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At least 523 records · Page 29Linked to original sources
PubMed1996

Functional significance of the early component of the human blink reflex.

The relationship between the size of the first electromyographic (EMG) component of the cutaneous blink reflex (R1) and onset of eyelid closure in human adults was determined in 4 experiments in which R1 size was varied by different means: change in stimulus intensity, paired stimulation, and warning. Two-phase lid movements were frequently seen, with an early small movement followed by a large rapid movement. All experiments showed that larger R1s were associated with shorter latencies of both movements. This covariation was general across participants and was independent of shifts in the excitability of the blink reflex pathways indexed by R1 latency, R2 latency, and R2 area (R2 is the more prolonged, later EMG component). The results indicate that R1 acts first to evoke an early lid movement and second to facilitate eyelid closure by the later R2 burst. Identification of this second behavioral function for R1 aids the interpretation of other findings and encourages its use as a model system.

Adolescent↗
PubMed2003

Nociceptive-specific blink reflex and glyceryl trinitrate infusion in healthy volunteers.

Glyceryl trinitrate (GTN) is known to induce early headache in healthy humans after intravenous infusion. Moreover, in animal models subcutaneous administration produces an increase in Fos expression in brainstem areas that are involved in trigeminal pain processing. In a double-blind crossover study, we tested the blink reflex before, during and immediately after GTN and placebo intravenous infusion in eight healthy volunteers using a new stimulation electrode that preferentially activates A-delta nociceptive afferent fibres. The initial hypothesis that GTN could induce an increase in the magnitude of the nociceptive blink reflex R2 component by stimulating activity of trigeminal nucleus caudalis wide dynamic range interneurones was not confirmed. Although mild headache was induced in six subjects, there was no significant change between the R2 area under the curve before and after drug vs. placebo.

Adult↗
PubMed2003

The effect of trigeminal nociceptive stimulation on blink reflexes and pain evoked by stimulation of the supraorbital nerve.

The aim of this study was to investigate the effect of painful conditioning stimuli on pain and blink reflexes to supraorbital nerve stimulation. Electromyograph activity was recorded bilaterally from the orbicularis oculi muscles in 13 normal participants in response to low (2.3 mA) and high-intensity (18.6 mA) electrical stimulation of the left supraorbital nerve before, during and after the application of ice to the left or right temple or immersion of the left hand in ice-water for 60 s. The pain evoked by the high-intensity electrical stimulus was greater during painful conditioning stimulation of the ipsilateral temple than during the recovery period afterwards, and was greater than during painful conditioning stimulation of the contralateral temple. These findings imply that spatial summation of nociceptive signals across different divisions of the trigeminal nerve can heighten pain. However, painful conditioning stimulation, particularly to the right temple, strongly suppressed the R2 component of the blink reflex to the low-intensity stimulus, and also suppressed R2 to the high-intensity stimulus. Thus, an inhibitory influence (e.g. diffuse noxious inhibitory controls) appeared to mask ipsilateral segmental facilitation of R2 during ice-induced headache. This finding contrasts with recent electrophysiological evidence of trigeminal sensitization in migraine.

Adult↗
PubMed1994

An experimental model to study the blink reflex.

A model to study the blink reflex in the experimental setting has been established. The behavioral, electrophysiologic, pathologic, and surgical methods and results obtained parallel those utilized and observed in the human and simulate the problem of facial paralysis. The observation that the blink can be elicited in an animal model, with the same stimuli as in humans, strengthens the value of this model, as do the similarities seen in the electrophysiologic recordings of NCV studies. The dual innervation of the rat eye sphincter allows application of the principle of selectively neurectomizing eye branches and "borrowing" motor-nerve fibers from the normal side, without causing eye-sphincter paralysis, a concept employed extensively in cross-facial nerve-grafting procedures in humans with facial paralysis.

Anastomosis, Surgical↗
PubMed1983

[Value of blink reflex studies in neurosurgical problems].

Blinking reflex studies were done in neurosurgical patients with processes in the posterior fossa and idiopathic trigeminal neuralgia. Alterations were found in space occupying, ischemic, and traumatic lesions of the trigemino-facial system. The analysis of the components of the blinking reflex can give hints to the site of the lesion and also to the prognosis of the underlying process.

Adult↗
PubMed1994

Learning of the conditioned eye-blink response is impaired by an antisense insulin-like growth factor I oligonucleotide.

The cerebellum is thought to be critically involved in learning and retention of several types of classically conditioned motor responses. We investigated whether insulin-like growth factor I (IGF-I) may constitute an intercellular mediator of a motor learning task because previous findings indicated that IGF-I from the inferior olive modulates glutamate-induced gamma-aminobutyric acid release by Purkinje cells in the cerebellar cortex. Synaptic plasticity of the Purkinje cell is thought to be instrumental in motor learning. We found that injection of an IGF-I antisense oligonucleotide in the inferior olive elicited a complete inhibition of conditioned eye-blink learning in freely moving rats. This blockage was reversible and recovered when the levels of cerebellar IGF-I returned to normal values. Injection of a sense oligonucleotide did not interfere with the acquisition of the conditioned response. On the other hand, retention of the conditioned response was not impaired by subsequent injection of the IGF-I antisense oligonucleotide, indicating that olivocerebellar IGF-I is essential for the acquisition of the conditioned eye-blink response but is not essential for its retention.

Animals↗
PubMed1995

Inactivation of the superior cerebellar peduncle blocks expression but not acquisition of the rabbit's classically conditioned eye-blink response.

The localization of sites of memory formation within the mammalian brain has proven to be a formidable task even for simple forms of learning and memory. Recent studies have demonstrated that reversibly inactivating a localized region of cerebellum, including the dorsal anterior interpositus nucleus, completely prevents acquisition of the conditioned eye-blink response with no effect upon subsequent learning without inactivation. This result indicates that the memory trace for this type of learning is located either (i) within this inactivated region of cerebellum or (ii) within some structure(s) efferent from the cerebellum to which output from the interpositus nucleus ultimately projects. To distinguish between these possibilities, two groups of rabbits were conditioned (by using two conditioning stimuli) while the output fibers of the interpositus (the superior cerebellar peduncle) were reversibly blocked with microinjections of the sodium channel blocker tetrodotoxin. Rabbits performed no conditioned responses during this inactivation training. However, training after inactivation revealed that the rabbits (trained with either conditioned stimulus) had fully learned the response during the previous inactivation training. Cerebellar output, therefore, does not appear to be essential for acquisition of the learned response. This result, coupled with the fact that inactivation of the appropriate region of cerebellum completely prevents learning, provides compelling evidence supporting the hypothesis that the essential memory trace for the classically conditioned eye-blink response is localized within the cerebellum.

Animals↗
PubMed2005

Blink reflex and auditory speech perception in prelingually cochlear-implanted children.

CONCLUSION: The results of this study show that R- prelingually cochlear-implanted children are not optimal candidates for cochlear implantation. However, if this group are implanted, other rehabilitation methods should be incorporated into their rehabilitation program in order to achieve better results and maximize the efficacy of their prosthesis. OBJECTIVE: To demonstrate that the blink reflex or auropalpebral reflex evaluation can be used as a prognostic factor for the assessment of auditory and speech perception levels in prelingually cochlear-implanted children. MATERIAL AND METHODS: In an observational, analytical, prospective study conducted at a single cochlear implant rehabilitation center in 85 prelingually cochlear-implanted children, the presence or absence of the blink reflex (BR) was evaluated and the results of auditory and speech perception tests were compared between reflex-positive (R+) and reflex-negative (R-) patients. To obtain the BR, four electrodes were applied in both the Nucleus and MED-EL systems and then stimulated by means of current levels higher than the previously detected most comfortable level of the patient until the reflex appeared. Auditory and speech perception levels were measured using the vowels-confusion test and the categorization of auditory perception scale. RESULTS: The mean results of auditory and speech perception tests were significantly higher in R+ compared to R- patients.

Auditory Threshold↗
PubMed2001

Observation distance and blinking rate measurement during on-site investigation: new electronic equipment.

Modern work activities often require an intense and prolonged visual effort on near objects. At the same time, occupational asthenopia caused by accommodation and binocularity overloading is a very common complaint in these working populations. Moreover, blinking rate seems to be a sensitive parameter with 'indoor-near-work operators', possibly increased by both chemical and physical environmental agents and decreased by cognitive effort. In this paper, a new piece of electronic equipment used to measure the observation distance and blinking rate is described.

Air Pollution, Indoor↗
PubMed1996

Accommodation, convergence, pupil diameter and eye blinks at a CRT display flickering near fusion limit.

This study investigates possible effects of temporally modulated light stimulation near critical fusion frequency (CFF) when subjects observe a cathode ray tube (CRT) operated at different refresh rates. Various visual functions were measured in a series of tests of 2.5 min duration. In experiment 1, at a repetition rate of 50 Hz mean pupil size was 0.055 mm smaller than at 300 Hz. The precision of convergence and accommodation in binocular vision was not affected. In experiment 2, 300 Hz was compared with the lowest frequency that did not produce visible flicker for each subject. At the lower rate (55 to 90 Hz), mean accommodation in monocular vision was 0.06 D weaker, median eye blink duration was 6% shorter, and mean eye blink interval was 15% longer. Individual differences and possible fatigue effects of intermittent light at visual display units are discussed.

Accommodation, Ocular↗
PubMed1997

The late blink reflex response abnormality due to lesion of the lateral tegmental field.

We report on a blink reflex abnormality observed in two patients, which provides additional information on the central pathways mediating this reflex. Autopsy was performed in one patient and MRI in the other. In the first patient there was a small lesion at the dorsal middle third of the lateral tegmental field and in the second patient at the level of the dorsal lower third of the medulla oblongata. In both patients the common finding was the absence of the late response (R2) ipsilateral to the side of the lesion, while the R2 response on the unaffected side was normal regardless of the side of the supraorbital nerve stimulation. The R1 responses were normal. This type of blink reflex abnormality has not been reported before and is referred to by us as 'tegmental type' of R2 abnormality. The results led to the conclusions that: (i) the crossed and uncrossed ascending trigeminofacial connections are mediated through the lateral tegmental field; (ii) the uncrossed trigeminofacial connection originates at the level of at least the lower medulla oblongata; (iii) the contralateral R2 response is established by way of an ascending pathway, which crosses the midline at the level of at least the lower third of the medulla oblongata.

Afferent Pathways↗
PubMed1993

Acute effects of the novel antidepressant venlafaxine on cognitive event-related potentials (P300), eye blink rate and mood in young healthy subjects.

Venlafaxine is a novel non-tricyclic antidepressant, which preclinically has demonstrated serotonin, norepinephrine, and dopamine reuptake inhibiting effects. In this study acute effects of single oral doses of placebo, 12.5 mg, 25 mg, and 50 mg venlafaxine on event-related potentials (ERPs), eye blink rate and mood were studied in 16 healthy subjects. ERPs were investigated in an auditory odd-ball paradigm before as well as 3 h after each drug intake. In addition to 17 EEG leads, vertical and horizontal EOGs were recorded. After EOG minimization and visual artefact rejection the peak latencies of the spatial average were determined by an automatic procedure. The applied methods of data acquisition, artefact processing, objective component determination and statistical analysis were successful in describing acute effects of venlafaxine on ERPs in normals. N1 and P2 latencies were not affected. An increase in P2 amplitude in the relevant central and frontal regions was seen, reflecting some effect on automatic information processing. Stimulus evaluation time was not affected, as P300 latency remained unchanged. P300 amplitude was not affected at the relevant central and parietal region. Blink rate was not changed. By means of the adjective checklist a dose-dependent decrease of "extroversion" and "high spirits" and an increase of "introversion" was observed. Our findings suggest that venlafaxine affects human information processing less than would be expected from the more centrally inhibiting classical antidepressants.

Adult↗
PubMed1980

Forces retaining a contact lens on the eye between blinks.

The forces retaining a contact lens on the eye between blinks are analyzed using quasi-static equilibrium equations. The main forces are: (1) the surface tension forces around the contact lens periphery pulling the lens toward the cornea, (2) the reaction pressure force underneath the lens countering the effects of the surface tension, and (3) the weight of the lens. The reaction pressure force on the posterior side of the contact lens arises as a consequence of lubrication phenomenon. The centered lens can never be in static equilibrium. However, since the time period associated with the inertia effect in a thin-film system is much longer than the time between consecutive blinks, a quasi-static analysis is applied.

Adhesiveness↗
PubMed1982

Effects of contact lens deformation on tear film pressures induced during blinking.

The pressures induced in a tear film between a contact lens and the eye during the initial stages of a blink are estimated by means of a flexible slider-bearing model. Calculations are made of the pressure distributions as functions of two nondimensional parameters, one of which is purely geometrical and the other involves the sliding velocity, the viscosity of the tear film, and the flexibility of the lens. For the dimensions and velocities which apply to a typical blink, it is found that the effects of soft lens deformation in reducing pressure can be significant, especially for small tear film thicknesses.

Blinking↗
PubMedDate not supplied

Effect of varying the intensity and train frequency of forelimb and cerebellar mossy fiber conditioned stimuli on the latency of conditioned eye-blink responses in decerebrate ferrets.

To study the role of the mossy fiber afferents to the cerebellum in classical eye-blink conditioning, in particular the timing of the conditioned responses, we compared the effects of varying a peripheral conditioned stimulus with the effects of corresponding variations of direct stimulation of the mossy fibers. In one set of experiments, decerebrate ferrets were trained in a Pavlovian eye-blink conditioning paradigm with electrical forelimb train stimulation as conditioned stimulus and electrical periorbital stimulation as the unconditioned stimulus. When stable conditioning had been achieved, the effect of increasing the intensity or frequency of the forelimb stimulation was tested. By increasing the intensity from 1 to 2 mA, or the train frequency from 50 to 100 Hz, an immediate decrease was induced in both the onset latency and the latency to peak of the conditioned response. If the conditioned stimulus intensity/frequency was maintained at the higher level, the response latencies gradually returned to preshift values. In a second set of experiments, the forelimb stimulation was replaced by direct train stimulation of the middle cerebellar peduncle as conditioned stimulus. Varying the frequency of the stimulus train between 50 and 100 Hz had effects that were almost identical to those obtained when using a forelimb conditioned stimulus. The functional meaning of the latency effect is discussed. It is also suggested that the results support the view that the conditioned stimulus is transmitted through the mossy fibers and that the mechanism for timing the conditioned response is situated in the cerebellum.

Animals↗
PubMed1990

Apomorphine-induced blinking and yawning in healthy volunteers.

Yawning and spontaneous blink rate (SBR) are two physiological reflexes which have been incompletely examined but one neurobiological step of these two behaviours seems, at least in part, dopamine-dependent. The reference dopaminergic agonist, apomorphine hydrochloride (0.5, 1, and 2 micrograms kg-1 s.c.), was compared with a placebo in a double-blind latin-square design, and was shown to induce yawning and increase SBR in a population of eight healthy volunteers. These two behavioral effects were not dose-related. The individual SBR differences were correlated with the individual number of yawns for all the four treatments at the 10-30 min interval. Thus, parallel yawning and SBR behaviour suggests a similar pharmacological mechanism. Apomorphine-induced yawning and blinking may be therefore of use in the evaluation of central dopaminergic pathways in man.

Adult↗
PubMed1982

Long latency components of the jaw jerk and blink reflex in man.

In the present study, the electromyographic (EMG) activity in the masseter and temporal muscles during about 200 ms after chin taps (jaw jerk response) was compared with the EMG activity in the orbicularis oculi after glabella tap (blink reflex). In two of ten subjects components with long latency and duration, analogous to blink reflex components BR2 and BR3, were found in the masseter and temporal muscles. They may represent the mechanical contraction which results in jaw closure. In two of the subjects chin taps were found to elicit late responses in the orbicularis oculi with the same latencies (25-30 and 80-100 ms) as BR2 and BR3 associated with glabella tap.

Adult↗