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Trends in Neurosciences Feb 2024Homeostatic reflexes are crucial for life, but the subpopulations of sensory neurons that stimulate these reflexes are largely unknown. A recent paper from Lovelace, Ma,...
Homeostatic reflexes are crucial for life, but the subpopulations of sensory neurons that stimulate these reflexes are largely unknown. A recent paper from Lovelace, Ma, and colleagues identified a population of sensory neurons in the cardiac ventricle that underlies the Bezold-Jarisch reflex and triggers syncope (fainting).
Topics: Humans; Reflex; Sensory Receptor Cells
PubMed: 38030510
DOI: 10.1016/j.tins.2023.11.007 -
Journal of Neurology Dec 2014In the late 1800s, Wilhelm Erb, Joseph Babinski, William Gowers, and others helped develop the neurologic examination as we know it today. Erb was one of the first to... (Review)
Review
In the late 1800s, Wilhelm Erb, Joseph Babinski, William Gowers, and others helped develop the neurologic examination as we know it today. Erb was one of the first to emphasize a detailed and systematic neurologic exam and was co-discoverer of the muscle stretch reflex, Gowers began studying the knee jerk shortly after it was described, and Babinski focused on finding reliable signs that could differentiate organic from hysterical paralysis. These physicians and others emphasized the bedside examination of reflexes, which have been an important part of the neurologic examination ever since. This review will focus on the history of the examination of the following muscle stretch and superficial/cutaneous reflexes: knee jerk, jaw jerk, deep abdominal reflexes, superficial abdominal reflexes, plantar reflex/Babinski sign, and palmomental reflex. The history of reflex grading will also be discussed.
Topics: History, 19th Century; History, 20th Century; History, 21st Century; Humans; Neurologic Examination; Reflex; Reflex, Abdominal; Reflex, Abnormal; Reflex, Babinski; Reflex, Stretch
PubMed: 24695995
DOI: 10.1007/s00415-014-7326-7 -
Journal of Neurophysiology Jan 2022Normal subjects can completely eliminate resistance upon imposed head-on-trunk rotations when they are asked to relax. It is not, however, clear how neck reflexes to...
Normal subjects can completely eliminate resistance upon imposed head-on-trunk rotations when they are asked to relax. It is not, however, clear how neck reflexes to stretch can be voluntarily suppressed. Reflexive responses might be modified by adjusting the gain of the reflex loop through descending control. Theoretically, necessary corrections upon interfering disturbances during coordinated motor performance requiring the interplay of relaxation/activation may be missing if muscle relaxation is taking place exclusively by this mechanism. It has been alternatively proposed that sensory information from the periphery may be allowed to "neutralize" neck reflexes if it is fed back with opposite sign to the structures driving the reflexes. Six healthy subjects were asked to relax while subjected to head-on-trunk rotations generated by a head motor. After any initial resistance had completely subsided, the head was unexpectedly exposed to "ramp-and-hold" perturbations of up to 2° amplitude and 0.7 s duration. Resistance to stretch consistently reappeared thereupon, suggesting that stretch reflex gain had not been set to zero during the previously achieved complete relaxation. Resistance to perturbations under these circumstances was compared with the forces generated when the same ramp-and-hold displacements were delivered unpredictably to the head held stationary. A quantitative model of neck proprioceptive reflexes suppression has been thus constructed. Gain scheduling or "motor set" cannot sufficiently account for the voluntary reflex suppression during slow passive head rotations. Instead, we propose as underlying mechanism, the "neutralization" of the controlling servo by means of continuous feedback tracking displacement and force signals from the periphery. Head stabilizing neck reflexes can be voluntarily suppressed or activated depending on the task at hand. By applying brief perturbations unexpectedly, both during passive head-on-trunk movements and at rest, we investigated the mechanism of voluntary suppression of resistance to stretch. A physiologically plausible, neuromechanical model of voluntary/reflexive interactions was constructed favoring feedback over reflex gain adjustments. Accordingly, muscle relaxation during imposed head movements is based on sensory feedback similarly to muscle contractions during purposeful movements.
Topics: Adult; Feedback, Sensory; Female; Humans; Male; Models, Biological; Movement; Neck; Proprioception; Reflex; Reflex, Stretch; Young Adult
PubMed: 34907798
DOI: 10.1152/jn.00297.2021 -
Science (New York, N.Y.) Jul 1973Soleus muscles of anesthetized cats were stretched and released by different amounts while their motor axons were stimulated. Muscle force increased, then gave way in...
Soleus muscles of anesthetized cats were stretched and released by different amounts while their motor axons were stimulated. Muscle force increased, then gave way in response to large stretch. In the presence of active stretch reflexes in decerebrate cats, the give in force was absent. We demonstrate that autogenetic reflexes can compensate for variations in muscular stiffness revealed when responses to stretch and release are compared.
Topics: Animals; Cats; Cerebral Decortication; Motor Neurons; Muscle Contraction; Muscle Spindles; Muscles; Reflex; Reflex, Monosynaptic; Reflex, Stretch; Spinal Nerve Roots
PubMed: 4268130
DOI: 10.1126/science.181.4095.182 -
Psychophysiology May 2009Reflexes are modulated by emotions. Much research has revealed that the startle reflexive eyeblink response is modulated by emotion, particularly in response to pictures...
Reflexes are modulated by emotions. Much research has revealed that the startle reflexive eyeblink response is modulated by emotion, particularly in response to pictures of emotional scenes. Investigations of other reflexes are limited. Recently, research suggested that the postauricular reflex in response to a startling noise was modulated by emotion. In particular, pleasant stimuli enhanced the postauricular reflex. However, these first investigations were limited: One experiment demonstrated only a marginal difference between the pleasant stimuli and neutral stimuli and the other lacked the typical neutral scene comparison. The present experiment was designed to assess whether significant emotion versus neutral differences would occur. Results demonstrated that pleasant stimuli, regardless of arousal level, evoked larger postauricular reflex activation than neutral and unpleasant emotional stimuli.
Topics: Arousal; Blinking; Ear Auricle; Emotions; Female; Fixation, Ocular; Humans; Male; Photic Stimulation; Reflex; Young Adult
PubMed: 19226306
DOI: 10.1111/j.1469-8986.2009.00794.x -
Pediatrics Mar 1990The evolution of tone and reflexes from 25 weeks postmenstrual age (gestational age plus chronologic age) to term in a population of 42 surviving infants is described....
The evolution of tone and reflexes from 25 weeks postmenstrual age (gestational age plus chronologic age) to term in a population of 42 surviving infants is described. The infants were born in 1983 at the Johns Hopkins Hospital, had birth weights less than 1300 g, were examined weekly until neonatal intensive care unit discharge, and did not develop cerebral palsy. Lower-extremity flexor tone was first detectable at 29 weeks post-menstrual age by the popliteal angle and heel to ear maneuvers. Flexor tone, recoil, and hyperreflexia were all noted 2 to 3 weeks earlier in the lower extremities (33 to 35 weeks) than in the upper extremities (35 to 37 weeks). Hip tone (35 to 37 weeks) followed knee flexor tone, but preceded shoulder tone (37 to 38 weeks). Trunk tone on ventral suspension emerged closer to term (36 to 40 weeks), and more than half of infants evaluated at term continued to demonstrate head lag when pulled to sitting position. The emergence of the primitive and pathologic reflexes reflects (both in timing and pattern) the evolution of tone: development of the reflexes in the lower extremities precedes that of those in the upper extremities, and development of the distal reflexes precedes that of the proximal. Maturation of tone, deep tendon reflexes, pathologic reflexes, and primitive reflexes occurs in an orderly, sequential manner, with a well-defined pattern: caudocephalad (lower extremities to upper extremities) and centripetal (distal to proximal).
Topics: Child Development; Female; Humans; Infant, Newborn; Infant, Premature; Male; Muscle Tonus; Reflex; Reflex, Abnormal; Reflex, Babinski; Reflex, Stretch
PubMed: 2304800
DOI: No ID Found -
Annales D'oto-laryngologie Et de... 1982Linked to the vestibular reflex, ontologically the most primitive, nuchal and visual proprioceptive afferent impulses heighten perception of movement and the position of... (Review)
Review
Linked to the vestibular reflex, ontologically the most primitive, nuchal and visual proprioceptive afferent impulses heighten perception of movement and the position of the head and body in space. The final goal of these reflexes appears to be maintenance of the visual axis and of posture. They are under cerebellar control which adapts responses according to sensory interactions, and probably increases reactions when a deficiency exists. Functional exploratory tests in patients with positional or postural vertigo should include the study of responses to separate or combined stimulation of these three types of receptor according to the three planes of the semicircular canals.
Topics: Animals; Cerebellum; Humans; Neck; Neural Pathways; Proprioception; Reflex; Vestibule, Labyrinth; Vision, Ocular
PubMed: 7049044
DOI: No ID Found -
Journal of Computational Neuroscience Jun 2011During posture control, reflexive feedback allows humans to efficiently compensate for unpredictable mechanical disturbances. Although reflexes are involuntary, humans...
During posture control, reflexive feedback allows humans to efficiently compensate for unpredictable mechanical disturbances. Although reflexes are involuntary, humans can adapt their reflexive settings to the characteristics of the disturbances. Reflex modulation is commonly studied by determining reflex gains: a set of parameters that quantify the contributions of Ia, Ib and II afferents to mechanical joint behavior. Many mechanisms, like presynaptic inhibition and fusimotor drive, can account for reflex gain modulations. The goal of this study was to investigate the effects of underlying neural and sensory mechanisms on mechanical joint behavior. A neuromusculoskeletal model was built, in which a pair of muscles actuated a limb, while being controlled by a model of 2,298 spiking neurons in six pairs of spinal populations. Identical to experiments, the endpoint of the limb was disturbed with force perturbations. System identification was used to quantify the control behavior with reflex gains. A sensitivity analysis was then performed on the neuromusculoskeletal model, determining the influence of the neural, sensory and synaptic parameters on the joint dynamics. The results showed that the lumped reflex gains positively correlate to their most direct neural substrates: the velocity gain with Ia afferent velocity feedback, the positional gain with muscle stretch over II afferents and the force feedback gain with Ib afferent feedback. However, position feedback and force feedback gains show strong interactions with other neural and sensory properties. These results give important insights in the effects of neural properties on joint dynamics and in the identifiability of reflex gains in experiments.
Topics: Humans; Models, Neurological; Muscle, Skeletal; Nerve Net; Nervous System Physiological Phenomena; Postural Balance; Reflex; Shoulder Joint
PubMed: 20865310
DOI: 10.1007/s10827-010-0278-8 -
Neurophysiologie Clinique = Clinical... May 2015We aimed to analyze functional changes at brainstem and spinal levels in essential tremor (ET), Parkinson's disease (PD) and coexisting essential tremor and Parkinson's...
OBJECTIVE
We aimed to analyze functional changes at brainstem and spinal levels in essential tremor (ET), Parkinson's disease (PD) and coexisting essential tremor and Parkinson's disease (ET-PD).
PATIENTS AND METHOD
Age- and gender-matched patients with tremor (15 ET, 7 ET with resting tremor, 25 ET-PD and 10 PD) and 12 healthy subjects were enrolled in the study. Diagnosis was established according to standardized clinical criteria. Electrophysiological studies included blink reflex (BR), auditory startle reaction (ASR) and long latency reflex (LLR).
RESULTS
Blink reflex was normal and similar in all groups. Probability of ASR was significantly lower in ET-PD group whereas it was similar to healthy subjects in ET and PD (P<0.001). LLR was recorded during voluntary activity in all three groups. LLR II was more common in ET, PD and ET-PD groups. LLR III was far more common in the PD group (n=3, 13.6% in ET; n=4, 16.0% in ET-PD and n=7, 46.7% in PD; p=0.037).
CONCLUSIONS
Despite the integrity of BR pathways, ASR and LLR show distinctive abnormalities in ET-PD. In our opinion, our electrophysiological findings support the hypothesis that ET-PD is a distinct entity.
Topics: Aged; Blinking; Brain Stem; Essential Tremor; Female; Humans; Male; Middle Aged; Parkinson Disease; Pyramidal Tracts; Reflex, Abnormal; Reflex, Startle
PubMed: 25892331
DOI: 10.1016/j.neucli.2015.01.001 -
HNO Jun 2016The laryngeal adductor reflex and the pharyngoglottal closure reflex protect the trachea and lower respiratory tract against the entrance of foreign material. The...
The laryngeal adductor reflex and the pharyngoglottal closure reflex protect the trachea and lower respiratory tract against the entrance of foreign material. The laryngeal expiration reflex and the cough reflex serve to propel foreign material, which has penetrated in the cranial direction. The inspiration reflex, the sniff reflex, and the swallowing reflex are further larynx-associated reflexes. In patients with dysphagia the laryngeal adductor reflex can be clinically tested with air pulses. The water swallow test serves to show the integrity of the cough reflex. The sniff reflex is useful to test the abduction function of the vocal folds. Future studies should address laryngeal reflexes more specifically, both for a better understanding of these life-supporting mechanisms and to improve diagnostic procedures in patients with impaired laryngeal function.
Topics: Diagnostic Techniques, Digestive System; Humans; Laryngeal Diseases; Larynx; Reflex, Abnormal
PubMed: 27240793
DOI: 10.1007/s00106-016-0169-z