Descriptive studies of H-reflex recovery curves in psychiatric patients

Relationships Between Hoffman Reflex Parameters, Trait Stress, and Athletic Performance

This study evaluated the relationships between trait stress, Hoffman reflex, and performance among 36 healthy amateur male athletes. We first obtained a trait stress questionnaire from participants and then assigned them to high- and low-stress groups. We next recorded Hoffman reflex data from the soleus and lateral gastrocnemius muscles and then examined their athletic performance on testing protocols separated by a 72-hour washout period. Performance testing utilized vertical jump height, 20 -m sprint time, and standing stork tests. There were significant correlations between (a) the standing stork test, vertical jump height, and trait stress and (b) H_max/ M_max ratios, threshold intensity ( H_th), the intensity of the H_max, and the intensity of the H_last. H_th, the intensity of H_max, and the intensity of H_last were significantly higher among the low-stress compared with the high-stress participant groups ( p < .05), despite participants' similar training history. We suggest that self-perceived psychological stress affects performance through neural adaptation.

The H-Reflex as a Biomarker for Spinal Disinhibition in Painful Diabetic Neuropathy

PURPOSE OF REVIEW

Neuropathic pain may arise from multiple mechanisms and locations. Efficacy of current treatments for painful diabetic neuropathy is limited to an unpredictable subset of patients, possibly reflecting diversity of pain generator mechanisms, and there is a lack of targeted treatments for individual patients. This review summarizes preclinical evidence supporting a role for spinal disinhibition in painful diabetic neuropathy, the physiology and pharmacology of rate-dependent depression (RDD) of the spinal H-reflex and the translational potential of using RDD as a biomarker of spinally mediated pain.

RECENT FINDINGS

Impaired RDD occurs in animal models of diabetes and was also detected in diabetic patients with painful vs painless neuropathy. RDD status can be determined using standard neurophysiological equipment. Loss of RDD may provide a clinical biomarker of spinal disinhibition, thereby enabling a personalized medicine approach to selection of current treatment options and enrichment of future clinical trial populations.

Schizophrenia and amyotrophic lateral sclerosis

Schizophrenia and amyotrophic lateral sclerosis (ALS) are central nervous system (CNS) disorders of unknown etiology. The association of these two disorders has been infrequently reported in the literature, but is not a rare occurrence. Various neuromuscular abnormalities involving the alpha-motor neuron have been described in some patients with schizophrenia. This report reviews the literature on schizophrenia, psychosis, and ALS and describes two additional cases of schizophrenia associated with ALS. The possibility that the neuromuscular dysfunction in schizophrenia may predispose to ALS and provide an explanation for the association of these two disorders is discussed. Additional research data are needed to test this hypothesis.

Spinal motoneuronal excitability in hyperkinesis: effects of the Jendrassik manoeuvre

H-reflex recovery functions and homosynaptic depression curves were studied in unmedicated hyperkinetic and control children in the presence and absence of the Jendrassik manoeuvre. The Jendrassik manoeuvre failed to affect recovery function reflex amplitude across or within groups, but reflex amplitude was augmented in the homosynaptic depression procedure for hyperkinetic children who failed to show recovery function facilitation. The absence of Jendrassik-associated reflex facilitation in children during the recovery function and during selective homosynaptic depression rates may reflect developmental influences on processes underlying this phenomenon. However, reflex augmentation in non-facilitating hyperkinetic subjects suggests that these processes are present in children and can be revealed under conditions of decreased motoneuronal excitability. These findings suggest that reduced gamma-efferent drive may contribute to decreased motoneuronal excitability observed in hyperkinetic children, but the possible role of other Jendrassik-activated influences, such as coactivation of alpha and gamma motoneurons or selective activation of alpha motoneurons by processes independent of increased gamma-efferent drive, cannot be excluded.

Specific imbalance of right and left sided motor neuron excitability in schizophrenia

Fifty-three psychiatric patients, 16 with schizophrenia, 19 with affective disorder, and 19 with schizo-affective disorder were diagnosed by Research Diagnostic Criteria. Hoffmann reflex recovery curves were measured in the right and left legs of each patient. In both affective disorder and schizo-affective disorder, recovery curve height in the right and left legs was highly correlated. In schizophrenia, recovery curve height in the right and left legs was not correlated. These results demonstrate a right-left asymmetry in motor neuron excitability specific to schizophrenia. The findings are compatible with a deficit in hemispheric transfer that is unique to schizophrenia. Other interpretations can be made, including diffuse cortical or subcortical dysfunction in schizophrenia which disrupts transfer or interpretation or intrahemispheric communication.

Effect of 5-hydroxytryptophan on H-reflex recovery curves in normal subjects and patients with affective disorders

The effect of the serotonin precursor DL-5-hydroxytryptophan (5-HTP) on the Hoffmann reflex recovery curve (HRRC) was studied in normal subjects and patients with affective illness. 5-HTP significantly decreased the HRRC in normal controls and in depressed and manic patients receiving treatment with lithium or antidepressants. 5-HTP increased the HRRC in unmedicated depressed and manic patients. These results provide further evidence for a serotonergic abnormality in the affective disorders.

Variations in the Hoffmann reflex recovery curve related to clinical manifestations of schizoaffective disorder

Recovery curves of the Hoffmann reflex (H reflex) were measured in both legs of 10 unmedicated inpatients with schizoaffective disorder, depressed type. Neither recovery curve height of the right leg nor that of the left leg was significantly correlated with clinical psychopathology, although a consistent negative relation was noted between recovery curve height of the left leg and psychopathology. Right-left differences in recovery curve height significantly correlated with both Brief Psychiatric Rating Scale and Hamilton Rating Scale for Depression ratings of psychopathology, such that relative elevation of the recovery curve of the right leg or relative lowering of the recovery curve of the left leg correlated with symptom severity. Three patients who later developed psychotic symptoms when treated with bupropion, a dopaminergic agent, had lower recovery curves, indicative of increased central dopaminergic activity. Relatively lower left-sided recovery curves may reflect increased dopaminergic activity on the right side of the brain in schizoaffective disorder, compared to the left in schizophrenia.

Spinal motoneuronal excitability during wakefulness and non-REM sleep in hyperkinesis

Variations in spinal motoneuronal excitability were assessed during wakefulness and non-REM sleep in hyperkinetic and normal children by determining the recovery cycle of the H-reflex following a conditioning stimulus. Reflex facilitation which generally occurs 100-300 msec after a conditioning stimulus was markedly reduced during sleep in both groups and during wakefulness as well in hyperkinetic subjects. Among possible mechanisms which might underlie the observed reductions in facilitation, emphasis is placed on decreased central excitability resulting from depressed fusimotor activity.

Effect of chlorpromazine on H-reflex recovery curves in normal subjects and schizophrenic patients

This study sought to determine the effect of chlorpromazine (CPZ) on a physiological measure, the H-reflex recovery curve (HRRC) and to determine whether the effect is different in normal subjects and schizophrenic patients. Eleven normal control subjects and 14 patients were administered 12.5 and 25.0 mg CPZ by IM injection. On the average. HRRCs measured 90 min after the injections were lower compared to pre-injection levels in both groups, at both doses. In general, the higher dose was more effective in both groups. Half of the patients, however, failed to respond to 12.5 mg, indicating that some schizophrenics are less sensitive than normals to CPZ. These results indicate that excessive dopamine activity or sensitivity may underlie abnormally high HRRCs in unmedicated psychotic patients.

Spinal motoneuronal excitability in hyperkinesis: H-reflex recovery function and homosynaptic depression during wakefulness

Variations in amplitude of the spinal monosynaptic H-reflex were examined during relaxed wakefulness in three unmedicated groups of subjects, hyperactive children (n=5), an age-matched group of control children (n=5), and a group of young adults (n=10), using techniques involving equal intensity percutaneous stimuli delivered in pairs or trains at varying rates. The paired-stimuli procedure generates a recovery function, the outstanding features of which are early depression, a peak of facilitation occurring between 100-300 msec, and complete recovery by 2-5 sec. Trains of stimuli delivered at rates greater than or equal to 1/sec effect a reduction in reflex amplitude which is termed homosynaptic depression. Both procedures revealed differences between hyperkinetic children and comparison groups. The paired-stimulus technique revealed a generalized reduction in excitability for hyperkinetic children for intervals extending up to 800 msec. In particular, hyperkinetic children were characterized by a significantly increased variability at the longer stimulus intervals. Hyperkinetic children also showed a more rapid reduction in reflex amplitude to initial stimuli in stimulus trains delivered at rates greater than or equal to 1/sec. Trains of stimuli at rates effecting facilitation in terms of the paired stimulus technique, i.e., 3,4 and 5/sec, revealed sustained amplitude enhancement for control subjects only. The recovery function data are consonant with spinal motoneuronal hypoexcitability in hyperkinetic children. Possible neruophysiological and neurochemical mechanisms underlying the reduced capability of hyperkinetic children to respond to rapidly delivered, repetitive stimuli are discussed.