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At least 235 records · Page 13Linked to original sources
PubMed1985

Effects of lisuride on blink reflex habituation in Parkinson disease.

The blink reflex presents a tendency to habituation (a gradual diminution of the amplitude of the response during repetitive stimulation). Electromyographic analysis of this reflex makes it possible to quantify this phenomenon. A lack of the habituation of the blink reflex is a typical feature of Parkinson disease. L-Dopa and amantadine, but not anticholinergic drugs, are able to partly reverse these abnormalities in blink reflex habituation to a normal pattern. Lisuride, a dopamine agonist with serotoninergic activity, has been recently proposed as antiparkinsonian agent. In our study we observed that lisuride has a positive effect on blink reflex habituation in Parkinson disease. A good correlation between the improvement of this electrophysiological parameter and clinical akinesia was seen. Mechanisms underlying the therapeutic effect of lisuride are complex, but this drug usually has a postsynaptic effect on D2 receptors. Our data suggest that these receptors play an important role in blink reflex habituation.

Adult↗
PubMed1984

Eye-blinking and cerebral ventricular size in chronic schizophrenic patients.

Spontaneous eye-blinking, a possible measure of central dopaminergic activity, was studied in 55 drug-free chronic schizophrenic patients subdivided by cerebral ventricular size. Blink rates were higher in schizophrenic patients than in normal control subjects, regardless of cerebral ventricle size. Neuroleptics lowered blink rates in patients with normal ventricles but did not affect blink rates in patients with large ventricles. Insofar as blinking is a dopaminergic parameter, these findings suggest that the dopamine hypothesis of schizophrenia is most relevant in patients with normal ventricles.

Adult↗
PubMed1987

Prognostic significance of the electrically elicited blink reflex in neonates.

The electrically elicited blink reflex was examined in ten normal neonates, 11 postasphyxial neonates, and 3 congenital hydrocephalus cases. The blink reflex was elicited in all cases. In normal neonates, the latencies and amplitudes were 10.9 +/- 0.7 msec and 159 +/- 62 microV at R1, 34.3 +/- 1.4 msec and 123 +/- 30 microV at R2, and 40.7 +/- 2.3 msec and 84 +/- 25 microV at R'2 respectively. Ischemic-hypoxic brain damage during the neonatal period mainly influenced the late components of the blink reflex. The blink reflex of the postasphyxial neonates showed significantly prolonged latencies of R2 and R'2. The amplitudes were increased in cases with a fair prognosis and decreased in cases with a poor prognosis. A case of congenital hydrocephalus with mental retardation also showed the prolonged latencies of R2 and R'2 in neonatal period. The blink reflex in neonates appears to be useful in predicting the outcome in cases of neonatal asphyxia and congenital hydrocephalus.

Asphyxia Neonatorum↗
PubMed1990

Auditory brain stem response and electrically elicited blink reflex in handicapped children.

The auditory brain stem response and the blink reflex were studied in 35 handicapped children in order to evaluate brain stem function. The auditory brain stem response and the blink reflex were abnormal in 20 and 16 cases, respectively. Of these, 14 had both auditory brain stem response and blink reflex abnormalities. The prevalence of auditory brain stem response and blink reflex abnormalities was high in severely handicapped children with difficulty in chewing or swallowing. The blink reflex was abnormal in four of 32 sides with a normal auditory brain stem response and 15 of 23 sides with an abnormal auditory brain stem response threshold, which reflects hearing loss or brain stem dysfunction. We conclude that the combined application of these two noninvasive tests is useful not only to delineate the extent of brain stem lesions but also to determine whether or not patients with an abnormal auditory brain stem response threshold have brain stem dysfunction.

Acoustic Stimulation↗
PubMed2000

Developmental changes in eye-blink conditioning and neuronal activity in the cerebellar interpositus nucleus.

Neuronal activity was recorded in the cerebellar interpositus nucleus in infant rats during classical conditioning of the eye-blink response. The percentage and amplitude of eye-blink conditioned responses increased as a function of postnatal age. Learning-specific neuronal activity in the cerebellum emerged ontogenetically in parallel with the eye-blink conditioned response. There were also age-specific changes in neuronal activity after the onset of the conditioned and unconditioned stimuli. The results indicate that the development of the eye-blink conditioned response may depend on the development of stimulus-evoked neuronal responses and learning-specific plasticity in the cerebellum. Functional immaturity in the afferent neural pathways may limit the induction of neural plasticity in the cerebellum and thereby limit the development of the eye-blink conditioned response.

Acoustic Stimulation↗
PubMed2000

The effect of warning stimulus modality on blink startle modification in reaction time tasks.

The present study investigated the effects of lead stimulus modality on modification of the acoustic startle reflex during three reaction time tasks. In Experiment 1, participants (N = 48) were required to press a button at the offset of one stimulus (task relevant) and to ignore presentations of a second (task irrelevant). Two tones that differed in pitch or two lights served as signal stimuli. Blink startle was elicited during some of the stimuli and during interstimulus intervals. Skin conductance responses were larger during task-relevant stimuli in both groups. Larger blink facilitation during task-relevant stimuli was found only in the group presented with auditory stimuli, whereas larger blink latency shortening during task-relevant stimuli was found in both groups. Experiment 2 (N = 32) used only a task-relevant stimulus. Blink magnitude facilitation was significant only in the group presented with tones, whereas blink latency shortening was significant in both groups. Experiment 3 (N = 80) used a go/nogo task that required participants to press a button if one element of a compound stimulus ended before the second, but not if the asynchrony was reversed. The offset asynchrony was varied between groups as a manipulation of task difficulty. Startle magnitude facilitation was larger during acoustic than during visual stimuli and larger in the easy condition. The present data indicate that startle facilitation in a reaction time task is affected by stimulus modality and by task demands. The effects of the task demands seem to be independent of lead stimulus modality.

Acoustic Stimulation↗
PubMed1999

Electrically elicited blink reflex in horses with trigeminal and facial nerve blocks.

OBJECTIVE: To reassess reference values for the components of the electrically induced blink reflex, document reference values for facial motor nerve conduction velocity, and demonstrate usefulness of the blink reflex as a diagnostic tool in peripheral facial and trigeminal nerve dysfunction in horses. ANIMALS: 10 healthy adult horses (8 males, 2 females) without neurologic abnormalities. PROCEDURE: Blink reflex tests were performed by electrical stimulation of the supraorbital nerve and facial (auriculopalpebral) nerve. Reflex and direct muscle-evoked potentials of the orbicularis oculi muscles were recorded from concentric needle electrodes inserted bilaterally in these muscles. Supraorbital and auriculopalpebral nerve blocks were performed by lidocaine hydrochloride injections. RESULTS: Supraorbital nerve stimulation elicited 2 or 3 ipsilateral and 1 contralateral reflex muscle potential in the orbicularis oculi muscles. Auriculopalpebral nerve stimulation elicited a direct and a reflex potential in the ipsilateral orbicularis oculi muscle. After left supraorbital nerve block, no responses could be elicited ipsilaterally or contralaterally upon stimulation of the blocked nerve, but bilateral responses were obtained upon stimulation of the right supraorbital nerve. After right auriculopalpebral nerve block, no responses were recorded from the right orbicularis oculi muscle upon stimulation of left or right supraorbital nerves. CONCLUSIONS AND CLINICAL RELEVANCE: Reference values for the components of the blink reflex and facial motor nerve conduction velocity will allow application of these tests to assist in the diagnosis of equine neurologic disorders involving the trigeminal and facial nerves, the brainstem, and the cranial end of the cervical segment of the spinal cord. This study reveals the usefulness of the blink reflex test in the diagnosis of peripheral trigeminal and facial nerve dysfunction in horses.

Animals↗
PubMed2003

The electrically elicited R2 blink reflex consists of distinct subcomponents.

In previous studies the later parts of the electrically evoked R2 blink reflex has been found to be more susceptible to the inhibitory effects of repetitive stimulation and prepulses. Consequently, it has been suggested that the R2 reflex may be composed of distinct subcomponents. However, as of yet, no study revealed electromyographical evidence for this hypothesis, probably due to a putative temporal overlap that makes it difficult to clearly separate distinct R2 subcomponents. In the present study we investigated the electrically evoked blink reflex in 26 healthy volunteers by using the paradigm of self-stimulation, which has been found to inhibit the R2 and may thus help to differentiate putative R2 subcomponents. In most of the participants self-stimulation resulted in inhibition of the reflex involving predominantly later sections of R2. In addition, in three subjects it was possible to clearly separate distinct R2 subcomponents. These findings suggest that the electrically elicited R2 blink reflex--like the acoustic blink response--consists of superimposed distinct subcomponents. Based on their differential modulation evoked by habituation, pre-stimulation and self-elicitation it is hypothesized that the early portions of the R2 represent the electrically evoked blink reflex, whereas the later sections belong to the generalized startle reaction in man. However, due to their temporal overlap a differentiation might not be possible in conventional recordings.

Adult↗
PubMed1992

[Multimodal evoked potentials and the blink reflex in patients with primary brainstem lesions].

In 17 patients with primary brainstem injury, out of 60 patients with severe head trauma, diagnostic and prognostic values of multimodal evoked potentials and blink reflex were evaluated in relation to clinical syndromes of the brainstem, the duration of coma and the outcome. Clinical classification of the brainstem syndromes according to Gerstenbrand and Rumpl was used for the evaluation of the clinical findings, the Innsbruck Coma Scale (ICS) for the evaluation of the coma level, and the Glasgow Outcome Scale (GOS) for the outcome. Analyses and measurements of the multimodal evoked potentials and blink reflex were used many times in the period of assessment (six months after the injury). The analysis of our results with multimodal evoked potentials and blink reflex revealed different correlation and sensitivity in relation to the clinical syndromes of the brainstem, the duration of coma and the outcome of the injury. The blink reflex and somatosensory evoked potentials had the best correlation and the greatest sensitivity, the auditory evoked potentials had somewhat, while the visual evoked potentials had none. Multimodal evoked potentials and blink reflex increase the specificity of the diagnosis of brainstem injury compared to clinical observation only, and improve prognostic reliability.

Adolescent↗
PubMed1992

Reflex blink to visual threat.

The requisite visual modalities for the reflex blink to visual threat have not been thoroughly studied. We identified five patients with different focal cerebral lesions documented on computerized tomography scan who had abnormal blink-to-threat reflexes. One had a homonymous hemianopia secondary to posterior cerebral artery occlusion; another had a unilateral parietal neglect; and a third had a frontal neglect. They did not blink in response to visual stimuli contralateral to their lesion. A cortically blind patient and one with Balint's syndrome did not have a blink response. Observation of these and other similar patients and animals previously reported suggests that the blink-to-threat reflex is cortically mediated and requires intact primary visual cortex as well as higher order mechanisms for visual attention mediated in the inferior parietal lobule and frontal eye fields.

Adult↗
PubMed1992

Changes in the activity of units of the cat motor cortex with rapid conditioning and extinction of a compound eye blink movement.

Patterns of spike activity were measured in the pericruciate cortex of conscious cats before and after development of a Pavlovian conditioned eye blink response. Unit activity was tested with presentations of a click conditioned stimulus (CS) and a hiss discriminative stimulus (DS) of similar intensity to the click. Unit discharge in response to the CS increased after conditioning, but not after backward conditioning when conditioned reflexes (CRs) were not performed. Rates of spontaneous, baseline discharge were not increased after conditioning with respect to rates of discharge measured in the naive state. It appeared that an increase in the ratio of CS-elicited discharge to background activity, together with an increase in the number of units responding to the CS after conditioning, supported discrimination of the CS from the DS and performance of the conditioned blink response. This is the first detailed characterization of patterns of a rapidly conditioned Pavlovian response. Activation of units by the CS preceded the onset of the CR, supporting the hypothesis that the activity played a role in initiating the conditioned eye blink movement. Extinction with retention of performance of the CR was associated with perseverance of the increased unit discharge in response to the CS. Extinction with substantially reduced performance of the CR was associated with diminution of the unit response to the CS below levels found with conditioning. Averages of patterns of spike activity elicited by the CS after conditioning showed components of discharge with onsets of 8-40 msec (alpha 1), 40-72 msec (alpha 2), 72-112 msec (beta), and greater than 112 msec (gamma), corresponding to each of four separate excitatory EMG components of the compound blink CR. Each component increased in magnitude after conditioning, relative to levels found in the naive state. The finding that long- as well as short-latency components of unit activation increased after conditioning supported the hypothesis that generation of both long- and short-latency blink CRs in normal animals may depend significantly on neural circuitry and mechanisms within the motor cortex.

Animals↗
PubMed1983

Three types of blink reflex evoked by supraorbital nerve, light flash and corneal stimulations.

Three types of blink reflex were evoked by 1) supraorbital nerve stimulation, 2) light flash stimulation and 3) corneal touch. The blink reflex response was recorded simultaneously for both eyes by electromyography of the orbicularis oculi muscles of the lower eyelid. After supraorbital nerve stimulation, ipsilateral early response (R1) and bilateral late responses (R2) were demonstrated. The light flash stimulation evoked the photic early and late responses. The latency times of the R1, R2 and the photic early responses were determined in 22 normal subjects. The corneal touch was exactly timed using a new device and the latency time of the corneal blink reflex was determined. The latency of the ipsilateral corneal blink reflex was significantly shorter than that of the contralateral reflex. The blink reflexes by supraorbital nerve stimulation and light flash were studied concurrently in 7 patients with neurological disorders of vascular origin. The photic reflex was disturbed by bilateral occipital lobe lesions and also by affection of the rostral midbrain. The reflexes were not affected by lesions in the medial longitudinal fasciculus but were disturbed by widespread brainstem lesions of Foville syndrome. Clinical significance of a combined use of the supraorbital nerve and light flash stimulation was emphasized.

Adult↗
PubMed1982

Measuring the average evoked response to light flashes: the contribution of eye-blink artifact to augmenting-reducing.

There have been numerous reports relating individual differences in stimulus intensity control to psychopathology and personality. Most of these studies record the averaged evoked response (AER) to light flashes of different brightness and assess the relationship between response amplitude and stimulus intensity. The present investigation used procedures commonly employed in these studies to examine the effects of eye blinks on the AER. Twenty normal subjects were tested twice over a 1-week interval while the AER and electroocculographic (EOG) response generated by a blink were recorded. The averaged EOG was digitally subtracted from the AER to yield a blink-corrected AER. Various comparisons of amplitude measures derived from corrected and uncorrected AERs and the averaged EOG revealed that blinking contributed a pronounced artifact that tended to reduce the magnitude of AER amplitude, especially to the more intense stimuli. These findings raise questions about the validity of interpretations drawn from studies of AER augmenting-reducing, very few of which control for eye-blink artifact. The linearity of the amplitude-intensity relationship for each subject was also assessed. This analysis revealed that the data points were poorly described by a straight line and therefore that the use of linear slope to characterize the amplitude-intensity relationship is unwarranted.

Blinking↗
PubMed1998

Optimal EMG signal bandwidth and interelectrode distance for the recording of acoustic, electrocutaneous, and photic blink reflexes.

The bandwidth for the recording of the orbicularis oculi blink reflex electromyogram (EMG) response is optimal when low-frequency artifacts, such as motion artifacts and cross-talk from other muscles, are maximally suppressed, whereas true EMG signal power is maximally retained. The optimal bandwidth was investigated for acoustic, electrocutaneous, and photic blink reflexes. Reflexes were recorded with varying bandwidth and interelectrode distances of 12 and 36 mm. Power spectra of the EMG signals were calculated and compared with a theoretical spectrum of the uncontaminated EMG signal. For both electrode distances, the optimal bandwidth was on the average 28-500 Hz for acoustic and electrocutaneous blink reflexes and 12-500 Hz for photic blinks. Using photic stimuli, however, a high-pass filter frequency larger than 12 Hz (probably at least 30 Hz) in combination with occlusion of the eye will be necessary to avoid influences of retinal potentials. Given the optimal bandwidth, a larger electrode spacing may be expected to moderately improve the detectability of small blinks in all stimulus conditions.

Acoustic Stimulation↗
PubMed1978

Blink reflex in facial-hypoglossal anastomosis.

The blink reflex was investigated in two patients after a facial-hypoglossal anastomosis had been performed. In each case the first component of the blink reflex could be demonstrated with normal latency on the operated side after ipsilateral supraorbital stimulation. These findings give further evidence that the first component of the blink reflex is not monosynaptic in nature. The second component of the blink reflex was distinctly retarded in the first case and was not seen at all in the second case. The second component of the blink reflex is influenced strongly by alteration of the intrabulbar and efferent part of the reflex circuits; it shows some correlation with voluntary motor activity.

Aged↗
PubMed2005

The role of the locus coeruleus in mediating the attentional blink: a neurocomputational theory.

The attentional blink refers to the transient impairment in perceiving the 2nd of 2 targets presented in close temporal proximity. In this article, the authors propose a neurobiological mechanism for this effect. The authors extend a recently developed computational model of the potentiating influence of the locus coeruleus-norepinephrine system on information processing and hypothesize that a refractoriness in the function of this system may account for the attentional blink. The model accurately simulates the time course of the attentional blink, including Lag 1 sparing. The theory also offers an account of the close relationship of the attentional blink to the electrophysiological P3 component. The authors report results from two behavioral experiments that support a critical prediction of their theory regarding the time course of Lag 1 sparing. Finally, the relationship between the authors' neurocomputational theory and existing cognitive theories of the attentional blink is discussed.

Adolescent↗
PubMed1996

Word meanings can be accessed but not reported during the attentional blink.

After the detection of a target item in a rapid stream of visual stimuli, there is a period of 400-600 ms during which subsequent targets are missed. This impairment has been labelled the 'attentional blink'. It has been suggested that, unlike an eye blink, the additional blink does not reflect a suppression of perceptual processing, but instead reflects a loss of information at a postperceptual stage, such as visual short-term memory. Here we provide electrophysiological evidence that words presented during the attentional blink period are analysed to the point of meaning extraction, even though these extracted meanings cannot be reported 1-2s later. This shows that the attentional blink does indeed reflect a loss of information at a postperceptual stage of processing, and provides a demonstration of the modularity of human brain function.

Adult↗
PubMed2005

Long time scale blinking kinetics of cyanine fluorophores conjugated to DNA and its effect on Förster resonance energy transfer.

The blinking kinetics of individual Cy5 fluorophores conjugated to DNA are directly measured using single-molecule spectroscopy. Under deoxygenated aqueous conditions, Cy5 fluorescence exhibits spontaneous and reversible on/off fluctuations with a period lasting seconds. This blinking is observed when directly exciting Cy5 with 640 nm light and by Forster resonance energy transfer (FRET). We find that Cy5 blinking is influenced by the proximity of the donor, the structure of the donor, the presence of 514 nm excitation, and FRET. In the context of single-molecule FRET, blinking of the acceptor produces anticorrelated donor-acceptor intensity fluctuations, which can be difficult to discern from variations in the interdye distance. Slow blinking is, in particular, problematic because it overlaps with biologically relevant time scales. By employing an alternating 514640 nm laser excitation scheme, we show that the dark states can be readily resolved and discriminated from FRET distance fluctuations.

Carbocyanines↗