Biomedical subjects

Avi Caspi

Publications and source records attributed to Avi Caspi.

8 recordsLinked to original sources

PubMed2006

Evidence for ocular motor deficits in developmental dyslexia: application of the double-step paradigm.

PURPOSE: Dyslexia is a language-based learning disability characterized by difficulties with reading, spelling, and writing. Persons with dyslexia often have deficits in processing rapid temporal sensory information. There is also evidence of sensorimotor deficits in persons with dyslexia. Whether these deficits include ocular motor problems is still an open question. Some previous studies have shown an increased saccadic latency in dyslexics, whereas others have not reproduced this finding. The purpose of the present study was to investigate saccadic latency in young adults with dyslexia during the double-step paradigm, a task that requires rapid sequential visual information processing and saccade generation. The study hypothesis was that dyslexics have a longer saccadic latency in the second orthogonal saccade, a task that nondyslexics parallel process and perform rapidly. METHODS: Eight students with dyslexia and eight age-matched control subjects participated in the study. Their eye movements were monitored with the scleral search coil technique in simple saccade trials and in the double-step paradigm. The second saccade was either orthogonal or colinear to the first. Intersaccadic interval and latency were calculated for the second saccade. RESULTS: No difference in saccadic latency was found for colinear second saccades; however, dyslexics had significantly longer latencies for orthogonal second saccades. This included a subset of subjects who had longer latencies for orthogonal than for colinear saccades. CONCLUSIONS: The findings indicate that under certain conditions, when the demand for rapid visual information processing is high and a rapid saccade sequence is required, some persons with dyslexia show ocular motor deficits manifested by longer saccadic latencies.

Adult↗

PubMed2005

Scaling of horizontal and vertical fixational eye movements.

Eye movements during fixation of a stationary target prevent the adaptation of the visual system to continuous illumination and inhibit fading of the image. These random, involuntary, small movements are restricted at long time scales so as to keep the target at the center of the field of view. Here we use detrended fluctuation analysis in order to study the properties of fixational eye movements at different time scales. Results show different scaling behavior between horizontal and vertical movements. When the small ballistic movements, i.e., microsaccades, are removed, the scaling exponents in both planes become similar. Our findings suggest that microsaccades enhance the persistence at short time scales mostly in the horizontal component and much less in the vertical component. This difference may be due to the need for continuously moving the eyes in the horizontal plane, in order to match the stereoscopic image for different viewing distances.

Adaptation, Physiological↗

PubMed2005

Phase-synchronization decay of fixational eye movements.

In nonstationary noisy systems the traditional cross-correlation method may not appropriately detect all cases of interdependencies between coupled systems. The phase-synchronization method was previously found useful in detecting synchronization in several systems. We here applied the phase-synchronization decay to study the synchronization between six combinations of binocular fixational eye movement components. We found that only two components were synchronized: the right and left horizontal with each other and the right and left vertical. Furthermore, the vertical-vertical components were much more synchronized than the horizontal.

Eye Movements↗

PubMed2004

The time course of visual information accrual guiding eye movement decisions.

Saccadic eye movements are the result of neural decisions about where to move the eyes. These decisions are based on visual information accumulated before the saccade; however, during an approximately 100-ms interval immediately before the initiation of an eye movement, new visual information cannot influence the decision. Does the brain simply ignore information presented during this brief interval or is the information used for the subsequent saccade? Our study examines how and when the brain integrates visual information through time to drive saccades during visual search. We introduce a new technique, saccade-contingent reverse correlation, that measures the time course of visual information accrual driving the first and second saccades. Observers searched for a contrast-defined target among distractors. Independent contrast noise was added to the target and distractors every 25 ms. Only noise presented in the time interval in which the brain accumulates information will influence the saccadic decisions. Therefore, we can retrieve the time course of saccadic information accrual by averaging the time course of the noise, aligned to saccade initiation, across all trials with saccades to distractors. Results show that before the first saccade, visual information is being accumulated simultaneously for the first and second saccades. Furthermore, information presented immediately before the first saccade is not used in making the first saccadic decision but instead is stored and used by the neural processes driving the second saccade.

Humans↗

PubMed2003

RITZ-5: randomized intravenous TeZosentan (an endothelin-A/B antagonist) for the treatment of pulmonary edema: a prospective, multicenter, double-blind, placebo-controlled study.

OBJECTIVES: The objective of this study was to evaluate the addition of intravenous (IV) tezosentan to standard therapy for patients with pulmonary edema. BACKGROUND: Tezosentan is an IV nonselective endothelin (ET)-1 antagonist that yields favorable hemodynamic effects in patients with acute congestive heart failure (CHF). METHODS: Pulmonary edema was defined as acute CHF leading to respiratory failure, as evidenced by an oxygen saturation (SO(2)) <90% by pulse oxymeter despite oxygen treatment. All patients received oxygen 8 l/min through a face mask, 3 mg of IV morphine, 80 mg of furosemide, and 1 to 3 mg/h continuous drip isosorbide-dinitrate according to their blood pressure level and were randomized to receive a placebo or tezosentan (50 or 100 mg/h) for up to 24 h. RESULTS: Eighty-four patients were randomized. The primary end point, the change in SO(2) from baseline to 1 h, was 9.1 +/- 6.3% in the placebo arm versus 7.6 +/- 10% in the tezosentan group (p = NS). The incidence of death, recurrent pulmonary edema, mechanical ventilation, and myocardial infarction during the first 24 h of treatment was 19% in both groups. Reduced baseline SO(2), lower echocardiographic ejection fraction, high baseline mean arterial blood pressure (MAP), and inappropriate vasodilation (MAP reduction at 30 min of <5% or >30%) correlated with worse outcomes. A post-hoc analysis revealed that the outcome of patients who received only 50 mg/h tezosentan was better than patients in the placebo group whereas patients receiving 100 mg/h had the worst outcomes. CONCLUSIONS: In the present study, tezosentan (an ET-1 antagonist) did not affect the outcome of pulmonary edema, possibly because of the high dose used.

Double-Blind Method↗

PubMed2003

Prior peripheral arterial disease and cerebrovascular disease are independent predictors of adverse outcome in patients with acute coronary syndromes: are we doing enough? Results from the Orbofiban in Patients with Unstable Coronary Syndromes-Thrombolysis In Myocardial Infarction (OPUS-TIMI) 16 study.

BACKGROUND: Cerebrovascular accidents (CVAs), transient ischemic attacks (TIAs), and peripheral arterial disease (PAD) frequently coexist with coronary artery disease (CAD) and were previously reported to adversely affect the prognosis of patients with chronic CAD. METHODS: We examined the effect of prior CVA/TIA or PAD (extra-cardiac vascular disease [EVD]) on the outcome of 10,281 patients with acute coronary syndromes enrolled in the Orbofiban in Patients with Unstable Coronary Syndromes-Thrombolysis in Myocardial Infarction (OPUS-TIMI) 16 trial of the oral glycoprotein IIb/IIIa antagonist orbofiban plus aspirin versus aspirin alone. We evaluated mortality, recurrent cardiac events, and stroke and used multivariate analysis to control for differences in baseline characteristics. RESULTS: Patients with EVD were older, had more coronary risk factors, had a history of CAD, and received more intensive medical treatment at baseline. The acute event in these patients was more often unstable angina pectoris and less commonly Q-wave myocardial infarction. With coronary angiography, patients with prior EVD more often had multivessel disease. During the 10 months of follow-up, the presence of EVD was predictive of an increased hazard of death, reinfarction, recurrent ischemia, stroke, and a composite of these events. Despite the increased severity of the CAD and increased risk of events, patients with EVD were treated less frequently with beta-blockers and more frequently with calcium blockers. Despite patients with EVD having a 45% higher incidence of hypercholesterolemia, lipid-lowering agents were prescribed in a similar percentage of patients as patients without EVD. CONCLUSION: In patients with acute coronary syndromes, the presence of prior CVA, TIA, or PAD is associated with more extensive CAD and worse outcome. These patients appear to receive less aggressive treatment, which may explain, at least in part, their worse outcome.

Aged↗

PubMed2002

Diffusion and directed motion in cellular transport.

We study the motion of a probe driven by microtubule-associated motors within a living eukaryotic cell. The measured mean square displacement, of engulfed 2 and 3 microm diameter microspheres shows enhanced diffusion scaling as t(3/2) at short times, with a clear crossover to ordinary or subdiffusive scaling, i.e., t(gamma) with gamma less than or equal to 1, at long times. Using optical tweezers we tried to move the engulfed bead within the cell in order to relate the anomalous diffusion scaling to the density of the network in which the bead is embedded. Results show that the larger beads, 2 and 3 microm diameter, must actively push the cytoskeleton filaments out of the way in order to move, whereas smaller beads of 1 microm diameter can be "rattled" within a cage. The 1 microm beads also perform an enhanced diffusion but with a smaller and less consistent exponent 1.2 approximately t(3/4). In the case of small beads, there may also be a Brownian contribution to the motion that results in a smaller exponent.

Biological Transport, Active↗

PubMedDate not supplied

Admission blood glucose level and mortality among hospitalized nondiabetic patients with heart failure.

BACKGROUND: The significance of admission blood glucose level in nondiabetic patients with heart failure (HF) is unknown. We examined the possible association between admission glucose levels and outcome in a large cohort of hospitalized patients with HF. METHODS: We analyzed the data of 4102 patients with HF, who were hospitalized during a prospective national survey. The present study focuses on a subgroup of 1122 nondiabetic patients with acute HF who were admitted because of acute HF or exacerbation of chronic HF. RESULTS: In-hospital mortality was twice as high in patients with admission blood glucose levels in the third tertile (7.2%) compared with the first (3%) and second (4%) tertiles (P = .02). Furthermore, mortality risk was correlated with admission glucose levels; each 18-mg/dL (1-mmol/L) increase in glucose level was associated with a 31% increased risk of in-hospital mortality (adjusted odds ratio, 1.31; 95% confidence interval, 1.10-1.57; P = .003) and a 12% increase in 60-day mortality (adjusted hazard ratio, 1.12; 95% confidence interval, 1.01-1.25; P = .04). Admission blood glucose levels remained an independent predictor of in-hospital and 60-day mortality even after the exclusion of 315 patients (28%) with acute myocardial infarction and HF. The 6- and 12-month mortality rates were similar in patients with and without abnormal admission blood glucose levels. CONCLUSIONS: Elevated admission blood glucose levels are associated with increased in-hospital and 60-day mortality, but not 6-month or 1-year mortality, in nondiabetic patients hospitalized because of HF.

Aged↗