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PubMedDate not supplied

Late blink reflex changes in patients with pure sensory stroke due to geniculo-thalamic infarct: a contribution to the long loop theory.

Seven patients with a pure sensory stroke due to a geniculo-thalamic infarct underwent blink reflex (BR) and median nerve somatosensory evoked potential studies to explore the mechanism subserving the R2 response. Both ipsilateral and contralateral R2 responses to stimulation of the affected side were significantly delayed in comparison with those obtained with stimulation of the nonaffected side (P < 0.001). Furthermore, in the five patients tested, cortical N20 following median nerve stimulation of the affected side was absent, delayed, or significantly reduced. These findings are consistent with the hypothesis of the transcortical generation of the late component of the BR. BR study appears to be a useful tool to assess long tract function, because changes have also been observed in patients with no demonstrable deficits on sensory examination.

Adaptation, Physiological↗
PubMed1982

The motion of a contact lens over the eye during blinking.

A simple model is proposed for the motion of a hard contact lens over the surface of the eye during a blink. This is analyzed to estimate the initial motion of the lens as the eye opens, and the results obtained are compared with the experimental ones already available.

Blinking↗
PubMed1986

Further studies of contact lens motion during blinking.

Contact lens motion is felt to be of increasing importance in connection with debris elimination, particularly in extended wear lenses. Thus an improved analysis is made of a simple model for investigating the initial motion of a hard contact lens over the eye during blinking. It is shown that the assumption of constant tear film thickness is a reasonable one. This greatly simplifies the analysis. Various vertical force vs. time variations are considered and lens velocity/time graphs and maximum lens displacement calculated. These are in good agreement with the results of experiment.

Blinking↗
PubMed1995

Blink-induced motion of a gas permeable contact lens.

The blink-induced dynamics of a gas permeable contact lens are analyzed. The lens is considered to be a planar, circular, porous disk of specified permeability. Specifically, this work investigates the effects of those variables that characterize the porous nature of the lens such as the permeability and thickness of the lens and the effective slip coefficient. The equations governing the dynamics of the tear film and of the lens are solved subject to physical constraints that limit the duration and extent of the lens motion. The motion of a permeable contact lens can be controlled by a proper choice of the lens material microstructure. Analysis of the results indicates that the motion of the lens is enhanced by lower values of the slip coefficient and higher values of the permeability, independent of the lens thickness. In addition, thicker lenses as well as thicker tear films cause the lens to squeeze faster and to slide slower.

Blinking↗
PubMed2006

Role of blink reflex in diagnosis of subclinical cranial neuropathy in diabetic mellitus type II.

BACKGROUND AND OBJECTIVES: Peripheral neuropathy (PN) is one of the late complications of diabetes mellitus. Cranial nerves III, VII, and V are among the most commonly affected in diabetic patients. Traditional electrodiagnosis (Edx) studies are a useful method for diagnosis of PN and symptomatic cranial neuropathy, and may not be useful for detecting subclinical involvement of cranial nerves. The main objective of this study is to evaluate the role of blink reflex (BR) for early diagnosis of cranial neuropathy in diabetic patients with PN. DESIGN: A prospective study was performed on NIDDM patients with PN. One hundred eighty-eight subjects were included in our study in which 142 acted as healthy subjects and 46 as diabetic patients. Patients were excluded with prior history of cranial nerve lesions, stroke, or any other disease with polyneuropathy or drug-induced neuropathy. Routine nerve conduction studies were performed, and only patients with PN were included in this study. RESULTS: Abnormalities were found in 54.4% of patients. R1, IR2, and CR2 were prolonged relative to the healthy group. Statistically there was no significant difference in R/D ratio of patients (P=0.201). Also, there was a positive correlation between R1, IR2, and CR2 latencies with duration of diabetes and severity of polyneuropathy, but not for R/D. The greatest correlation was shown in R1 latency (69.9% abnormality). CONCLUSION: BR is a noninvasive and very useful method for the evaluation and diagnosis of subclinical cranial nerve involvement in diabetic patients.

Adolescent↗
PubMed2006

The ratio of square wave jerk rates to blink rates distinguishes progressive supranuclear palsy from Parkinson disease.

BACKGROUND: Distinguishing progressive supranuclear palsy (PSP) from Parkinson disease (PD) may be difficult, particularly in the early stages, because the characteristic vertical supranuclear eye movement abnormalities of PSP may be absent or delayed until late in the course of the disease. In this study we investigated the usefulness of comparing the square wave jerk rate (SWJR) and blink rate (BR) in the differentiation of these two disorders. METHODS: We studied 10 patients with PD (PD group) and 5 patients with PSP (PSP group) who met published diagnostic criteria. The SWJR and BR were measured from video recordings and were used to calculate a ratio (SWJR:BR). RESULTS: The PSP group exhibited a significantly higher SWJR, higher SWJR:BR, and lower BR than did the PD group. No patient with PSP exhibited a SWJR:BR of < 3; however, one patient with PD had a SWJR:BR of 5.3, creating overlap between the two groups. CONCLUSIONS: The SWJR:BR is a simple and reasonably useful clinical measure to distinguish established PSP from PD. Determining the value of this measure in differentiating early PSP from PD requires a prospective study.

Aged↗
PubMedDate not supplied

The learning-related activity that develops in the pontine nuclei during classical eye-blink conditioning is dependent on the interpositus nucleus.

A growing body of research now implicates the cerebellum in the formation and storage of the critical neural plasticity that subserves the classically conditioned eye-blink response. Previous anatomical, physiological, and behavioral research suggests that auditory-conditioned stimulus information is routed to the cerebellum by the pontine nuclei. However, it has also been observed from multiple unit recordings that some populations of pontine cells, in addition to showing auditory-evoked responses, also show changes in activity that is learning-related. It is unknown whether this learning-related activity is generated by the pontine cells or whether it is generated by some other structure and projected to the pontine nuclei. Because the cerebellum has been implicated in the formation of the essential plasticity that subserves this learned behavior, we examined how multiple unit recordings of learning-related activity within the pontine nuclei are affected by reversible inactivation of the interpositus nucleus of the cerebellum. The results indicated clearly that when the interpositus nucleus was inactivated, the learning-related activity in the pontine nuclei was abolished completely and the auditory stimulus-evoked activity was unaffected. In contract, when the facial nucleus was inactivated, both the auditory stimulus and the learning-related activity were still present. These results indicate that the learning-related activity exhibited by some populations of pontine nuclei cells is dependent on the interpositus nucleus and may represent feedback from the cerebellum.

Animals↗
PubMed2003

New objects, not new features, trigger the attentional blink.

When two different targets must be selected from a rapid serial visual presentation (RSVP) of images, perception of the second target will be markedly reduced if it is presented within about a half second of the first. Known as the attentional blink (AB), this effect reflects temporal limitations in attentional processes enabling awareness of image representations. I tested whether these limitations occur at an object or feature level of processing by presenting (in RSVP) multiple images of the same (old) object depicted in different orientations. Targets were defined by new features added either to this or to a new object. When the first target feature appeared on the old object, no AB effects were found even when the second target was a new object. When a new object carried the first target feature, an AB effect was found even when the second target feature appeared on the same "new" object. The AB appears to reflect limitations in the creation of new object representations, rather than temporal limitations of awareness per se.

Adult↗
PubMed2003

Electrophysiological evidence of visual encoding deficits in a cross-modal attentional blink paradigm.

Two experiments are reported in which two target stimuli, T1 and T2, were presented at variable stimulus onset asynchronies (SOAs). In Experiment 1, T1 and T2 were visual stimuli embedded in a rapid serial visual presentation (RSVP) stream of distractors. Participants were asked to report T1 and T2 at the end of the stream. In Experiment 2, T1 was an auditory stimulus, and T2 a visual stimulus embedded in an RSVP stream. Participants made a speeded discriminative response to T1, and reported T2 at the end of the stream. An attentional blink (AB) effect was observed in both experiments: T2 report suffered at short SOA compared to long SOA. During the AB, the amplitude of the P300 component of the event-related potential (ERP) locked to T2 onset was sensibly reduced in both experiments. Behavioral and ERP results were very similar across the two experiments. Implications for models of the AB effect are discussed.

Attention↗
PubMed2005

The meaning of the mask matters: evidence of conceptual interference in the attentional blink.

The rapid serial visual presentation (RSVP) experiment reported here investigated the role of conceptual interference in the attentional blink (AB). Subjects were presented with RSVP streams that contained five stimuli: Target 1, a distractor, Target 2, a second distractor, and a symbol mask. Target 1 was a green letter, Target 2 was a red letter, and the distractors were either white letters or white digits. The stimuli were presented in a font typically seen on the face of a digital watch. Thus, "S" and "O" were identical to "5" and "0," respectively. This allowed us to present streams that were conceptually different even though featurally identical: The two letter targets were followed by distractors that were recognized either as "5" and "0" or as "S" and "O." The AB was substantially attenuated when subjects were told the distractors were digits rather than letters. This result indicates that conceptual interference plays a role in the AB.

Adult↗
PubMed2006

Functional connectivity between trigeminal and occipital nerves revealed by occipital nerve blockade and nociceptive blink reflexes.

Headache syndromes often suggest occipital and neck involvement, although it is still unknown to what extent branches of segment C1-C3 contribute actively to primary headache. Pain within the occipital area may be referred to the trigeminal territory. However, a modulation of trigeminal transmission by affecting cervical input in humans has not been elucidated so far. A convergence of cervical and trigeminal input at the level of the caudal part of the trigeminal nucleus in the brainstem has been suggested due to anatomical and neurophysiological studies in animals. We examined the R2 components of the nociceptive blink reflex responses in 15 healthy subjects before and after unilateral nerve blockade of the greater occipital nerve with 5 ml prilocain (1%). R2 response areas (AUC) decreased and the R2 latencies increased significantly after the nerve blockade only on the side of injection. AUC and latencies on the non-injection side remained stable. Thresholds for sensory or pain perception did not differ significantly between the repeated measurements on both sides. Our findings extend previous results related to anatomical and functional convergence of trigeminal and cervical afferent pathways in animals and suggest that the modulation of this pathway is of potential benefit in primary headache disorders.

Adult↗
PubMed2006

Abnormal blink reflex studies in a patient with supraorbital neuralgia.

A 44-year-old female with gabapentin-responsive supraorbital neuralgia is presented. She had pre- and post-treatment nociceptive-specific blink reflexes carried out which tracked the good clinical outcome from treatment. The results of the electrophysiological testing imply some central component to the pathophysiology of supra-orbital neuralgia.

Adult↗
PubMed2006

Blink reflex R2 amplitudes in cervicogenic headache, chronic tension-type headache and migraine.

Blink reflex R2 amplitude was investigated in seven patients with cervicogenic headache (CEH), 12 patients with chronic tension-type headache, 23 patients with migraine (10 with aura) and 17 headache-free controls. Standard electrical stimulation of the supraorbital nerve was applied and the response was recorded from the ipsilateral and the contralateral orbicularis oculi muscles. Low R2 amplitude was found in CEH patients compared with control subjects. Headache is unilateral in CEH and the ipsilateral and contralateral responses after stimulation on the painful side were most depressed. R2 amplitude was not significantly affected in migraine and tension headache patients. The results suggest that lower brainstem excitability is reduced in CEH. A state of hypoactivity may be present in caudal trigeminal nucleus neurons on the symptomatic side.

Adult↗
PubMed1996

Distinct early and late subcomponents of the photic blink reflex: response characteristics in patients with retrogeniculate lesions.

To assess cortical contributions to the photic blink reflex, signal averaged electromyograms (EMG) were compared for responses to strobe flashes presented within the blind and sighted hemifields of 13 patients with occipital lobe lesions. Reflexes evoked by flashes within the scotoma were virtually identical to those evoked by flashes within the intact visual field. This suggests that both the early and late components of this reflex (R50 and R80, respectively) are mediated by subcortical structures that do not require, or benefit from, conscious visual processing. Additional findings included larger R80s at the eyelid contralateral to the lesion, regardless of stimulated hemifield. This presumably reflects the loss of a tonic descending influence of visual cortex onto the motor limb of the reflex arc. The R80 was also larger for stimuli activating the crossed (temporal hemifield) rather than the uncrossed (nasal hemifield) afferent pathway.

Adult↗
PubMed2004

Automatic removal of eye movement and blink artifacts from EEG data using blind component separation.

Signals from eye movements and blinks can be orders of magnitude larger than brain-generated electrical potentials and are one of the main sources of artifacts in electroencephalographic (EEG) data. Rejecting contaminated trials causes substantial data loss, and restricting eye movements/blinks limits the experimental designs possible and may impact the cognitive processes under investigation. This article presents a method based on blind source separation (BSS) for automatic removal of electroocular artifacts from EEG data. BBS is a signal-processing methodology that includes independent component analysis (ICA). In contrast to previously explored ICA-based methods for artifact removal, this method is automated. Moreover, the BSS algorithm described herein can isolate correlated electroocular components with a high degree of accuracy. Although the focus is on eliminating ocular artifacts in EEG data, the approach can be extended to other sources of EEG contamination such as cardiac signals, environmental noise, and electrode drift, and adapted for use with magnetoencephalographic (MEG) data, a magnetic correlate of EEG.

Algorithms↗
PubMed2005

Psychopathy, startle blink modulation, and electrodermal reactivity in twin men.

Psychopathy is a personality disorder with interpersonal-emotional and antisocial deviance facets. This study investigated these facets of psychopathy prospectively using normal-range personality traits in a community sample of young adult men who completed a picture-viewing task that included startle blink and skin conductance measures, like tasks used to study psychopathy in incarcerated men. Consistent with prior research, scores on the interpersonal-emotional facet of psychopathy ("fearless dominance") were associated with deficient fear-potentiated startle. Conversely, scores on the social deviance facet of psychopathy ("impulsive antisociality") were associated with smaller overall skin conductance magnitudes. Participants high in fearless dominance also exhibited deficient skin conductance magnitudes specifically to aversive pictures. Findings encourage further investigation of psychopathy and its etiology in community samples.

Affect↗
PubMed1980

The value of brain stem auditory, visual and somatosensory evoked potentials and blink reflexes in the diagnosis of multiple sclerosis.

Cervical and cortical somatosensory evoked potentials (SEP) following electrical stimulation of the median nerve and blink reflexes (BR) following electrical stimulation of the supraorbital nerve were recorded in 30 normal subjects aged 20-49 years. Subjects aged 40-49 had longer SEP latencies than subjects aged 20-39 years. A total of 29 slightly affected patients with multiple sclerosis (MS) aged 26-49 years, including four patients without clinical signs (suspected MS) and 19 patients with signs indicating only one lesion (possible MS) were examined by low-rate random-stimulated brain stem auditory (BAEP), checkerboard pattern-reversal visual evoked potentials (VEP), SEP and BR. Abnormal recordings by at least one of the examinations were found in all but three patients, and by all four tests in five patients. In patients with definite or probably MS, demonstration of clinically recognized or subclinical lesions was of minor diagnostic value, in contrast to the importance such findings had in patients with suspected or possible MS. Silent lesions were shown by at least one of the tests in the four suspected and in 13 of the possible MS patients, so these 17 patients could be transferred to a more certain diagnostic category. This reclassification was most often due to the BAEP recording. In patients with spinal signs, the combination of BAEP and VEP recording was sufficiently efficient. In patients with optic neuritis a combination of BAEP and SEP was preferred. No abnormal recordings were found in 15 normal subjects examined by all four tests.

Adult↗
PubMed1985

The blink reflex and somatosensory evoked potential in optic neuritis in south India.

Optic Neuritis (ON) proceeds to multiple sclerosis (MS) in a considerable number of patients. The blink reflex (BR) and somatosensory evoked potential (SSEP) are useful non-invasive tests that can detect silent lesions in the central nervous system in patients with clinically suspect MS. In the present study, the BR and SSEP were done in 20 healthy controls and 20 patients with ON. Abnormalities of the SSEP were seen in 20%, and of the BR in 30% of the patients with ON. On combining the results of SSEP and BR studies, 45% of the ON patients were seen to have abnormalities. Over a short period of follow-up, 2 of the 20 ON patients developed clinical MS and both of them had had abnormalities of the BR. These findings suggest that ON proceeding to MS in India may be more common than suspected at present.

Adolescent↗