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At least 613 records · Page 34Linked to original sources
PubMed1998

Effects of stimulus modality and task condition on blink startle modification and on electrodermal responses.

Participants in Experiments 1 and 2 performed a discrimination and counting task to assess the effect of lead stimulus modality on attentional modification of the acoustic startle reflex. Modality of the discrimination stimuli was changed across subjects. Electrodermal responses were larger during task-relevant stimuli than during task-irrelevant stimuli in all conditions. Larger blink magnitude facilitation was found during auditory and visual task-relevant stimuli, but not for tactile stimuli. Experiment 3 used acoustic, visual, and tactile conditioned stimuli (CSs) in differential conditioning with an aversive unconditioned stimulus (US). Startle magnitude facilitation and electrodermal responses were larger during a CS that preceded the US than during a CS that was presented alone regardless of lead stimulus modality. Although not unequivocal, the present data pose problems for attentional accounts of blink modification that emphasize the importance of lead stimulus modality.

Adolescent↗
PubMed1998

[Hyperexcitability of the blink reflex in a child with opsoclonus-myoclonus syndrome].

A 13-month-old girl developed opsoclonus-myoclonus syndrome in association with neuroblastoma. She showed irritability, hyperhidrosis and a bad temper. Serum and urinary vanilmandelic acid, homovanilic acid and catecholamines were elevated at the same time. Chest CT demonstrated the presence of neuroblastoma in the paravertebral region. Cranial CT and MRI revealed no abnormal findings. Brainstem auditory-evoked potentials and short latency somatosensory evoked potentials were normal, whereas blink reflex showed long duration and high amplitude of late components (R2 and R2') indicating hyperexcitability of the interneurons in the lower brainstem. These findings improved gradually as opsoclonus disappeared. Her neurologic symptoms resolved completely within 2 years after the resection of the tumor. The hyperexcitability of the blink reflex may indicate the hyperactivity of the neurons in the brainstem reticular formation responsible for the abnormal saccadic eye movements (opsoclonus), which could be caused by the oversecretion of dopamine or by the supersensitivity of dopaminergic receptors.

Blinking↗
PubMedDate not supplied

[Behavioral differences in childhood depression: study of blinking and auto-manipulation].

Different investigations have studied the evolution of childhood depression but little research has been based on the observation of behavior. This work aims at analysing two singular behaviors: eye blink and auto-manipulation. This paper compares the results obtained on day A(hospital admission, before treatment) and on day D (discharge, after clinical improvement) during a standardized interview recorded in video with children aged 8-13 years, hospitalized for a major depressive episode and for a control group. The results show a significant decrease in eye blink frequency and the mean auto-manipulation duration after clinical improvement. The discussion raises the question of the role of anxiety in the development of these behavioral modifications.

Adolescent↗
PubMed1976

[Examination of blinking-rate in a simulated four hour driving task].

In a driving simulation task performance and physiological measurement of strain was registered on 3 subjects in 9 experiments. The time-variant behaviour of blinking-rate was examined together with performance, self-rating and physiological strain. The correlating results make blinking-rate a possible indicator for activation of willingness to good performance. A multidimensional concept for assessment of the degree of individual fatigue is presented and validated in respect of working-time.

Adult↗
PubMed2004

Acute stress impairs trace eye blink conditioning in females without altering the unconditioned response.

Exposure to an acute stressor of inescapable swimming or intermittent tail shocks impairs classical eye blink conditioning 24h later in female rats. This effect is often attributed to a deficit in "learning," but since stress has been shown to induce analgesia, an alternative explanation is that stressor exposure reduces conditioning by lessening the perceived intensity of the unconditioned stimulus (US). To address this possibility we examined the amplitude of the unconditioned response (UR) during training and found that although exposure to the stressor impaired trace conditioning, there was no difference in the UR amplitude. We also found that eye blink responses to different US intensities (4-12 V) in the absence of training were unaffected by stressor exposure. Taken together, these experiments indicate that the stress-induced impairment of conditioning in females is not due to a decreased perception of US strength.

Analysis of Variance↗
PubMed1999

Identification of differently timed motor components of conditioned blink responses.

Electromyographic recordings were made from the orbicularis oculi muscles of cats in order to identify differently timed motor components of conditioned eye blink responses (CRs). Conditioning was established rapidly by pairing electrical stimulation of the hypothalamus (HS) with a click conditioned stimulus (CS) and a glabella tap unconditioned stimulus (US). Analysis of the EMG responses disclosed five different motor components of the CR that could be distinguished and characterized according to their latencies of occurrence. Four were associated with an increase in EMG activity elicited by the CS (16-48 ms, alpha(1); 48-80 ms, alpha(2); 80 to 120 ms, beta; >/=120 ms, gamma), and one was associated with a decrease in activity (16 to 60 ms, alpha(i)). Analysis of the amplitudes of the different components of the CR during the course of conditioning and extinction disclosed that short latency, alpha(1) components of the CRs were acquired and extinguished in a manner equivalent to longer latency components of the CRs. The observations supported the hypothesis that short and long latency components of blink responses represented comparable rather than substantially different forms of Pavlovian conditioning. The alpha(2) response was present before conditioning began, and increased with other components after conditioning. The alpha(i) response component was also observed prior to conditioning, and represents a previously undetected, inhibitory consequence of presenting weak (70 dB) acoustic stimuli. It could play a role in conditioned inhibition, latent inhibition and blocking as well as suppression of the conditioned motor response during extinction.

Adaptation, Physiological↗
PubMed2005

Single molecule blinking and photobleaching separated by wide-field fluorescence microscopy.

Single molecule fluorescence detection of Atto590 in poly(vinyl alcohol) was achieved by using a wide-field epifluorescence microscope with CCD-camera detection. Image sequences are obtained from which the time traces of the detected molecules are built. We find a distinctive difference between the time evolution of the fluorescence originating from the molecules detected in the first image of the sequence compared to the time evolution of the fluorescence of the molecules detected in each image of the sequence. Atto590 shows very long blinking times and photobleaching and photoblinking that are both quadratically dependent on the irradiation power density. Our approach allows kinetic separation of photobleaching from blinking. The possibility of choosing different ensembles of molecules is demonstrated and taken advantage of for this aim. Initially dark molecules or low emitting ones that might be overlooked are important to describe the complete ensemble behavior.

Fluorescent Dyes↗
PubMed2006

Photon counting statistics for blinking CdSe-ZnS quantum dots: a Lévy walk process.

We analyze photon statistics of blinking CdSe-ZnS nanocrystals interacting with a continuous wave laser field, showing that the process is described by a ballistic Lévy walk. In particular, we show that Mandel's Q parameter, describing the fluctuations of the photon counts, is increasing with time even in the limit of long time. This behavior is in agreement with the theory of Silbey and co-workers (Jung et al. Chem. Phys. 2002, 284, 181), and in contrast to all existing examples where Q approaches a constant, independent of time in the long time limit. We then analyze the distribution of the time averaged intensities, showing that they exhibit a nonergodic behavior, namely, the time averages remain random even in the limit of a long measurement time. In particular, the distribution of occupation times in the on-state compares favorably to a theory of weak ergodicity breaking of blinking nanocrystals. We show how our data analysis yields information on the amplitudes of power-law decaying on and off time distributions, information not available using standard data analysis of on and off time histograms. Photon statistics reveals fluctuations in the intensity of the bright state indicating that it is composed of several states. Photon statistics exhibits a Lévy walk behavior also when an ensemble of 100 dots is investigated, indicating that the strange kinetics can be observed already at the level of small ensembles.

Journal Article↗
PubMed2006

Coverage-mediated suppression of blinking in solid state quantum dot conjugated organic composite nanostructures.

Size-correlated single-molecule fluorescence measurements on CdSe quantum dots functionalized with oligo(phenylene vinylene) (OPV) ligands exhibit modified fluorescence intermittency (blinking) statistics that are highly sensitive to the degree of ligand coverage on the quantum dot surface. As evidenced by a distinct surface height signature, fully covered CdSe-OPV nanostructures (approximately 25 ligands) show complete suppression of blinking in the solid state on an integration time scale of 1 s. Some access to dark states is observed on finer time scales (100 ms) with average persistence times significantly shorter than those from ZnS-capped CdSe quantum dots. This effect is interpreted as resulting from charge transport from photoexcited OPV into vacant trap sites on the quantum dot surface. These results suggest exciting new applications of composite quantum dot/organic systems in optoelectronic systems.

Cadmium Compounds↗
PubMed2006

Quenching and blinking of fluorescence of a single dye molecule bound to gold nanoparticles.

A fluorescein derivative (SAMSA) bound to gold nanoparticles of different diameters is investigated by time-resolved fluorescence at the single molecule level in a wide dynamic range, from nanosecond to second time scale. The significant decrease of both SAMSA excited state lifetime and fluorescence quantum yield observed upon binding to gold nanoparticles can be essentially traced back to an increase of the nonradiative deactivation rate, probably due to energy transfer, that depends on the nanoparticle size. A slow single molecule fluorescence blinking, in the ms time scale, has a marked dependence on the excitation intensity both under single and under two photon excitation. The blinking dynamics is limited by a low probability nonlinear excitation to a high energy state from which a transition to a dark state occurs. The results point out a strong coupling between the vibro-electronic configuration of the dye and the plasmonic features of the metal nanoparticles that provide dye radiationless deactivation channels on a wide dynamic range.

Biophysical Phenomena↗
PubMed2002

Interpretation revealed in the blink of an eye: depressive bias in the resolution of ambiguity.

Self-report measures of interpretation have been criticized on methodological grounds. An approach is introduced in this article that enables the assessment of interpretive bias with a greater degree of methodological rigor than previously has been the case. Psychophysiological researchers have established that the magnitude of the human blink reflex is augmented when elicited during negative rather than neutral imagery. The 1st experiment demonstrates that the blink reflex is sensitive to the emotional valence of imagery evoked by interpretations imposed on ambiguous stimuli. In the 2nd experiment, this measure is used to assess interpretations imposed on ambiguous stimuli by individuals who differ in depression levels. The findings are consistent with the hypothesis that depression is associated with a negative interpretive bias.

Adolescent↗
PubMed1990

Hippocampectomy disrupts trace eye-blink conditioning in rabbits.

The role of the hippocampus (HPC) in trace eye-blink conditioning was evaluated using a 100-ms tone conditioned stimulus (CS), a 300- or 500-ms trace interval, and a 150-ms air puff unconditioned stimulus (UCS). Rabbits received complete hippocampectomy (dorsal & ventral), sham lesions, or neocortical lesions. Hippocampectomy produced differential effects in relation to the trace interval used. With a 300-ms trace interval, HPC-lesioned Ss showed profound resistance to extinction after acquisition. With a 500-ms trace interval, HPC-lesioned Ss did not learn the task (only 22% conditioned responses (CRs) after 25 sessions, whereas controls showed greater than 80% after 10 sessions), and on the few trials in which a CR occurred, most were "nonadaptive" short-latency CRs (i.e., they started during or just after the CS and always terminated prior to UCS onset). The authors conclude that the HPC encodes a temporal relationship between CS and UCS, and when the trace interval is long enough (e.g., 500 ms), that the HPC is necessary for associative learning of the conditioned eye-blink response.

Animals↗
PubMed2006

Re-examining the origins of spectral blinking in single-molecule and single-nanoparticle SERS.

Single metal nanoparticles and nanoaggregates are known to emit intense bursts of surface-enhanced Raman scattering (SERS) in an intermittent on and off fashion. The characteristic "blinking" timescales range from milliseconds to seconds. Here we report detailed temperature dependence (both heating and cooling) and light-intensity studies to further examine the origins of this intriguing phenomenon. The results indicate that blinking SERS contains both a thermo-activated component and a light-induced component. Several lines of evidence suggest that the observed fluctuations are caused by thermally activated diffusion of individual molecules on the particle surface, coupled with photo-induced electron transfer and structural relaxation of surface active sites or atomic-scale roughness features.

Nanoparticles↗
PubMed2006

Accurate and unbiased estimation of power-law exponents from single-emitter blinking data.

Single emitter blinking with a power-law distribution for the on and off times has been observed on a variety of systems including semiconductor nanocrystals, conjugated polymers, fluorescent proteins, and organic fluorophores. The origin of this behavior is still under debate. Reliable estimation of power exponents from experimental data is crucial in validating the various models under consideration. We derive a maximum likelihood estimator for power-law distributed data and analyze its accuracy as a function of data set size and power exponent both analytically and numerically. Results are compared to least-squares fitting of the double logarithmically transformed probability density. We demonstrate that least-squares fitting introduces a severe bias in the estimation result and that the maximum likelihood procedure is superior in retrieving the correct exponent and reducing the statistical error. For a data set as small as 50 data points, the error margins of the maximum likelihood estimator are already below 7%, giving the possibility to quantify blinking behavior when data set size is limited, e.g., due to photobleaching.

Computer Simulation↗
PubMed2005

Ca2+ blinks: rapid nanoscopic store calcium signaling.

Luminal Ca(2+) in the endoplasmic and sarcoplasmic reticulum (ER/SR) plays an important role in regulating vital biological processes, including store-operated capacitative Ca(2+) entry, Ca(2+)-induced Ca(2+) release, and ER/SR stress-mediated cell death. We report rapid and substantial decreases in luminal [Ca(2+)], called "Ca(2+) blinks," within nanometer-sized stores (the junctional cisternae of the SR) during elementary Ca(2+) release events in heart cells. Blinks mirror small local increases in cytoplasmic Ca(2+),orCa(2+) sparks, but changes of [Ca(2+)] in the connected free SR network were below detection. Store microanatomy suggests that diffusional strictures may account for this paradox. Surprisingly, the nadir of the store depletion trails the peak of the spark by about 10 ms, and the refilling of local store occurs with a rate constant of 35 s(-1), which is approximately 6-fold faster than the recovery of local Ca(2+) release after a spark. These data suggest that both local store depletion and some time-dependent inhibitory mechanism contribute to spark termination and refractoriness. Visualization of local store Ca(2+) signaling thus broadens our understanding of cardiac store Ca(2+) regulation and function and opens the possibility for local regulation of diverse store-dependent functions.

Animals↗
PubMed2005

Nonergodicity of blinking nanocrystals and other Lévy-walk processes.

We investigate the nonergodic properties of blinking nanocrystals modeled by a Lévy-walk stochastic process. Using a nonergodic mean field approach we calculate the distribution functions of the time averaged intensity correlation function. We show that these distributions are not delta peaked on the ensemble average correlation function values; instead they are W or U shaped. Beyond blinking nanocrystals our results describe ergodicity breaking in systems modeled by Lévy walks , for example, certain types of chaotic maps and spin dynamics to name a few.

Journal Article↗
PubMed2005

Insights into the control of attentional set in ADHD using the attentional blink paradigm.

BACKGROUND: Previous work on visual selective attention in Attention Deficit Hyperactivity Disorder (ADHD) has utilised spatial search paradigms. This study compared ADHD to control children on a temporal search task using Rapid Serial Visual Presentation (RSVP). In addition, the effects of irrelevant singleton distractors on search performance were examined. METHOD: In each condition, subjects reported the identity of a red letter 'probe' in a sequence of white letters which appeared one after the other at a central fixation point. The temporal position of the probe varied from an initial target, which was distinguished by surrounding asterisks. The target was reported in addition to the probe in condition 2, but not in the baseline condition 1. In a third condition, the initial target was not reported, but one of the asterisks appeared as a colour singleton on some trials. RESULTS: All children displayed an 'attentional blink' with probe detection reduced when it appeared at close temporal relations relative to the target. This 'blink' reduced over time, and there were no group differences in the recovery of performance, although ADHD children made more errors overall. The ADHD group were also more vulnerable than controls to distraction from irrelevant singletons in condition 3. CONCLUSION: Although the basic mechanisms of selective attention were not impaired in children with ADHD, these children appeared to require more resources to execute the task and were more vulnerable to distraction by irrelevant singletons, indicating deficits in the maintenance of attentional control.

Adolescent↗