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PubMedDate not supplied

Causes of the instability of R3 component of electrically evoked blink reflex: role of the attention to the stimulus.

The causes of the spontaneous sharp amplitude variations of R3 component of electrically evoked blink reflex have been analyzed, in 10 subjects 24-30 years, in different experimental conditions: a) neutral condition, b) selective attention to the stimulus; distraction from the stimulus: c) by looking at a poster rich with images and d) by signaling from sequences of numbers three targets. In the situations where the subject does not play attention to the experimental set up, (a), or is distracted from it (c), the R3 response shows the maximal amplitude, whereas in condition of greater attention to the stimulus (b), R3 appears sharply reduced in amplitude. Where attentive levels are high but not focused on the stimulus (d), the reduction of the third reflex response is lesser. The reciprocal modifications with respect to the other responses R1 and R2 are also discussed.

Adult↗
PubMedDate not supplied

[Diagnostic and prognostic significance of long latency reflexes, somatosensory evoked potentials and the blink reflex in cerebral ischemia].

In order to determine diagnostic and prognostic value of long latency reflexes, blink reflex and somatosensory evoked potentials in patients with ischemic brain disease (IBD), examinations were done in 32 patients of both sexes with IBD, average age 44-76 years. First examinations were performed within first week of the onset of IBD and in majority of patients repeated after 3 and 6 months. Changes of electrophysiological characteristics compared with the degree of IBD, clinical presentation, localization, extent of infarction zone (measured by CT) and functional recovery where analyzed. Electrophysiological changes were predominantly associated with amplitude of physiological response and were in correlation with the degree of IBD, localization and the extent of infarction zone. Latencies were prolonged only in case of subcortical ischemic lesions. Correlation between functional recovery and electrophysiological changes was present only within the structures responsible for certain components of electrophysiological responses and localization of ischemic lesion. In conclusion, electrophysiological examinations are of high diagnostic and predictive value in IBD.

Adult↗
PubMed1996

Blink reflex: normal values and its findings on peripheral facial paralysis.

OBJECTIVE: To establish the normal values of blink reflex (BR) in healthy subjects and investigate the manifestations of BR in patients with peripheral facial paralysis (PFP). METHODS: BR was investigated in 23 patients with PFP and 50 healthy persons serving as control. While stimulating the supraorbital nerve on one side, the reflex responses of bilateral inferior-orbicularis oculi were recorded respectively, in which the two components recorded on the ipsilateral side of stimulation were named R1, R2 and the contralateral one, R2'. RESULTS: There was no significant difference between sexes, sides and among various groups of age R1, R2 and R2'. The mean latency of R1 was 10 msec and R2, R2', 29 msec. The absolute values of the amplitude were of relatively smaller significance due to their great variance, whereas the amplitude ratio between two sides was of some value. All patients showed absent response, delayed latency or/and abnormal amplitude on the paretic side, regardless of the side of stimulation, indicating a typically efferent involvement. CONCLUSION: BR is another objective and noninvasive test for facial paralysis in evaluating the lesion site, scope and the abnormality degree, and predicting the prognosis if combined with the clinical conditions.

Adolescent↗
PubMedDate not supplied

Electrically induced blink reflex in horses.

The electrically induced blink reflex was studied electromyographically in 21 healthy adult, detomidine-sedated horses. Using surface electrodes, the supraorbital nerve was electrically stimulated at the supraorbital foramen. The responses were recorded from the ipsilateral and contralateral orbicularis oculi muscles with concentric needle electrodes inserted in the lateral aspect of the ventral eyelids. Ipsilateral and contralateral recordings were made on successive stimulations of the same side of the face, maintaining a constant stimulus intensity. The electromyographically recorded responses consisted of an early R1 response in the orbicularis oculi muscle ipsilateral to the side of stimulation, a bilateral late response (ipsilateral R2 and contralateral Rc) and a third, R3 response, in the ipsilateral orbicularis oculi muscle. All the responses were polyphasic muscle potentials of variable duration and peak to peak amplitudes. The reflex latency of the R1 response was, as in man, fairly stable. The R2 response showed greater variability both within and between individual horses. The Rc response was recorded in only 13 of the 21 horses and showed a slightly longer latency than the corresponding R2. The R3 response, which is significantly related to pain sensation in man, appeared in 19 horses and showed the greatest variability in latency.

Animals↗
PubMedDate not supplied

[Changes in blink reflex (OM) after lesions of the nervous system in various locations].

Electrically evoked blink reflex (BR) as a one of the non-invasive methods is used to diagnose function of central nervous system, specially of brainstem. It seems that this method is not fully appreciated in neurological practice. On the basis of literature and own experience the authors present typical pictures of BR on EMG analysis related to the lesions of respective parts of reflex arc and suprasegmental structures involving pyramidal and extrapyramidal tracts.

Blinking↗
PubMedDate not supplied

A field method for blink reflex latency R-1 (BRL R-1) and prediction equations for adults and children.

PURPOSE: To develop a field worthy apparatus for blink reflex latency R-1 (BRL R-1), to compare mechanical and electrical stimulation, to define a standardized measurement of BRL R-1, to test a field worthy procedure and to produce population-based prediction equations. METHODS: A special low voltage electromyographic (EMG) recording system was constructed which is uninfluenced by electrical and magnetic field. The supraorbital notches were stimulated mechanically using a small hammer and electrically using a stimulus of 2.0 ms duration and 2-5 mA 13. A computer program was developed which substracts the baseline for all data points and sums R-1 for 10 tests by identifying the noise floor or baseline of the EMG recording and the noise envelope. The beginning of R-1 and R-2 is defined as 2 times the noise amplitude of this envelope. BRL R-1 was compared after tap and after electrical stimulation in 16 subjects. Prediction equations were developed from data of 240 adults and 163 children unexposed to chemicals. RESULTS: Mechanically and electrically elicited mean BRL R-1 in 16 subjects was identical at 12.6 ms on the right and 12.7 ms vs 12.5 on the left. In adults, BRL R-1 depended on age. In children BRL R-1 was age, weight and height dependent. CONCLUSION: BRL R-1 elicited by supraorbital tap is field worthy, computer defined and identical to electrical BRL.

Adolescent↗
PubMedDate not supplied

Contralateral early blink reflex in multifocal motor neuropathy.

Multifocal motor neuropathy (MMN) is a clinical entity affecting the peripheral nerve system mainly. We present here a Colombian man, 37 year-old, who presented MMN, and interestingly, displayed abnormal responses in the blink reflex after electrical stimulation of the supraorbital nerves. These findings allow us to suggest that the lesion distribution in MMN mostly the subclinical one, seems to be more widespread than usually thought.

Adult↗
PubMed1977

Electrically elicited blink reflex in normal neonates.

The electrically elicited blink reflex was tested in 30 full-term neonates. Of the two distinctly separate responses, early component R1 and late component R2, R1 was recorded in all but three infants. Its latency, 12.1+/-1.0 msec (mean+/-SD), was significantly greater than that in adults (10.6+/-0.8 msec) despite a considerably shorter length of the reflex arc in infants. Unlike the response in adults, R2 was elicited in only 20 of 30 infants, mostly on the side ipsilateral to the stimulus. The reduction of reflex excitability of R2 in neonates must occur primarily at the level of interneurons since oligosynaptic R1 was elicited with ease whereas polysynaptic R2 was not.

Age Factors↗
PubMed1984

Blink comparator.

A newly designed blink comparator functions by presenting similar images that are alternated rapidly by varying the illumination. The device allows one to detect small changes easily without tedious measurements or study; it also serves as a stereo viewer.

Fluorescein Angiography↗
PubMed1976

Electrophysiological study of Bell palsy: electrically elicited blink reflex in assessment of prognosis.

The electrically elicited blink reflex was tested serially in 81 patients with Bell palsy. In 56 patients, the reflex returned before excitability of the distal segment of the facial nerve was lost, indicating recovery of conduction across the involved segment before distal degeneration. These patients generally showed a good clinical recovery within a few months after onset. The reflex latency, however, was considerably prolonged during the first month, suggesting demyelination or other pathologic change. The reflex latency was reduced considerably during the second month and returned to normal levels during the third or fourth months. In the remaining 25 patients, direct response to facial nerve stimulation became unelicitable before reflex responses returned, indicating distal degeneration of the nerve. In this group of patients, clinical recovery was prolonged and generally incomplete.

Adolescent↗
PubMed1976

Blink nystagmus.

A pattern of eye movement similar to vestibular nystagmus associated with blink is characterized. This artifact can be seen in asymptomatic, otologically normal subjects and is considered to have different meaning than lateral conjugate deviation of the eyes on forced closure of the lids (Cogan sign). Since this nystagmus artifact is most evident during electronystagmographic testing for spontaneous and semispontaneous nystagmus, its importance can be overestimated. Simultaneous monitoring of horizontal and vertical eye movement presently provides a definitive means of identification.

Diagnosis, Differential↗
PubMed1976

Recovery curves of the blink reflex during wakefulness and sleep.

The paired shock technique was used to study the effect of sleep on the excitability of the short latency R1 and long latency R2 components of the electrically elicited blink reflex. During wakefulness, R1 returned, after transient potentiation, to its original level in about 150 ms following the conditioning stimulus. Contrastingly, R2 remained profoundly suppressed up to 800 ms, suggesting sustained reduction of excitability of the polysynpatic reflex pathways after the passage of a preceeding impulse. During non-REM and REM sleep, the recovery curve of R1 was similar in character, although different in time course to the one obtained during wakefulness. However, R2 was potentiated rather than suppressed by the conditioning stimulus during both phases of sleep. These findings indicate that, during sleep, the polysynpatic reflex pathways are not inhibited by a preceeding impulse to the same degree as in wakefulness.

Adult↗
PubMed2004

The attentional blink: resource depletion or temporary loss of control?

Identification of the second of two targets is impaired if it is presented less than about 500 ms after the first. Theoretical accounts of this second-target deficit, known as attentional blink (AB), have relied on some form of limited attentional resource that is allocated to the leading target at the expense of the trailing target. Three experiments in the present study reveal a failure of resource-limitation accounts to explain why the AB is absent when the targets consist of a stream of three items belonging to the same category (e.g., letters or digits). The AB is reinstated, however, if an item from a different category is inserted in the target string. This result, and all major results in the AB literature, is explained by the hypothesis that the AB arises from a temporary loss of control over the prevailing attentional set. This lapse in control renders the observer vulnerable to an exogenously-triggered switch in attentional set.

Analysis of Variance↗
PubMed2005

The attentional blink is not a unitary phenomenon.

Identification of the second of two targets is impaired if it is presented less than about 500 ms after the first. Three models of this second-target deficit, known as attentional blink (AB), were compared: resource-depletion, bottleneck, and temporary loss of control (TLC). Five experiments, in which three sequential targets were inserted in a stream of distractors, showed that identification accuracy for the leading target depended on an attentional switch whose magnitude varied with distractor-target similarity. In contrast, accuracy for the trailing target depended on similarity between the target and the trailing mask. These results strongly suggest that the AB is not a unitary phenomenon. Resource-depletion was ruled out as a viable account. The effect of attentional switching was handled naturally by the TLC model, while bottleneck models offered the best account of the effect of backward masking.

Attention↗
PubMed1977

Neural mechanisms of the corneal blinking reflex in cats.

Neural mechanisms of the blinking reflex elicited by corneal stimulation were analyzed with electrophysiological techniques in the encéphale isolé cat. (1) Mechanical and electrical stimulation elicited two successive responses of the electromyogram of the orbicularis oculi. Neuromuscular unit studies revealed that the same unit was excited twice and that the latencies of both responses corresponded well with the two EMG responses. (2) The late response was easily affected by anoxia and pentobarbital administration, and was also abolished with the slow-wave sleep stage. (3) Both responses were abolished by ipsilateral transection between the inferior colliculus and genu of the facial nerve. (4) Compared with the latencies of the EMG, the sum of the conduction times through the sensory trigeminal nucleus and the facial nucleus corresponded with the latency of the early response. The sum of the conduction times through the reticular formation, added to the former reflex arc, corresponded to the latency of the late response. (5) The reflex pathway of the early response is consistent with a three-neuron arc passing through the sensory trigeminal nucleus and the facial nucleus. The late response may employ a multisynaptic arc passing through the brain stem medial reticular formation between the sensory trigeminal nucleus and the facial nucleus.

Animals↗
PubMed1979

Brain stem auditory evoked potentials and blink reflexes in quiescent multiple sclerosis.

Brain stem auditory evoked potentials (BAEP) and blink reflexes (BR) were studied in 25 patients with multiple sclerosis (MS), the diagnosis being definite according to McAlpine's criteria, in the quiescent phase, without signs of brain stem involvement. BAEP abnormalities were found in 64% of the cases and BR abnormalities in 60%. A good correlation between the two tests was found in most patients. The abnormalities consisted of delayed latencies and/or high intraindividual variability in shape and latency of BAEP and BR components. It seems that demyelination of brain stem pathways results not only in conduction slowing but also in more serious dysfunction of the generators of the evoked components.

Adolescent↗
PubMed1979

[Abolition by naloxone of the inhibitory effect of peripheral electrical stimulation on the blink reflex].

The effects of a low frequency (2 c/sec) peripheral stimulation (electro-acupuncture, EA) on the nociceptive (R2) response of the blink reflex elicited by supra-orbital nerve stimulation (0.1 msec, 1 shock/8 sec) were studied in 10 healthy subjects. EA stimulation produced a very significant inhibition of the reflex in 8 subjects. Double-blind injection of naloxone (0.8 mg) reversed this inhibition while no signiificant change was observed with placebo. These results suggest that EA stimulation induces the release of endogenous opiates.

Adult↗
PubMed1979

Effects of stimulus frequency on the blink reflex during rest and a task.

Blink reflexes were studied in 84 healthy subjects, applying 4 different stimulation frequencies. The experiments were subdivided into 3 periods: rest, binary choice task and final rest period. Independent of the applied stimulation frequency, an increment of R1 during the task was found, and it was concluded that R1 amplitude reflects the state of arousal of the subject. Within each of the 3 periods, R1 amplitudes decreased independently of the applied frequency, while R2 amplitudes decreased dependent on the applied frequency, i.e. at lower frequencies a smaller decrement in time could be observed. It was concluded that R2 habituated at frequencies lower than those so far reported.

Analog-Digital Conversion↗