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Autonomic Neuroscience : Basic &... Nov 2020Autonomic alterations at the onset of exercise are critical to redistribute cardiac output towards the contracting muscles while preventing a fall in arterial pressure... (Review)
Review
Autonomic alterations at the onset of exercise are critical to redistribute cardiac output towards the contracting muscles while preventing a fall in arterial pressure due to excessive vasodilation within the contracting muscles. Neural mechanisms responsible for these adjustments include central command, the exercise pressor reflex, and arterial and cardiopulmonary baroreflexes. The exercise pressor reflex evokes reflex increases in sympathetic activity to the heart and systemic vessels and decreases in parasympathetic activity to the heart, which increases blood pressure (BP), heart rate, and total peripheral resistance through vasoconstriction of systemic vessels. In this review, we discuss recent advancements in our understanding of exercise pressor reflex function in health and disease. Specifically, we discuss emerging evidence suggesting that sympathetic vasoconstrictor drive to the contracting and non-contracting skeletal muscle is differentially controlled by central command and the metaboreflex in healthy conditions. Further, we discuss evidence from animal and human studies showing that cardiovascular diseases, including hypertension, diabetes, and heart failure, lead to an altered exercise pressor reflex function. We also provide an update on the mechanisms thought to underlie this altered exercise pressor reflex function in each of these diseases. Although these mechanisms are complex, multifactorial, and dependent on the etiology of the disease, there is a clear consensus that several mechanisms are involved. Ultimately, approaches targeting these mechanisms are clinically significant as they provide alternative therapeutic strategies to prevent adverse cardiovascular events while also reducing symptoms of exercise intolerance.
Topics: Animals; Diabetes Mellitus; Exercise; Heart Failure; Humans; Hypertension; Muscle, Skeletal; Reflex; Sympathetic Nervous System
PubMed: 32861944
DOI: 10.1016/j.autneu.2020.102698 -
Clinical Neurophysiology : Official... Dec 2023Cortical myoclonus is thought to result from abnormal electrical discharges arising in the sensorimotor cortex. Given the ease of recording of cortical discharges,... (Review)
Review
Cortical myoclonus is thought to result from abnormal electrical discharges arising in the sensorimotor cortex. Given the ease of recording of cortical discharges, electrophysiological features of cortical myoclonus have been better characterized than those of subcortical forms, and electrophysiological criteria for cortical myoclonus have been proposed. These include the presence of giant somatosensory evoked potentials, enhanced long-latency reflexes, electroencephalographic discharges time-locked to individual myoclonic jerks and significant cortico-muscular connectivity. Other features that are assumed to support the cortical origin of myoclonus are short-duration electromyographic bursts, the presence of both positive and negative myoclonus and cranial-caudal progression of the jerks. While these criteria are widely used in clinical practice and research settings, their application can be difficult in practice and, as a result, they are fulfilled only by a minority of patients. In this review we reappraise the evidence that led to the definition of the electrophysiological criteria of cortical myoclonus, highlighting possible methodological incongruencies and misconceptions. We believe that, at present, the diagnostic accuracy of cortical myoclonus can be increased only by combining observations from multiple tests, according to their pathophysiological rationale; nevertheless, larger studies are needed to standardise the methods, to resolve methodological issues, to establish the diagnostic criteria sensitivity and specificity and to develop further methods that might be useful to clarify the pathophysiology of myoclonus.
Topics: Humans; Myoclonus; Evoked Potentials, Somatosensory; Electroencephalography; Reflex; Neurophysiology; Electromyography
PubMed: 37948946
DOI: 10.1016/j.clinph.2023.10.007 -
BMC Geriatrics Jun 2024Late-life depression (LLD) is a prevalent neuropsychiatric disorder in the older population. While LLD exhibits high mortality rates, depressive symptoms in older adults...
BACKGROUND
Late-life depression (LLD) is a prevalent neuropsychiatric disorder in the older population. While LLD exhibits high mortality rates, depressive symptoms in older adults are often masked by physical health conditions. In younger adults, depression is associated with deficits in pupil light reflex and eye blink rate, suggesting the potential use of these responses as biomarkers for LLD.
METHODS
We conducted a study using video-based eye-tracking to investigate pupil and blink responses in LLD patients (n = 25), older (OLD) healthy controls (n = 29), and younger (YOUNG) healthy controls (n = 25). The aim was to determine whether there were alterations in pupil and blink responses in LLD compared to both OLD and YOUNG groups.
RESULTS
LLD patients displayed significantly higher blink rates and dampened pupil constriction responses compared to OLD and YOUNG controls. While tonic pupil size in YOUNG differed from that of OLD, LLD patients did not exhibit a significant difference compared to OLD and YOUNG controls. GDS-15 scores in older adults correlated with light and darkness reflex response variability and blink rates. PHQ-15 scores showed a correlation with blink rates, while MoCA scores correlated with tonic pupil sizes.
CONCLUSIONS
The findings demonstrate that LLD patients display altered pupil and blink behavior compared to OLD and YOUNG controls. These altered responses correlated differently with the severity of depressive, somatic, and cognitive symptoms, indicating their potential as objective biomarkers for LLD.
Topics: Humans; Male; Aged; Female; Blinking; Reflex, Pupillary; Depression; Aged, 80 and over; Middle Aged; Adult; Pupil; Darkness; Young Adult; Light
PubMed: 38914987
DOI: 10.1186/s12877-024-05034-w -
The Australian and New Zealand Journal... Sep 2023
Topics: Humans; Reflex
PubMed: 37042302
DOI: 10.1177/00048674231166891 -
Spinal Cord Series and Cases 2020Sacral reflexes are important to allow the SCI practitioner to gain information about the state of the sacral spinal cord segments. The presence of the bulbocavernosus... (Review)
Review
Sacral reflexes are important to allow the SCI practitioner to gain information about the state of the sacral spinal cord segments. The presence of the bulbocavernosus and/or the anal wink reflex indicate an intact spinal reflex arc and reflex conal autonomic function (as part of the upper motor neuron syndrome); their absence defines a lower motor neuron syndrome. The assessment of sacral reflexes helps predict the type of bladder, bowel and sexual functions and the related therapeutic interventions. We suggest adding the sacral component of the International Standards for the Assessment of Autonomic Function after SCI (ISAFSCI) to the International Standards for the Neurologic Classification of Spinal Cord Injury (ISNCSCI) examination so there can be a detailed description of these important functions. As an alternative, the performance of sacral reflexes should be routinely required as part of the neurologic examination after SCI. Whether the sacral motor neuron system is classified as upper or lower motor neuron injury is also quite useful and as such should be present in the ISCNSCI.
Topics: Humans; Neurologic Examination; Reflex; Sacrococcygeal Region; Spinal Cord Injuries
PubMed: 31934355
DOI: 10.1038/s41394-019-0252-2 -
Scientific Reports Apr 2023We study how falling hoverflies use sensory cues to trigger appropriate roll righting behavior. Before being released in a free fall, flies were placed upside-down with...
We study how falling hoverflies use sensory cues to trigger appropriate roll righting behavior. Before being released in a free fall, flies were placed upside-down with their legs contacting the substrate. The prior leg proprioceptive information about their initial orientation sufficed for the flies to right themselves properly. However, flies also use visual and antennal cues to recover faster and disambiguate sensory conflicts. Surprisingly, in one of the experimental conditions tested, hoverflies flew upside-down while still actively flapping their wings. In all the other conditions, flies were able to right themselves using two roll dynamics: fast ([Formula: see text]50ms) and slow ([Formula: see text]110ms) in the presence of consistent and conflicting cues, respectively. These findings suggest that a nonlinear sensory integration of the three types of sensory cues occurred. A ring attractor model was developed and discussed to account for this cue integration process.
Topics: Animals; Reflex, Righting; Proprioception; Diptera; Cues
PubMed: 37061548
DOI: 10.1038/s41598-023-33302-z -
American Journal of Physiology.... Nov 2021The gastrointestinal tract has its own "brain," the enteric nervous system or ENS, that executes routine housekeeping functions of digestion. The dorsal vagal complex in... (Review)
Review
The gastrointestinal tract has its own "brain," the enteric nervous system or ENS, that executes routine housekeeping functions of digestion. The dorsal vagal complex in the central nervous system (CNS) brainstem, however, organizes vagovagal reflexes and establishes interconnections between the entire neuroaxis of the CNS and the gut. Thus, the dorsal vagal complex links the "CNS brain" to the "ENS brain." This brain-gut connectome provides reflex adjustments that optimize digestion and assimilation of nutrients and fluid. Vagovagal circuitry also generates the plasticity and adaptability needed to maintain homeostasis to coordinate among organs and to react to environmental situations. Arguably, this dynamic flexibility provided by the vagal circuitry may, in some circumstances, lead to or complicate maladaptive disorders.
Topics: Animals; Brain; Enteric Nervous System; Gastrointestinal Tract; Humans; Neuronal Plasticity; Reflex; Vagus Nerve
PubMed: 34643086
DOI: 10.1152/ajpgi.00214.2021 -
Journal of Neurology Oct 2022Current diagnostic criteria for bilateral vestibulopathy (BV) primarily involve measurements of vestibular reflexes. Perceptual self-motion thresholds however, are not...
OBJECTIVE
Current diagnostic criteria for bilateral vestibulopathy (BV) primarily involve measurements of vestibular reflexes. Perceptual self-motion thresholds however, are not routinely measured and their clinical value in this specific population is not yet fully determined. Objectives of this study were (1) to compare perceptual self-motion thresholds between BV patients and control subjects, and (2) to explore patterns of self-motion perception performance and vestibular function in BV patients.
METHODS
Thirty-seven BV patients and 34 control subjects were included in this study. Perceptual self-motion thresholds were measured in both groups using a CAREN platform (Motek Medical BV, Amsterdam, The Netherlands). Vestibular function was evaluated (only in BV patients) by the caloric test, torsion swing test, video head impulse test of all semicircular canals, and cervical- and ocular vestibular-evoked myogenic potentials. Differences in thresholds between both groups were analyzed. Hierarchical cluster analysis was performed to visualize patterns between self-motion perception and vestibular function within the group of BV patients.
RESULTS
Perceptual self-motion thresholds were significantly higher in BV patients compared to control subjects, regarding nearly all rotations and translations (depending on the age group) (p ≤ 0.001). Cluster analysis showed that within the group of BV patients, higher perceptual self-motion thresholds were generally associated with lower vestibular test results (significant for yaw rotation, caloric test, torsion swing test, and video head impulse test (p ≤ 0.001)).
CONCLUSION
Self-motion perception is significantly decreased in BV patients compared to control subjects regarding nearly all rotations and translations. Furthermore, decreased self-motion perception is generally associated with lower residual vestibular function in BV patients.
TRIAL REGISTRATION
Trial registration number NL52768.068.15/METC.
Topics: Bilateral Vestibulopathy; Head Impulse Test; Humans; Motion Perception; Reflex, Vestibulo-Ocular; Vestibular Evoked Myogenic Potentials
PubMed: 34263351
DOI: 10.1007/s00415-021-10695-3 -
European Journal of Pain (London,... Nov 2022The mechanisms of pain perception in individuals with masochistic behaviour (MB) remain poorly documented. We hypothesized that MB is associated with context-specific...
BACKGROUND
The mechanisms of pain perception in individuals with masochistic behaviour (MB) remain poorly documented. We hypothesized that MB is associated with context-specific changes in descending pain modulation.
METHODS
We compared the effects of four standardized sets of images with positive (erotic), negative (mutilations), masochistic or neutral emotional valences on the RIII nociceptive reflex evoked by electrical stimulation of the sural nerve and recorded on the ipsilateral biceps femoris in 15 controls and 15 men routinely engaging in MB. We systematically assessed the RIII reflex threshold and recruitment curves (up to the tolerance threshold), thermal (heat and cold) pain thresholds measured on the upper and lower limbs and responses to the pain sensitivity questionnaire, to compare basal pain perception between our two groups of participants. We also assessed anxiety, depression, empathy, alexithymia, high sensation seeking and catastrophizing, to investigate their potential influence on the emotional modulation of pain.
RESULTS
Thermal pain thresholds, RIII reflex recruitment curves, and responses to the psychological and pain sensitivity questionnaires were similar in the two groups. Neutral, positive and negative images modulated the RIII reflex similarly in the two groups. By contrast, masochistic images induced a significant (p < 0.01) decrease in RIII reflex responses in subjects with MB, whereas it tended to increase these responses in control subjects.
CONCLUSIONS
Our data suggest that psychological profile, basal pain sensitivity and the emotional modulation of pain are normal in individuals with MB but that these subjects selectively engage descending pain inhibition in the masochistic context.
SIGNIFICANCE
Decrease pain perception related to masochistic behaviours is associated with specific activation of descending pain inhibition.
Topics: Electric Stimulation; Humans; Male; Pain; Pain Perception; Pain Threshold; Reflex
PubMed: 36094743
DOI: 10.1002/ejp.2037 -
Autonomic Neuroscience : Basic &... May 2021Sepsis is a serious medical condition in which immune dysfunction plays a key role. Previous treatments focused on chemotherapy to control immune function; however, a... (Review)
Review
Sepsis is a serious medical condition in which immune dysfunction plays a key role. Previous treatments focused on chemotherapy to control immune function; however, a recognized effective compound or treatment has yet to be developed. Recent advances indicate that a neuromodulation approach with nerve stimulation allows developing a therapeutic strategy to control inflammation and improve organ functions in sepsis. As a quick, non-invasive technique of peripheral nerve stimulation, acupuncture has emerged as a promising therapy to provide significant advantages for immunomodulation in acute inflammation. Acupuncture obtains its regulatory effect by activating the somatic-autonomic-immune reflexes, including the somatic-sympathetic-splenic reflex, the somatic-sympathetic-adrenal reflex, the somatic-vagal-splenic reflex and the somatic-vagal-adrenal reflex, which produces a systemic effect. The peripheral nerve stimulation also induces local reflexes such as the somatic-sympathetic-lung-reflex, which then produces local effects. These mechanisms offer scientific guidance to design acupuncture protocols for immunomodulation and inflammation control, leading to an evidence-based comprehensive therapy recommendation.
Topics: Acupuncture Therapy; Autonomic Nervous System; Humans; Reflex; Sepsis; Sympathetic Nervous System
PubMed: 33684727
DOI: 10.1016/j.autneu.2021.102793