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At least 217 records · Page 12Linked to original sources
PubMed2004

Neural correlates of conscious perception in the attentional blink.

If attending to a target in a rapid stream of visual stimuli within the next 400 ms or so, a second target in the stream is frequently not detected by an observer. This so-called attentional blink can provide a comparison of neural signals elicited by identical stimuli that, in one condition, reach conscious awareness and, in the other, fail to be selected for awareness. In the present study, using event-related functional magnetic resonance imaging (fMRI), differences of neural activation were studied in an attentional blink experiment in order to identify brain regions putatively involved in controlling the access of information to consciousness. Subjects viewed a rapid stream of black letters in which the second target (T2) was either presented within or outside the attentional blink period, or not at all. We observed an increase in activation for detected as compared to missed T2 presented during the attentional blink in frontal and parietal cortices. In contrast, in occipitotemporal regions activation was increased for missed as compared to detected T2. Furthermore, in several frontal and parietal areas, missed targets were associated with increased activity if compared to the condition in which no second target was presented. Finally, a selective decrease in activation for detected T2 presented during the attentional blink was observed in areas associated with emotional and predominantly automatic processing. While activations in occipitotemporal regions might mainly reflect duration of attentive search, the frontoparietal areas seem to be involved in a highly distributed network controlling visual awareness.

Adult↗
PubMed2006

Increased spontaneous eye blink rate following prolonged wakefulness.

Sleep deprivation (SD) is a technique of sleep-wake manipulation which has been used to treat depression. Changes in neurotransmitter systems, that are also involved in the effects of the antidepressant drugs, have been suggested as the possible mechanisms of action of SD. However, the therapeutic effect of SD is acute and transient, while antidepressant effects of drug treatments are gradual and stable. SD might work throughout mechanisms that are different from those mediating drug's effects. In the present study we analyzed the role of dopamine activity in SD. Spontaneous eye blink rate provides a non invasive measure of central dopamine activity. We assessed eye blink rate across prolonged wakefulness (from 10:00 a.m. to 07:00 a.m.) in 25 young normal subjects. Eye blink rate increased at the end of the wakefulness period. Blink rates and sleepiness as assessed by Karolinska Sleepiness Scale correlated positively with time spent awake. We propose that increased blink rate might reflect a dopamine activation that counteracts sleep drive. Antidepressant effects of sleep deprivation might be related to activation of the physiological mechanisms which regulate wake maintenance.

Adolescent↗
PubMed2000

Identification of Poppelreuter-like pictures as indexed by blinking.

Blinking was recorded in 28 adult participants during the identification of superimposed pictures (similar to Poppelreuter figures), some of which had been presented individually in an earlier study phase. Participants were required to name the pictures at the end of the identification phase. The percentage of correct identifications was greater for combinations formed by old than new pictures, and decreased as the number of pictures in the combination increased. Attentional demands associated with mental load (number of pictures) affected both the rate of blinks produced during the identification process and the latency of the first blink produced after the stimulus onset. The first blink latency increased as the number of pictures increased, and also depended on material to be identified, with longer latencies associated with novel combinations. We suggest that blinking may be used as an index of memory processes involved in visual identification, even in absence of overt (verbal) responses.

Adult↗
PubMed1996

The mental nerve blink reflex in the diagnosis of lesions of the inferior alveolar nerve following orthognathic surgery of the mandible.

The purpose of this study was to evaluate the diagnostic value of a new modification of the blink reflex test with stimulation of the distribution of the mental nerve in iatrogenic lesions of the inferior alveolar nerve. The test was performed on 23 patients undergoing orthognathic surgery of the mandible, most of them (20) with bilateral sagittal split osteotomies. The function of the inferior alveolar nerve was studied preoperatively, and 2 weeks, 2 months, 6 months and 1 year postoperatively with both mental nerve blink reflex test and clinical neurosensory testing. The objective electrophysiological test proved to be useful in the diagnosis and follow-up of sensory impairment of the inferior alveolar nerve. The results of the mental nerve blink reflex test and clinical neurosensory testing were closely related. The results of the two tests did not differ statistically significantly in the two first postoperative examinations. The positive predictive value of the mental nerve blink reflex test was better than that of clinical neurosensory testing: an initially abnormal reflex response predicted persistent subjective sensory symptoms after one year more reliably than did altered sensation at the first two examinations. Irrespective of the possible coexistent sensory symptoms and signs, a normal mental nerve blink reflex within 2 months after operation also predicted a reasonably good sensory recovery at 1 year.

Adolescent↗
PubMed2003

Attentional blink modulation in a reaction time task: performance feedback, warning stimulus modality, and task difficulty.

The present research investigated the effect of performance feedback on the modulation of the acoustic startle reflex in a Go/NoGo reaction time task. Experiment 1 (n = 120) crossed warning stimulus modality (acoustic, visual, and tactile) with the provision of feedback in a between subject design. Provision of performance feedback increased the number of errors committed and reduced reaction time, but did not affect blink modulation significantly. Attentional blink latency and magnitude modulation was larger during acoustic than during visual and larger during visual than during tactile warning stimuli. In comparison to control blinks, latency shortening was significant in all modality conditions whereas magnitude facilitation was not significant during tactile warning stimuli. Experiment 2 (n = 80) employed visual warning stimuli only and crossed the provision of feedback with task difficulty. Feedback and difficulty affected accuracy and reaction time. Whereas blink latency shortening was not affected, blink magnitude modulation was smallest in the Easy/No Feedback and the Difficult/Feedback conditions.

Acoustic Stimulation↗
PubMed2001

Corneal topography changes after a 15 second pause in blinking.

PURPOSE: To examine the effect of a short pause in blinking on the quantitative topographic parameters of the corneal surface. SETTING: Refractive corneal surgery unit of a university eye hospital. METHODS: Using a TMS-1 instrument (Computed Anatomy, Inc.), corneal topographic parameters were measured 5 and 15 seconds after a complete blink in 12 healthy subjects. The main outcome measures were changes in the surface regularity index (SRI) and the surface asymmetry index (SAI). RESULTS: During the pause in blinking, the mean SRI value increased from 0.18 +/- 0.19 (SD) to 0.30 +/- 0.19 (P <.02) and the SAI from 0.21 +/- 0.08 to 0.24 +/- 0.10 (P =.079, not statistically significant). There were no significant changes in the values for potential visual acuity, corneal refractive power, or astigmatism. CONCLUSION: The results indicated a significant change in corneal topography during even a short pause in blinking. In follow-up studies using corneal topography, all measurements should be done at a fixed time after a complete blink.

Adult↗
PubMed2000

P300 and blink instructions.

OBJECTIVES: The effects of instructions to refrain from blinking on the P300 event-related brain potential (ERP) from auditory and visual stimuli were assessed. METHODS: An oddball paradigm was employed in which young adult subjects (n = 20) silently counted the infrequent target stimuli and were given either no instructions or told "do not blink" in different conditions, with auditory and visual stimulus tasks employed for all subjects. ERPs were recorded from the midline electrodes, with amplitude and latency of the P300 and other components obtained. RESULTS: P300 amplitude for both modalities and target/standard stimulus conditions was smaller and visual peak latency longer in the "do not blink" condition. Blink instructions did not directly affect the other components. CONCLUSIONS: Instructions to refrain from blinking can decrease P300 amplitude and can increase peak latency.

Acoustic Stimulation↗
PubMed2001

The attentional blink is immune to masking-induced data limits.

The attentional blink is the robust finding that processing a masked item (T1) hinders the subsequent identification of a backwards masked second item (T2), which follows soon after the first one. There has been some debate about the theoretically important relation between the difficulty of T1 processing and the ensuing blink. In Experiment 1 we manipulated the difficulty of T1 in such a way as to affect the quality of data without altering the amount of resources allocated to its identification. We found no relation between the accuracy of T1 identification and the blink. In Experiment 2, the same difficulty manipulation was applied to T2, and we observed an additive pattern with the blink. Together, this pattern of results indicates that a data-limited difficulty manipulation does not affect the blink, whether applied to T1 or T2. In Experiment 3 we used an individual differences methodology to show that performance in the traditional "stream"-like presentation (rapid serial visual presentation) was highly correlated with performance in our modified "target mask, target mask" paradigm, thus allowing for comparisons beyond the present methodology to much of the previous literature that has used the stream paradigm.

Adult↗
PubMed2006

Automatic removal of the eye blink artifact from EEG using an ICA-based template matching approach.

Independent component analysis (ICA) proves to be effective in the removing the ocular artifact from electroencephalogram recordings (EEG). While using ICA in ocular artifact correction, a crucial step is to correctly identify the artifact components among the decomposed independent components. In most previous works, this step of selecting the artifact components was manually implemented, which is time consuming and inconvenient when dealing with a large amount of EEG data. We present a new method which automatically selects the eye blink artifact components based on the pattern of their scalp topographies, which can be exemplified as a template matching approach. The feasibility of using a fixed template for singling out the eye blink component after ICA decomposition was validated by an experiment in which 18 subjects among the 21 subjects involved exhibited a highly consistent pattern of eye blink scalp topographies. Since only the spatial feature is employed for singling out the eye blink component, the proposed method is very efficient and easy to implement. Objective evaluation of the real results shows that the proposed algorithm can remove the eye blink artifact from the EEG while causing little distortion to the underlying brain activities.

Algorithms↗
PubMed1999

Blink duration as an indicator of driver sleepiness in professional bus drivers.

This study focused on eyeblink duration as a measure of sleepiness in on-road driving and on the driving performance of professional bus drivers with polysomnographically confirmed mild obstructive Sleep Apnea Syndrome (OSAS). Ten bus drivers with OSAS and their matched controls participated in the study. The Maintenance of Wakefulness Test (MWT) and a monotonous on-road driving task were completed. Eyeblink duration and frequency and speed control were measured while driving. Lane-keeping was evaluated by the supervisor in the car. Subsequent to these tasks, drivers with OSAS received continuous positive airway pressure treatment (nasal CPAP). After nine weeks of treatment, the tasks were repeated. Prior to treatment the average blink duration in the driving task was significantly longer and sleep latency in the MWT was significantly shorter for bus drivers with OSAS than for controls (mean blink duration 82.3 ms; 51.9 ms and mean sleep latency 23.2 min; 35.4 min), indicating increased daytime sleepiness. Subsequent to treatment both measures in drivers with OSAS decreased to the level of the controls. Treatment effects in MWT and blink duration in on-road driving also correlated significantly. No significant differences between the groups appeared in average blink frequency or driving performance in terms of maintenance of speed. No significant lane drifting appeared either. These results support earlier findings on blink duration as an indicator of increased sleepiness and have important implications for those involved in the transport technological industry. The findings also suggest that nasal CPAP treatment is effective in reducing excessive daytime sleepiness.

Adult↗
PubMed2002

Blink effect on slow vergence.

Blinks are known to change the kinematic properties of fast eye movements, probably by changes in the brain stem circuits. To determine whether slow disconjugate (slow vergence) eye movements are affected by blinks under natural viewing conditions, we elicited airpuff-evoked trigeminal blinks randomly during ongoing steady slow vergence eye movements. Lid and binocular eye movements were recorded by the scleral search coil method. Slow vergence eye movements showed a peak of vergence velocity during the final part of the blink, which depends on the stimulus direction. We propose that the direction-specific blink effect on slow vergence may be caused by changes in brain stem premotor circuits.

Adult↗
PubMed2003

Attentional blink modulation during sustained and after discrete lead stimuli presented in three sensory modalities.

Previous studies found larger attentional modulation of acoustic blinks during task-relevant than during task-irrelevant acoustic or visual, but not tactile, lead stimuli. Moreover, blink modulation was larger overall during acoustic lead stimuli. The present experiment investigated whether these results reflect modality specificity of attentional blink modulation or effects of continuous stimulation. Participants performed a discrimination and counting task with acoustic, visual, or tactile lead stimuli. Stimuli were presented sustained or consisted of two short discrete stimuli. The sustained condition replicated previous results. In the discrete condition, blinks were larger during task-relevant than during task-irrelevant stimuli in all groups regardless of lead stimulus modality. Thus, previous results that seemed consistent with modality-specific accounts of attentional blink modulation reflect effects of continuous stimulus input.

Acoustic Stimulation↗
PubMed2004

The effect of stimulus modality and task difficulty on attentional modulation of blink startle.

The effects of the sensory modality of the lead stimulus and of task difficulty on attentional modulation of the electrical and acoustic blink reflex were examined. Participants performed a discrimination and counting task with either two acoustic, two visual, or two tactile lead stimuli. In Experiment 1, facilitation of the electrically elicited blink was greater during task-relevant than during task-irrelevant lead stimuli. Increasing task difficulty enhanced magnitude facilitation for acoustic lead stimuli. In Experiment 2, acoustic blink facilitation was greater during task-relevant lead stimuli, but was unaffected by task difficulty. Experiment 3 showed that a further increase in task difficulty did not affect acoustic blink facilitation during visual lead stimuli. The observation that blink reflexes are facilitated by attention in the present task domain is consistent across a range of stimulus modality and task difficulty conditions.

Acoustic Stimulation↗
PubMed1995

Partial restoration of blink reflex function after spinal accessory-facial nerve anastomosis.

Functional motor control requires perfect matching of the central connections of motoneurons with their peripheral inputs. It is not known, however, to what extent these central circuits are influenced by target muscles, either during development or after a lesion. Surgical interventions aimed at restoring function after peripheral nerve lesions provide an opportunity for studying this interaction in the mature human nervous system. A patient was studied in whom the spinal accessory nerve was anastomosed into a lesioned facial nerve, allowing voluntary contractions of the previously paralysed muscles. This procedure, in addition to replacing the facial neurons at peripheral synapses, allowed a new short latency trigeminospinal accessory reflex of the R1 blink reflex type to be demonstrated, implying that trigeminal neurons had sprouted towards spinal accessory motoneurons over a distance of at least 1 cm. These results show an unexpected influence of the periphery in remodelling central connectivity in humans. The motoneuronal excitability for this R1 reflex response was therefore studied to compare the convergent properties of facial motoneurons (normal side) with those of the spinal accessory motoneurons (operated side) using a classic double shock technique with variable interstimulus intervals (conditioning test stimulus). On the normal side, conditioning stimuli (to the ipsilateral or contralateral infraliminar supraorbital nerve) produced a clearcut facilitation of the R1 blink reflex when the interstimulus interval was 30-80 ms. By contrast, a similar procedure had no effect on the R1 blink reflex mediated via the trigeminal-spinal accessory reflex arc. These data indicate that despite the heterotopic sprouting of some axons from neurons in the XIth nucleus, motoneurons involved in the newly formed reflex arc remain totally inexcitable by other trigeminal afferents and seem unable to ensure a physiological functioning of the normal blink reflex. Thus the functional relevance of the recovered R1 blink response remains unclear.

Accessory Nerve↗
PubMed1996

Evaluation of the somatosensory evoked blink response in patients with neurological disorders.

BACKGROUND: The somatosensory evoked blink response (SBR) is a characteristic reflex blink elicited by electrical stimulation of peripheral nerves or other anatomical sites. METHODS: 139 patients with neurological disorders were examined for presence of the SBR. Although the SBR was not usually elicitable, it was present in a subset of patients with Parkinson's disease and with hemifacial spasm. It was also present in a patient with Guillain-Barré syndrome before the recovery phase. The latency of the EMG activities responsible for the SBR was significantly shorter than that of the startle blink. CONCLUSIONS: The SBR is not a variant of the startle blink, but is a release phenomenon transmitted via the brainstem reticular formation. This response may be clinically relevant in disorders associated with brainstem lesions and abnormal blinking.

Blinking↗
PubMed2002

Nociceptive quality of the laser-evoked blink reflex in humans.

Laser radiant-heat pulses selectively excite the free nerve endings in the superficial layers of the skin and activate mechano-thermal nociceptive afferents; when directed to the perioral or supraorbital skin, high-intensity laser pulses evoke a blink-like response in the orbicularis oculi muscle (the laser blink reflex, LBR). We investigated the functional properties (startle or nociceptive origin) of the LBR and sought to characterize its central pathways. Using high-intensity CO(2)-laser stimulation of the perioral or supraorbital regions and electromyographic (EMG) recordings from the orbicularis oculi muscles, we did five experiments in 20 healthy volunteers. First, to investigate whether the LBR is a startle response, we studied its habituation to expected rhythmic stimuli and to unexpected arrhythmic stimuli. To assess its possible nociceptive quality, we studied changes in the LBR and the R2 component of the electrical blink reflex after a lidocaine-induced supraorbital nerve block and after intramuscular injection of the opiate fentanyl and the opiate-antagonist naloxone. To characterize the central pathways for the LBR, we investigated the interaction between the LBR and the three components of the blink reflex (R1, R2, and R3) by delivering laser pulses to the perioral or supraorbital regions before or after electrical stimulation of the supraorbital nerve at various interstimulus intervals. Finally, to gain further information on the central LBR pathways, using two identical CO(2)-laser stimulators, we studied the LBR recovery curves with paired laser pulses delivered to adjacent forehead points at interstimulus intervals from 250 ms to 1.5 s. The LBR withstood relatively high-frequency rhythmic stimulations, and unexpected laser pulses failed to evoke larger responses. When lidocaine began to induce hypoalgesia (about 5 min after the injection), the LBR was abolished, whereas R2 was only partly suppressed 10 min after the injection. Fentanyl injection induced strong, naloxone-reversible, LBR suppression (the response decreased to 25.3% of predrug values at 10 min and to 4% at 20 min), whereas R2 remained appreciably unchanged. Whether directed to the perioral or supraorbital regions, preceding laser pulses strongly suppressed R2 and R3 though not R1. Conversely, preceding electrical stimuli to the supraorbital nerve suppressed the LBR. In response to paired stimuli, the LBR recovered significantly faster than R2. These findings indicate that the LBR is a nociceptive reflex, which shares part of the interneuron chain mediating the nonnociceptive R2 blink reflex, probably in the medullary reticular formation. The LBR may prove useful for studying the pathophysiology of orofacial pain syndromes.

Adult↗
PubMed1984

Blinking and associated eye movements in humans, guinea pigs, and rabbits.

Recordings of upper eyelid movements in humans, guinea pigs, and rabbits demonstrated that all three species displayed qualitatively similar patterns of eyelid movement. The relation between amplitude, duration, and maximum velocity in rabbits and humans was nearly identical. Guinea pig blinks were faster than those of rabbit and man. Electromyographic (EMG) recordings in humans demonstrated that the orbicularis oculis muscle participated in downward movement of the upper eyelid during blinks and eyelid closure but did not participate actively in the downward lid movement occurring with gaze changes. When looking straight ahead, the estimated stiffness and viscosity of the upper eyelid were 10 g/mm and 0.38 g X s X mm-1 for humans and 1.17 g/mm and 0.062 g X s X mm-1 for rabbits. Upward and abducting rotations of the eye accompanied blinks in rabbits and guinea pigs. Simultaneously, the eyeball retracted (translational movement) into the orbit. These translational and rotational eye movements resulted from contraction of the retractor bulbi muscle and cocontraction of antagonistic extraocular muscles. The data suggested that humans also retracted the eye during voluntary blinks. The retraction produced a rotation of the eye toward a "primary position" rather than a rotation in one specific direction. The relationship between the maximum velocity, duration, and amplitude of the down phase of a blink may be expressed as a single equation, maximum velocity = c X average velocity, where c is a constant. The same relationship, with a similar value for c, also describes saccadic eye movements and rapid skeletal movements. This implies that all three movements employ comparable neural mechanisms.

Animals↗
PubMed1997

Different effects of levodopa and apomorphine on blink reflex recovery cycle in essential blepharospasm.

With the aim of assessing dopaminergic responsiveness in essential blepharospasm, we investigated the effects of oral levodopa and subcutaneous apomorphine on blink reflex recovery cycle in 7 blepharospasm patients. We found that in blepharospasm the excitability of the blink reflex recovery cycle was increased compared with control subjects. The oral administration of levodopa/carbidopa (500/50 mg) did not significantly modify the blink reflex recovery cycle. The 50 micrograms/kg dose of apomorphine decreased the amplitude of conditioned responses at 300 and 500 ms, whereas the 10 micrograms/kg dose was ineffective. We conclude that the excitability of the blink reflex recovery cycle in blepharospasm is partly under dopaminergic control. The partial normalization of the blink reflex recovery cycle excitability observed with 50 micrograms/kg apomorphine is consistent with the reported clinical efficacy of the drug in this condition.

Administration, Oral↗