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PubMed1980

[Alteration of the early R1-component of the blink reflex in coma: topographical and prognostic value (author's transl)].

Alteration of the early component of the blink reflex (delayed latency or abolished reflex) is considered to be relatively specific for pontine lesions (multiple sclerosis, vacular lesions of the brain-stem, neoplasms, syringes); provided, the trigeminal and facial nerve are unaffected. In comatose patients the electrically, by stimulation of the supraorbital nerve elicited blink reflex was super-imposed (50 or 100 responses) with the LAB 8/e-computer (off-line). It was found that the R1 component was abolished even in cases with supratentorial lesions and secondary brain-stem alterations, while no specific pontine lesions were demonstrated by neuropathological examination. Therefore it is suggested that delayed or abolished blink reflexes in coma due to supratentorial mass lesions are not concluslive for pontine lesions: they rather may reflect an unspecific secondary brain-stem alteration. Recording of the EEG reveals that in some cases the extinction of the early blink reflex precedes corresponding EEG alterations; this may be a matter of prognostic value.

Adolescent↗
PubMed1981

[The optic blink reflex: stimulus dependency, excitability and habituation (author's transl)].

Stimulus dependency, excitability and habituation of the flash-induced optic blink reflex were examined by means of an electrooculogram. The results were clearly dependent on the background illumination. In a 30 Lux illuminated room, the blink amplitude and the excitability increased with an increasing stimulus intensity. In a dark room, a low flash intensity was sufficient to produce both high level blink amplitude and excitability which could not be increased by a greater stimulus intensity. The optic blink reflex habituated only very slowly depending on the variability between the stimuli.

Adolescent↗
PubMedDate not supplied

[The spectral-correlational analysis of the electrical activity of the rabbit brain in the organization of a goal-directed blinking reaction ].

At organization of the blinking reaction directed to a cessation of the motivational hunger dominant the spectral power of biopotentials of the frontal, sensorimotor cortical areas and the blinking cortical centres of both eyes, VMH and LH increases in the range of the delta- and theta-frequencies. Coherence (Coh) of electrical activity of the frontal and sensorimotor cortical areas increases, Coh between potentials of the swallowing cortical area and the blinking cortical zones corresponding to the trained and non-trained eyes is being asymmetrically reconstructed. Coh function of the electrical activity of the LH, VMH and potentials of different cortical areas changes uniformly. Coh of electrical activity of the VMH and LH, NIII and MPO increases in the whole analysed frequency range, Coh between potentials of the MPO and LPO, LPO and VMH increases in the delta- and decreases in the theta- and alpha-frequency ranges. It is suggested that in the process of preparation of the goal-directed reaction all the cerebral cortex areas and subcortical structures under study related to alimentary motivation and the blinking function are involved into the dominant constellation.

Analog-Digital Conversion↗
PubMedDate not supplied

Magnetically elicited blink reflex: an alternative to conventional electrical stimulation.

Magnetically and electrically elicited blink reflexes were studied in 11 normal subjects and in 5 patients with partial peripheral facial nerve palsy. Both methods were able to elicit a reproducible blink reflex. In both groups the latencies of the magnetically elicited reflexes were equal to those that followed electrical stimulation. The magnetic stimulation technique offered 2 advantages over the electrical stimulation: (1) it was less painful and therefore better tolerated and (2) the coil position in the middle of the forehead was sufficient to elicit a bilateral blink reflex because the windings of the stimulation coil excited both supraorbital nerves simultaneously. This bilateral response enables one to reduce the number of stimuli and can be used in the examination of patients that have peripheral facial nerve palsies without the concomitant impairment of the reflex pathway in the brainstem. The magnetic technique can also elicit a blink reflex at stimulation points distant from the supraorbital notch. This finding offers an alternative explanation of the late responses of facial muscles following transcranial magnetic stimulation of the motor cortex.

Adult↗
PubMedDate not supplied

Changes in blink rates of Nigerian schizophrenics treated with chlorpromazine.

Chlorpromazine was administered over a 4-8 week period to 40 schizophrenic patients who had not received previous neuroleptic drug treatment out of a total of 222 schizophrenic patients seen during the study period. Pre-treatment spontaneous eye blink rate was high in the 40 schizophrenics when compared to 34 normal controls, (22 vs 14 blinks/min respectively, t = 17.04, df = 72, p < 0.001). Clinical improvement in the schizophrenic patients correlated with a significant reduction in their pre-treatment versus post-treatment spontaneous eye blink rate (22 vs 9 blinks/min, t = 18.83, df = 78, p < 0.001). The blink rate in the clinically-well schizophrenic patients did not however, reach the level obtained in the normal controls but rather was lowered significantly (9 vs 14 blinks/min, t = 8.11, df = 72, p < 0.001). Blink rate changes in schizophrenic patients on neuroleptic treatment may serve as a quick bedside assessment of clinical improvement and can also be a pointer to those patients who may have sub-clinical drug induced parkinsonism.

Adult↗
PubMedDate not supplied

Blink reflex recovery cycle in patients with blepharospasm unilaterally treated with botulinum toxin.

To determine whether Botulinum Toxin Type A (BTXA) has an effect on the Central Nervous System, the authors studied the excitability of the blink reflex recovery cycle in 12 patients with blepharospasm before and 3 weeks after unilateral BTXA injections. To avoid recording from severely denervated muscles, the R2 response of the blink reflex was obtained from the untreated orbicularis oculi with both ipsilateral and contralateral supraorbital nerve stimulation. Baseline recovery curves were compared with a control group (n = 11) and showed an enhanced recovery of the R2 component. There were no significant differences between the recovery curves of the R2 component of the blink reflex taken before BTXA treatment and those taken after treatment. This finding confirms that BTXA does not modify the excitability of brainstem interneurons that mediate the bilateral R2 response of the blink reflex in patients with blepharospasm.

Adult↗
PubMed1998

Blink rate in pediatric complex partial seizure disorder.

This study examined spontaneous blink rate, a putative measure of dopamine function, in 30 children with complex partial epilepsy and 61 normal children. The children with epilepsy had significantly lower blink rates than the normal children in a conversation and a verbal recall task, particularly if they had a schizophrenia-like psychosis, EEG evidence for left focal epileptic activity, illogical thinking, discourse deficits, and distractibility. They modulated their blink rates across a listening, a conversation, and a verbal recall task like the normal children. Given previously reported low blink rates in schizophrenic children, these findings suggest that children with complex partial epilepsy or schizophrenia might have similar biological features.

Analysis of Variance↗
PubMed1976

Visual pattern evoked responses and blink reflexes in assessment of MS diagnosis. A clinical study of 135 multiple sclerosis/pathol.

VEPs were measured after pattern reversal in 135 MS patients and 30 control subjects. Neurological findings were documented in a standard manner. An extensive ophthalmological examination of all subjects was part of the study. The latency of P2 was abnormally delayed in 82% of the "definite", in 60% of the "probable" and in 65% of the "possible" MS groups respectively. The VEP was more often delayed in relation to ophthalmological disturbances. Changes in the MS classification had to be made in more than 10% of the patients, due to delay of VEP latency. These were patients with a "spinal" form of MS, which is known to create diagnostic problems. Optically and electrically evoked blink reflexes were recorded in 107 MS patients. All patients with mesencephalic lesions had delayed responses of the optically evoked reflex. 74% of the patients with caudal brainstem lesions had delayed latencies of the components of the electrically evoked blink reflex. The blink reflex was delayed in 18 additional patients without brainstem signs. The possibility of delineating clinically silent brainstem lesions by investigating blink reflexes is discussed.

Adolescent↗
PubMed1976

The blink reflex in coma and after recovery from coma.

Comparative studies of the blink reflex in a series of head injuries through the stages of coma and recovery from coma in a series of miscellaneous hemispheral lesions, and in a normal series, reveals that, although the principal centre for the R1 component of the blink reflex seems to be localised in the upper pons, the seat of the R2 late component is in the reticular system. The reappearance of this late component of the blink reflex in our cases of coma although seeming to depend on the integrity of the mesencephalic formation, correlates with the recovery of the patient's alertness. On the other hand, habituation of this reflex depends on the integrity of global cognitive function, rather than on any localised centre. The roles of the cortex, selective attention, and emotional factors, are discussed. The recovery of the normal habituation of the blink reflex obtained by glabellar tapping was found to be a useful sign in the follow up of patients recovering from concussion and other lesions, such as subdural haematomas and brain tumours, with global mental impairment.

Adult↗
PubMed2004

Effects of eyelid closure, blinks, and eye movements on the electroencephalogram.

OBJECTIVE: To characterize the effects of the eyeball and eyelid positions during eyeblinks on electroencephalographic (EEG) potentials. METHODS: Movements of the upper eyelids and eyes were measured in two healthy subjects using the magnetic search coil technique during horizontal and vertical eye rotations, eyeblinks, and lid closure. Corresponding signal changes were recorded simultaneously on the electroencephalogram (EEG). RESULTS: Spontaneous blinks produced small eye movements directed down and inward, whereas slow or forced blinks were associated with delayed upward eye rotations (i.e. Bell's phenomenon); both types of blinks caused positive EEG potentials with bifrontal distribution maximum at Fp1 and Fp2. CONCLUSIONS: In prior reports, these positive EEG artifacts have been attributed to upward eyeball rotation during blinks-Bell's phenomenon. By contrast, our findings indicate that movements of the eyelid contribute to a greater extent to these EEG potentials than do upward eyeball rotations. SIGNIFICANCE: Care is required in attributing EEG artifacts to movements of either eyeball or eyelid, since our findings suggest that they both contribute to these potentials.

Adult↗
PubMed1998

Efficacy of gold weight implants in facial nerve palsy: quantitative alterations in blinking.

Deficient eyelid closure is a major visual threat to patients with unresolved facial nerve palsy. Gold weight implants assisted eyelid closure in patients with paresis of the orbicularis oculi, ameliorating patient complaints of dry eye, excessive tearing, and corneal epithelial breakdown. We used dynamic measures to assess the efficacy of upper eyelid gold weight implantation surgery for facial nerve palsy. The search coil technique was used to record spontaneous blinks bilaterally in six patients, before and after unilateral gold weight implantations into the upper eyelid in severe facial nerve palsy. In uncomplicated facial nerve palsy, the amplitude of blink down-phases for the paretic eyelid was 28.6 +/- 5.7% of the amplitude of the contralateral, normal eyelid. Following corrective surgery, closure of the paretic eyelid improved to 42.6 +/- 7.5% (P < 0.05). There was not a commensurate increase in the peak velocity of blink down-phases, suggesting that gold weight effects are mediated by a passive improvement in blink dynamics.

Adult↗
PubMed1999

The attentional blink reflects retrieval competition among multiple rapid serial visual presentation items: tests of an interference model.

When people respond to a target (T1) in a rapid serial visual presentation stream, their perception of a subsequent target (T2) is impaired if the intertarget stimulus onset asynchrony is between about 100 and 500 ms. Three experiments supported the interference model's (K. L. Shapiro, J. E. Raymond, & K. M. Arnell, 1994) claim that this attentional blink reflects competition for retrieval among multiple items in visual short-term memory. Experiments 1 and 2 revealed that items appearing during the blink are named as T2 on an above-chance proportion of trials when T2 must be identified. Experiment 3 demonstrated that both the size of the blink and sensitivity to T2 reflected the number of items competing for retrieval as T2; such competition, moreover, occurred at a conceptual or categorical level rather than at a purely visual one. The relationship between the interference and alternative models of the attentional blink is discussed.

Adolescent↗
PubMed2006

The beneficial effects of additional task load, positive affect, and instruction on the attentional blink.

The attentional blink reflects the impaired ability to identify the 2nd of 2 targets presented in close succession--a phenomenon that is generally thought to reflect a fundamental cognitive limitation. However, the fundamental nature of this impairment has recently been called into question by the counterintuitive finding that task-irrelevant mental activity improves attentional blink performance (C. N. L. Olivers & S. Nieuwenhuis, 2005). The present study found a reduced attentional blink when participants concurrently performed an additional memory task, viewed pictures of positive affective content, or were instructed to focus less on the task. These findings support the hypothesis that the attentional blink is due to an overinvestment of attentional resources in stimulus processing, a suboptimal processing mode that can be counteracted by manipulations promoting divided attention.

Adolescent↗
PubMed2004

Is consciousness a gradual phenomenon? Evidence for an all-or-none bifurcation during the attentional blink.

Several theories of the neural correlates of consciousness assume that there is a continuum of perception, associated with a gradual change in the intensity of brain activation. But some models, considering reverberation of neural activity as necessary for conscious perception, predict a sharp nonlinear transition between unconscious and conscious processing. We asked participants to evaluate the visibility of target words on a continuous scale during the attentional blink, which is known to impede explicit reports. Participants used this continuous scale in an all-or-none fashion: Targets presented during the blink were either identified as well as targets presented outside the blink period or not detected at all. We suggest that a stochastic nonlinear bifurcation in neural activity underlies the all-or-none perception observed during the attentional blink.

Adult↗
PubMed1975

Blink reflex in Huntingon's chorea and Parkinson's disease.

The electrically-evoked late response (R2) of the blink reflex has been determined in 8 well-documented cases of Huntington's chorea and in 19 Parkinsonian patients. The results obtained from the two groups are compared with those from 10 normal subjects. A statistically significant difference of some components of the blink reflex was obtained when the three groups were compared. In both pathological conditions, the habituation index, latency and differential latency can be considered to represent the opposite extremes from the same scale, providing further evidence of the neurophysiological antagonism between the two disease states. The blink reflex pattern in Huntington's chorea probably reflects a diminished brain-stem interneurone basal activity through an over-inhibition of dopaminergic receptors in the striatum. The electrophysiological analysis of the blink reflex in incipient Huntington's chorea can provide an objective diagnostic assessment. It might be an effective method of detection for dopaminergic-activated carriers asking for genetic counseling.

Adult↗
PubMed2006

Analysis method for measuring submicroscopic distances with blinking quantum dots.

A method is described that takes advantage of the intermittency ("blinking") in the fluorescence of quantum dots (QDs) to measure absolute positions of closely spaced QDs. The concept is that even if two QDs are separated by only tens of nanometers, the position of each QD is resolvable if the point spread function of each can be imaged independently of the other. In the case of QDs, this is possible if each QD separately blinks completely on and off during a time-lapse sequence. To demonstrate the principle of this method, time-lapse sequences of single blinking QDs were acquired and the centroids of the point spread functions determined. Images of the blinking QDs were then overlapped in software, pixel by pixel, generating a range of submicroscopic distances between QD pairs. Methods were developed for analyzing the overlapped time sequences of the QD pairs so that the positions of the QDs and the distances between them could be determined without prior knowledge of the single QD positions. We subsequently used this method to measure the end-to-end length of a 122-basepair double-stranded DNA fragment.

Biotinylation↗
PubMed1975

Simultaneous disappearances of both images during binocular rivalry of contours and effect on eye-blink rate.

Simultaneous disappearances of both rivalry images were reported by 28 women who reported on the rivalry 3.2 degree diagonal rivalry contours for 10 min. of continuous viewing. The data support the notion that suppression of images during binocular rivalry is independent in both eyes. In a second study, 48 women reported simultaneous disappearances during the rivalry of 3.2 degree vertical and horizontal contours for 10 min. of continuous viewing under one of two blink-rate instruction conditions. Fewer simultaneous disappearances were reported by Ss instructed to blink every 5 sec. than by Ss instructed to blink every 15 sec. Blinking may reduce the probability of simultaneous disappearances in rivalry. In both studies, the fusion squares surrounding the rivalry stimuli were continuously perceived.

Eyelids↗
PubMed1990

Depression, Eye Blink Rate, Psychomotor Retardation, and Electroconvulsive Therapy-Enhanced Dopamine Receptor Sensitivity.

The effect of electroconvulsive therapy (ECT) and antidepressant drugs on eye blink rates and on a measure of psychomotor retardation was compared in two samples of neuroleptic-free subjects suffering from DSM III major depression and matched on admission by Hamilton and psychomotor retardation scores. Both treatments caused a significant change in eye blink and psychomotor retardation measures. There was no significant difference between treatment groups, although the ECT-treated subjects included those with the largest eye-blink increases. There was no correlation between Hamilton scores and eye blink rates or psychomotor retardation scores for any of the groups or stages of treatment.

Journal Article↗