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Physiological Reports Nov 2023Cutaneous reflex modulation during rhythmic ambulation is an important motor control mechanism to help minimize stumbling following an unexpected perturbation. Previous...
Cutaneous reflex modulation during rhythmic ambulation is an important motor control mechanism to help minimize stumbling following an unexpected perturbation. Previous literature found individuals with chronic ankle instability (CAI) experience altered reflex patterns compared to healthy controls. Considering CAI is characterized by intermittent feelings of ankle instability, researchers have speculated that these alterations are related to perceived instability. Our purpose was to determine whether variability and magnitude of cutaneous reflex amplitudes can predict perceived instability levels following sural nerve stimulation during gait. Forty subjects walked while receiving random stimulations and reported their perceived instability. Middle latency reflexes among lower leg muscles were calculated using data derived from surface electromyography. Hierarchical logistical regressions revealed a positive relationship between reflex variability of the peroneus longus and lateral gastrocnemius muscles and perceived instability during midstance. This suggests subjects with consistent reflexes following sural nerve stimulation develop a certain level of perceptual expectation resulting in generally lower feelings of ankle instability, while subjects with more variable motor outputs perceive greater instability at the supraspinal level. Cutaneous reflex variability during stance may be an important objective outcome measure to monitor neuromuscular recovery throughout a rehabilitation or as a potential predictor of future lateral ankle sprains.
Topics: Humans; Ankle; Ankle Joint; Gait; Muscle, Skeletal; Electromyography; Reflex; Joint Instability
PubMed: 37994398
DOI: 10.14814/phy2.15880 -
Pain Medicine (Malden, Mass.) Oct 2023The nociceptive flexion reflex (NFR) is a polysynaptic and multisegmental spinal reflex that develops in response to a noxious stimulus and is characterized by the...
BACKGROUND
The nociceptive flexion reflex (NFR) is a polysynaptic and multisegmental spinal reflex that develops in response to a noxious stimulus and is characterized by the withdrawal of the affected body part. The NFR possesses two excitatory components: early RII and late RIII. Late RIII is derived from high-threshold cutaneous afferent A-delta fibers, which are prone to injury early in the course of diabetes mellitus (DM) and may lead to neuropathic pain. We investigated NFR in patients with DM with different types of polyneuropathies to analyze the role of NFR in small fiber neuropathy (SFN).
METHODS
We included 37 patients with DM and 20 healthy participants of similar age and sex. We performed the Composite Autonomic Neuropathy Scale-31, modified Toronto Neuropathy Scale, and routine nerve conduction studies. We grouped the patients into large fiber neuropathy (LFN), SFN, and no overt neurological symptom/sign groups. In all participants, NFR was recorded on anterior tibial (AT) and biceps femoris (BF) muscles after train stimuli on the sole of the foot, and NFR-RIII findings were compared.
RESULTS
We identified 11 patients with LFN, 15 with SFN, and 11 with no overt neurological symptoms or signs. The RIII response on the AT was absent in 22 (60%) patients with DM and 8 (40%) healthy participants. The RIII response on the BF was absent in 31 (73.8%) patients and 7 (35%) healthy participants (P = .001). In DM, the latency of RIII was prolonged, and the magnitude was reduced. Abnormal findings were seen in all subgroups; however, they were more prominent in patients with LFN compared to other groups.
CONCLUSIONS
The NFR-RIII was abnormal in patients with DM even before the emergence of the neuropathic symptoms. The pattern of involvement before neuropathic symptoms was possibly related to an earlier loss of A-delta fibers.
Topics: Humans; Pain Measurement; Small Fiber Neuropathy; Nociception; Reflex; Foot; Pain Threshold; Electric Stimulation
PubMed: 37294833
DOI: 10.1093/pm/pnad077 -
American Journal of Otolaryngology 2023Head rotation produces a vestibulo-ocular reflex (VOR). In horizontal rotation, not only lateral semicircular canals but also posterior semicircular canals are...
BACKGROUND
Head rotation produces a vestibulo-ocular reflex (VOR). In horizontal rotation, not only lateral semicircular canals but also posterior semicircular canals are stimulated, because posterior canals cupulae are not horizontal in the sitting position. Therefore, theoretical nystagmus is horizontal and torsional. Convection of endolymph does not occur, because the centre of head rotation is a dens of the second cervical vertebra, not the center of lateral canal. Although per-rotational nystagmus is a result of VOR, whether it could be explained by the movement of cupula remains undetermined. To answer this question, we analysed per-rotational nystagmus using three-dimensional video-oculography.
OBJECTIVE
To clarify whether per-rotational nystagmus is the same as the physical movement of cupula (theoretical nystagmus).
MATERIALS AND METHODS
Five healthy human were evaluated. The participant's head was rotated (sinusoidal yaw rotation) manually (frequency, 0.33 Hz; amplitude, 60°). The experiment was performed in a dark, with the participant's eyes open. Nystagmus was recorded and converted into digital data.
RESULTS
In all participants, the direction of nystagmus was rightward on rightward rotation and leftward on leftward rotation. In all participants, nystagmus was purely horizontal.
CONCLUSIONS
Practical per-rotational nystagmus differs completely from the theoretical nystagmus. Therefore, VOR is strongly influenced by the central nervous system.
Topics: Humans; Reflex, Vestibulo-Ocular; Nystagmus, Pathologic; Semicircular Canals; Movement
PubMed: 37329697
DOI: 10.1016/j.amjoto.2023.103947 -
Current Biology : CB Dec 2023Terrestrial vertebrates blink, but most aquatic vertebrates do not. How and why did blinking evolve? A recent study looks at this through the eyes of a mudskipper, fish...
Terrestrial vertebrates blink, but most aquatic vertebrates do not. How and why did blinking evolve? A recent study looks at this through the eyes of a mudskipper, fish that stay on land for long periods and blink.
Topics: Animals; Blinking; Eye; Fishes; Biomechanical Phenomena
PubMed: 38113840
DOI: 10.1016/j.cub.2023.10.019 -
Psychiatry Research Nov 2023There is a growing body of evidence indicative of changes in autonomic nervous system (ANS) activity in patients with disorders of the central nervous system (CNS).... (Review)
Review
There is a growing body of evidence indicative of changes in autonomic nervous system (ANS) activity in patients with disorders of the central nervous system (CNS). Non-invasive measures of the ANS, including heart rate variability (HRV), electrodermal activity (EDA), and pupillary light reflex (PLR) may have value as markers of symptom severity, subtype, risk profile, and/or treatment response. In this paper we provide an introduction into the anatomy and physiology of EDA and review the literature published after 2007 in which EDA was an outcome measure of cortical stimulation with transcranial magnetic stimulation (TMS). Eleven studies were included and considered regarding the potential of EDA as an outcome measure reflecting ANS activity in TMS research and treatment. These studies are summarized according to study population, experimental methodology, cortical region targeted, and correlation with other measures of ANS activity. Results indicate that EDA changes vary with the frequency and target of TMS. Inhibitory TMS to the dorsolateral prefrontal cortex (dlPFC) was the most common paradigm in these studies, consistently resulting in decreased EDA.
Topics: Humans; Transcranial Magnetic Stimulation; Galvanic Skin Response; Autonomic Nervous System; Prefrontal Cortex
PubMed: 37839318
DOI: 10.1016/j.psychres.2023.115535 -
Respiratory Physiology & Neurobiology Jul 2023Two conventional doctrines govern airway mechanosensory interpretation: One-Sensor Theory (OST) and Line-Labeled Theory (LLT). In OST, one afferent fiber connects to a...
Two conventional doctrines govern airway mechanosensory interpretation: One-Sensor Theory (OST) and Line-Labeled Theory (LLT). In OST, one afferent fiber connects to a single sensor. In LLT, a different type of sensor sends signals via its specific line to a particular brain region to evoke its reflex. Thus, airway slowly adapting receptors (SARs) inhibit breathing and rapidly adapting receptors (RARs) stimulate breathing. However, recent studies show many different mechanosensors connect to a single afferent fiber (Multiple-Sensor Theory, MST). That is, SARs and RARs may send different types of information through the same afferent pathway, indicating different information has been integrated at the sensory unit level. Thus, a sensory unit is not merely a transducer (textbook concept), but also a processor. MST is a conceptual shift. Data generated over last eight decades under OST require re-interpretation.
Topics: Respiratory System; Respiration; Afferent Pathways; Reflex; Lung; Vagus Nerve
PubMed: 37149207
DOI: 10.1016/j.resp.2023.104071 -
Harefuah Aug 2023The video head impulse test (vHIT) is a new tool in the vestibular tests' arsenal. It is based on the clinical Head Impulse Test, where the integrity of the...
The video head impulse test (vHIT) is a new tool in the vestibular tests' arsenal. It is based on the clinical Head Impulse Test, where the integrity of the vestibulo-ocular reflex is tested by high frequency excitation of the semi-circular canals. The vHIT system is composed of an accelerometer measuring the head movements, and a high frequency infra-red camera for eye tracking mounted on a light-weighted goggles. The main measures obtained are the vestibulo-ocular reflex gain - the ratio between the head and eye velocities, and the recording of corrective saccades taking place during the head movement (covered saccades) or following it (overt saccades).
Topics: Humans; Head Impulse Test; Saccades; Reflex, Vestibulo-Ocular; Semicircular Canals
PubMed: 37561035
DOI: No ID Found -
Journal of Neuroengineering and... Aug 2023Understanding of the human body's internal processes to maintain balance is fundamental to simulate postural control behaviour. The body uses multiple sensory systems'... (Review)
Review
Understanding of the human body's internal processes to maintain balance is fundamental to simulate postural control behaviour. The body uses multiple sensory systems' information to obtain a reliable estimate about the current body state. This information is used to control the reactive behaviour to maintain balance. To predict a certain motion behaviour with knowledge of the muscle forces, forward dynamic simulations of biomechanical human models can be utilized. We aim to use predictive postural control simulations to give therapy recommendations to patients suffering from postural disorders in the future. It is important to know which types of modelling approaches already exist to apply such predictive forward dynamic simulations. Current literature provides different models that aim to simulate human postural control. We conducted a systematic literature research to identify the different approaches of postural control models. The different approaches are discussed regarding their applied biomechanical models, sensory representation, sensory integration, and control methods in standing and gait simulations. We searched on Scopus, Web of Science and PubMed using a search string, scanned 1253 records, and found 102 studies to be eligible for inclusion. The included studies use different ways for sensory representation and integration, although underlying neural processes still remain unclear. We found that for postural control optimal control methods like linear quadratic regulators and model predictive control methods are used less, when models' level of details is increasing, and nonlinearities become more important. Considering musculoskeletal models, reflex-based and PD controllers are mainly applied and show promising results, as they aim to create human-like motion behaviour considering physiological processes.
Topics: Humans; Postural Balance; Gait; Motion; Muscles; Reflex
PubMed: 37605197
DOI: 10.1186/s12984-023-01235-3 -
Archives of Disease in Childhood May 2024Paediatric asthma is an increasing global healthcare problem for which current treatments are not always effective. This review explores how abnormal triggering of the... (Review)
Review
Paediatric asthma is an increasing global healthcare problem for which current treatments are not always effective. This review explores how abnormal triggering of the autonomic diving reflex might be important in explaining research findings and the real-world experience of asthma. It hypothesises that the way in which stress during pregnancy is associated with childhood asthma could be through effects on the developing nervous system. This results in increased parasympathetic responsiveness and specifically, excessive triggering of the diving reflex in response to wetting and cooling of the face and nose as occurs with upper airway infections and allergic rhinitis. In aquatic mammals the reflex importantly includes the contraction of airway smooth muscle to minimise lung volume and prevent nitrogen narcosis from diving at depth. Misfiring of this reflex in humans could result in the pathological airway narrowing that occurs in asthma. The diving reflex, and possibly also smooth muscle, is a vestigial remnant of our aquatic past. The hypothesis further suggests that classically conditioned reflex responses to neutral cues and contexts that were present at the same time as the stimuli that initially caused symptoms, become of themselves ongoing triggers of recurrent wheeze. Symptoms occurring in this way, irrespective of the presence of allergens and ongoing airway sensitisation, explain why allergen avoidance is poorly effective in alleviating wheeze and why asthma is made worse by stress. Interventions to suppress the diving reflex and to prevent reflex conditioned wheezing could result in more effective asthma management.
Topics: Humans; Asthma; Respiratory Sounds; Child; Autonomic Nervous System; Female; Diving Reflex; Pregnancy; Stress, Psychological
PubMed: 37648401
DOI: 10.1136/archdischild-2023-325441 -
Journal of Hypertension Jul 2023The blood pressure (BP) regulatory impact of the arterial baroreflex has been well established in health and disease. Under normotensive conditions, we have previously...
BACKGROUND
The blood pressure (BP) regulatory impact of the arterial baroreflex has been well established in health and disease. Under normotensive conditions, we have previously demonstrated functional differences in the central processing of the left versus right aortic baroreceptor afferent input. However, it is unknown if lateralization in aortic baroreflex function remains evident during hypertension.
METHOD
We therefore, investigated the effects of laterality on the expression of baroreflex-driven cardiovascular reflexes in a genetic model of essential hypertension, the spontaneously hypertensive rat (SHR). Anesthetized male SHRs (total n = 9) were instrumented for left, right, and bilateral aortic depressor nerve (ADN) stimulation (1-40 Hz, 0.2 ms, and 0.4 mA for 20 s) and measurement of mean arterial pressure (MAP), heart rate (HR), mesenteric vascular resistance (MVR), and femoral vascular resistance (FVR).
RESULTS
Left right, and bilateral ADN stimulation evoked frequency-dependent decreases in MAP, HR, MVR, and FVR. Left and bilateral ADN stimulation evoked greater reflex reductions in MAP, HR, MVR, and FVR compared with right-sided stimulation. Reflex bradycardia to bilateral stimulation was larger relative to both left-sided and right-sided stimulation. Reflex depressor and vascular resistance responses to bilateral stimulation mimicked those of the left-sided stimulation. These data indicate a left-side dominance in the central integration of aortic baroreceptor afferent input. Furthermore, reflex summation due to bilateral stimulation is only evident on the reflex bradycardic response, and does not drive further reductions in BP, suggesting that reflex depressor responses in the SHRs are primarily driven by changes in vascular resistance.
CONCLUSION
Together, these results indicate that lateralization in aortic baroreflex function is not only evident under normotensive conditions but also extends to hypertensive conditions.
Topics: Rats; Animals; Male; Rats, Inbred SHR; Pressoreceptors; Electric Stimulation; Blood Pressure; Baroreflex; Hypertension; Heart Rate; Aorta
PubMed: 37074354
DOI: 10.1097/HJH.0000000000003448