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At least 73 records · Page 4Linked to original sources
PubMed2005

The effects of affective picture stimuli on blink modulation in adults and children.

Two experiments examined blink modulation during viewing of pleasant, neutral and unpleasant picture stimuli in non-selected adults (N = 21) and children (N = 60) and children with anxiety disorders (N = 12). Blink reflexes were elicited by a white noise probe of 105 dB at lead stimulus intervals of 60, 240, 3500, and 5000 ms and during intertrial intervals. Blink modulation during unpleasant pictures was significantly different from blink modulation during neutral pictures at the 60 ms lead interval in children whereas adults showed no significant differences. Picture content had no differential effect on the extent of blink modulation for adults or children at the 240 ms lead interval. At the long lead intervals, blink modulation during unpleasant and pleasant pictures was significantly larger than during neutral pictures in adults. Picture valence did not differentially affect the extent of blink modulation at long lead intervals in children. Comparing the extent of blink modulation in anxious and non-selected children, blinks were significantly modulated during unpleasant pictures at the 60 ms lead interval for both groups. However, the extent of blink modulation was larger overall at this very short lead interval in anxious children. Children did not differ at other lead intervals.

Adolescent↗
PubMed2006

Automated protocol for evaluation of electromagnetic component separation (APECS): Application of a framework for evaluating statistical methods of blink extraction from multichannel EEG.

OBJECTIVE: We present APECS (Automated Protocol for Evaluation of Electromagnetic Component Separation), a framework for evaluating the accuracy of blind source separation algorithms in removing artifacts from EEG data. APECS applies multiple, automated procedures to quantify the extent to which blinks are removed, and the degree to which nonocular activity is left intact. METHODS: APECS was used to evaluate blink removal using three BSS algorithms: Second-Order Blind Inference (SOBI) and two Independent Component Analysis (ICA) implementations, FastICA and Infomax. The algorithms were applied to a series of blink-free EEG datasets, which were contaminated with real or simulated blinks. Extracted components were assumed to contain blink activity if correlation of their spatial projectors to a predefined blink template exceeded some threshold, and if polarity inverted above and below the eyes. Blink-related components were then subtracted to produce filtered data. The success of each data decomposition is evaluated through the use of multiple, automated metrics, to determine which decomposition best approximates the ideal solution (complete separation of blink from nonblink activity). RESULTS: The outcomes for the evaluation measures were generally congruent, but also provided different and complementary information about the quality of each data decomposition. Under our testing framework, Infomax outperformed both FastICA and SOBI. Best results were achieved when blink activity loaded onto a single component. CONCLUSIONS: Multiple metrics, both quantitative and qualitative, are important in evaluating algorithms for artifact extraction. SIGNIFICANCE: Failure to achieve complete separation of blink from nonblink activity can affect experimental outcomes, as illustrated here, using an ERP study of word-nonword discrimination. This illustrates the importance of methods for evaluation of artifact extraction results.

Algorithms↗
PubMed2005

Neural correlates of eye blinking; improved by simultaneous fMRI and EOG measurement.

Neural correlates of eye blink in healthy human subjects can be investigated using functional magnetic resonance imaging. However, the focus of most previous studies has been on intentional eye blinking. The goal of the present study was to examine the neural correlates of spontaneous eye blinking with the help of EOG measurements during data acquisition of fMRI. After the removal of the pulse artifact in the EOG signal, EOG waveform clearly indicates eye blinking, which was equivalent to those measured outside of the MRI scanner. On the basis of this detection, each blinking event can be used as a temporal cue for the event-related fMRI. In a comparison, we also investigated the neural correlates of blink inhibition. Based on the brain activation pattern, the activation of the bilateral parahippocampal, the visual cortex was commonly observed for both conditions. The additional activation of the precentral gyrus, corresponding to blink inhibition, and the right medial frontal gyrus, corresponding to spontaneous blinking were observed. Based on these results, we conclude that the medial frontal gyrus is responsible for spontaneous eye blinking, whereas precentral activation appears to be related to blink inhibition.

Adult↗
PubMed2005

Event related fMRI studies of voluntary and inhibited eye blinking using a time marker of EOG.

Electrooculogram (EOG) measurements, along with infrared measurements, are commonly used to record eye blinking during functional magnetic resonance imaging (fMRI). We report herein, on the use of EOG in measuring voluntary and inhibited eye blinking during echo planar imaging (EPI) in an MR scanner. The inhibited eye blinking occurred during the period, in which subjects were requested not to blink their eyes. After the removal of gradient-field induced artifacts from the EOG signal, the waveform of the EOG clearly showed both voluntary and inhibited eye blinking. Using these data, each voluntary or inhibited eye-blinking event was used as the temporal cue for an event related fMRI. Activation of the bilateral parahippocampal, precentral gyrus and left supplementary motor area was observed for voluntary eye blinking, whereas the medial/superior frontal, precentral, cingulate, precuneus, and superior temporal gyrus appears to be involved in inhibited eye blinking. Based on these experimental results, we propose that the precentral gyrus is responsible for both voluntary and inhibited eye blinking. The parietal area (precuneus and superior temporal gyrus) appears to be exclusively related to inhibited eye blinking.

Adult↗
PubMed2005

The effect of antireflection film use on blink rate and asthenopic symptoms during visual display terminal work.

PURPOSE: To investigate the effect of visual display terminal antireflection (AR) films on blink rate and subjective symptoms of asthenopia. METHODS: This was a nonrandomized, prospective clinical trial in which 7 healthy volunteers underwent blink rate measurements with a blink rate recording system while viewing a DVD on a computer display for 10 minutes. The measurements were carried out without an AR film on terminal displays initially. The same tasks were performed on the next day with an AR film on the displays. The subjects were also required to score their symptoms of asthenopia on a visual analog scale before and just after DVD viewing. The changes in blink rate and asthenopia scores with AR film use were assessed by the Student t test. RESULTS: The mean baseline blink rate was 15.7 +/- 5.9 blinks /min, which decreased significantly to 9.6 +/- 4.3 blinks/min after DVD viewing without an AR film (P < 0.05). The mean baseline and final blink rates for DVD viewing with an AR film were 14.6 +/- 9.2 and 14.3 +/- 9.2 blinks/min, respectively. There were no significant differences between baseline and final blink rates after DVD viewing with an AR film (P > 0.05). The mean cumulative visual analog asthenopic symptom score after DVD viewing without an AR film was 72 +/- 18% compared with the mean cumulative symptom score of 52 +/- 11% after DVD viewing with an AR film. The difference was statistically significant (P < 0.05). CONCLUSIONS: Visual display terminal work appears to be associated with asthenopic symptoms and decreased blink rates. The use of AR films on computer displays may prevent both reflections of light from screen surfaces and reduction in blink rates resulting in fewer asthenopic symptoms.

Adult↗
PubMed2000

Fear conditioned potentiation of the acoustic blink reflex in patients with cerebellar lesions.

OBJECTIVE: To investigate whether the human cerebellum takes part in fear conditioned potentiation of the acoustic blink reflex. METHODS: A group of 10 cerebellar patients (eight patients with lesions involving the medial cerebellum, two patients with circumscribed lesions of the cerebellar hemispheres) was compared with a group of 16 age and sex matched healthy control subjects. The fear conditioned potentiation paradigm consisted of three phases. During the first, habituation phase subjects received 20 successive acoustic blink stimuli. In the subsequent fear conditioning phase, subjects passed through 20 paired presentations of the unconditioned fear stimulus (US; an electric shock) and the conditioned stimulus (CS; a light). Thereafter, subjects underwent the potentiation phase, which consisted of a pseudorandom order of 12 trials of the acoustic blink stimulus alone, 12 acoustic blink stimuli paired with the conditioned stimulus, and six conditioned stimuli paired with the unconditioned stimulus. The EMG of the acoustic blink reflex was recorded at the orbicularis oculi muscles. The potentiation effect was determined as the difference in normalised peak amplitude of the blink reflex evoked by pairs of CS and acoustic blink stimuli and evoked by the acoustic stimulus alone. RESULTS: In the habituation phase, short term habituation of the acoustic blink reflex was preserved in all cerebellar patients. However, in the potentiation phase, the potentiation effect of the blink reflex was significantly reduced in patients with medial cerebellar lesions compared with the controls (mean (SD) potentiation effect (%), patients: -6.4 (15.3), controls: 21.6 (35.6)), but was within normal limits in the two patients with lateral lesions. CONCLUSIONS: The present findings suggest that the human medial cerebellum is involved in associative learning of non-specific aversive reactions-that is, the fear conditioned potentiation of the acoustic blink reflex.

Adolescent↗
PubMed2000

Neurophysiological aspects of eye and eyelid movements during blinking in humans.

The neural relationships between eyelid movements and eye movements during spontaneous, voluntary, and reflex blinking in a group of healthy subjects were examined. Electromyographic (EMG) recording of the orbicularis oculi (OO) muscles was performed using surface electrodes. Concurrently, horizontal and vertical eye positions were recorded by means of the double magnetic induction (DMI) ring method. In addition, movement of the upper eyelid was measured by a specially designed search coil, placed on the upper eyelid. The reflex blink was elicited electrically by supraorbital nerve stimulation either on the right or the left side. It is found that disconjugate oblique eye movements accompany spontaneous, voluntary as well as reflex blinking. Depending on the gaze position before blinking, the amplitude of horizontal and vertical components of the eye movement during blinking varies in a systematic way. With adduction and downward gaze the amplitude is minimal. With abduction the horizontal amplitude increases, whereas with upward gaze the vertical amplitude increases. Unilateral electrical supraorbital nerve stimulation at low currents elicits eye movements with a bilateral late component. At stimulus intensities approximately two to three times above the threshold, the early ipsilateral blink reflex response (R(1)) in the OO muscle can be observed together with an early ipsilateral eye movement component at a latency of approximately 15 ms. In addition, during the electrical blink reflex, early ipsilateral and late bilateral components can also be identified in the upper eyelid movement. In contrast to the late bilateral component of upper eyelid movement, the early ipsilateral component of upper eyelid movement appears to open the eye to a greater degree. This early ipsilateral component of upper eyelid movement occurs more or less simultaneously with the early eye movement component. It is suggested that both early ipsilateral movements following electrical stimulation do not have a central neural origin. Late components of the eye movements slightly precede the late components of the eyelid movement. Synchrony between late components of eyelid movements and eye movements as well as similarity of oblique eye movement components in different types of blinking suggest the existence of a premotor neural structure acting as a generator that coordinates impulses to different subnuclei of the oculomotor nucleus as well as the facial nerve nucleus during blinking independent from the ocular saccadic and/or vergence system. The profile and direction of the eye movement rotation during blinking gives support to the idea that it may be secondary to eyeball retraction; an extra cocontraction of the inferior and superior rectus muscle would be sufficient to explain both eye retraction and rotation in the horizontal vertical and torsional planes.

Adult↗
PubMed2001

Increased attentional blink after focal cerebral lesions.

BACKGROUND: Once a person identifies a visual object, the ability to detect a second object is impaired for the next few hundred milliseconds. This attentional blink is reported to increase in subjects with neglect due to acute right hemisphere lesions. METHOD: To examine neural substrates of the attentional blink, the authors examined the performance of 13 subjects with chronic focal brain lesions visualized by MRI and nine control subjects without neurologic impairments on a rapid serial visual presentation task that used letters as targets. RESULTS: Attentional blink length in the lesion group was more than twice that of controls (p < 0.05). The magnitude of the attentional blink deficit was greatest when the second target appeared 200 ms after the first target, recovering close to baseline by 1,200 ms. Abnormal attentional blink occurred (even in the absence of neglect) with lesions in the occipitotemporal areas (associated with "object" vision) and the prefrontal cortices (thought to mediate visual working memory). CONCLUSIONS: Attentional blink length and attentional blink magnitude measure different components of the attentional blink process. Abnormal attentional blink can occur with different chronic focal brain lesions in a network of structures for vision and attention, and it has no special status in hemispatial neglect. Abnormal attentional blink may help explain difficulties on rapid, visually demanding cognitive tasks such as reading and automobile driving and may explain performance deficits in brain damaged patients with nonspatial disorders of visual processing.

Adult↗
PubMed1993

Blinking in patients with memory disorders during short term memory tasks.

The occurrence of blinking during short term memory tasks was analyzed for 32 subjects divided into three groups: 12 memory impaired patients, 10 elderly normals (age-matched to the patients), and 10 young normals. The subjects were participating in a study of brain evoked potentials accompanying memory activities. They were instructed not to blink during the performance of the memory tasks for reasons related to the quality of the recorded potentials. In this context, the withholding of blinking can be considered a secondary task. Blinking during the short term memory tasks was inversely related to performance accuracy (r = -.57). Age, mini-mental score and reaction time were also significantly related to the frequency of blinking. Dividing the memory patients into two groups according to the incidence of blinking, ("high-blinking" and "low-blinking"), revealed a significant difference in overall task accuracy with the high-blinking group performing more poorly than the low-blinking group.

Adult↗
PubMed2004

The effects of lead stimulus and reflex stimulus modality on modulation of the blink reflex at very short, short, and long lead intervals.

The blink reflex is modulated if a weak lead stimulus precedes the blink-eliciting stimulus. In two experiments, we examined the effects of the sensory modality of the lead and blink-eliciting stimuli on blink modulation. Acoustic, visual, or tactile lead stimuli were followed by an acoustic (Experiment 1) or an electrotactile (Experiment 2) blink-eliciting stimulus at lead intervals of -30, 0, 30, 60, 120, 240, 360, and 4,500 msec. The inhibition of blink magnitude at the short (60- to 360-msec) lead intervals and the facilitation of blink magnitude at the long (4,500-msec) lead interval observed for each lead stimulus modality was relatively unaffected by the blink-eliciting stimulus modality. The facilitation of blink magnitude at the very short (-30- to 30-msec) lead intervals was dependent on the combination of the lead and the blink-eliciting stimulus modalities. Modality specific and nonspecific processes operate at different levels of perceptual processing.

Acoustic Stimulation↗
PubMed1995

Electrical stimulation of the pontine omnipause area inhibits eye blink.

BACKGROUND: Single-unit recordings of pontine omnipause neurons (OPN) in the monkey have shown that these neurons cease firing for saccades in all directions. OPNs are located in pontine nucleus raphe' interpositus and are known to inhibit a variety of target neurons, including saccadic burst neurons. Recently, a single-unit investigation of these same OPNs revealed that they pause for blinks as well as saccades. Electrical microstimulation of the OPN area has been shown to inhibit saccadic eye movements in all directions. The present study is designed to determine if OPN area microstimulation inhibits blinks as well as saccades. METHODS: Two rhesus monkeys were trained to track visual targets for a reward. Eye and lid position were measured using the electromagnetic search coil technique. The pontine OPN area was located using single-unit recording and microstimulation techniques. OPN stimulation was delivered just before and during the presentation of air puffs to elicit blinks. RESULTS: OPN are microstimulation inhibited air puff-induced blinks as well as saccades. The threshold current for inhibiting blinks was generally slightly higher than for inhibiting saccades. CONCLUSIONS: Although OPN area stimulation inhibits blinks as well as saccades, the mechanisms for inhibiting these behaviors appears to be different. OPNs are known to inhibit saccadic burst neurons, but there is no evidence that these neurons inhibit orbicularis oculi motoneurons which burst for blinks. Moreover, the temporal pattern of OPN activity makes it unlikely that they directly suppress blinks. The OPN region appears to be important for eye retraction during blinks and may be associated with other pontine areas which control blinks.

Animals↗
PubMed1994

The effects of gender and birth control pill use on spontaneous blink rates.

BACKGROUND: Two major reference works suggest that men and women blink spontaneously at different rates, but they disagree with regard to which gender blinks faster. METHODS: Spontaneous blink rates of 59 males and 86 females, 44 of whom were taking birth control (BC) pills, were measured for 5 consecutive minutes. Schirmer test results and tear break-up times (TBUTs) were also obtained. RESULTS: Females taking BC pills blinked at a mean rate of 19.6 times per minute, females not taking birth control pills blinked 14.9 times per minute, and males blinked 14.5 times per minute. There were very large differences between blink rates for individuals in each of the groups. No strong associations were found between spontaneous blink rates and a history of contact lens use, tear break-up time, Schirmer test results, temperature or humidity in the examination room, subject age, or menstrual cycle phase. CONCLUSIONS: The 32 percent increase in mean blink rate for females taking BC pills suggests that the pills affect at least one of the mechanisms that control spontaneous blinking, but it is unclear how they accomplish this.

Adult↗
PubMed1996

Quantitative videographic analysis of blinking in normal subjects and patients with dry eye.

OBJECTIVE: To study patterns of eye blinking in normal subjects and patients with dry eye. METHODS: We developed an automated, noninvasive blink monitor that permits quantitative analysis of 6 parameters of blinking. We used this method under normal conditions and then examined the effects on the patterns of blinking in patients with dry eye; several steps in this method were designed to exacerbate or ameliorate ocular surface desiccation. RESULTS: The mean (+/-SD), maximum, and coefficient of variation of the interblinking time in normal subjects and patients with dry eye were 4.0 +/- 2.0 and 1.5 +/- 0.9 seconds, 8.9 +/- 4.0 and 4.2 +/- 2.4 seconds, and 55% +/- 21% and 65% +/- 24%, respectively. Those values for the blinking time were 0.20 +/- 0.04 and 0.27 +/- 0.16 seconds, 0.35 +/- 0.12 and 0.99 +/- 1.30 seconds, and 23% +/- 9% and 46% +/- 34%, respectively. The use of artificial tears or spectacles with moist panels and moist inserts tended to normalize the patterns of blinking in the patients with dry eye, whereas exposure to wind made them more abnormal. CONCLUSIONS: Our technique permitted a rigorous analysis of blinking that was previously unavailable. We have shown that local ocular surface conditions alone can significantly affect patterns of blinking. This method should be applicable to studying psychologic and any other factors that may influence blinking.

Adolescent↗
PubMed2003

Experimental evaluation of eye-blink parameters as a drowsiness measure.

Drowsiness and increased tendency to fall asleep during daytime is still a generally underestimated problem. An increased tendency to fall asleep limits the efficiency at work and substantially increases the risk of accidents. Reduced alertness is difficult to assess, particularly under real life settings. Most of the available measuring procedures are laboratory-oriented and their applicability under field conditions is limited; their validity and sensitivity are often a matter of controversy. The spontaneous eye blink is considered to be a suitable ocular indicator for fatigue diagnostics. To evaluate eye blink parameters as a drowsiness indicator, a contact-free method for the measurement of spontaneous eye blinks was developed. An infrared sensor clipped to an eyeglass frame records eyelid movements continuously. In a series of sessions with 60 healthy adult participants, the validity of spontaneous blink parameters was investigated. The subjective state was determined by means of questionnaires immediately before the recording of eye blinks. The results show that several parameters of the spontaneous eye blink can be used as indicators in fatigue diagnostics. The parameters blink duration and reopening time in particular change reliably with increasing drowsiness. Furthermore, the proportion of long closure duration blinks proves to be an informative parameter. The results demonstrate that the measurement of eye blink parameters provides reliable information about drowsiness/sleepiness, which may also be applied to the continuous monitoring of the tendency to fall asleep.

Activities of Daily Living↗
PubMed2002

Differentiating between reflex and spontaneous blinks using simultaneous recording of the orbicularis oculi electromyogram and the electro-oculogram in startle research.

The present study documents the differences between reflex and spontaneous blinks by recording the vertical electro-oculogram (EOG) along with the orbicularis oculi electromyogram (OO-EMG). EOG and OO-EMG were applied without fixation of the head in 15 freely moving children during an auditory startle experiment. Results revealed that the easily-recorded EOG shows the same relationships between orbicularis oculi contraction and velocity of lid movement in startle blinks as the head-constraining methods, e.g. the magnetic search coil, used in previous studies. The OO-EMG onset occurred before the EOG onset in most reflex blinks while no such pattern occurred for spontaneous blinks. In comparison with spontaneous blinks, reflex blinks showed a shorter duration between onset and peak and between onset and offset in OO-EMG and EOG. In addition, reflex blinks showed greater OO-EMG activity and smaller EOG-recorded lid movements compared with spontaneous blinks. Simultaneous recording of OO-EMG and EOG can distinguish reflex from spontaneous blinks and lid saccades in populations, e.g. children, that cannot tolerate head restraint and in experiments permitting or requiring movement.

Blinking↗
PubMed2005

Blink rate decreases with eyelid squint.

PURPOSE: We hypothesize that eyelid squint inhibits blink rate. This is part of a larger hypothesis that, because eyelid squint improves vision under conditions of optical defocus and/or glare, and reduced blink rate is assumed to contribute to dry eye symptoms, eyelid squint is part of the mechanism resulting in asthenopia. This study investigates the effect of voluntary eyelid squint on blink activity and on electromyography (EMG) measures from the orbicularis oculi. METHODS: Ten subjects (18 to 38 years of age) performed 3 1-minute trials each (Latin Square order) of voluntary target squint levels of 5%, 20%, 35%, and 50% with respect to previously demonstrated 0% (relaxed) and 100% (maximum) squint levels. EMG recordings using surface electrodes were obtained from the orbicularis muscle. Vertical dimension of the palpebral fissure and eye lid blinks were measured with an ISCAN eye tracker and video recorder. RESULTS: Each target squint level produced significant changes (p<0.0001) in ocular aperture size, EMG power, and EMG amplitude. For target voluntary squint levels of 5%, 20%, 35%, and 50%, the mean squint responses were 24%, 35%, 42%, and 53%, respectively. Blink rate was inversely related to both target squint level and squint response (p<0.0001), decreasing from 15 blinks per minute at 0% squint to 7.5 blinks per minute at 5% target voluntary squint and to 4 blinks per minute at 50% target voluntary squint. CONCLUSIONS: Voluntary eyelid squint significantly reduces blink rate by an average of 50% or more dependent on attempted level. Further study is required to determine if involuntary squint causes the same. All tested levels of voluntary squint resulted in an EMG signal from the orbicularis muscle that is measurably different from resting state. This indicates that EMG can be used as a reliable indicator of eyelid squint.

Adult↗
PubMed1989

Blinking and corneal sensitivity.

We have investigated the relationship between corneal sensitivity and blinking patterns. Using a group of 9 young normal subjects, measurements were made of blink patterns, central and peripheral corneal sensitivity and lid margin sensitivity both before and after use of topical corneal anaesthetic, proxymetacaine hydrochloride (Alcaine). Blink patterns were recorded through concealed filming and were later analysed in terms of blink frequency and the type of blinks (proportion of complete, incomplete, twitch and forced blinks). Blink rate was significantly lower following anaesthetic administration, but the relative proportion of blink types remained unchanged. We speculate that one of the factors responsible for normal involuntary blinks is the imminent break-up of the tear film which is sensed by the cornea.

Adult↗
PubMed2002

Eyelid movements: behavioral studies of blinking in humans under different stimulus conditions.

The kinematics and neurophysiological aspects of eyelid movements were examined during spontaneous, voluntary, air puff, and electrically induced blinking in healthy human subjects, using the direct magnetic search coil technique simultaneously with electromyographic recording of the orbicularis oculi muscles (OO-EMG). For OO-EMG recordings, surface electrodes were attached to the lower eyelids. To measure the vertical lid displacement, a search coil with a diameter of 3 mm was placed 1 mm from the rim on the upper eyelid on a marked position. Blink registrations were performed from the zero position and from 28 randomly chosen positions. Blinks elicited by electrical stimulation of the supraorbital nerve had shortest duration and were least variable. In contrast, spontaneous blinks had longer duration and greater variability. Blinks induced by air puff had a slightly longer duration and similar variability as electrically induced blinks. There was a correlation between the maximal down phase amplitude and the integrated OO-EMG. Blink duration and maximal down phase amplitude were affected by eye position. Eyes positioned 30 degrees above horizontal displayed the shortest down phase duration and the largest maximal down phase amplitude and velocity. At 30 degrees below horizontal, blinks had the longest total duration, the longest down phase duration, and the lowest maximal down phase amplitude and velocity. The simultaneously recorded integrated OO-EMG was largest in the 30 degrees downward position. In four subjects, the average blinking data showed a linear relation between eye position and OO-EMG, maximal down phase amplitude, and maximal downward velocity.

Adult↗