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At least 289 records · Page 16Linked to original sources
PubMed1996

Time on task and blink effects on saccade duration.

Changes in saccade duration, saccade amplitude and slope of the regression line relating amplitude and duration were assessed during a 2 hour air traffic control simulating task. Mean duration significantly increased as a function of time on task (TOT). Saccade amplitude decreased during the beginning part of the two hour period, increased in the middle and decreased in the final part of task performance. Differences in saccade duration were also assessed for saccades occurring during and independent of eye blinks. When matched for amplitude, electrooculographically measured saccades occurring during a blink were significantly slower than those occurring independent of a blink. Our results suggest caution in interpreting saccade velocity change as an index of 'fatigue' since most of the reduction in average saccade velocity may be secondary to increases in blink frequency.

Blinking↗
PubMed2005

Spontaneous eye blink analysis in the normal individual.

PURPOSE: Spontaneous eye blink activity in the primary eye position and its relationship to age and gender were assessed using digital image processing techniques to quantify blink opening and closing time. METHODS: One hundred-and-eighty healthy volunteers (90 males and 90 females), divided into the age groups 0-3, 4-12, 13-20, 21-40, 41-60 and > or = 60 years old, were evaluated prospectively. They were videotaped digitally in a standard setting and the images were transferred to a personal computer (Macintosh 400) and processed with the iMovie software. Blink opening and closing time were measured at 30 frames/second. The data were then subjected to statistical analysis. RESULTS: The closing time was significantly longer than the opening time for all ages and both genders. Elderly individuals (> or = 41 years old) and women had significantly longer closing times. CONCLUSION: Image processing techniques made possible the observation of differences in spontaneous eye blink opening and closing time in relation to age and gender.

Adolescent↗
PubMed1995

The effect of the low blink rate in rabbits on topical drug penetration.

PURPOSE: The low rate of blinking in the rabbit as compared to the human suggests that there may be a greater contact time for drugs applied topically in the animal. However, there have been no experiments performed to examine this belief directly. METHODS: A small drop containing either fluorescein or FITC Dextran was applied to the eye of a rabbit without the use of tranquilizer or anesthetic. Subsequently, the change in the fluorescence of the precorneal tear film was followed with a noninvasive fluorometer. RESULTS AND CONCLUSION: The animal did not blink for 20-30 min. after the instillation. With either fluorophore, the tear film fluorescence remained constant after the first few minutes and fell precipitously at the first blink. Comparison with the loss kinetics in the human eye, an exponential decline with an average rate constant of 0.16 min-1, indicates that the AUC will be 3 times greater in the rabbit, and the penetration of a drug can be overestimated to the same degree from the low blink rate alone. There was a rise in the corneal fluorescence, attributable to penetration of the fluorophore, after the eye was washed at the end of the experiment. This was used to estimate the epithelial permeability which averaged 1.5 x 10(-4) cm hr for fluorescein and 1.9 x 10(-5) cm hr-1 for FITC Dextran. For most drugs, however, the epithelial permeability is sufficiently high that all the material present in the tear film will partition into the cornea in a few minutes. Considerations of contact time become irrelevant under these circumstances.

Absorption↗
PubMed1983

Spontaneous eye-blink rates and dopaminergic systems.

A series of studies demonstrated a possible relationship between eye-blink rate and central dopamine activity. First, apomorphine and other dopamine agonists acutely increased blink rate in monkeys, an effect blocked by sulpiride. Secondly, parkinsonian patients with levodopa-induced dyskinesia exhibited twice the mean blink rate (21 blinks/min) of other parkinsonians (11 blinks/min, P less than 0.002) whereas the more symptomatic of the nondyskinetic patients had a very slow rate (3 blinks/min, P less than 0.01). Thirdly, schizophrenic patients had an elevated mean blink (31 vs 23 blinks/min for normals, P less than 0.05) which was normalized by neuroleptic treatment. Thus, the correlation with central dopamine activity may also prove clinically useful in selected neuropsychiatric disorders.

Animals↗
PubMed1990

Blink rates in schizophrenia.

In schizophrenia, blink rates are frequently elevated and the peak of the electroencephalographic alpha rhythm is often absent or of a lower frequency. Emerging evidence suggests that both blinks and the alpha rhythm may be controlled by a linked neuroanatomical circuit that begins in rostral pons and involves several subcortical structures as well as the occipital cortex. Blink-alpha abnormalities in schizophrenia further suggest that this blink-alpha neurocircuit may be a locus of the pathophysiological process of this disorder.

Arousal↗
PubMed1990

Blink reflex recovery after electrical stimulation of the reinnervated orbicularis oculi muscle in dogs.

The paralytic lagophthalmos following palpebral nerve neurotmesis and consequent peripheral denervation of the orbicularis oculi muscle is often associated with harmful effects on the exposed cornea. This study investigated how daily electrical stimulation affects the blink reflex recovery of this muscle after its reinnervation. Six dogs underwent unilateral facial nerve neurotmesis with immediate epineurial repair of the palpebral nerve. Three dogs were randomly chosen to receive electrical stimulation of the reinnervated orbicularis oculi muscles for 75 days. The remaining 3 dogs were controls (nonstimulated muscles). During the study, the reinnervated orbicularis oculi muscle electrophysiology and blink reflex recovery were investigated. The Student's t test was used for statistical analysis. The results can be summarized as follows: (1) between 30 and 50 days, the minimum mean stimulus intensities evoking complete up-per palpebral closure of the stimulated muscles were significantly lower than those of the nonstimulated muscles (p less than 0.01) and (2) the stimulated muscles recovered complete closure of the interpalpebral fissure (blink reflex) at 49.6 days, significantly earlier (p less than 0.01) than the nonstimulated muscles (72.6 days). It is concluded that daily electrical stimulation of the orbicularis oculi muscles, if started immediately after epineurial repair of the palpebral nerve neurotmesis, promotes a faster blink reflex recovery in the dog model.

Animals↗
PubMed2000

Failure to identify the target does not prevent the attentional blink effect.

The attentional blink has been attributed to capacity limitations at a central level of processing. We tested whether failure to identify the target would eliminate the blink. Two agnostic patients were presented with streams of letters, which they were able to identify, and streams of pictures, which they were unable to identify. The dual-task involved identification of a target and detection of a probe. With letters the duration of the blink was equivalent to that of the control subjects. A prolonged blink was observed in both patients for pictures irrespective of whether the target was identified. This result indicates that failure to identify the target does nevertheless mobilize attentional resources sufficiently to prevent detection of a second target stimulus.

Aged↗
PubMed2001

Spreading of the tears after a blink: velocity and stabilization time in healthy eyes.

PURPOSE: To quantify the tear spreading velocity and stabilization time after blinks in healthy patients. METHODS: Video recordings (magnification, x130) were made of the movements of naturally occurring particles in the tear film while patients blinked naturally. After each blink, tear spreading velocity was computed every 40 milliseconds from particle displacements determined from a frame-by-frame analysis of the records. RESULTS: After a blink, tears moved rapidly upward over the cornea. Forty milliseconds after passage of the lid, the velocity was 7.34 +/- 2.73 mm/s (mean +/- standard deviation, n = 20). The time to tear stabilization (i.e., zero velocity) was 1.05 +/- 0.30 seconds. The decay of spreading velocity with time was well described by a logarithmic function for all individual patient data (R2 range, 0.88-0.99; n = 20). We have shown that initial velocity and stabilization time are independent descriptors of tear spreading. Meibomian gland expression markedly reduced initial velocity leaving a normal stabilization time, whereas inhalation of an irritant reduced stabilization time leaving a normal initial velocity. In a patient with Sjögren syndrome, punctal plugs rapidly restored initial velocity and stabilization time from near zero values to normal values. CONCLUSION: We provide normal values for two descriptors of tear spreading, namely initial velocity and time to stabilization. These values can be modified by manipulations that alter tear constituents. Consequently, these descriptors may provide a basis for quantitative, noninvasive tear assessment.

Adolescent↗
PubMed1991

Effect of visual display unit use on blink rate and tear stability.

In the literature, there is evidence supporting the notion that visual display unit (VDU) use decreases the blink rate and possibly reduces the stability of the precorneal tear film. In this investigation the blink rate and tear stability were measured using noninvasive techniques, in relation to VDU use. In normal healthy subjects, the results show an average 5-fold drop in blink rate during VDU use but tear stability appears to be unaffected. During VDU use a significant relation was found to exist between the interval between blinks and the stability of the precorneal tear film.

Adolescent↗
PubMed2001

Evaluation of blink reflex results obtained from workers previously diagnosed with solvent-induced toxic encephalopathy.

We reviewed blink reflexes recorded from 51 railroad workers with long-term occupational exposure to solvents who were diagnosed by others with solvent-induced toxic encephalopathy. No worker fulfilled conventional clinical criteria for dementia or trigeminal mononeuropathy. All workers had normal R1 and R2 blink reflex latencies. R1 latencies correlated significantly with several nerve conduction measures, including F wave latencies, suggesting that some intersubject variability reflected intrinsic conduction properties, not isolated brain-stem function. Although normal, the workers' R1 latencies were significantly prolonged compared with historical control groups, including gender-matched control subjects of similar mean age (11.2 ms vs 9.9 ms; P < 0.0001). Stepwise multiple regression models demonstrated significant associations of R1 latency with age and use of CNS-active prescription medications (P = 0.003), but duration of occupational solvent exposure did not enter into the models. Paradoxically, workers using CNS-active medications had significantly shorter R1 latencies compared with workers not using such medications (10.9 vs 11.7 ms; P = 0.01). Job title, another potential surrogate measure of exposure, was not significantly related to reflex latencies. The geographical site of predominant solvent exposure did influence R1 latency, and workers from one site had longer exposure duration and longer R1 latencies than remaining workers. However, an interaction between age and exposure duration (r = 0.39; P = 0.003) confounded interpretation of this observation. Disability or work status, mental status findings, or classification of encephalopathy did not influence blink reflex latencies. The overall results do not support, but do not entirely exclude, a possible relationship between subclinical blink reflex abnormalities and occupational exposure to solvents. Nevertheless, it is clear from these results that the small group differences in R1 latency between exposed workers and control subjects are of no diagnostic importance and of uncertain physiologic importance, and they may reflect unrecognized confounders and technical factors.

Adult↗
PubMed1990

Effects of stimulus repetition, duration, and rise time on startle blink and automatically elicited P300.

Intense auditory stimuli of sudden onset evoke not only startle blinks but also an event-related potential component resembling classic P300, even when subjects have no assigned task. To more closely examine the relationship of this P300 to startle, event-related potentials and eyeblink were recorded from 16 young adults in three paradigms designed to produce wide variation in startle amplitude: an Habituation series of 30-ms, 105dBA white noise bursts, a Duration paradigm which presented 105dB noise bursts for 3, 10, 30, or 90 ms, and a Rise Time paradigm which varied the rise/fall times (3, 15, 30, and 45 ms) of 110dBA, 1000-Hz tone bursts. Subjects received two runs of each paradigm. Only on the final Duration and Rise Time runs were stimuli explicitly task relevant; on those runs subjects rated verbally, midway in each 8.4-s interstimulus interval, the disturbingness of the prior sound. Although even the briefest noise bursts evoked parietal P300 as well as startle blink, P300 did not behave like startle. P300 habituated more slowly than did blink amplitude, was more responsive to sustained noise than were blink, N110, and P190, and most importantly, did not show the sensitivity to stimulus rise time manifested by these measures. These findings suggest that the amplitude of automatically elicited P300 is not governed by the same mechanisms as startle amplitude, but behaves more like a defense response.

Adolescent↗
PubMed1997

The effect of unconditional stimulus modality and intensity on blink startle and electrodermal responses.

Attentional accounts of blink facilitation during Pavlovian conditioning predict enhanced reflexes if reflex and unconditional stimuli (US) are from the same modality. Emotional accounts emphasize the importance of US intensity. In Experiment 1, we crossed US modality (tone vs. shock) and intensity in a 2 x 2 between-subjects design. US intensity but not US modality affected blink facilitation. In Experiment 2, we demonstrated that the results from Experiment 1 were not due to the motor task requirements employed. In Experiment 3, we used a within-subjects design to investigate the effects of US modality and intensity. Contrary to predictions derived from an attentional account, blink facilitation was larger during conditional stimuli that preceded shock than during those that preceded tones. The present results are not consistent with an attentional account of blink facilitation during Pavlovian conditioning in humans.

Acoustic Stimulation↗
PubMed1997

The effect of emotional and attentional processes on blink startle modulation and on electrodermal responses.

Emotional accounts of startle modulation predict that startle is facilitated if elicited during aversive foreground stimuli. Attentional accounts hold that startle is enhanced if startle-eliciting stimulus and foreground stimulus are in the same modality. Visual and acoustic foreground stimuli and acoustic startle probes were employed in aversive differential conditioning and in a stimulus discrimination task. Differential conditioning was evident in electrodermal responses and blink latency shortening in both modalities, but effects on magnitude facilitation were found only for visual stimuli. In the discrimination task, skin conductance responses, blink latency shortening, and blink magnitude facilitation were larger during to-be-attended stimuli regardless of stimulus modality. The present results support the notion that attention and emotion can affect blink startle modulation during foreground stimuli.

Adolescent↗
PubMed2006

Attentional blink and prepulse inhibition of startle are positively correlated.

Although a link between the attentional blink and prepulse startle inhibition has been considered, no evidence of this relationship has been reported. We delivered acoustic startle probes during rapid serial visual presentations in which the relative positions of two targets (targets 1 and 2) was varied within a stream of distractors. Startle probes were presented at 100 ms lead intervals relative to onset of a target or distractor. We found positive correlations between visual prepulse inhibition and attentional blink effects across participants. As the magnitude of prepulse inhibition with target and distractor lead stimuli increased, deficits in identifying target 2 during the attentional blink increased, suggesting similar processes underlying these phenomena. Whereas prepulse inhibition may reveal the strength of inhibition to protect stimulus processing, attentional blink may index the rate of recovery from similar inhibitory processes.

Adult↗
PubMed1994

Blinking and the release reflexes: are they clinically useful?

OBJECTIVE: To review the clinical utility of blinking and the release reflexes, palmomental, glabellar, grasp, and snout, as an important part of the bedside neurological examination. DESIGN: Articles published from 1966 to 1993 that addressed blinking or the release reflexes were identified by searching the MEDLINE database. Thirty-seven references provided clinically useful and applicable information. RESULTS: There is controversy regarding the optimal method of clinical elicitation of these reflexes. The release reflexes are frequently seen as an incidental abnormality in the elderly. A positive grasp reflex, especially if asymmetrical, is sensitive but not specific for abnormal brain function. Lack of habituation is more important than the mere presence or absence of a reflex. The brainstem circuits involved in the regulation of blinking and the release reflexes are discussed, as are their abnormalities in a variety of clinical settings. CONCLUSION: Blinking and the release reflexes have clinical utility in the diagnosis and bedside clinical assessment of diseases as diverse as frontal lobe lesions, hydrocephalus, multiple sclerosis, Parkinson's disease, Alzheimer's disease and other dementias, falls in the elderly, ageing, HIV-encephalopathy, schizophrenia, tumors in the region of the sylvian aqueduct and recovery from head trauma.

Blinking↗
PubMed1982

The nature of normal blinking patterns.

The blinking patterns of 20 normal subjects were examined under controlled experimental conditions. While the mean blink rate was 12.55 blinks/min, there were marked variations between individuals. As well, each subject displayed a characteristic pattern of blinking, mixing inter-blink periods of shorter and longer durations in a regular fashion.

Adult↗
PubMed1987

Relation between blink frequency and break-up time?

A possible correlation between break-up time (BUT) and blink frequency was investigated in 32 healthy persons (17 females and 15 males) and in 29 patients suffering from primary Sjögren's syndrome (27 females and 2 males). A significant negative correlation, was found between BUT and blink frequency. In persons with high BUT, the blink frequency is low, probably just sufficient to prevent spontaneous tear breaks. In persons with low BUT, i.e. the Sjögren patients, the blink frequency is high, and tear fluid breaks are mostly prevented.

Adult↗
PubMed1984

The eye blink electro-oculogram.

An electro-oculogram (EOG) was derived from potentials recorded from electrodes placed above and below the eye during voluntary vertical eye movements. Concurrent measurement of the amplitude of eye blink potentials recorded from the same electrodes produced curves which were highly correlated with the EOG measured from stereotyped eye movements. Recordings from a patient with a missing globe, owing to trauma, revealed eye movement and blink responses only from the intact side. A patient with no light perception showed blink responses which were less variable than responses measured during attempts voluntarily to move the eyes vertically in 60 degrees excursions. An EOG calculated by measurement of eye blink potentials may be possible in clinical situations where traditional electro-oculography techniques are not feasible.

Adaptation, Ocular↗