measured intracellular calcium ([Ca2+]i) signaling in podocytes from their freshly isolated glomeruli. We determined that in comparison to non‐diabetic rats, which have a rapid elevation of [Ca2+]i levels in response to ATP (40 μM) that returns to baseline within 2 min, podocytes from T1D rats had reduced peak response amplitudes (0.53 ± 0.04 vs. 0.34±0.02, p&lt;0.001). Furthermore, podocytes of glomeruli isolated from diabetic rats had prolonged sustained elevation of [Ca2+]i level, which was not observed in non‐diabetic rats. Additionally, we used P2 specific antagonists to determine which receptors resulted in the altered calcium response curve in T1D podocytes. We found that pharmacological inhibition of P2X7 and P2X4 (10 μM A438079 and 5‐BDBD, respectively) altered the calcium curve dynamics, but did not significantly reduce the total [Ca2+]i level over a 5 min time period, as determined by area under the curve (AUC) measurements. Similarly, inhibition of P2Y1 (1 μM MRS2500) changed the [Ca2+]i curve response, but did not reduce the AUC. Combining both P2X7 and P2X4 inhibitors reduced the AUC; however, did not completely eliminate podocyte purinergic signaling (51.42 ± 5.52 vs 30.39 ± 5.00). Combined inhibition of P2X7, P2X4, and P2Y1 resulted in the near complete elimination of [Ca2+]i release in response to ATP (AUC, 51.42 ± 5.52 vs 10.57 ± 2.56, p&lt;0.001). These results demonstrate that T1D increases ionotropic purinergic signaling in podocytes; however, does not eliminate metabotropic signaling. These studies establish the potential for targeting both P2X4 and P2X7 for therapeutic intervention in T1D.Support or Funding InformationNational Institutes of Health grants T32 HL134643 and R35 HL135749, and Department of Veteran Affairs I01 BX004024

Sound-Field Speech Evoked Auditory Brainstem Response in Cochlear-Implant Recipients

Background and ObjectivesCurrently limited information is available on speech stimuli processing at the subcortical level in the recipients of cochlear implant (CI). Speech processing in the brainstem level is measured using speech-auditory brainstem response (S-ABR). The purpose of the present study was to measure the S-ABR components in the sound-field presentation in CI recipients, and compare with normal hearing (NH) children.Subjects and MethodsIn this descriptive-analytical study, participants were divided in two groups: patients with CIs; and NH group. The CI group consisted of 20 prelingual hearing impairment children (mean age=8.90 ± 0.79 years), with ipsilateral CIs (right side). The control group consisted of 20 healthy NH children, with comparable age and sex distribution. The S-ABR was evoked by the 40-ms synthesized /da/ syllable stimulus that was indicated in the sound-field presentation.ResultsSound-field S-ABR measured in the CI recipients indicated statistically significant delayed latencies, than in the NH group. In addition, these results demonstrated that the frequency following response peak amplitude was significantly higher in CI recipients, than in the NH counterparts (p<0.05). Finally, the neural phase locking were significantly lower in CI recipients (p<0.05). ConclusionsThe findings of sound-field S-ABR demonstrated that CI recipients have neural encoding deficits in temporal and spectral domains at the brainstem level; therefore, the sound-field S-ABR can be considered an efficient clinical procedure to assess the speech process in CI recipients.

Changes in the disparity vergence main sequence after treatment of symptomatic convergence insufficiency in children

This study investigates the underlying physiological mechanisms that may lead to improved outcomes for symptomatic convergence insufficiency (CI) patients after 12 weeks of office-based vergence/accommodation therapy (OBVAT) by evaluating the change in the main sequence of vergence and saccadic eye movements. In this prospective trial, 12 participants with symptomatic CI were recruited and treated with 12 weeks of OBVAT. Outcome measures included the objective assessment of the following: peak velocity, time to peak velocity, latency, response amplitude, and clinical changes in the near point of convergence (NPC), positive fusional vergence (PFV) and symptoms via the Convergence Insufficiency Symptom Survey (CISS). Ten of the twelve participants (83%) were categorized as “successful” and two were “improved” based on pre-determined published criteria (CISS, NPC, PFV). There were statistically significant changes in peak velocity, time to peak velocity, and response amplitude for both 4° and 6° symmetrical convergence and divergence eye movements. There was a significant change in the main sequence ratio for convergence post-OBVAT compared to baseline measurements (P=0.007) but not for divergence or saccadic responses. Phasic/step vergence movements adjust the underlying neural control of convergence and are critical within a vision therapy program for CI patients.

The Effect of Stroke on Middle Cerebral Artery Blood Flow Velocity Dynamics During Exercise.

Previous work demonstrates that older adults have a lower response in the middle cerebral artery velocity (MCAv) to an acute bout of moderate-intensity exercise when compared with young adults. However, no information exists regarding MCAv response to exercise after stroke. We tested whether MCAv response to an acute bout of moderate-intensity exercise differed between participants 3 months after stroke and an age- and sex-matched control group of older adults (CON). A secondary objective was to compare MCAv response between the stroke- and non-stroke-affected MCAv. Using transcranial Doppler ultrasound, we recorded MCAv during a 90-second baseline (BL) followed by a 6-minute moderate-intensity exercise bout using a recumbent stepper. Heart rate (HR), end-tidal CO2 (PETCO2), and beat-to-beat mean arterial blood pressure (MAP) were additional variables of interest. The MCAv response measures included BL, peak response amplitude (Amp), time delay (TD), and time constant (τ). The Amp was significantly lower in the stroke-affected MCAv compared with CON (P < 0.01) and in the nonaffected MCAv compared with CON (P = 0.03). No between-group differences were found between TD and τ. No significant differences were found during exercise for PETCO2 and MAP while HR was lower in participants with stroke (P < 0.01). Within the group of participants with stroke, no differences were found between the stroke-affected and non-stroke-affected sides for any measures. Resolution of the dynamic response profile has the potential to increase our understanding of the cerebrovascular control mechanisms and test cerebrovascular response to physical therapy-driven interventions such as exercise.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A284).

Characterizing gait abnormalities in patients with cervical spondylotic myelopathy: a neuromuscular analysis

Background ContextGait impairment is a hallmark of cervical spondylotic myelopathy (CSM). It has been shown to affect quality of life but has not been well defined. Further electromyographic (EMG) characterization of the gait cycle may help elucidate the true neuromuscular pathology with implications on prognosis and rehabilitation techniques. PurposeThis study compares neuromuscular activity in patients with CSM to that of healthy age-matched controls. Study DesignNonrandomized, prospective, concurrent control cohort study. MethodsNeuromuscular activity was measured in 40 patients with symptomatic CSM during a series of over-ground gait trials at a self-selected speed before surgical intervention. External oblique, multifidus, erector spinae, rectus femoris, semitendinosus, tibialis anterior, medial gastrocnemius, and medial deltoid were assessed. Identical measurements were taken in 25 healthy control patients. Differences in time of muscle onset, peak EMG, time to peak EMG, and integrated electromyography (iEMG) were assessed using one-way ANOVA. ResultsThere were no significant differences between patients with CSM and healthy controls with respect to time of muscle contraction onset. Peak EMG muscle activity was significantly higher in the medial deltoid of patients with CSM (39.3% vs. 23.3% sMVC, p=.042), but no other differences were seen in the remaining muscles tested. They also demonstrated significantly longer time to peak EMG muscle activity compared with controls in 5 of the 8 muscles tested, including the multifidus (20.2 vs. 16.8 ms, p=.050), erector spinae (18.2 vs. 8.9 ms, p<.001), semitendinosis (26.3 vs. 22.4 ms, p=.037), tibialis anterior (14.7 vs. 11.0 ms, p=.050), and medial deltoid (24.2 vs. 9.2 ms, p<.001). Compared with controls, patients with CSM demonstrated significantly higher iEMG activity in the semitendinosis (586.5% vs. 272.5 sMVC, p=.047) and medial deltoid (87.62% vs. 22.5% sMVC, p=.008). ConclusionsThe onset of muscle activity is not delayed in CSM patients, but many key muscles take longer to fully contract. This produces a situation in which patients with CSM are unable to fully fire their muscles with sufficient speed to maintain a normal gait. The core and lower extremity muscles do not contract with increased peak amplitude in response, but the deltoid and hamstring muscles are more active, suggesting compensatory activity as patients attempt to maintain balance. The end result is less efficient ambulation. These findings provide a more nuanced understanding of gait in individuals suffering from CSM and may have implications on rehabilitation protocols.