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PubMed2004

Electromyographic assessment of blink reflexes correlates with a clinical scale of depth of sedation/anaesthesia and BIS during propofol administration.

BACKGROUND: General anaesthesia is characterized by loss of consciousness, amnesia and obtundation of reflex responses to noxious stimuli. Quantifying the blink reflex may reflect the depression of reflex arches induced by anaesthetics and thus being informative on the anaesthetic state. METHODS: The relation between the electrically evoked blink reflexes and the depth of sedation and anaesthesia induced with intravenous propofol was investigated. Twenty patients received propofol by target-controlled infusion to create a stepwise deepening of sedation and anaesthesia. Depth of anaesthesia was assessed using the observer's assessment of anaesthesia and sedation (OAAS) scale, and by bispectral EEG analysis (BIS). Probit analysis was used to estimate the predicted propofol effect site concentrations producing unconsciousness, no response to noxious stimulation, and loss of blink reflex components. RESULTS: Latency of the first (R1) and second (R2) blink component increased, whereas duration and area decreased with increasing depth of sedation and anaesthesia. A reasonably strong correlation between OAAS and the areas of R1 and R2 components was found (Spearman's rho = 0.92 and 0.89). The areas of R1 and R2 and the OAAS also correlated with BIS (Spearman's rho = 0.91, 0.88 and 0.90). EC(50) and EC(95) for loss of R1 were 2.8 (95% CI: 2.5-3.2) micro g/ml and 4.6 (95% CI: 4.1-5.5) micro g/ml, respectively. CONCLUSIONS: Our results suggest that the differential sensitivity of the components of the blink reflex could be useful in monitoring depth of sedation and light levels of anaesthesia during the administration of propofol. Both OAAS and BIS correlate similarly with the blink reflex components.

Adult↗
PubMed1999

Blink reflex R2 changes and localisation of lesions in the lower brainstem (Wallenberg's syndrome): an electrophysiological and MRI study.

OBJECTIVES: Pathways of late blink reflexes are detected by high resolution MRI. Electronically matched stroke lesions superimposed to an anatomical atlas show the suspected course. METHODS: Fifteen patients with infarction of the lower brainstem, MRI lesions and electrically elicited blink reflexes were examined. The involved structures in patients with R2 and R2c blink reflex changes were identified by biplane high resolution MRI with individual slices matched to an anatomical atlas at 10 different levels using digital postprocessing methods. RESULTS: The blink reflexes were normal in five of 15 patients (33%) and showed loss or delay of R2 and R2c to stimulation ipsilaterally to lesion (R2-i and R2c-i) in eight (53%). Loss or delay of R2-i/R2c-i was seen in lesions covering the entire trigeminal spinal tract and nucleus (TSTN) at at least one level. These infarctions were located more dorsally within the medulla. Patients with normal blink reflexes showed lesions sparing or involving the TSTN only partially. They more often had incomplete Wallenberg's syndromes and MRI lesions were located more ventrally. CONCLUSIONS: Using digital postprocessing MRI methods it was possible to identify central pathways of late blink reflex in patients with Wallenberg's syndrome. This method is suggested as a new approach to identify incompletely understood functional structures of the brainstem.

Aged↗
PubMed2002

The physiological mechanisms of 2 Hz electroacupuncture: a study using blink and H reflex.

Our previous studies have shown that the cerebral cortex modulates the physiological mechanisms of acupuncture. However, the role of the brain stem and spinal cord in acupuncture remains unclear. The present study investigated the action of the brain stem and spinal cord in acupuncture. A total of eight healthy adult volunteers were studied. Electrical stimulation of the supraorbital nerve in the supraorbital foramen was used to evoke the blink reflex. Electrical stimulation of the posterior tibial nerve in the right popliteal fossa was used to evoke the H reflex. Electroacupuncture (EA) of 2 Hz was applied to the Zusanli acupoint in the right or left leg. The area of the R1 and R2 components of the blink reflex, and the greatest H/M ratio and H-M interval of the H reflex were measured before EA, during EA and at various post-EA periods. These data were analyzed quantitatively by a computerized electromyographic examination system. The results indicate that EA did not change the R1 and ipsilateral R2 components of the blink reflex. EA depressed the contralateral R2 component of the blink reflex 10 minutes and 40 minutes after the start of EA, but not after 5 minutes. EA applied to the Zusanli acupoint did not change the H/M ratio or the H-M interval of the H reflex. The results of this study indicate that 2 Hz EA of the Zusanli acupoint does not change the R1 component of the blink reflex, and the H/M ratio and the H-M interval of the H reflex, suggesting that 2 Hz EA does not change the monosynaptic reflex in the brain stem and spinal cord in humans. We also found that EA at 2 Hz depressed the contralateral but not the ipsilateral R2 component of the blink reflex, suggesting that longer pathways, perhaps including the cerebral cortex, may play a role in the physiological mechanisms responsible for the effectiveness of acupuncture.

Adult↗
PubMed2000

Blink-perturbed saccades in monkey. II. Superior colliculus activity.

Trigeminal reflex blinks evoked near the onset of a saccade cause profound spatial-temporal perturbations of the saccade that are typically compensated in mid-flight. This paper investigates the influence of reflex blinks on the discharge properties of saccade-related burst neurons (SRBNs) in intermediate and deep layers of the monkey superior colliculus (SC). Twenty-nine SRBNs, recorded in three monkeys, were tested in the blink-perturbation paradigm. We report that the air puff stimuli, used to elicit blinks, resulted in a short-latency ( approximately 10 ms) transient suppression of saccade-related SRBN activity. Shortly after this suppression (within 10-30 ms), all neurons resumed their activity, and their burst discharge then continued until the perturbed saccade ended near the extinguished target. This was found regardless whether the compensatory movement was into the cell's movement field or not. In the limited number of trials where no compensation occurred, the neurons typically stopped firing well before the end of the eye movement. Several aspects of the saccade-related activity could be further quantified for 25 SRBNs. It appeared that 1) the increase in duration of the high-frequency burst was well correlated with the (two- to threefold) increase in duration of the perturbed movement. 2) The number of spikes in the burst for control and perturbed saccades was quite similar. On average, the number of spikes increased only 14%, whereas the mean firing rate in the burst decreased by 52%. 3) An identical number of spikes were obtained between control and perturbed responses when burst and postsaccadic activity were both included in the spike count. 4) The decrease of the mean firing rate in the burst was well correlated with the decrease in the velocity of perturbed saccades. 5) Monotonic relations between instantaneous firing rate and dynamic motor error were obtained for control responses but not for perturbed responses. And 6) the high-frequency burst of SRBNs with short-lead and long-lead presaccadic activity (also referred to as burst and buildup neurons, respectively) showed very similar features. Our findings show that blinking interacts with the saccade premotor system already at the level of the SC. The data also indicate that a neural mechanism, rather than passive elastic restoring forces within the oculomotor plant, underlies the compensation for blink-related perturbations. We propose that these interactions occur downstream from the motor SC and that the latter may encode the desired displacement vector of the eyes by sending an approximately fixed number of spikes to the brainstem saccadic burst generator.

Animals↗
PubMed2001

Blink artifact elimination in electroencephalographic records based on discrete cosine transform domain modeling.

A method for eliminating blink artifacts that contaminate electroencephalographic (EEG) records is introduced. The proposed method enables a direct estimation of blink artifacts without the use of the simultaneously recorded electroculargraphic (EOG) signal. The estimation of blink artifacts in the EEG was achieved by modeling in the discrete cosine transform (DCT) domain. The DCT coefficients of the blink artifact were sufficiently represented by a system transfer function with a low model order of 4. Two cases were investigated: one was blink artifact elimination for the background EEG and the other was for the somatosensory evoked potentials. The effectiveness of the proposed method was demonstrated in an experimental study based on actual EEG data of 11 healthy subjects. The simplicity and effectiveness of the proposed method suggest that blink artifact elimination using DCT domain modeling can possibly be applied in various areas of neuroscience for improving EEG quality.

Adolescent↗
PubMed2006

Serial measurements of higher-order aberrations after blinking in normal subjects.

PURPOSE: To investigate sequential changes in the optical quality of normal eyes associated with blinking. METHODS: Ocular higher-order aberrations (HOAs) were measured sequentially by using a wavefront sensor for 30 seconds in 20 eyes of 20 normal subjects. During the measurement, subjects were forced to blink every 10 seconds. The obtained aberration data were analyzed in the central 4-mm diameter for coma-like, spherical-like, and total HOAs up to the sixth-order Zernike polynomials. RESULTS: The serial changes in the HOAs with blinking were classified into four groups by pattern: stable (25%), small-fluctuation (45%), sawtooth (20%), and others (10%). In the subjects with the sawtooth pattern, the total HOAs increased significantly (P < 0.001, one-way repeated-measures ANOVA) with time between blinks. Increased total HOAs and coma-like aberrations in the subjects with the sawtooth pattern suggested that the inferosuperior asymmetric change in tear film thickness is responsible. CONCLUSIONS: Dynamic changes in HOAs after blinking showed variations even in clinically normal subjects. Serial measurements of HOAs may be useful in evaluating the dynamic changes in tear film and the effects on the quality of vision after blinking.

Adult↗
PubMed1994

Blink rate: a possible measure of fatigue.

The literature on blink rate as a measure of fatigue is reviewed. The evidence of increases in blink rate as a function of time on task is compelling. However, variables other than time on task also affect blink rate. These variables range from perceptual demandingness of the task to cognitive variables. Other aspects of blinking, such as flurries of blinks, timing with respect to information-processing demands, and blink closure duration, are reviewed as additional variables sensitive to task demands and fatigue effects.

Blinking↗
PubMed2004

No evidence of the usefulness of eye blinking as a marker for central dopaminergic activity.

This study aimed to evaluate eye blinking as a marker for central dopaminergic activity by investigating the effects of sulpiride (D2-antagonist) and lisuride (D2-agonist) on spontaneous eye blinks. Twelve healthy subjects were included in a randomized, double-blind, placebo-controlled, three-period crossover trial. They received sulpiride 400 mg, lisuride 0.2 mg and placebo on different occasions. Eye blinks, prolactin, finger tapping, eye movements and visual analogue scales were measured at baseline and regularly for 12 h after administration. No effect of sulpiride or lisuride was observed on the number of eye blinks. Sulpiride caused an increase in prolactin (643 U/ml) [confidence interval (CI) 549-737). Lisuride caused a decrease in smooth pursuit eye movements (-4.1%) (CI -7.3 to -0.9) and visual analogue scales for mood (-2.1 mm) (CI -3.7 to -0.4). Spontaneous eye blink rate was not affected by sulpiride and lisuride, which makes eye blinking not suitable as a marker for central D2 activity.

Adult↗
PubMed2005

Nerve stimulation for regional anesthesia of the face: use of the blink reflex to confirm the localization of the trigeminal nerve.

UNLABELLED: A blink reflex is a bilateral eyelid closure in response to nociceptive stimuli. We hypothesized that elicitation of a blink by a stimulating needle may enhance performing regional anesthesia of the face. Thirty outpatients undergoing cutaneous surgery of the face were studied. A 2.5-cm insulated beveled stimulating needle was inserted at the emergence of the infraorbital nerve. On elicitation of a bilateral blink with 0.5 mA of stimulating current, bupivacaine 0.5% 3-7 mL was injected. Operative conditions were excellent. Blink response can be used to localize superficial branches of the trigeminal nerve. Elicitation of a blink response during nerve stimulation results in successful trigeminal block. IMPLICATIONS: Elicitation of a blink response during nerve stimulation results in successful trigeminal block.

Aged↗
PubMed2001

Spontaneous blinks as a criterion of visual fatigue during prolonged work on visual display terminals.

Visual fatigue caused by prolonged work viewing a Visual Display Terminals (VDT) and of work reading a hard-copy were assessed by electromyogram (EMG) waveform and electrooculogram (EOG) waveform in spontaneous blinks as objective criteria, and by questionnaire of subjective feeling, and by task performance. The duration and the amplitude of the EMG of the orbicularis ocular muscle on the right side and the EOG of the vertical direction to the eyelid were measured for 10 subjects who participated in a figure task consisting of the addition of single-digit numbers on a VDT work or a work with a hard-copy. The mean values of the duration and the amplitude of the EMG and the EOG were evaluated by the averaging of 10 waveforms of the spontaneous blinks for all subjects. The time lag from the EMG to the EOG in the process of the generation of spontaneous blinks was also analyzed. These five parameters were evaluated during the work time. The mean values for the duration of the EMG increased gradually during the work time, but the amplitude did not show significant difference between the prework and a work time. There was no significant change of the duration of the EOG, but the mean amplitude of the EOG decreased as the work time progressed, and the time lag significantly extended. The blinks frequency increased relatively when using a VDT. The rate of fluctuation for these parameters was higher during use of a VDT than use of a hard-copy. The time lag at five hours of VDT work was extended by 90% based on the value at the pre-work. The symptoms of general fatigue and fatigue of the eyes increased linearly during the VDT work for six hours. The results indicated a significant correlation between the objective parameters for the activity of the spontaneous blinks, i.e., duration and amplitude of EMG and EOG, and the time lag between EMG and EOG, and the subjective feeling was recognized in the time course of the task. These experimental results suggested that the parameters regarding the EMG and the EOG for the spontaneous blinks were effective indices for assessing visual fatigue during prolonged VDT work.

Adult↗
PubMed2004

Comparison of blinking behavior during listening to and speaking in Japanese and English.

Blinking behavior during conversation may be different between conditions in listening and responding to questions because sifting attention from external to internal is possibly associated. The purpose of this study was to compare blinking behavior, duration, heart rates, and mental states during the tasks of listening to and responding to questions in Japanese and English. Participants were 67 (35 men and 32 women) undergraduate students. Blink rate while responding to questions in English did not differ from that while responding to questions in Japanese, but blink rate while listening to questions in English was significantly reduced compared to that while listening to Japanese. While anxiety and uneasiness were increased by the English conversation, blink rate and heart rate were decreased. Blinking behavior may be related to thinking and attention.

Adult↗
PubMed2000

[Dissociation of voluntary eye closure--to keep the eyes closed and to blink--following right hemisphere stroke].

We report a case of a unique eye sign following right hemispheric infarction. This patient was a 78 year old right-handed woman. There was a history of a left hemispheric stroke 1 year previously. On admission, she showed left hemianopia, dysarthria, mild left central facial paresis, bilateral sensory deficit and quadriparesis which were marked on the left side. Babinski sign was elicited on the left. She did not have anosognosia or visual neglect. She had mild orofacial apraxia, but ideomotor and ideational apraxia was absent. There was no motor impersistence. Magnetic resonance imaging of the brain revealed a recent infarction in the territory of the right middle cerebral artery and an old infarction in the left tempro-parietal lobe. The patient could not open her eyelids to verbal command or voluntarily until about two weeks later, when she became able to open her eyes but showed difficulty keeping her left eye closed. She was aware of this problem and could repeat the command and comprehend what was requested to her. On verbal command to close the eyes, her right eye would be closed continuously and excessively and the left eye would only blink. When requested to blink, however, she could blink correctly without excessive eye closure. Spontaneous, reflex and voluntary blinking were normal. Her eyes were closed normally during sleep. Blepharospasm was not seen. The patient showed a striking dissociation between a failure to close her eyes continuously and a preserved ability to blink voluntarily. We suggest that her ability to contract palpebral portion of her left orbicularis oculi muscle is preserved. Regarding the mechanism of the voluntary eye closure system, separate control mechanisms should exist on closing eyes continuously and blinking.

Aged↗
PubMed2002

Blink reflex in the prediction of outcome of idiopathic peripheral partial facioparesis: follow-up study.

AIM: To determine the value of the blink reflex as a predictor of outcome of idiopathic peripheral partial facial paresis. METHOD: The study included 30 patients suffering from acute idiopathic peripheral facioparesis and 30 age- and sex-matched healthy controls. Patients with symptomatic disease were excluded on the basis of neuroradiologic and laboratory findings. We stimulated the supraorbital foramen and recorded the evoked response from both orbiculares oculi muscles. We measured the ipsilateral early phasic component (R1) and bilateral late tonic component (ipsilateral R2 and contralateral R2) immediately, and a week and 6 months after the first test. RESULTS: In the acute phase of idiopathic peripheral partial facioparesis, the blink reflex showed slightly prolonged latencies and greatly reduced amplitudes of both R1 and R2 and the normal latencies and amplitudes of R2. All subjects showed clinical symptoms and typical electromyographic (EMG) changes, whereas 24 had blink reflex abnormalities. One week after the onset, all patients were still symptomatic and showed EMG changes, but blink reflex abnormalities remained in only 11 patients. Six months after the onset, 21 patients became asymptomatic and showed no EMG changes, 7 had no clinical symptoms but showed chronic neurogenic EMG changes, whereas 2 showed both clinical symptoms and EMG changes. Blink reflex abnormalities were observed in 6 patients. The amplitudes of R1 immediately and one week after the onset were the best predictors of residual motor deficit. CONCLUSION: Blink reflex is a useful tool for follow-up and recovery prognosis in patients with partial idiopathic facioparesis, especially in the early recovery phase.

Adult↗
PubMed1992

[Localization of level of lesions in internuclear ophthalmoplegia through assessment of masseter and blink reflex].

The masseter and blink reflexes were investigated in 100 patients with internuclear ophthalmoplegia due to multiple sclerosis (58 patients) or lacunar brainstem infarction (42 patients). In unilateral internuclear ophthalmoplegia, 38 of 60 patients (63.3%) had masseter reflex abnormalities, two patients (3.3%) showed changes of the blink reflex R1 component, and 13 patients (21.7%) combined alterations of the masseter reflex and the blink reflex R1 component. 46 (86.8%) of these 53 patients with electrophysiological abnormalities had unilateral changes, which were ipsilateral to the medial longitudinal fasciculus lesion in 42 patients (91.3%). In bilateral internuclear ophthalmoplegia, 24 of 40 patients (60.0%) had abnormalities of the masseter reflex, two (5.0%) showed changes of the blink reflex R1, and nine (22.5%) combined alterations of the masseter reflex and the blink reflex R1 component. 20 (57.1%) of these 35 patients with electrophysiological abnormalities had bilateral changes. Thus, masseter reflex abnormalities indicating midbrain lesions were seen in 63.3% and 60.0%, respectively, of unilateral and bilateral internuclear ophthalmoplegia. Blink reflex R1 component changes with or without impairment of the masseter reflex indicating rostral pontine to midpontine lesions occurred in 25.0% and 27.5%, respectively. These figures correspond to the results of postmortem examinations and to theoretical considerations based on the length of the medial longitudinal fasciculus.

Adult↗
PubMed1992

Increases in excitability of neurons of the motor cortex of cats after rapid acquisition of eye blink conditioning.

Measurements were made of resting potentials, input resistance, and excitability to intracellularly applied, depolarizing current pulses in neurons of the pericruciate cortex of conscious cats before and after acquisition of a rapidly conditioned eye blink reflex (CR). Neuronal excitability increased after conditioning, and an increased input resistance was found to be correlated with the increased level of excitability. No associated changes were found in resting potentials as a consequence of conditioning. When cells were divided into groups according to the latency of spike activity elicited by a click conditioned stimulus (CS) in relation to four separate excitatory EMG components of the compound blink CR, excitability increases were found in cells with increased spike activity at alpha 1 (8-40 msec), alpha 2 (40-72 msec), beta (72-112 msec), and gamma (112-160 msec) latencies after delivery of the CS. Also, the proportion of cells with high excitability (less than 0.7 nA required for spike elicitation) was increased at each latency period after conditioning. Increases in later components of spike discharge could also be found in the cells with increases in earlier components of discharge and increased excitability. The findings suggested that excitability increases facilitated a responsiveness to the CS that supported production of long- as well as short-latency components of the blink CR. Many of the changes in neuronal properties found after rapid eye blink conditioning, such as the increases in excitability and resistance and in the proportion of CS-excitable cells, resembled changes found earlier after acquisition of a slowly developing Pavlovian blink CR, using the same click CS and tap unconditioned stimulus without addition of a hypothalamic stimulus. The possibility should be considered that the (10-100 times) more rapidly acquired form of eye blink conditioning does not represent a different form of conditioning, but instead a change in the rate of conditioning supported by the more rapid production of increases in neural excitability.

Animals↗
PubMed1991

Upper eyelid movements measured with a search coil during blinks and vertical saccades.

Upper eyelid movements were recorded in nine human subjects by mounting a miniature coil of wire directly on the eyelid and subjecting the search coil to a vertically directed alternating magnetic field. The metrics of blinks and lid movements accompanying saccades were described by "main sequence" relationships, linking maximum velocity to amplitude and duration to amplitude. In general, lid movements were faster than those reported previously in the literature, but there was considerable intersubject variability. On average, the main sequence relationships for blinks were independent of either starting lid position or whether the blinks were generated spontaneously, reflexively, or voluntarily. For the down phase of the average blink, both the maximum velocity and duration increased almost linearly with amplitude. The maximum velocity of the down phase was faster than that of the up phase. For lid movements accompanying vertical saccades, the maximum velocities in the up and down directions were similar and increased nonlinearly with amplitude, saturating at about 120 mm/sec (approximately 450 degrees/sec). Duration increased approximately linearly with amplitude. The down phases of blinks were much faster than those of saccade-related lid movements. By comparison, the maximum velocities of the up phase of blinks and of saccade-related lid movements were almost equal. The large intersubject variability suggests caution when using normative data to interpret abnormal lid motion for clinical purposes.

Adult↗
PubMed1991

[A study of blink reflex in person with severely handicapped].

1) We evaluated blink reflex from 50 cases of severe handicapped. 7 cases (14%) had normal blink reflex. Abnormality of prolonged latency or no response of blink reflex was much more easily seen on R2 and R2' than R1, and dysfunction of spinal trigeminal complex or bulbar reticular formation might be existed in those cases. 2) We found abnormal blink reflex had some relationship with mental disturbance or bulbar function. Result of ABR and head CT also suggested that some kinds of cerebral factors might influenced to blink reflex of severe handicapped cases. 3) Blink reflex was one of the useful records for severe handicapped patients to evaluated underline pathogenesis of brain stem function.

Adult↗
PubMed1981

Drug effect on blink rates in rhesus monkeys: preliminary studies.

Various drugs that alter central monoamine activity were given to monkeys to determine effects on blink rate. Chronic pargyline treatment raised the mean +/- SD blink rate slightly to 18.2 +/- 5.3 blinks/90 sec. When phenylethylamine was added to chronic pargyline treatment, blinks increased from a base line of 16.8 +/- 7.6 blinks/90 sec to 37 +/- 15 blinks/90 sec. Apomorphine (0.36 mg/kg) raised blinks from a base lone of 12.2 +/- 2.8 blinks/90 sec. to 41.9 +/- 10.3 blinks/90 sec. and reversed a decrease in blinking caused by haloperidol. The neurochemical basis of blinking and implications for tardive dyskinesia are discussed.

Animals↗