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At least 145 records · Page 8Linked to original sources
PubMed2000

Baseline blink rates and the effect of visual task difficulty and position of gaze.

PURPOSE: To compare the baseline blink rates (BBR) measured under different (baseline) conditions, and to compare the blink rates measured when performing two visual tasks of different levels of difficulty at two positions of gaze. METHODS: In the first single masked experiment, BBR were measured under three different conditions - (i) conversation with the subjects (ii) taking the visual acuity and (iii) keeping the subjects waiting in an empty examination room. In the second single masked experiment, the subjects were required to perform an easy task (reading normal English words) and a difficult task (reading mirror-image English words) at primary gaze and down gaze. The orders of the tasks performed were randomly allocated. RESULTS: BBR taken under the three different conditions were significantly different from each other. No significant difference was found between the blink rates measured when performing the two reading tasks if they were performed at the same position of gaze. The mean blink rates were significantly lower when performing the tasks at down gaze than when performing the tasks at primary gaze. No significant differences were found between BBR-waiting and blink rate measured when the subject was doing the easy task at primary gaze, and between BBR-VA and blink rate measured when the subject was performing the difficult task at primary gaze. CONCLUSIONS: BBR measured under different (baseline) conditions produced different results so it is important for investigators to describe the baseline condition very clearly in studies where BBR are measured. Our results also indicated that mean blink rate was affected by the position of gaze and not the level of task difficulty.

Adult↗
PubMed2001

The misclassification of blinks as saccades: implications for investigations of eye movement dysfunction in schizophrenia.

It is important to have a simple. accurate method for recording eye movements. Of the two popular approaches commonly adopted, electro-oculography (EOG) and infrared oculography (IROG), IROG is often accepted as the more accurate, and it is the method that is currently used most frequently to examine eye movements in schizophrenia. This study investigated whether the misclassification of blinks as saccades affects saccade rates when the presence of a blink is determined using only IROG recordings of eye position. Both vertical electro-oculography (VEOG), which can be used to objectively identify blinks, and IROG were recorded while 17 schizophrenia patients and 19 healthy controls were presented with sinusoidal stimuli. Of the blinks identified with the VEOG for the total group of participants, a substantial number (37%) were misclassified as catch-up and anticipatory saccades when only the IROG was used. Furthermore, in the schizophrenia group, but not in the healthy control group, the use of the IROG led to a significant misclassification of blinks as anticipatory saccades. Therefore, when IROG alone is used to identify blinks, the misclassification of blinks as saccades is likely to introduce measurement error into estimates of saccade rates, particularly estimates of anticipatory saccade rates in schizophrenia patients.

Adult↗
PubMed2002

The effect of apomorphine on blink kinematics in subhuman primates with and without facial nerve palsy.

PURPOSE: The purpose of this study was to document the effect of acutely delivered apomorphine, a dopamine receptor agonist with both D1 and D2 properties, on blink rate and the amplitude-velocity characteristics of eyelid kinematics in a group of nonhuman primates. METHODS: Three cynomolgus and two rhesus macaques underwent baseline recordings for eyelid kinematics, using the Robinson search coil technique. Next, each animal received a 0.15-mg/kg subcutaneous injection of apomorphine. Recordings were taken at 45 and 90 minutes, respectively, after injection. Blink rates per minute were obtained, and main sequence relationships were calculated for every animal. The data were pooled for each eyelid, excluding one monkey who was affected by facial nerve palsy and was analyzed separately. RESULTS: Monkeys with normal facial musculature and normal baseline blink rates showed consistently longer, faster blinks after apomorphine. The main sequence relationship, although tending to be lower, was not statistically different from baseline. One monkey, with prior facial nerve palsy and a very steep amplitude versus peak velocity relationship, showed normalization of the main sequence slope after apomorphine at both 45 and 90 minutes after injection. CONCLUSIONS: Apomorphine consistently lowers blink rate and changed blink metrics in normal monkeys and, more dramatically, in a monkey with facial nerve palsy. These findings add credence to models in which dopamine deficiency plays a role in the modulation of blink kinematics.

Animals↗
PubMed1995

Blink rate as an index of dopamine function in adults with mental retardation and repetitive behavior disorders.

Direct observation of blink rate was used as a noninvasive, in vivo estimate of dopamine function in adults with mental retardation and repetitive behavior disorders. Blink rate as measured in groups of stereotypy, compulsion, and control subjects was highly stable. Subjects with stereotypies had significantly lower blink rates than did control subjects. Although blink rates for compulsive subjects were not significantly different from those of control subjects, a subgroup of compulsive subjects with comorbid stereotypic behaviors displayed significantly lower blink rates. Significant inverse correlations were found for blink rate and severity of repetitive behavior disorder and for blink rate and ratings of motor slowness. These findings support the hypothesis that stereotyped behavior among adults with mental retardation is mediated by hypodopaminergic function.

Adult↗
PubMed1996

Eye-blink rates and depression. Is the antidepressant effect of sleep deprivation mediated by the dopamine system?

A series of studies demonstrated a possible correlation between eye-blink rate and central dopamine activity. The hypothesis has been put forward that the antidepressant effect of sleep deprivation (SD) is mediated by an enhanced dopamine release resulting in an amphetaminelike action of SD. Therefore, the blink rates of 12 drug-naive patients with major depression and 12 healthy controls were compared before and after SD and before and after 2.5 mg bromocriptine as a dopaminergic challenge. The main result of the study was that the depressed patients had a significantly higher increase of blinking after SD both with and without a dopaminergic challenge. Basal eye-blink rate was not different in nonretarded major depression patients compared to controls. Sleep deprivation increased blink rate in depression patients but not in controls, and the increase was proportional to improvements in depressive state after sleep deprivation. Bromocriptine did not increase blink rate 1 hour after application. This result is consistent with the hypothesis that antidepressant SD acts through dopamine release, although it is not conclusive, because other neurotransmitters like acetylcholine may be involved in the regulation of blinking.

Adult↗
PubMed1978

A simple device to improve blinking.

A blink beeper was devised to remind patients with incomplete or infrequent blinking to blink completely and at normal intervals; the beeper worked by transmitting an audible tone every ten seconds through an earphone. In three postkeratoplasty patients, this simplistic approach not only resulted in a complete blink at regular intervals, but seemed to condition this response to continue when the blink beeper was taken away; this resulted in healing of large chronic epithelial defects. The blink beeper has also proved valuable in patients with either punctate epithelial erosions or those who wore hard contact lenses unsuccessfully because of infrequent or incomplete blinking.

Adolescent↗
PubMed1999

Relation between tear breakup time and spontaneous blink rate.

Blinking plays an important role in maintaining corneal integrity by spreading of the tear film. Although there are studies reporting on blink rate and tear stability, a consensus has not been reached. Therefore, the blink rate and tear breakup time (TBUT) test were performed in 159 healthy young females. The mean TBUT and blink rate values observed were 18.9 seconds and 18.6 blinks/min, respectively. A significant correlation (r = 0.74, p < 0.05) between TBUT and blink rate was found. These results demonstrate that blink rate may be dependent on TBUT, at least among subjects with TBUT less than 19 seconds. Thus, blink rate may depend not only on cortical stimuli but also on the stability of the tear film.

Journal Article↗
PubMed1995

Effects of ocular surface area and blink rate on tear dynamics.

OBJECTIVE: To study the effects of exposed ocular surface area and blink rate on tear dynamics by the measurement of tear evaporation under a range of conditions. METHODS: Tear evaporation was measured in three gaze positions in 15 normal volunteers, and the ocular surface area was determined as a function of the width of the palpebral fissure. In 17 normal volunteers, the effect of blink rate on tear evaporation was assessed. RESULTS: The ocular surface area was 1.2 +/- 0.27, 2.2 +/- 0.39, and 3.0 +/- 0.33 cm2 with patients looking down, ahead, and up, respectively. The corresponding tear evaporation rates per eye were 7.0 +/- 3.5, 17.6 +/- 6.6, and 23.7 +/- 6.3 x 10(-7) g/s, respectively. The tear evaporation per square meter also increased proportionally with the ocular surface area. When the blink rate was changed from 10 to 60 per minute, the tear evaporation did not change in those individuals with evaporation rates more than 7.8 x 10(-7) g/s per square centimeter, whereas it did increase with the blink rate in those whose evaporation rates were lower. CONCLUSIONS: Ocular surface area and blink rate affect tear dynamics. Moderate palpebral fissure width and blink rate are necessary for the prevention of desiccation of the ocular surface.

Adult↗
PubMed2002

Objective evaluation of infraorbital nerve involvement in maxillary lesions by means of the blink reflex.

OBJECTIVE: To objectively evaluate the effects of maxillary lesions on the infraorbital nerve (ION). METHODS: We investigated the latencies (R1, R2) of the blink reflex, stimulating the infraorbital foramen electrically (18 mA, 0.2 millisecond). Twenty-two patients with unilateral maxillary lesions were enrolled. RESULTS: Ten patients showed delayed or absent R1 on the lesion side. Four of 20 patients showed delayed difference in R2 latency. Ten (77%) of 13 patients with lesions along the ION pathway showed an abnormal blink reflex. Only 3 patients demonstrated a normal blink reflex despite a lesion along the pathway of the ION. All patients whose ION pathway was intact showed a normal blink reflex. CONCLUSIONS: These results suggested that lesions along the ION pathway may impair the afferent pathway of the blink reflex. The blink reflex may be valuable to evaluate maxillary lesions objectively. Furthermore, R1 is more effective than R2 in detecting ION defects.

Adult↗
PubMed1997

Spontaneous eye blinking, a measure of dopaminergic function, in children with acquired immunodeficiency syndrome.

OBJECTIVE: To investigate possible alterations in dopaminergic function in children with acquired immunodeficiency syndrome by evaluating spontaneous eye blink rate, a putative measure of central dopaminergic function. DESIGN: Evaluation of previously videotaped test sessions of a consecutive case series of 50 children (mean age, 5.2 years; range, 2-12 years) with acquired immunodeficiency syndrome. SETTING: Government medical research center. RESULTS: Intrarater reliability was high, expected co-variation of blink rate with age and concurrent mental activity were confirmed, and obtained rates were similar to published data. Higher blink rates, suggestive of increased dopaminergic function, were associated with more severe cortical atrophy (P < .05) and white matter abnormality (P < .05) on computed tomographic brain scans. The presence or severity of basal ganglia calcifications did not seem to influence blink rate. In addition, higher blink rates were associated with higher ratings of depressed affect (P < .05) and lower ratings of hyperactive behaviors (P < .05) during other test activities. CONCLUSIONS: The higher blink rates in human immunodeficiency virus-infected children with more severe cortical abnormalities suggest increased central dopamine activity compared with that in children without cortical computed tomographic brain scan abnormalities. Thus, as a result of structural brain abnormalities, neurotransmitter levels in children with acquired immunodeficiency syndrome may vary and this may be reflected in their socioemotional functioning.

AIDS Dementia Complex↗
PubMed1990

Seasonal independence of low prolactin concentration and high spontaneous eye blink rates in unipolar and bipolar II seasonal affective disorder.

Twenty-four subjects with seasonal affective disorder (SAD: bipolar II, n = 14; unipolar, n = 10) and 20 normal controls were assessed for early follicular basal serum prolactin (PRL) concentration in winter and summer. Luteal basal PRL concentration was assessed in winter. The PRL values represented the mean of three values derived during a 45-minute period. A subset of 17 subjects with SAD and 11 controls were also assessed for spontaneous eye blinking via a polygraphic recording in winter and summer. In winter, compared with controls, subjects with SAD were characterized by significantly lower follicular (10.1 vs 4.5 micrograms/L, respectively) and luteal (14.4 vs 7.4 micrograms/L, respectively) PRL values and by significantly higher eye blink rates (30 vs 61 blinks per 3 minutes, respectively). In summer, controls and subjects with SAD showed similar significant differences in follicular PRL values (9.3 vs 3.9 micrograms/L, respectively) and eye blink rates (25 vs 67 blinks per 3 minutes, respectively). No significant differences in PRL values or eye blink rates were found between the bipolar II and unipolar forms of SAD in either season. Results were discussed in terms of dopamine functioning.

Adult↗
PubMed2004

Systematic temporal variation in the rate of spontaneous eye blinking in human infants.

The rate of spontaneous eye blinking, a putative index of central dopamine activity based on neuropharmacological and clinical research, has been linked to cognitive activity and behavioral state. Although many species have been studied, few researchers have examined spontaneous eye blinking in human infants. Human infants between 10 and 12 weeks of age were observed before, during, and after a feeding or during attention to visual stimuli. Infants blinked spontaneously several times per minute, and their blinking rate increased during feeding and after the appearance of new visual stimuli. These systematic changes in the rate of spontaneous blinking under controlled conditions suggest that spontaneous blinking rate may reflect reliable variation in central nervous system activity that underlies behavioral and cognitive responses to salient or novel stimuli.

Attention↗
PubMed2001

Measuring the human retinal oxygenation response to a hyperoxic challenge using MRI: eliminating blinking artifacts and demonstrating proof of concept.

The retinal oxygenation response to a hyperoxic challenge measured using MRI appears to be an early and accurate marker of retinopathy risk in experimental models, with promising clinical potential. However, the application of this technique in humans is limited by blinking artifacts that can confound detection of subtle signal intensity changes. We asked subjects to refrain from blinking during a 12-s fast low-angle shot (FLASH) image, and to blink if needed during the following 3-s rest period. This no-blink blink cycle was repeated sequentially 20 times during either room-air or 100% oxygen breathing. Significant change (P < 0.05) was detected for the first time from the resultant blinking-artifact-free images in the preretinal vitreous oxygen tension (upper limit of about 13 mm Hg (1.8 KPa, N = 3)) following a 10-min hyperoxic inhalation challenge. These results provide the proof-of-concept data needed for future MRI evaluation of the retinal oxygenation response and human retinopathy, such as diabetic retinopathy.

Artifacts↗
PubMed1993

Types and time course of the alterations induced in monkey blink movements by botulinum toxin.

The alterations induced in eyelid movement metrics subsequent to unilateral injections of botulinum toxin type A into the orbicularis oculi muscle were studied in chronic alert monkeys using the search coil technique. Botulinum toxin caused rapid paralysis of blinks in the treated eyelid. The amplitude and peak velocity of blinks generated by this eyelid remained at or below 20% of that of the fellow, untreated eyelid for 10-20 days. Blink amplitude gain increased linearly thereafter, attaining control values by 40-60 days after injection. Recovery of blink peak velocity was slower. The adaptive alterations in blink duration that were observed during the acute phase of toxin paralysis suggest that the mechanisms responsible for blink reflex plasticity may produce bilateral adjustments in eyelid function. Taken together, these data establish a quantitative data base that can be exploited in order to: (1) better understand the neural adaptive mechanisms that operate during eyelid movements and (2) allow quantitative comparisons between current treatment protocols that employ botulinum toxin and protocols that may lead to improvements in the treatment of chronic eyelid spasm (blepharospasm).

Animals↗
PubMedDate not supplied

Blinks as an index of cognitive activity during reading.

Horizontal and vertical EOG recordings of eye movements were analyzed to determine the spatial and temporal distribution of blinks and the patterns of eye movements (saccades and fixation pauses) exhibited by six subjects during the reading of stories presented in two formats (on paper and on a VDT). The frequency and placement of blinks was not affected by the presentation condition. Blinks were determined to be non-randomly distributed during reading. Significantly more blinks (36%) occurred in conjunction with saccades than the proportion of time consumed by saccades (12%) would predict. Significantly more blinks (36%) occurred in the vicinity of line change saccades, which accounts for 15% of reading time, and with fixation pauses associated with regressions (42%), which accounts for 26% of reading time, than with fixation pauses during normal reading (22%), which accounts for 60% of reading time. The results of the study suggest that blink behavior during reading is under perceptual and cognitive control.

Adult↗
PubMed2004

Ultrasonic visualization of the effect of blinking on the lacrimal pump mechanism.

BACKGROUND: The role of the lacrimal sac (LS) and the medial canthal tendon in the lacrimal pump mechanism is controversial. This study used ultrasonic visualization to analyze this phenomenon. METHODS: Movements of the LS and the medial canthal tendon during blinking were visualized with sonography. In addition, the maximal profile area of the LS was measured before and after blinking using 15-MHz sonography in 14 individuals with a normal lacrimal drainage system and in six patients with lacrimal duct obstruction. RESULTS: The upper part of the LS could be located as an echolucent structure between the lacrimal bone and the medial canthal tendon. The medial canthal tendon appeared to compress the LS during lid closure and release the LS during lid opening. The measured profile area of the visible normal LS at the compression time decreased by 50%. The dilated LS of patients with obstruction could also be compressed by the orbital muscle on blinking, but the maximum area decrease was only 15.5%. CONCLUSION: The findings imply that the lacrimal part of the orbicularis muscle contracts during blinking, with the medial canthal tendon compressing the LS in a cranial direction. Completion of lid closure then compresses both canaliculi and LS, forcing the intrasacral fluid through the drainage system. The expansion of the LS during the opening phase of the blink causes suction, and after opening of the punctal areas the canaliculi and LS vacuum breaks to reload with tear fluid. These findings demonstrate the importance of the orbicularis muscle and the medial canthal tendon for the lacrimal pump mechanism during blinking.

Adult↗
PubMed1994

Blink rate in childhood schizophrenia spectrum disorder.

Spontaneous blink rate, a putative measure of dopamine function, was measured in schizophrenic, schizotypal, and normal children, aged 5.6-13.2 years during three different cognitive tasks. Unlike that of schizophrenic adults, the blink rate of the schizophrenic children who were not on neuroleptics was significantly lower than that of the normal children. There were no statistically significant differences, however, in the blink rates of the neuroleptic-treated schizophrenic children and the normal children. The schizophrenic and schizotypal children had similar spontaneous blink rates. Within each diagnostic group, the blink rate was lowest for listening, intermediate for conversation, and highest for verbal recall. These findings highlight the need to examine the relationship between age, blink rate, and dopamine function in childhood-onset schizophrenia spectrum disorder.

Adolescent↗
PubMed1991

MPTP lesions and dopaminergic drugs alter eye blink rate in African green monkeys.

Eye blink rates were studied in African green monkeys following relatively specific destruction of substantia nigra and its dopamine projections with the neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Monkeys treated with MPTP had a significantly lower blink rate than controls over a period from two to five and a half months after treatment. Furthermore, the degree of parkinsonism expressed in treated animals was inversely correlated with blink rate. Pharmacologic studies further supported the role of dopamine receptors in the regulation of blink rate. PHNO (4-propyl-9-hydroxynaphoxazine), a potent and highly specific D2 agonist, effective in alleviating parkinsonism, caused a significant transient increase in blink rate, while sulpiride, a D2 antagonist, caused a decrease and blocked the effect of PHNO. Apomorphine and haloperidol, although less specific, had potent and predictable effects based on their interactions with dopamine systems. Blink rate may provide a nonintrusive measure of central dopamine activity that would help to evaluate the progress of Parkinson's disease or treatments which attempt to restore dopamine function.

Animals↗