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At least 163 records · Page 9Linked to original sources
PubMed1993

Spontaneous eye blink rate in winter seasonal affective disorder.

We investigated spontaneous eye-blink rates in 19 drug-free patients with winter seasonal affective disorder (SAD) and 18 normal control subjects. At baseline, there were no significant differences between the two groups (mean +/- SD blink rate: 15/minute +/- 8 vs. 15/minute +/- 7). Light therapy (10,000 lux: 1 hour each morning for 1 week) produced no significant change in mean (+/- SD) blink rates either in 10 SAD patients (13/minute +/- 8 vs. 10/minute +/- 7) or in 12 normal control subjects (15/minute +/- 6 vs. 14/minute +/- 6). A post hoc exploratory analysis of the effect of light therapy on premenopausal female subjects (5 patients and 9 control subjects) showed a significant decrease in mean (+/- SD) blink rate in the patients after treatment (17 +/- 6 vs. 12 +/- 8 compared with 15 +/- 7 vs. 16 +/- 5). These results do not support the idea that an elevated blink rate may be a general biological marker in SAD, but they suggest a possible link between light treatment and mechanisms that regulate blink rate in premenopausal SAD patients.

Adult↗
PubMed1994

Discharge of identified deep cerebellar nuclei neurons related to eye blinks in the alert cat.

The activity of identified cerebellar nuclear neurons was recorded in the alert cat during blinks induced by corneal air puffs, light flashes and tones. Eyelid response to air puffs consisted of an early (16.5 +/- 2.7 ms) downward movement followed by two to three late downward steps. Blinks induced by flashes or tones presented longer latencies (52.6 +/- 4.8 and 50.1 +/- 8.0 ms). Type A neurons (n = 86) increased their spike activity in coincidence with the beginning of the blink, regardless of the stimulus modality. The late eyelid downward responses were accompanied by corresponding increases in the firing rate of the neuron. Type A neurons were activated mostly from the red nucleus (48/86) or the restiform body (24/86). Type B neurons (n = 30) fired a brief burst of spikes slightly preceding the blink, followed by a noticeable decrease in their firing rate. As for type A, the discharge response of type B neurons was always the same regardless of the sensory modality. These neurons were activated from the red nucleus (18/30), oculomotor complex (6/30) and restiform body (6/30). Although no precise temporal coupling was found between the beginning of the neuronal response and the start of either the stimulus or the motor response, linear regression analysis demonstrated significant relationships between mean firing rate of type A and B neurons and eyelid position, velocity and/or acceleration. Deep cerebellar nuclei neurons presented here seem to be directly involved in the execution of reflexively induced blinks following the smaller details of eyelid motor performance. The opposite behavior of type A and B cells suggests an interplay of reciprocal actions to determine the ongoing displacements of the lid. Finally, the cerebellum seems to influence blinks through a spread action on many brainstem sites and not exclusively on the red nucleus.

Acoustic Stimulation↗
PubMed2005

A novel method for assessing variations in visual acuity after the blink.

A novel instrument was developed to assess the visual acuity in correlation with time after blink. The method uses an optical blink detector which triggers the display of a random target symbol on a computer monitor. The delay time between blink and symbol display varies randomly from blink to blink, the exposure duration is fixed at 100 ms. The subject has to identify the correct symbol, a score is kept of the correct responses in correlation to delay time. The recovery of visual acuity after blink was measured for subjects wearing two types of bifocal contact lenses and a control group of non-contact lens wearers. All groups required between 200 and 500 ms to achieve their best visual acuity. Subjects wearing the translating bifocal lenses recovered their vision significantly faster than the subjects wearing no lens or the simultaneous vision bifocal lens.

Adult↗
PubMed2006

Correlates of eye blinking as determined by synthetic aperture magnetometry.

OBJECTIVE: To evaluate the spatiotemporal characteristics of ocular and cerebral current sources during voluntary eyeblinking. METHODS: Whole-head magnetoencephalographic (MEG) recordings were acquired during voluntary blinking in eight healthy adults and analysed using synthetic aperture magnetometry (SAM). RESULTS: Fronto-temporal MEG sensors showed a large slow wave lasting approximately 400 ms and a small burst of activity with frequencies above 30 Hz at the initiation of the blink. Group maps of blink-related oscillatory activity at frequencies between 1-18 Hz and 32-64 Hz showed increased activity in and around the orbits during the 400 ms following blink onset. Increased oscillatory activity occurred in occipital regions 200 ms after blink onset at frequencies between 18 and 64 Hz. CONCLUSIONS: Blink-related MEG signals are recorded in the regions of the eyes and in the occipital cortex. The anterior activation is likely a combination of muscle contraction and eyelid currents. Occipital activation likely represents neural processes concerned with re-establishing the visual image after transient ocular occlusion. SIGNIFICANCE: The possibility of eyeblink-related fields should be considered when interpreting frontal and occipital source activities during SAM analyses.

Adult↗
PubMed1997

Gravity, blink rate, and lacrimal drainage capacity.

PURPOSE: To investigate the influence of gravity and blink rate on lacrimal drainage capacity and to learn whether lacrimal pump function can be measured with the drop test. METHODS: The drop test for lacrimal drainage capacity was performed in 20 test subjects, aged 12 to 30 years. Drops of a known volume of lukewarm saline solution were repeatedly instilled in the tear film for 3 minutes. Excessive saline solution was then removed, and the volume drained by the lacrimal passages was calculated. The drop test was performed both with the nasolacrimal duct in a 45-degree position and with the nasolacrimal duct in a horizontal position. The drop test was performed two times in each position, with the individual reading and not reading. A lower blink rate was induced by reading. RESULTS: There was a high correlation between blink rate and lacrimal drainage when the nasolacrimal duct was in a horizontal position. The volume drained with each blink was approximately 2 microliters. However, when gravity acted upon the fluid in the lacrimal sac-nasolacrimal duct in the direction of the tear flow, the lacrimal drainage capacity showed a significant but variable increase, and there was no significant correlation between blink rate and lacrimal drainage capacity. CONCLUSIONS: Lacrimal drainage capacity in young individuals was significantly affected by both blink rate and gravity. Lacrimal pump function can be measured quantitatively with the drop test.

Administration, Topical↗
PubMed1995

Prevention of blinking alters iris configuration in pigment dispersion syndrome and in normal eyes.

PURPOSE: To examine the effect of blinking on iris configuration and aqueous humor distribution between the posterior and anterior chambers in eyes with pigment dispersion syndrome compared with healthy eyes. METHODS: High-resolution, anterior segment ultrasound biomicroscopy was performed on ten eyes of ten patients with untreated pigment dispersion syndrome and on ten control subjects. Patients were scanned continuously for 15 minutes or until the maximal change in iris configuration occurred. During this time, the eyelids were held open mechanically, and blinking was prevented. Eyes then were rescanned immediately after blinking. RESULTS: Initial iris configuration was concave in all eyes with pigment dispersion syndrome, whereas in control eyes it was concave in four eyes, planar in four eyes, and convex in two eyes. Iridozonular contact occurred in eyes with pigment dispersion syndrome only. Iridolenticular contact was greater in eyes with pigment dispersion syndrome than in control eyes. Analysis of covariance controlling for age, sex, and refractive error showed pigment dispersion syndrome to be a significant predictor of increased iris concavity. During continuous scanning, the mean change in iris position, from most concave to most convex, and mean time to the maximal change in iris configuration were greater for eyes with pigment dispersion syndrome than in control eyes and were related to the degree of initial iris concavity only (analysis of covariance). In six eyes with pigment dispersion syndrome, the eye cup was removed, normal blinking was permitted, and the eye was rescanned. The iris resumed a concave configuration in all eyes. CONCLUSION: Increased iris concavity in pigment dispersion syndrome appears to be related to increased iridolenticular contact. This creates an anatomic configuration that predisposes to reverse pupillary block. The accumulation of aqueous humor in the posterior chamber, when blinking is prevented, alters iris position in pigment dispersion syndrome and in healthy eyes and increases iridozonular and iridociliary-process distances while minimizing iridolenticular contact. Normal blinking appears to create transient vector forces which promote aqueous humor flow from the posterior to anterior chamber.

Adult↗
PubMed2002

Test-retest reliability of the somatosensory blink reflex and its inhibition.

Prepulse inhibition (PPI) involves inhibition of the blink reflex by a weak stimulus or prepulse presented immediately prior to the blink reflex-eliciting stimulus. Ten subjects were tested for PPI two times each day with a 60 min pause between tests, for 4 days spaced 1 week apart. Both the somatosensory blink reflex and its inhibition by an acoustic prepulse, presented 50, 100, 200, 400 and 800 ms prior to the reflex-eliciting stimulus, were investigated. The results showed very high reliability for the blink reflex across all eight tests (Chronbach's alpha=0.98). Inhibition of the reflex by a prepulse displayed alphas of >0.94, and percentage of PPI also displayed significant reliability. Blink latency also displayed high reliability. In sum, the reliability of the somatosensory blink reflex and its inhibition is very high.

Adult↗
PubMed2001

Attentional modulation of blink startle at long, short, and very short lead intervals.

The present research investigated attentional blink startle modulation at lead intervals of 60, 240 and 3500 ms. Letters printed in Gothic or standard fonts, which differed in rated interest, but not valence, served as lead stimuli. Experiment 1 established that identifying letters as vowels/consonants took longer than reading the letters and that performance in both tasks was slower if letters were printed in Gothic font. In Experiment 2, acoustic blink eliciting stimuli were presented 60, 240 and 3500 ms after onset of the letters in Gothic and in standard font and during intertrial intervals. Half the participants (Group Task) were asked to identify the letters as vowels/consonants whereas the others (Group No-Task) did not perform a task. Relative to control responses, blinks during letters were facilitated at 60 and 3500 ms lead intervals and inhibited at the 240 ms lead interval for both conditions in Group Task. Differences in blink modulation across lead intervals were found in Group No-Task only during Gothic letters with blinks at the 3500 ms lead interval facilitated relative to control blinks. The present results confirm previous findings indicating that attentional processes can modulate startle at very short lead intervals.

Adolescent↗
PubMed1998

Serotonergic modulation of eye blinks in cat and monkey.

Serotonergic modulation of spontaneous and reflexive blinking was studied in four cats and one monkey. In cats, facial nucleus injections of the type-2 serotonin receptor (5-HT2) antagonist ketanserin tended to increase the latency of the first (R1) and second (R2) components of the blink reflex to supraorbital nerve stimulation. Injections of serotonin tended to increase and of ketanserin, to decrease the duration and amplitude of R2. Serotonin also produced unilateral blepharospasm and hemifacial spasm. In the monkey, the 5-HT2 agonist 2,5-dimethoxy-4-iodoamphetamine increased spontaneous blink frequency while ketanserin decreased both peak blink velocity and spontaneous blink frequency. These findings in cat and monkey indicate that serotonergic innervation of the facial nucleus has a behaviorally important role in modulation of spontaneous and reflexive blinks and suggest that dysfunction of serotonergic systems could be important to the pathophysiology of some cases of blepharospasm.

Animals↗
PubMed1999

Contingent negative variation indicates phasic arousal for externally cued unilateral eye blink in human subjects.

The contingent negative variation (CNV) as a slow cortical potential was used to investigate cortical processing of externally cued, voluntary unilateral eye blink. Probands blinked as a response within a modified two-stimulus reaction time paradigm. Reaction time and amplitudes of CNV were determined. The activity of the orbicularis oculi muscles (OO) was registered by surface electromyography (EMG). Probands who performed unilateral eye blinks with accurately inhibiting contralateral OO activity showed a significantly higher negativity of the early CNV component compared with the bilateral eye blink condition. This effect was confined to the beginning of unilateral blinking performance. It is suggested that the unilateral eye blink is a challenging motor task, initially requiring an increased cortically driven arousal and attention as revealed by increased early CNV components.

Adult↗
PubMed1999

Role of proprioception in the control of lid position during reflex and conditioned blink responses in the alert behaving cat.

The contribution of the orbicularis oculi muscle to the determination of lid position, and the putative role of eyelid proprioception in the control of reflex and conditioned eye blinks, were studied in alert behaving cats. Upper lid movements and the electromyographic activity of the orbicularis oculi muscle were recorded during reflexively evoked blinks and during the classical conditioning of the eyelid response. Blinks were evoked by air puffs, flashes and electrical stimulation of the supraorbitary branch of the trigeminal nerve. Eyelid responses were conditioned with a trace classical conditioning paradigm consisting of a short, weak air puff, followed 250 ms later by a long, strong air puff. Orbicularis oculi muscle activation during reflex blinks was independent of lid position and was not modified by the presence of weights acting in the upward or downward directions. Local anesthesia of the supraorbital nerve reduced blinks evoked by air puffs applied to the lower jaw, but did not affect flash-evoked blinks. No relationship was established between initial lid position and the first downward component of conditioned eyelid responses. In contrast, initial lid position was related to the first upward component of the same conditioned response. It is concluded that orbicularis oculi motor units receive no feedback proprioceptive signals from the eyelid, other than those coming from cutaneous receptors, and that lid position is determined by the activity of the levator palpebrae superioris muscle. The lack of sensory information about lid position in facial motoneurons probably has some functional implications on the central control of cognitive and emotional facial expressions.

Air↗
PubMed2003

Blink reflex alterations in recently diagnosed diabetic patients.

OBJECTIVE: The aim of the present study was to determine the frequency of blink reflex alterations and to examine the influence of hyperglycemia in inducing the alterations in recently diagnosed Type 2 diabetes mellitus patients. METHODS: A cross-sectional study was carried out on patients having asymptomatic diabetes with a period of evolution under 10 years. In all 47 patients (26 women and 21 men), serum glycemia levels were determined and the latency onset of the blink reflex components were measured. RESULTS: The average patient age was 44.5+/-11.0 (mean+/-SD) years with a diabetes evolution period of 4.3+/-2.9 (mean+/-SD) years. After a fasting serum glucose test, the diabetic patients were catalogued as normoglycemic (< or =126 mg/dl) or as hyperglycemic (> 26 mg/dl) and subjected to a blink reflex test. The results obtained from the diabetic patients were compared with those from a non-diabetic control group. 14.8-31.9% of the diabetic patients showed alterations in blink reflex component latencies. The differences compared with the control group were significant (p<0.05). CONCLUSIONS: Diabetes, as is well-known, can affect the central and peripheral nervous system and there does not appear to be a link between glycemic levels and blink reflex components. However, blink reflex alterations were present even in diabetic patients with a relatively short period of disease evolution.

Blinking↗
PubMed1982

An investigation of spontaneous eye blinks during lipreading.

The role of spontaneous eye blinks was investigated for a lipreading task involving a videotaped recording of 20 sentences and a 948-word passage. Blinks were recorded electro-oculographically on one channel of a chart recorder while the audio correlate of the visual message was recorded simultaneously on the second channel. A comparison of the two records indicated that blink suppression occurred while the subjects lipread compared to times when no visual information was presented. The data also show that (a) subjects tended to blink during the visual pauses that occurred while the passage was being presented and (b) better lipreaders blinked less frequently than did poorer lipreaders. These results are examined in relation to the hypothesis that attention and blink rate are inversely related.

Adult↗
PubMed2001

Blink duration as a measure of low-level anaesthetic sedation.

BACKGROUND AND OBJECTIVE: Variability in blink duration was examined to see whether it was sensitive to sevoflurane sedation at 0.05 and 0.1 minimum alveolar concentration (MAC). METHODS: Blinks were measured with an infrared transducer in eight subjects. Sedation was scored using a visual analogue scale (VAS). RESULTS: At baseline, 0.05 and 0.1 MAC sevoflurane, respectively, the overall median value of blink duration and its interquartile range were 95 (80-110) ms, 198 (163-245) ms and 210 (130-980) ms. The median percentage of blinks exceeding 500 ms was 0% (0-0.7%), 33.3% (25.5-34.7%) and 25% (15.7-63.3%) respectively. Values during 0.05 and 0.1 MAC sevoflurane were significantly different from baseline (P < 0.035) but not from each other. Baseline visual analogue scales showed large intersubject variability. Compared with baseline, VAS scores were higher at 0.05 MAC (P < 0.035) but not at 0.1 MAC. After discontinuing sevoflurane, median blink duration returned to baseline with a recovery half-life of 2.6 min (R2 = 0.95). Conclusion Blink duration is a sensitive measure of sevoflurane sedation even at 0.05 MAC.

Adult↗
PubMed2001

Recovery cycle of the blink reflex and exteroceptive suppression of temporalis muscle activity in migraine and tension-type headache.

Brain stem interneuronal excitability can be assessed by recording the recovery cycle of the blink reflex and exteroceptive suppression of temporalis muscle activity. Abnormal endogenous pain control mechanisms due to disturbed brain stem interneuronal activity have been implicated in the pathogenesis of tension-type headaches. The blink reflex, exteroceptive suppression of temporalis muscle activity, and the recovery curve of both the R2 component of the blink reflex and the ES2 component of the exteroceptive suppression of the temporalis muscle activity were studied in 20 patients with migraine without aura, 32 patients with tension-type headache, and 20 normal controls. In our study, the blink reflex was elicited by stimulation of the supraorbital nerve; the exteroceptive suppression of the temporalis muscle activity was elicited by applying electrical shocks to the labial commissure, both on the lower and upper sides. The recovery cycle was established by delivering paired shocks at different interstimulus intervals. Comparisons were made between normal control subjects, patients with migraine without aura, and patients with tension-type headache. The latency of R1, R2, and R2', the amplitude and size of the R2 and R2' components of the blink reflex, the latency and duration of the ES1 and ES2 components, and the recovery curve of the ES2 component of the temporalis muscle activity did not differ between groups. However, the recovery curve of the R2 component of the blink reflex diminished in patients with tension-type headache compared with the other groups. Our findings indicate reduced excitability of the brain stem interneurons in patients with tension-type headache.

Adult↗
PubMed1998

Somatosensory-evoked blink response: investigation of the physiological mechanisms.

The somatosensory-evoked blink response (SBR) is a newly identified blink reflex elicited by electrical stimulation of peripheral nerves. The present study was performed to investigate the physiological mechanism underlying the SBR elicited by median nerve stimulation in normal subjects. The peripheral afferents responsible for the SBR included low-threshold cutaneous fibres. In the SBR-positive subjects, the late (R2) component of the blink reflex elicited by supraorbital nerve stimulation and the SBR facilitated each other when both responses were induced at the same time, but they each caused long-lasting inhibition in the other when one stimulus was given as a conditioning stimulus. The extent of inhibition was correlated with the size of the preceding SBR. In the SBR-negative subjects, simultaneous inhibition of R2 was observed when median nerve stimulation was applied as a conditioning stimulus. Brainstem excitability, as evaluated by blink-reflex recovery studies, did not differ between SBR-positive and SBR-negative subjects. Therefore, based on anatomical and physiological findings, it appears that the reflex pathways of the SBR and R2 converge within the brainstem and compete with each other, presumably by presynaptic inhibition at the premotor level, before entering the common blink-reflex pathway. The influence of median nerve stimulation upon tonic contraction of the orbicularis oculi muscle was studied to detect the latent SBR. There was not only a facilitatory period corresponding to the SBR but also an active inhibitory period (exteroceptive suppression), suggesting that the mechanism generating the SBR is not only influenced by blink-reflex volleys but also by active exteroceptive suppression. Thus, the SBR may appear as a result of integration of facilitatory and inhibitory mechanisms within the brainstem.

Adult↗
PubMed1994

Tear film lipid layer thickness as a function of blinking.

Alterations in the tear film lipid layer as a function of blinking were investigated using a custom-designed specular reflection monitoring system. The tear film lipid layer of 104 subjects under conditions of normal ("baseline") blinking and "forceful" blinking was quantitated on the basis of specific interference colors. Deliberate, forceful blinking was found to significantly increase the lipid layer thickness (LLT) of the tear film. The magnitude of increase was found to be correlated with the baseline LLT values; individuals with baseline LLT values of 75-150 nm demonstrated a mean increase in LLT of 33 nm following forceful blinking, whereas subjects with baseline LLT values < or = 60 nm experienced a mean increase of 19 nm. The difference in the magnitude of increase between the groups was highly significant (p = 0.0001). The data suggest that, in addition to playing a role in the spreading of lipid across the tear film, the blinking mechanism may be important in the maintenance of the lipid layer by augmenting the expression of lipids from the meibomian glands.

Adolescent↗
PubMed1985

Eye-blink rate in Tourette's syndrome.

Gilles de la Tourette's syndrome is a hyperkinetic movement disorder in which an etiological role for dopaminergic hyperactivity has been proposed. Blink rate, a putative correlate of central dopamine activity, is commonly held to be elevated in Tourette's syndrome, a finding that would be consistent with the "dopamine" hypothesis of this disorder. In 19 patients who had Tourette's syndrome, however, blink rates during placebo treatment were identical with those of 49 index controls during reading and quiet sitting. Blink rate did correlate, however, with both the number and severity of tics. Pimozide treatment did not reduce blinking in the patients. It should be noted that nine of the patients were adolescents for whom there were not adequate age-matched controls, a fact which could obscure a blink rate elevation in this group. Insofar as blink rate is a putative correlate of central dopamine activity, these results are not consistent with elevated brain dopamine activity in adult patients who have Tourette's syndrome.

Adolescent↗