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PubMed2006

Subjective sleepiness, simulated driving performance and blink duration: examining individual differences.

The present study aimed to provide subject-specific estimates of the relation between subjective sleepiness measured with the Karolinska Sleepiness Scale (KSS) and blink duration (BLINKD) and lane drifting calculated as the standard deviation of the lateral position (SDLAT) in a high-fidelity moving base driving simulator. Five male and five female shift workers were recruited to participate in a 2-h drive (08:00-10:00 hours) after a normal night sleep and after working a night shift. Subjective sleepiness was rated on the KSS in 5-min intervals during the drive, electro-occulogram (EOG) was measured continuously to calculate BLINKD, and SDLAT was collected from the simulator. A mixed model anova showed a significant (P < 0.001) effect of the KSS for both dependent variables. A test for a quadratic trend suggests a curvilinear effect with a steeper increase at high KSS levels for both SDLAT (P < 0.001) and BLINKD (P = 0.003). Large individual differences were observed for the intercept (P < 0.001), suggesting that subjects differed in their overall driving performance and blink duration independent of sleepiness levels. The results have implications for any application that needs prediction at the subject level (e.g. driver fatigue warning systems) as well as for research design and the interpretation of group average data.

Adult↗
PubMed2004

Suppression of pain and the R2 component of the blink reflex during optokinetic stimulation.

The effect of exposure to a rotating optokinetic drum on the electrically evoked blink reflex was investigated in 20 healthy volunteers. Pain ratings and the area under the curve of the R2 component of the blink reflex to innocuous and nociceptive trigeminal stimulation decreased substantially during and after optokinetic stimulation. At low shock intensities, R2 decreased most during optokinetic stimulation in subjects who did not develop symptoms of motion sickness. In contrast, during the recovery period after optokinetic stimulation, suppression of R2 to moderate and intense stimuli was greatest in the most nauseated subjects. These findings suggest that a mechanism that suppresses symptoms of motion sickness during sensory conflict also inhibits activity in wide dynamic range neurones in the trigeminal nucleus caudalis. Nausea in the absence of sensory conflict may inhibit R2 to intense electrical stimulation by provoking diffuse noxious inhibitory controls.

Adaptation, Physiological↗
PubMed1991

The effect of an acoustic warning stimulus upon the electrically elicited blink reflex in humans.

In a warned Go/No-Go reaction time experiment blink reflexes were elicited electrically immediately before, at, and shortly after the onset of a low intensity acoustic warning stimulus. This provided the opportunity to study the mutual effects of two stimuli of different modalities arriving at the facial nucleus. The warning stimulus was followed after 3 s by an acoustic response stimulus. Sixteen subjects participated in the experiment. They were informed by the response stimulus if a response (a voluntary blink of the right eye) was required. R1 magnitude was increased from 10 ms to 100 ms after warning stimulus onset, with a pronounced peak at 50 ms. The bilateral late component R2 was enhanced when the reflex eliciting stimulus preceded the warning stimulus. Between 20 ms and 30 ms after warning stimulus onset, R2 returned to control level, whereas an eliciting stimulus presented 40 ms or later after warning stimulus onset produced a pronounced inhibition. R2 latency was facilitated immediately after warning stimulus onset. It was concluded that the mutual effects of stimuli of different modalities can be interpreted only if the moment of arrival at the motor nucleus is taken into consideration.

Adult↗
PubMed1991

Startle and emotion: lateral acoustic probes and the bilateral blink.

The affect-startle effect describes the modulation of the reflexive eyeblink response to a probe startle stimulus as a function of foreground emotional valence. Larger blinks occur during viewing of unpleasant slide foregrounds, relative to positive foregrounds. This effect has been obtained repeatedly using binaural acoustic startle probes. The current study examines this phenomenon for monaural probes administered to the left and right ears in separate blocks. Startle probes were presented during and between exposures to pleasant, neutral, and unpleasant slides, with the ear of presentation counterbalanced across subjects. Left monaural probes produced blink magnitudes that increased linearly from pleasant to unpleasant slide foregrounds, and appeared to be independent of attention or interest. Right monaural probes did not vary with foreground valence. These findings suggest that the startle probe indexes emotional processing that is lateralized in the central nervous system.

Adult↗
PubMed1990

The blink reflex in cluster headache.

To investigate the involvement of the trigeminal system in cluster headache, in twelve subjects the electrically-elicited blink reflex during a symptomatic period was examined. In eleven cases, the amplitude of the contralateral R2 response on the symptomatic side was significantly lower, at the same stimulus intensity, than on the asymptomatic side (p = 0.005). The blink reflex can be useful to evaluate biological and drug-induced phenomena in cluster headache.

Adult↗
PubMedDate not supplied

Effects of monotherapy and polytherapy on the blink reflex in epileptic patients.

We performed the blink reflex (BR) in 20 normal volunteers, 13 epileptic patients receiving antiepileptic drug (AED) monotherapy, and 13 epileptic patients receiving AED polytherapy. Comparison of R1, ipsilateral and contralateral R2 and VIIth nerve latencies in the three groups showed no statistically significant differences R1 and VIIth nerve latencies among the three groups. There were statistically significant differences between the polytherapy group and the monotherapy and control groups in comparisons of ipsilateral and contralateral R2. There were no significant differences between the monotherapy group and the control group for ipsilateral and contralateral R2. We hypothesized that AED polytherapy might interfere with synaptic transmission in the polysynaptic pathway of the blink reflex, prolonging the latency of R2. These results provide further evidence of the pathophysiologic effects associated with polytherapy in epileptic patients.

Adolescent↗
PubMed1990

Lesch-Nyhan syndrome with delayed onset of self-mutilation: hyperactivity of interneurons at the brainstem and blink reflex.

We studied a case of Lesch-Nyhan syndrome with delayed onset of self-mutilation. Athetotic cerebral palsy and mental retardation were diagnosed at 1 year old, but the disease was not suspected until age 8 years when he began biting his lips and fingers. There was no obvious alteration of catecholamine in urine and CSF. We attempted to induce a series of blink reflexes by electric, mechanical and photic procedures. The R1 amplitude increased and the latency of the R2 shortened compared with controls. This shows that not only orbicularis motoneuron itself, but also uncrossed interneurons, are in a state of hyperexcitability. The contralateral R2 was poor which was in favour of hypoexcitability of the crossed interneurons at the brainstem. The significant large response was obtained by photic procedure which was in favour of hyperexcitability of the motoneurons. Therefore, it is demonstrated that a thorough examination of blink reflexes provides a useful method for examination of a state of the underlying neural activity.

Blinking↗
PubMed1998

Voluntary eyelid contraction modifies the blink reflex recovery cycle.

In order to determine the extent to which the recovery cycle of the blink reflex is modified by voluntary contraction of the eyelids we investigated the electrically elicited blink reflex with paired stimuli of identical intensity in 9 healthy subjects. We pseudorandomly administered two interstimulus intervals (150 ms and 250 ms) in three different conditions of voluntary contraction of the orbicularis oculi muscle (relaxed, mild lid closure and strong lid closure). Our results show that inhibition of the R2 response following the second stimulus is significantly reduced with voluntary contraction. In addition, we found significantly larger amplitudes and shorter latencies of R1 and R2 with voluntary contraction. We conclude that in healthy subjects, voluntary eyelid contraction causes facilitation or disinhibition not only in the nuclei of the seventh cranial nerve, but also in the polysynaptic pathway of the R2. The possible implications on the interpretation of clinical data are discussed.

Adult↗
PubMed1995

Soft lens movement: effect of blink rate on lens settling.

Little is understood about the mechanism by which soft lenses settle on the eye, although it has been suggested that lens base curve, steepening with in-eye lens dehydration or tear film changes may influence lens movement in the initial period of wear. In this study, we investigated the role of postlens tear fluid expulsion by assessing lens movement in 20 subjects wearing 38% water content hydrogel lenses for 10 min under three different conditions: 10 blinks/min, 30 blinks/min and eye closure. Over the 10 min wearing period, the total decrease in median lens movement for the 10 blinks/min condition was 0.07 mm, which was not a significant change (Friedman ANOVA, p = 0.13), while significant decreases occurred with conditions of 30 blinks/min (0.19 mm, p = 0.004) and eye closure (0.43 mm, p = 0.0001). As expected, lens movement under the three conditions was the same at insertion, but was significantly higher thereafter for the slower blink rate condition compared to the faster blink rate or eye closure conditions (Wilcoxon test, Z = 2.8 and -3.0, p = 0.006 and 0.003, respectively). Based on these findings, we postulate the model that the extent of lens settling and the degree of postinsertion lens movement are determined by the timeaverage pressure for postlens tear film expulsion exerted on the lens by the eyelids.

Adult↗
PubMed1993

Blinking, alpha brain waves and smoking in schizophrenia.

Blink rates (BR) and alpha brain waves were studied in 13 schizophrenic and 13 healthy smokers under conditions of smoking deprivation as well as smoking saturation and under different task conditions of smooth pursuit eye movements. Task conditions significantly changed BR and alpha power; smoking enhanced BR and alpha frequency, the latter effect being especially pronounced in schizophrenics for F3-F4 leadings. Concerning BR, groups differed significantly as long as smoking quantity was not statistically controlled. BR, alpha power and smoking quantity were consistently correlated above chance levels. Results are discussed with respect to the blink alpha neurocircuit model.

Adult↗
PubMed1985

Jaw, blink and corneal reflex latencies in multiple sclerosis.

Jaw, blink and corneal reflexes, which all involve the trigeminal system, were recorded in 54 patients with multiple sclerosis; thirty-seven of these patients were classified as having definite multiple sclerosis and 17 as indefinite multiple sclerosis, according to Schumacher's criteria. The jaw reflex was abnormal less frequently than either of the other two reflexes, but in four cases it was the only abnormal reflex found. Testing a combination of two or three trigeminal reflexes did not yield a higher incidence of abnormalities than testing the blink or corneal reflex alone. Nine patients showed abnormal reflexes which were unexpected on the basis of clinical symptoms. The combined recordings demonstrate at least one abnormal reflex in 74% of the patients. The various types of reflex abnormalities reflect major damage to different parts of the trigeminal system and may therefore make an important contribution to the diagnosis of multiple sclerosis.

Adult↗
PubMed1989

Abnormalities of the blink reflex in Gilles de la Tourette syndrome.

The blink reflex and it's recovery cycle were studied in 26 patients with Gilles de la Tourette syndrome and 10 controls. There was a significant increase in the mean duration of the R2 response. The amplitude of the R2 response following paired shocks (mean R2[T]/R2[C]%) was 11%, 40% and 52% of the conditioning stimulus with intervals of 200 ms, 500 ms and 1 second in the patients, compared with 10%, 17% and 32% respectively in the controls. Half the patients, however, had normal recovery cycles and voluntary suppression of tics and blinks reduced the amplitude of R2 in all patients. These results suggest increased excitability of brainstem interneurons in Gilles de la Tourette syndrome.

Adult↗
PubMed1990

Blink reflexes and magnetic resonance imaging in focal unilateral central trigeminal pathway demyelination.

The electrically elicited blink reflex allows quantitative analysis of the corneal reflex which traverses the trigeminal and facial nerves and the brainstem. Two patients presenting with symptomatic unilateral trigeminal lesions are described, in whom the blink reflexes showed conduction block and slowing at predictable sites in the central pathways, and magnetic resonance imaging confirmed precisely the clinical and electrophysiological localisation.

Adult↗
PubMed2005

Eye complaints in the office environment: precorneal tear film integrity influenced by eye blinking efficiency.

To achieve a common base for understanding work related eye complaints in the office environment, it is necessary to merge approaches from indoor air science, occupational health, and ophthalmology. Based on database searches, it is concluded that precorneal tear film (PTF) alteration leads to eye complaints that may be caused by: (1) thermal factors (low relative humidity; high room temperature); (2) demanding task content (attention decreases blinking and widens the exposed ocular surface area); and (3) individual characteristics (for example, tear film alterations, blinking anomalies, gland dysfunctions, and use of contact lenses). These factors and conditions are able to progressively increase water evaporation and faster thinning of the PTF, which causes dryness and dry spot formation on the cornea, possibly followed by corneal and conjunctiva epithelial alterations and eye complaints. Another possible cause of eye complaints is certain irritating chemical compounds, in addition to oxidation mixtures that are formed in reactions between ozone and unsaturated organic compounds (alkenes). The effect may be exacerbated by low relative humidity.

Air Pollutants, Occupational↗
PubMed2003

Relative contributions of eyelid and eye-retraction motor systems to reflex and classically conditioned blink responses in the rabbit.

Early compensatory mechanisms between eyelid and eye-retraction motor systems following selective nerve and/or muscle lesions were studied in behaving rabbits. Reflex and conditioned eyelid responses were recorded in 1). controls and following 2). facial nerve section, 3). retractor bulbi muscle removal, and 4). facial nerve section and retractor bulbi muscle removal. Animals were classically conditioned with a delay paradigm by using a tone (350 ms, 600 Hz, 90 dB) as conditioned stimulus, followed 250 ms later by an air puff (100 ms, 3 kg/cm(2)) as unconditioned stimulus. Conditioned eyelid responses generated in the absence of the facial motor system (i.e., by the almost sole action of the retractor bulbi motor system) presented a wavy profile, due to the succession of eye-retraction movements. Learned eyelid responses generated in the absence of the eye-retraction motor system (i.e., by the almost exclusive action of the facial motor system) were similar to those of controls, but were reduced in amplitude and peak velocity. Finally, the isolated action of the extraocular recti muscle produced very small eyelid movements during both reflex and learned eyelid responses. Although each of these motor systems could act independently of the others, the motor result of their joint action did not coincide with the simple addition of their separate actions. Both facial and eye-retraction motor systems appear to be necessary for normal eyelid closure during blinking in rabbits. Central reorganization to compensate for loss of either of these systems may explain why the response of each system in isolation cannot be added linearly to obtain normal blink response magnitudes and profiles.

Animals↗
PubMed1999

Discharge profiles of abducens, accessory abducens, and orbicularis oculi motoneurons during reflex and conditioned blinks in alert cats.

The discharge profiles of identified abducens, accessory abducens, and orbicularis oculi motoneurons have been recorded extra- and intracellularly in alert behaving cats during spontaneous, reflexively evoked, and classically conditioned eyelid responses. The movement of the upper lid and the electromyographic activity of the orbicularis oculi muscle also were recorded. Animals were conditioned by short, weak air puffs or 350-ms tones as conditioned stimuli (CS) and long, strong air puffs as unconditioned stimulus (US) using both trace and delayed conditioning paradigms. Motoneurons were identified by antidromic activation from their respective cranial nerves. Orbicularis oculi and accessory abducens motoneurons fired an early, double burst of action potentials (at 4-6 and 10-16 ms) in response to air puffs or to the electrical stimulation of the supraorbital nerve. Orbicularis oculi, but not accessory abducens, motoneurons fired in response to flash and tone presentations. Only 10-15% of recorded abducens motoneurons fired a late, weak burst after air puff, supraorbital nerve, and flash stimulations. Spontaneous fasciculations of the orbicularis oculi muscle and the activity of single orbicularis oculi motoneurons that generated them also were recorded. The activation of orbicularis oculi motoneurons during the acquisition of classically conditioned eyelid responses happened in a gradual, sequential manner. Initially, some putative excitatory synaptic potentials were observed in the time window corresponding to the CS-US interval; by the second to the fourth conditioning session, some isolated action potentials appeared that increased in number until some small movements were noticed in eyelid position traces. No accessory abducens motoneuron fired and no abducens motoneuron modified their discharge rate for conditioned eyelid responses. The firing of orbicularis oculi motoneurons was related linearly to lid velocity during reflex blinks but to lid position during conditioned responses, a fact indicating the different neural origin and coding of both types of motor commands. The power spectra of both reflex and conditioned lid responses showed a dominant peak at approximately 20 Hz. The wavy appearance of both reflex and conditioned eyelid responses was clearly the result of the high phasic activity of orbicularis oculi motor units. Orbicularis oculi motoneuron membrane potentials oscillated at approximately 20 Hz after supraorbital nerve stimulation and during other reflex and conditioned eyelid movements. The oscillation seemed to be the result of both intrinsic (spike afterhyperpolarization lasting approximately 50 ms, and late depolarizations) and extrinsic properties of the motoneuronal pool and of the circuits involved in eye blinks.

Abducens Nerve↗
PubMed1999

The electrically elicited startle blink reflex in patients with schizophrenia: A threshold study of different reflex components.

The electrically elicited blink reflex consists of three components (R1, R2, R3). In humans the excitability of these components is influenced by attentional states. In particular, distraction from the stimulus leads to facilitation of the bilateral R2 and R3. The present study was performed in order to investigate the excitability of the different components of the electrically evoked blink reflex in 13 patients with schizophrenia and 13 normal controls under standard conditions. Therefore, the thresholds of the distinct components were determined without any inhibitory or facilitatory procedure. There was no significant difference in R1 and R2 thresholds between patients and controls. In contrast, the R3 threshold was significantly reduced in schizophrenic patients (R3 threshold = 17.5 mA in normal subjects, 10.5 mA in patients, p = 0. 0001). In recent studies the R3 magnitude was found to be highly susceptible to changes in the attentional state of normal subjects. The lower threshold of R3 in patients with schizophrenia might therefore be a neurophysiological marker of attentional dysfunctions in schizophrenia.

Adult↗
PubMed1984

Blink reflex in hemiplegia.

Data about the influence of hemispheric lesions on the blink reflex are conflicting. 21 hemiplegic patients and 11 control subjects were investigated. The duration, latency and electric area of electrically evoked blink reflex responses were evaluated by common electromyographic techniques. A depression of the ipsilateral and the consensual late response after stimulation of the paretic side was the most evident finding. However, also a certain increase of the early response and a depression of the late response of the paretic side independent of the side of stimulation emerged. Concerning the parameters taken into account, the evaluation of the latency period seems to be the most significant and reliable. Determination of the electric area provides additional useful data which, however, may easily lead to mistakes.

Adult↗