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At least 631 records · Page 35Linked to original sources
PubMed1971

Blink reflex studies in patients with Parkinsonism before and during therapy.

Electrophysiological analysis of the blink reflex makes it possible to quantitate the reflex changes observed in pathology. The authors therefore propose a `habituation index' to be determined by recording the electromyographic reflex response during stimulation at controlled frequencies. Several populations of subjects were tested. It was confirmed that marked differences in blink reflex habituation exist between normals and patients with Parkinson's disease. It was also found that when patients with Parkinsonism were treated with the classical anticholinergic drugs their habituation index remained virtually unchanged. However, treatment with either l-dopa or amantadine caused a rise in the index in almost all patients tested. On the basis of these findings it is suggested that these two new drugs have a highly similar mechanism of action.

Amantadine↗
PubMed1978

Reflex arc of the first component of the human blink reflex: a single motoneurone study.

Latency variation of consecutive responses of single orbicularis oculi motoneurones in the first component of the electrically elicited blink reflex was 2.6 times larger than that of the H reflex of the soleus muscle fibres. Some motoneurones showed bimodal latency distribution or double responses or both at an interval of about 4-5 ms. Typical first component responses were sometimes obtained by contralateral stimulation. Central conduction time in the brainstem, estimated for 15 motoneurones, was between 2.4 and 6.6 ms. It is concluded that the first component of the blink reflex is conducted through an oligosynaptic arc including one or more interneurones.

Adult↗
PubMed1979

Blink reflexes in severe traumatic coma.

Blink reflexes were studied in 21 patients in coma after severe head injury. Our observations suggest that blink reflexes are a simple, objective, neurophysiological test to evaluate brainstem function. Correlations between these reflexes and the anatomoclinical stanges of coma and the Glasgow coma scale have been established. Presence of the early R1 component shows the integrity of at least a part of the pontine structures. The appearance of the late R2 component is correlated with a better chance of recovery from coma.

Acute Disease↗
PubMed1979

Reciprocal reflex activity in ocular muscles: implications in spontaneous blinking and Bell's phenomenon.

Levator palpebrae (m. lev. palp.) and rectus superior (m. rect. sup.) are two synergistic muscles in vertical gaze movements. However, they show an antagonistic behavior during electrically induced blink and glabellar reflexes. This can be considered as an easy and useful method for their differentiation in the electrophysiological study of certain oculopalpebral motor disorders. Blinking consists of a series of reflex activities, the most outstanding ones being an early m. lev. palp. basal activity inhibition, followed by the activation of the orbicularis oculi muscle and a brief increase in m. rect. sup. activity (reflex Bell phenomenon). This coordinated reflex organization could be perfectly related to that known in other human nociceptive reflexes.

Amyotrophic Lateral Sclerosis↗
PubMed1978

Eye blink and schizophrenia: psychosis or tardive dyskinesia?

The author found abnormalities of ocular movement including abnormal blink rate and blink reflex to glabellar tap in 34 of 44 medication-free schizophrenic patients. It is not clear whether these signs represent part of the pathology of schizophrenia or result from withdrawal of neuroleptic treatment.

Dyskinesia, Drug-Induced↗
PubMed1978

Cyclic alterations of blink reflexes: an EEG and EMG study during wakefulness and sleep.

Studies of the blink reflex were undertaken in twelve normal subjects during wakefulness and different sleep stages. The early R1 and the late R2 components of the reflex were analyzed. R1 was present in only one subject during stage I sleep and subsequently disappeared in stage II to IV. In all subjects, R2 was gradually diminished and totally disappeared during stage IV. During the REM stage, R1 was seen in only four-out-of-twelve subjects but all R2 returned. Alterations of R1 and R2 of the blink reflex during different sleep stages suggest that the underlying mechanism includes both supranuclear and infranuclear activities. Our finding strengthens further the notion of dual hyponogenic mechanisms for sleep.

Adult↗
PubMed1978

The effect of induced hyperthermia on the blink reflex in multiple sclerosis.

In 76 patients with multiple sclerosis, the blink reflex was elicted electrically at normal body temperature and during induced hyperthermia to observe the effect on conduction within the reflex pathway through the brainstem. Special attention was directed to 31 patients with electrophysiologic evidence of reflex slowing, presumably because of demyelination in the reflex pathway. Hyperthermia did not induce any significant changes in mean reflex latency, amplitude, or duration in either the overall group of 76 or in the 31 patients with baseline blink reflex abnormalities. While the mean reflex latency did not change, 13 (33 percent) of 39 abnormal R1 responses from the 31 patients changed by 1.5 msec or more during hyperthermia, whereas change of similar magnitude was noted in only three (3 percent) of 90 normal R1 responses.

Body Temperature↗
PubMed1976

[Neuron activities of the motor cortex during conditioned eye blink reflex in rabbits (author's transl)].

Effects of the tone (CS) on neurons of the motor cortex were investigated in naive, pseudoconditioned, and conditioned rabbits. Conditioning to eye blink reflex was made by a combination of CS and air puff (US). Effects of electrical stimulation of the subcortical structures were also observed on the cortical neurons associated with the conditioned reflex. The results were as follows. (1) Proportion of neurons which significantly increased the firing rate in response to the CS, type E, was higher in the conditioned group than in other two groups. On the other hand, no group difference was found in the proportion of neurons which significantly decreased the firing rate to the stimulus, type I. (2) Most of the type E neurons in the conditioned rabbits began to fire at latencies of about 50 to 100 msec after the CS, preceding about 200 msec to the appearance of the peripheral conditioned responses (EMG). (3) Most of the type E neurons in the conditioned animals were more easily affected by stimulation of the medial geniculate body and the brain stem reticular formation. Based on the results mentioned above, it is concluded that in the rabbits conditioned to the eye blink reflex, excitability of neurons in the motor cortex is enhanced by the tone (CS), and by electrical stimulation to the medial geniculate body and the brain stem reticular formation.

Action Potentials↗
PubMed1977

Diurnal rhythms of visual accommodation and blink responses: implication for flight-deck visual standards.

The major purpose of this study was to determine whether 24-h variations in accommodation responses occur and, if they do, whether they should be considered in setting visual standards for flight-deck tasks. A recently developed servo-controlled optometer and focus stimulator were used to obtain monocular accommodation response data on four college-age subjects. No 24-h rhythm in accommodation was shown. Heart rate and blink rate also were measured and periodicity analysis showed a mean 24-h rhythm for both; however, blink rate periodograms were significant (p less than or equal to 0.003) for only two of the four subjects. Thus, with the qualifications that college students were tested instead of pilots and that they performed monocular laboratory tasks imstead of binocular flight-deck task, it is concluded that 24-h rhythms in accommodation responses need not be considered in setting visual standards for flight-deck task.

Accommodation, Ocular↗
PubMedDate not supplied

[Defensive dominant detected by an unconditioned blinking reflex].

Multiple stimulation of rabbit leg with short DC pulses of both threshold and subthreshold intensities creates in corresponding areas of CNS a focus of excitation with dominant properties: summation, inertia et al. When an unconditioned reflex (blinking) was used as in agent exposing defensive dominant, it was found that summation in the dominant focus may occur without a conjugate inhibition of the subdominant center. During summation the dominant center is not uniform. Depending on the level of excitation in the dominant focus, the subdominant focus may be both in inhibitory state (no blinking in response to the subdominant stimulus) and in a state of enhanced excitation (the reflex to its proper stimulus increases). Multiple pairings of two subthreshold stimulations (of leg and eyelid) result in the establishment of a temporary connection with two-way conductivity.

Animals↗
PubMed1994

Human blink startle during aversive and nonaversive Pavlovian conditioning.

Potentiation of blink startle during aversive and nonaversive Pavlovian single-cue conditioning was assessed in human Ss. In Experiment 1 (N = 89), the conditioning group received paired presentations of a visual conditioned stimulus (CS) and an unconditioned stimulus (US), whereas the control group was presented with a random sequence. The US was an electric shock for half the Ss and a nonaversive reaction time task for the other half. Electrodermal conditioning was evident regardless of the nature of the US, but blink potentiation was found only in the conditioning group that had been trained with the aversive US. These results were replicated in Experiment 2 (N = 65), in which a nonaversive US of increased motivational significance was used. Thus, only aversive conditioning seems to affect the affective valence of the CS, at least as reflected by changes in a skeletal reflex.

Adolescent↗
PubMed1975

Lead-stimulation effects of human cardiac orienting and blink reflexes.

Innocuous prestimulation can inhibit or facilitate a startle reflex in lower animals, depending on its lead time and on whether it is dircrete or continues throughout the lead interval. Similar effects of lead stimulation on the unconditioned blink reflex were found in human subjects, but human subjects also showed an effect not seen in lower animals. Under conditions of temporal and stimulus uncertainty, the presentation of discrete stimuli at lead times that have no effect in rats produced blink facilitation as well as pronounced cardiac decelerations during the lead interval in man. The article suggests that this effect might be mediated by an attentional process and that it could be dissociated from effects produced by a classical arousal mechanism.

Acoustic Stimulation↗
PubMed1984

Persistence of the blink reflex to sudden illumination in a comatose patient. A clinical and pathologic study.

A persistent blink reflex to light (BRL) was observed in a patient who became comatose after a cardiac arrest. Postmortem examination revealed severe hypoxic ganglion cell necrosis of the cerebral and cerebellar cortex, the basal ganglia, the hypothalamus, nuclei in the brain stem, and the superior colliculi. The pretectum was unaffected. These findings suggest that the afferent fibers of the BRL enter the brain stem not in the superior colliculus, but in the pretectum.

Aged↗
PubMed1989

Prognostic value of electrically elicited blink reflex in neonates.

The electrically elicited blink reflex (BR) was evaluated in 80 normal neonates and 12 neonates with neurologic abnormalities. In normal subjects, R1 and bilateral R2 responses were elicited both while awake and in a quiet sleep state. Whereas the R1 response was consistently elicited in the active sleep state, as well as while awake, the ipsilateral R2 response was markedly suppressed and the contralateral R2 response was almost absent. The BR in neonates with neurologic abnormalities showed the following variable results: normal, prolonged latency, or suppressed response at initial recording. Abnormal BRs were detected in most neonates with respiratory or sucking problems. While neonates in whom a suppressed response or prolonged latency persisted for over three months had a poor prognosis, those with normal BRs or early correction of the BR abnormality had almost normal development. The BR appears to be useful not only to evaluate brain-stem function in the neonatal period but also to predict subsequent outcome.

Blinking↗
PubMed1996

Blink reflex recovery curves in blepharospasm, torticollis spasmodica, and hemifacial spasm.

R1 and R2 blink reflex responses to single and paired stimuli were investigated in 23 control subjects, 21 patients with blepharospasm (BSP), 20 patients with torticollis spasmodica (TS), and 23 with hemifacial spasm (HFS). For paired stimuli, we compared measurements of area and peak responses at two and three times R2 threshold. R1 and R2 indices were calculated as the average of the recovery values at 0.5-, 0.3-, and 0.21-s interstimulus intervals to test individual patients. Peak amplitude measurements at three times R2 threshold were optimal. The R2 index was abnormal in 67% of BSP patients, 37% of TS patients, and 50% of HFS patients on the affected side and 20% on the unaffected side. A normal R2 index in one third of patients with BSP may indicate that different pathophysiological mechanisms are involved in this type of focal dystonia.

Adult↗
PubMed1996

Reduced brain stem excitability in mitochondrial myopathy: evidence for early detection with blink reflex habituation studies.

Blink reflex (BR) was studied in 17 patients with histochemically and genetically confirmed mitochondrial myopathy (MM). Fourteen patients had chronic progressive external ophthalmoplegia (CPEO) associated with a mild to moderate craniosomatic myopathy without any symptoms or signs of central nervous system (CNS) involvement, 2 myoclonic epilepsy with ragged red fibers syndrome, and 1 Kearns-Sayre syndrome. The mean latencies of the early (R1) and late (R2) responses were prolonged (P < 0.01 and P < 0.001, respectively), and the corresponding amplitudes decreased (P < 0.001). Increased habituation of the reflex was clearly observed in 10 out of 14 patients tested (71.4%), 9 of whom presented CPEO. These findings suggest that the brain stem reticular network is in a state of basal inhibition which is presumably due to a subclinical impairment of the cerebral cellular metabolism. Multimodal evoked potentials revealed abnormalities suggestive of CNS involvement in 7 out of 17 patients (41.2%), 4 of whom had CPEO. These observations document the validity of BR in detecting clinically silent brain stem impairment in patients with apparently pure MM and provide important clues for a further understanding of the underlying pathophysiology.

Adolescent↗
PubMed1997

Pain-evoked blink reflex.

The electrically evoked blink reflex (BR) consists of an ipsilateral R1 component (R1) at 11 ms and two bilateral components R2 at 33 ms and R3 at 83 ms. It is still unclear whether the R2 is mediated by activation of tactile or nociceptive afferents. For testing the nociceptive hypothesis, nociceptors of the supraorbital nerve were selectively activated by infrared laser stimuli in 10 subjects. Only painful laser stimuli evoked a bilateral early polyphasic BR response (LR2) at 71 ms. Stimulation of infraorbital and mental nerve dermatomes was equally effective. A late bilateral reflex response at 130 ms was occasionally observed. Regarding the nociceptor activation time of about 40 ms, onset latencies were within the range of the electrically evoked R2 and R3, respectively. The good accordance of R2 and LR2 may be due to activation of identical nociceptive fibers or to convergence of electrically evoked tactile and laser-elicited nociceptive input onto common multireceptive neurons.

Adult↗
PubMed1999

Blink reflex induced by controlled, ballistic mechanical impacts.

The blink reflex was induced by a defined mechanical impact covering the range from light touch to a hard, painful stroke, and by an electrical current. In both modes of stimulation, the R3--but not the R2--thresholds were correlated with subjective pain thresholds, suggesting a connection between R3 and nociceptor activation. However, R3 magnitude did not increase systematically with increasing levels of subjectively felt pain. The R3, induced by painful impacts, habituated quickly and was strongly affected by attention. The functional significance of the R3 component is discussed.

Adult↗