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Results for “Recruitment, Neurophysiological”

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At least 19 recordsLinked to original sources
PubMed2004

The effect of acupuncture on alpha-motoneuron excitability.

The effect of short duration and sustained manual acupuncture on alpha-motoneuron excitability was studied using the Soleus H-reflex. The acupuncture points GB-34 and SP-9 were needled and stimulated manually. Normalised H-reflex and M-wave recruitment curves were constructed and the ratio of the slope of the ascending part of the H-reflex recruitment curve (Hslp) to the slope of the ascending part of the M-wave recruitment curve (Mslp) was used for assessing changes in alpha-motoneuron excitability. Sustained manual acupuncture caused significant reduction of alpha-motoneuron excitability, while short duration manual acupuncture had no effect. The reduction of alpha-motoneuron excitability following sustained manual acupuncture occurred fifteen minutes after cessation of acupuncture and was still present at 30 minutes. The relationship between perceived intensity of acupuncture sensation (Deqi) and changes in alpha-motoneuron excitability was also studied, but no significant correlation was found. This study indicates that manual acupuncture would be useful in clinical conditions associated with increased alpha-motoneuron excitability and that when using acupuncture for these conditions, higher intensity of perceived acupuncture sensation (Deqi) may not result in greater degree of reduction in alpha-motoneuron excitability.

Acupuncture↗
PubMed1994

The retroperitoneal incision. An evaluation of postoperative flank 'bulge'.

OBJECTIVES: To determine if intercostal nerve injury is related to postoperative flank "bulge" and to determine whether the extent of the retroperitoneal incision is related to the incidence of flank bulge following abdominal aortic aneurysm repair. DESIGN: Bilateral dissection of the 11th intercostal nerve on seven cadavers; neurophysiological evaluation of five patients, three with a flank bulge and two without; and retrospective analysis of the extent of retroperitoneal incision and incidence of postoperative flank bulge in 63 consecutive patients. SETTING: Urban academic medical center. PATIENTS: Sixty-three consecutive patients who underwent retroperitoneal repair of an abdominal aortic aneurysm and neurophysiological evaluation of five volunteer patients. INTERVENTIONS: Retroperitoneal repair of abdominal aortic aneurysms. MAIN OUTCOME MEASURE: Reduction of injury to the 11th intercostal nerve by avoiding extension of the retroperitoneal incision into the intercostal space. RESULTS: Of 14 dissections of 11th intercostal nerves, there were bifurcations of the main trunk within the intercostal space in four, at the tip of the 11th rib in seven, and at least 2 cm distal to the tip of the rib in three. Neurophysiological evaluation revealed iterative discharges, polyphasia, fibrillation potentials, and altered recruitment patterns compatible with intercostal nerve injury in patients with a bulge but not in the opposite abdominal wall musculature or in patients without a bulge. Seven (11.11%) of 63 patients had a bulge. Thirty-one of 63 patients had incisions into the 11th intercostal space in which a bulge developed in six (19.35%). Thirty-two patients had incisions that avoided extension into the intercostal space; a bulge developed in one (0.03%) (P = .53). CONCLUSIONS: Postoperative bulge is related to intercostal nerve injury with subsequent paralysis of abdominal wall musculature. Intercostal nerve injury can be reduced by avoiding extension of the incision into the 11th intercostal space.

Action Potentials↗
PubMed2026

Age-related differences in motor unit behaviours and maximal strength: A systematic review and meta-analysis.

Ageing is associated with a decline in strength; however, the neural mechanisms underpinning these changes remain poorly understood. Motor unit discharge rate (MUDR) and recruitment threshold (MURT) regulate the magnitude of motoneuron output through rate coding and orderly recruitment, while discharge rate variability (MUDRV) reflects the steadiness of motoneuron output. Yet, age-related differences in these properties remain inconsistent across the literature. Therefore, this systematic review and meta-analysis quantified age-related differences in motor unit behaviours and their contribution to maximal isometric strength. Electronic databases (Medline, Embase, Scopus, PsycINFO, Ovid Emcare, CENTRAL, and Web of Science) were searched up to May 2025, yielding 1493 records; of these, 48 studies met the inclusion criteria. Standardised mean differences (SMDs) were calculated using random-effects models to compare older and younger adults, and methodological quality was assessed using the AXIS tool. Older adults exhibited markedly lower maximal strength than younger adults (SMD = -1.01; 95% CI -1.22, -0.79). MUDR was lower in older adults across all contraction intensities, with greater reductions at high forces (> 60% maximal voluntary contraction (MVC): SMD =&#x202f;-0.65; 95% CI -0.96, -0.34) compared to low forces (< 30% MVC: SMD = -0.34; 95% CI -0.50, -0.18). Discharge rate variability was greater (SMD = 0.44; 95% CI 0.15, 0.72), whereas recruitment thresholds relative to MVC were lower (SMD = -0.42; 95% CI -0.80, -0.03) in older adults. Collectively, these findings suggest that age-related alterations in motor unit discharge behaviour may contribute, at least in part, to reduced maximal strength in older adults.

Aging↗
PubMed1984

Evidence of motor neuron involvement in chronic respiratory insufficiency.

Nineteen patients with chronic respiratory insufficiency, mean age 61.4 +/- 12.2, have been investigated with pulmonary function tests, clinical neurological examination and neurophysiological methods including motor and sensory conduction studies and needle electromyography. None of them had conditions known to affect the peripheral nervous system such as diabetes, alcoholism, or uraemia. The motor and sensory conduction studies showed only a reduced mean amplitude of the ulnar nerve SAP and of the compound muscle action potential of the APB and EDB muscles. The EMG was abnormal in 94.7% of the cases and showed an increased percentage of polyphasic potentials and a reduced recruitment pattern of motor units firing at high frequency. The data seem to support the hypothesis of an involvement of motor neurons in this condition although the evidence for a neuropathy is lacking.

Chronic Disease↗
PubMed1976

[Experimental study of vestibular neurectomy].

The authors describe an experimental study carried out on baboons. After unilateral vestibular neurectomy, the behaviour disorders on the one hand, and on the other, modifications and temporal development of reflex muotatic excitability of the spine using Hoffmann's reflex method are analyzed. As far as behaviour is concerned, a four-day period of motor restriction following the operation causes more marked residual disorders in comparison with controls. From the neurophysiological point of view, neurectomy results in seriously disordered spinal reflexes characterized by ipsilateral hypo-excitability developing in there stages: a tw-day initial critical phase during which the disorders are at their worst, a four-day recuperative stage with partial regression of the disorders, finally a chronic compensation stage in which spinal excitability returns to normal after several months.

Animals↗
PubMed1977

Integral storage and voiding reflexes. Neurophysiologic concept of continence and micturition.

It is a common clinical misconception to regard the spinal micturition reflex center as fundamentally overactive and dependent on cerebral inhibition. Initiation and cessation of micturition is simplistically viewed as a manifestation of voluntary withdrawal and resumption of inhibitory corticospinal "regulation''. This view is in conflict with basic neurophysiologic experimental data. Actually, the organization of the micturition reflex is extremely complex. It is affected by multiple sources of facilitative and inhibitory influence, peripheral as well as central. During the past half century, at least twelve reflexes involved in urine storage and coordinated micturition have been described by various neurologic investigators. In this article the integral reflexes are identified and described. A functional organization of the integral reflexes which includes a modern concept of their role in the physiology of urine storage and micturition is presented. It is implicit that overactivity or functional failure of any one or combination of the integral reflexes may cause a significant disorder of lower urinary tract function.

Humans↗
PubMed1994

Independence of soleus H-reflex tests in control and spastic subjects shown by principal components analysis.

Different soleus H-reflex tests are used in the study of neurophysiological mechanisms of motor control. We studied the interdependence pattern of a number of soleus H-reflex tests, i.e., vibratory inhibition, the ratio of the reflex response to direct muscle potential (H/M ratio) and the homonymous recovery curve with a principal components analysis in 48 healthy controls and 38 patients with signs of the upper motoneuron syndrome. In controls, the analysis showed 3 independent principal components (PCs). Vibratory inhibition and H/M ratio loaded on separate components. Late facilitation and late inhibition variables of the recovery curve loaded on the third component due to the positive correlation (P < 0.001) between these variables. In spastic patients the analysis identified 4 independent PCs corresponding with vibratory inhibition, H/M ratio, late facilitation and late inhibition variables, respectively. The findings suggest that the mutual independence of the different soleus H-reflex tests in patients with the upper motoneuron syndrome has retained the control situation to a large extent.

Adolescent↗
PubMed1984

Neurophysiological changes following traumatic spinal lesions in man.

Neurophysiological observations were made on normal subjects and on 57 patients who had had injuries to the spinal cord. The amplitude of the muscle compound action potential (M response) recorded from triceps surae in response to supramaximal stimulation of the tibial nerve was reduced in the patients indicating that there are changes in motor units below the level of a spinal lesion in man. In the patients who were clinically spastic it was found that: (1) The proportion of the triceps surae motoneuron pool reflexly activated either by tapping the Achilles tendon or by stimulating the tibial nerve just below the threshold of the alpha motoneuron axons (H reflex) was greater than in normal subjects. This can be explained by an increase in the excitability of central reflex pathways. (2) Vibration of the tendo Achilles depressed the H reflex less effectively than in normal subjects. This may indicate altered transmission in the premotoneuronal portion of the H reflex pathway. (3) The H reflex elicited 50 and 100 ms after a standardised conditioning stimulus to the tibial nerve and expressed as percentage of the unconditioned reflex was greater than in normal subjects. This could reflect a change in the excitability of motoneurons or of interneurons.

Adolescent↗
PubMed1978

Impaired synaptic potentiation processes in the hippocampus of aged, memory-deficient rats.

A series of neurophysiological experiments was performed on the Schaffercommissural system of the hippocampus of aged and young anesthetized Fischer rats. The aged Fisher rats were previously found to exhibit retention performance deficits. No obvious differences were found between aged and young animals in amplitude, latency, stimulation threshold, or wave forms of typical synaptic responses when these were elicited by control (0.3 Hz) stimulation pulses. Further, the temporal curves of facilitation during a paired-pulse series were not different in aged and young animals. However, aged and young synapses showed consistently different responses during repetitive stimulation. Synapses of aged animals were deficient in frequency potentiation processes during 12 Hz stimulation; and the aged animals exhibited a delayed rise of post-tetanic synaptic potentiation following a 5 sec, 100 Hz stimulation train. Moreover, aged synapses 'exhausted' more rapidly during continuous 4 Hz stimulation. Throughout these studies a biphasic pattern of potentiation was observed during repetitive stimulation (brief potentiation, depression, renewed potentiation). Aged animals were deficient primarily in development of the second phase of potentiation. This pattern suggests an age-related impairment of some secondary process of potentiation, leading to an increased tendency to synaptic depression during and after stimulation. The possibility that the impaired hippocampal synaptic plasticity may be related to reported deficient behavioral plasticity in the aged animals is considered.

Action Potentials↗
PubMed2003

Exploring the neural basis of cognitive reserve.

There is epidemiologic and imaging evidence for the presence of cognitive reserve, but the neurophysiologic substrate of CR has not been established. In order to test the hypothesis that CR is related to aspects of neural processing, we used fMRI to image 19 healthy young adults while they performed a nonverbal recognition test. There were two task conditions. A low demand condition required encoding and recognition of single items and a titrated demand condition required the subject to encode and then recognize a larger list of items, with the study list size for each subject adjusted prior to scanning such that recognition accuracy was 75%. We hypothesized that individual differences in cognitive reserve are related to changes in neural activity as subjects moved from the low to the titrated demand task. To test this, we examined the correlation between subjects' fMRI activation and NART scores. This analysis was implemented voxel-wise in a whole brain fMRI dataset. During both the study and test phases of the recognition memory task we noted areas where, across subjects, there were significant positive and negative correlations between change in activation from low to titrated demand and the NART score. These correlations support our hypothesis that neural processing differs across individuals as a function of CR. This differential processing may help explain individual differences in capacity, and may underlie reserve against age-related or other pathologic changes.

Adaptation, Physiological↗
PubMed1979

Open-biopsy electromyography. Direct correlation of a pattern of excessively recruited, pathologically small motor unit potentials with histologic evidence of neuropathy.

Open-biopsy electromyography (EMG) of two muscles of a 29-year-old man with slowly progressive proximal weakness demonstrated a striking pattern of excessively recruited, pathologically small motor unit potentials. This pattern is usually equated with myopathy. Histologic study of tissue enclosing the recording sites, however, yielded evidence of neurogenic disease alone. In muscle, this included isolated and small groups of atrophic type I, IIA, and IIB fibers, and in intramuscular nerve a loss of myelinated fibers with connective tissue and Schwann cell proliferation. The EMG pattern is considered to reflect a reduced number of activated muscle fibers within motor units due to random neurogenic involvement of terminal axons.

Adult↗
PubMed1989

Relapsing bilateral brachial plexopathy during pregnancy. Report of a case.

We describe a case of relapsing bilateral brachial plexopathy occurring during pregnancy and the postpartum period. This condition is known to occur with a familial predilection, but it has not been previously reported on a sporadic basis. The outcome was poor and associated with several psychosocial consequences.

Adult↗