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At least 667 records · Page 37Linked to original sources
PubMed2000

Direct estimates of processing delays in the attentional blink.

When two targets (T1 and T2) are presented in rapid succession, identification of T2 is often impaired (attentional blink: AB). The two-stage model accounts for the AB deficit by assuming that: (a) T2 is delayed in Stage 1 while Stage 2 is busy processing T1, and (b) T2 is vulnerable to masking while delayed. We report converging evidence for the model by evaluating these assumptions independently of the AB deficit itself. The results show that: (a) response times for T2 identification decreased as the lag between T1 and T2 was increased; (b) response times for T2 decreased across lags only if T1 was masked; and (c) accuracy of T2 identification increased as the stimulus-onset asynchrony between T2 and the trailing mask was increased.

Attention↗
PubMed1997

Blink reflex in patients with Wallenberg's syndrome.

Knowledge of the neural circuits involved in Wallenberg's syndrome (WS) is incomplete. Study of the blink reflex (BR) in patients with WS can help in reaching a better understanding of the physiopathology underlying clinical symptoms and may help in the prediction of clinical outcome. We evaluated the BR in response to supraorbital nerve electrical stimuli in 20 patients with WS. All patients were studied within the 1st week after onset of symptoms, and 10 of them were also studied repeatedly during a follow-up period of 3-12 months. At the first examination the long latency bilateral responses (R2 and R2c) to stimulation of the supraorbital nerve of the affected side were absent in 11, delayed in 4, and normal in 5 patients. At follow-up, there was a normalization of the BR in all patients who had absent or delayed responses at the first examination except for one patient whose responses remained absent at the 9th month. Late responses elicited on the side of the lesion by stimulation of the non-affected supraorbital nerve were normal in all but one patient. This patient died from cardiorespiratory arrest within the 1st month of the illness. One patient with normal BR responses also died in the acute phase. The BR is abnormal in most patients with acute WS and tends to normalize in a mean period of 7 months. BR pattern is not a predictor of early fatal complications in patients with this syndrome.

Adult↗
PubMed2002

Long-term depression of the human blink reflex.

Long-term depression (LTD) of synaptic transmission is reliably induced by low-frequency stimulation (LFS) of presynaptic nerve fibers in vitro. Many experiments suggest that LTD of basal transmission is not readily induced either in awake or anesthetized animals in vivo. In order to fill the gap between the in vitro cell studies and the in vivo situation, the effect of LFS on trigeminal somatosensory processing in healthy volunteers was investigated. Excitability of trigeminal sensory neurons was tested by applying the blink reflex (BR) elicited by electric stimulation of supraorbital nerve afferents. LFS of these afferents induced a significant reduction of the BR integral, a significant increase of the BR onset latency and a significant decrease of the stimulus intensity ratings. This depressive effect on the BR lasted for at least 1 h after the end of LFS. Thus, this study documented for the first time a long-term depression of trigeminal somatosensory processing in healthy volunteers.

Adult↗
PubMed2003

Transcranial magnetic stimulation to right parietal cortex modifies the attentional blink.

The 'attentional blink' (AB) reflects a limitation in the ability to identify multiple items in a stream of rapidly presented information. Repetitive transcranial magnetic stimulation (rTMS), applied to a site over the right posterior parietal cortex, reduced the magnitude of the AB to visual stimuli, whilst no effect of rTMS was found when stimulation took place at a control site. The data confirm that the posterior parietal cortex may play a critical role in temporal as well as spatial aspects of visual attention.

Adult↗
PubMed2005

Heterosynaptic long-term depression of craniofacial nociception: divergent effects on pain perception and blink reflex in man.

Noxious low-frequency stimulation (LFS) of presynaptic nerve fibers induces long-term depression (LTD) of synaptic transmission. In vitro studies suggest a sole homosynaptic effect. Consequently, the present study addressed the hypothesis that LTD of craniofacial nociception in man is mediated by a homosynaptic mechanism. Nociceptive supraorbital afferents were excited by electric pulses via a concentric electrode in ten healthy volunteers. The electrically evoked bilateral blink reflex (BR) was recorded from both orbicularis oculi muscles by surface electrodes. The BR was evoked in blocks of ten electric stimuli each (0.1 Hz) with an interblock interval of 8 min. Conditioning noxious LFS (1 Hz, 20 min) was applied via concentric electrode either to the same site as BR test stimuli (ipsilateral) or to the corresponding contralateral forehead area (contralateral). LFS and test stimulus intensities corresponded to about threefold the pain threshold. After three baseline stimulus blocks, either conditioning ipsilateral or contralateral LFS were applied or stimulation was interrupted for 20 min as a control task. Afterwards, test stimulation blocks were continued for 40 min. Each volunteer participated in all three sessions on different days. Noxious LFS induced LTD of the BR independently from the side of conditioning stimulation. Pain perception decreased after ipsilateral LFS but not after contralateral LFS. The bilateral effect of noxious LFS on the BR provides evidence for heterosynaptic LTD based on bilateral projections of supraorbital nerve afferents onto spinal trigeminal nuclei. The divergent effect on pain perception may be due to a preferential contralateral projection of nociceptive afferents onto reflex interneurons but not onto trigeminothalamic projection neurons.

Adult↗
PubMed2006

Influence of age and gender on the jaw-stretch and blink reflexes.

The aim of this study is to investigate the influence of age and gender on jaw-stretch and blink reflexes (BR). Thirty "young" (26.5+/-0.7 years) and thirty "old" (47.8+/-1.8 years) healthy adults were included. Short-latency stretch reflex responses were evoked in the masseter and temporalis muscles by fast jaw-stretches, and BR in orbicularis oculi muscle were evoked by painful electrical pulses (0.5 ms duration), delivered by a concentric electrode placed on the left lower forehead close to the supraorbital foramen. For the jaw-stretch reflex, the pre-stimulus EMG activity in the old subjects was significantly lower than that of the young subjects in the right and left masseter and temporalis muscles (P<0.006), whereas there was no difference in the results between males and females. The normalized peak-to-peak amplitude of the EMG in the left masseter and left and right temporalis muscles was significantly lower in the old subjects compared with the young subjects (P<0.02). Females had significantly higher normalized peak-to-peak EMG amplitudes compared with males in the right masseter and left temporalis muscles (P<0.05). The old subjects had significantly lower root mean square (RMS) (P=0.01) and average (P<0.02) BR values in the right and left orbicularis oculi muscles, and lower area under the curve (AUC) (P=0.02) values in the left orbicularis oculi muscle compared with the young subjects. Female subjects had significantly lower AUC (P=0.02) in the left orbicularis oculi muscle compared with males. The old subjects had significantly later offset (P<0.003) and longer duration (P<0.001) in the left orbicularis oculi compared with the young subjects. The results of the present study demonstrated a significant effect of both age and gender on stretch and BR and suggested that these variables should be taken into consideration in the interpretation of brainstem reflexes in basic and clinical studies.

Adult↗
PubMed2006

Blink reflexes in patients with atypical odontalgia and matched healthy controls.

Atypical odontalgia (AO) is an orofacial pain condition which has been suggested to involve neuropathic pain mechanisms. The aim of this study was to use a brain stem reflex to investigate craniofacial nociceptive mechanisms in AO. In 38 AO patients and 27 matched healthy controls, the R2 component of the blink reflex (BR) was elicited using a "nociceptive-specific" electrode and recorded with surface electromyography electrodes on both orbicularis oculi muscles. The BR was tested by stimulation of both sides of the face of the participants before, during, and after an intraoral pain provocation test with capsaicin. The data were analyzed with three- and four-way mixed-model analyses of variance. The root mean square value of the ipsilateral R2 (R2i) was significantly reduced in patients compared with controls (P=0.046). No differences in R2 between stimulation sides were detected in either group (P>0.757). In all participants, R2 responses and the intensity of the pain evoked by the electrical stimulus were decreased during and after application of capsaicin compared with baseline (P<0.001). In patients, R2i onset latencies were significantly prolonged compared with controls (P=0.031). The present data show disturbances in the central processing of craniofacial information and that endogenous pain inhibitory systems in AO patients and healthy controls were activated to a similar degree by an acute intraoral nociceptive input. Additional clinical research with AO patients will be needed to determine to what extent neuropathic pain mechanisms are involved in this pain condition.

Adult↗
PubMed2005

[Blinking activity during visual display terminal work. Part 1: Ocular discomfort and pathophysiological principles].

Up to three-fourths of visual display operators complain about ocular discomfort after lengthy work at a monitor. The increase of displays at work has resulted in a problem area with growing impact for the economy and healthcare. Symptoms overlapping the complaints of dry eye disease point to the joint pathophysiological origin. In numerous studies the drastic decrease in blinking frequency was shown to be an essential cause of dry eye symptoms. Lid movements not only have the purpose of smoothing the precorneal tear film ("windshield effect"), but also affect the composition and stability of the different layers. Unfortunately, previous work has often been limited by the heterogeneity of measurement settings, leading to inconsistent results.

Blinking↗
PubMed2002

Facilitation of local information processing in the attentional blink as indexed by the shooting line illusion.

Perception of the second of two rapidly sequential targets is impaired if the temporal lag between them is relatively short. This attentional blink (AB) is said to occur because the first target preoccupies attentional resources, leading to a shortage of attention for, and subsequent failure of judgement of, the second target. In the present study, we examined whether the attention which is preoccupied by the first target carries the common characteristic of spatial attention, that is local facilitation of information processing. To index the facilitation, we presented an attention-sensitive probe known as the shooting line illusion in which observers see a progressively drawn line from the attended end to the other. We found that illusory motion was perceived to emanate from the end where the first target was presented. This result demonstrates the inherently spatial nature of attention, even when it is defined by temporal and symbolic variables.

Adult↗
PubMed1982

Depressive effect of high frequency peripheral conditioning stimulation upon the nociceptive component of the human blink reflex. Lack of naloxone effect.

High frequency (100 Hz) low intensity (2 mA) peripheral conditioning stimulation of either segmental or heterosegmental cutaneous nerves induced non-naloxone-reversible depression of the nociceptive component of the human blink reflex. Electrophysiological studies suggest that this depression is due to a local synaptic inhibitory mechanism involving convergence interactions between several cutaneous afferents onto a same internuncial pool in the trigemino-facial path.

Acoustic Stimulation↗
PubMed1982

Unilateral reduction of the early and late blink reflex component in hemiparkinson syndrome.

Electrically evoked blink reflexes were recorded in 10 patients with unilateral tremor and/or rigor, mostly diagnosed as hemiparkinson syndrome. Five of the patients could be investigated before and after stereotaxic thalamo-subthalamotomy. The EMG activity of the early and late components was quantified by means of averaging and integrations techniques. In addition, the latencies of the reflex components were determined. The major finding was a unilateral decrease of the EMG activity of both the early and late components confined to the clinically affected side. This pattern points to a lowered state of excitability of neurons in or close to the facial nucleus, probably due to a dysfunction of contralateral EPMS structures. A loss of facilitatory influences from EPMS centers, e.g. the nigro-striatal system, on brain stem neurons in the area of the facial nucleus appears most probable. The latencies of the early and late components were mostly normal. After stereotaxic surgery, the BR activity was decreased bilaterally. The difference between the affected and unaffected sides, however, was nearly unchanged. At present an unspecific postoperative effect cannot be excluded.

Adult↗
PubMed1985

Changes in the recruitment pattern of single motor units in the blink reflex of patients with parkinsonism and hemiplegia.

The recruitment pattern of single motor units (SMUs) was studied in the early (R1) and late (R2) blink reflex components in normal subjects (15), patients with parkinsonism (10) and with hemiplegia due to hemispheral lesions (5). Reflexes were evoked by constant current stimuli applied to the supraorbital nerve. SMU discharges were recorded in the preseptal part of the lower eyelid using a bipolar needle electrode. Thresholds of R1 and R2, latencies at the thresholds and the number of discharges in R2 were determined. In parkinsonism, the recruitment of SMUs in R1 was impaired, suggesting that the malfunction of the basal ganglia in this disorder is associated with a reduced excitability of neurons in the pontine brain-stem. In hemiplegia, the recruitment in both R1 and R2 could be impaired. The orderly function of neurones in the pontine and medullary pathways of these components appears to require facilitatory hemispheral influences. Signs of disinhibition occasionally found in R1 may point to an imbalance between facilitatory and inhibitory hemispheral influences upon the pontine pathway.

Adult↗
PubMed1985

Habituation of the blink reflex: computer assisted quantitative analysis.

The electrically evoked blink reflex (BR) was elicited in 20 healthy volunteers, varying the stimulus interval by a computer JN 110. Latencies, amplitudes, reflex duration and reflex areas of early and late components of the BR were analysed by a computer program testing the signal-to-noise ratio, the response configuration and frequency distribution. Changes in habituation related to the stimulus interval can be illustrated best by the progressive diminution of R2 areas. Computing the habituation in relation to the stimulation frequency by a standardized program seems to be a quantitative method to assess habituation in various diseases and during treatment studies.

Blinking↗
PubMed1991

Dipole models of eye movements and blinks.

Average EOGs were recorded from 4 subjects for vertical and horizontal eye movements of 15 degrees away from and back to a central fixation point, and for eyeblinks while looking at the fixation point. Using spatio-temporal dipole modelling, several alternative dipole models of the electrical activity of the eyes were compared. A reasonable fit was only obtained if the equivalent dipoles were allowed to take up different locations and orientations depending on the type of eye activity. It appears that (a) the equivalent ocular dipole is located away from the axis of rotation of the eyeball, (b) eyelid movements contribute to a change in location of the dipole in vertical eye movements and blinks, and (c) some of the apparent dipole movement is due to inadequacy of the 3-shell spherical head model near to the eyes. Consequences of the results for eye-artifact correction are discussed.

Adult↗
PubMed1986

Blink reflex elicited by auditory stimulation in the rabbit.

The pathway of the blink reflex, elicited by auditory stimulation, was investigated electrophysiologically. The reflex was recorded as microvibrations of the eyelid and was named the auditory-evoked eyelid microvibration (AMV). Pharmacophysiological studies suggest that AMV is closely related to the midbrain reticular formation and studies of electrical lesions in the midbrain reticular formation support this. Lesions in several parts of the central nervous system provide evidence that the inferior colliculus has an important role in AMV, and the cerebral cortex may have an inhibitory influence. Studies of brainstem transections indicate that the reflex pathway of AMV exists between the lower midbrain and the upper medulla. Because of its ease and simplicity, AMV is believed to be a useful test for evaluation of the function of the brainstem.

Acoustic Stimulation↗
PubMed1989

The relationship of eyelid movement to the blink reflex.

Although the blink reflex is a standard neurophysiological investigation its relationship with eyelid movement has not been clearly established. We studied normal subjects and patients with unilateral facial paralysis to define the pattern of eyelid movement following glabellar tap, supraorbital nerve stimulation, facial nerve stimulation and direct corneal stimulation. We found that eyelid closure did not necessarily occur in a single movement. Following glabellar tap the first component of a two-stage movement was initiated by levator palpebrae relaxation while with supraorbital nerve stimulation orbicularis oculi contraction produced the first movement. The compound muscle action potential following direct facial nerve stimulation produced only minimal eyelid movement, the major closure being associated with a longer latency orbicularis oculi reflex. Corneal stimulation elicited a single component eyelid movement. Thus, the pattern of eyelid movement differed for each stimulus reflecting variations in orbicularis oculi contraction and levator palpebrae inhibition.

Adult↗
PubMed1992

A correlation study between blink reflex habituation and clinical state in patients with Parkinson's disease.

The neurologic states and activities of daily life of patients with Parkinson's disease were evaluated using a rating scale with subitems, and subsequently the neurologic disturbance scores and the daily activity impairment scores were obtained. Subjects consisted of 19 normal controls, and 55 ambulatory patients without marked dyskinesia who were on various anti-parkinsonian drugs. Blink reflex was elicited by paired electrical stimulation over the supraorbital nerve. The interval time between the conditioning stimulation and the test stimulation was set at 200 ms, and 5 serial ipsilateral maximal R2 amplitudes on the stimulated side were measured. The mean of the paired maximal R2 amplitude ratio (test/conditioning), expressed as a percentage, was defined as the habituation index. The habituation indices in normal controls and those with Parkinson's disease were 17.1 +/- 7.6 and 51.9 +/- 29.3, respectively (P less than 0.01). The degree of akinesia, rigidity, balance/gait and dysarthria was positively correlated with the habituation index (P less than 0.01), while tremor was not. On the whole the habituation index was found to have a significant correlation not only with the neurologic disturbance score but also with the daily activity impairment score (P less than 0.01).

Activities of Daily Living↗
PubMed1995

Contralateral early blink reflex in patients with HTLV-I associated myelopathy/tropical spastic paraparesis.

Thirty-two Japanese patients with HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) were studied by means of the electrically elicited blink reflex and three responses (R1, R2, R3) were registered. 69% of the patients displayed a uni- or bilateral crossed R1 response (R1k) as compared to 11% in the control group. A positive correlation between R1k and an exaggerated jaw jerk reflex was found in the patients. Central abnormalities of the nervous system with diminished presynaptic inhibition acting in the interneuronal input of the brainstem of HAM/TSP patients was the most likely cause. It could lead to the unmasking of crossed trigemino-facial pathway reflex which is present in the normal population from birth. These results strongly support the supraspinal involvement of the central nervous system (CNS) in HAM/TSP more than usually thought.

Action Potentials↗