All is not lost: Post-saccadic contributions to the perceptual omission of intra-saccadic streaks.

Saccades rapidly jerk the eye into new positions, yet we rarely experience the motion streaks imposed on the retinal image. Here we examined spatial and temporal properties of post-saccadic masking-one potential explanation of this perceptual omission. Observers judged the motion direction of a target stimulus, a Gaussian blob, that moved vertically upwards or downwards and then back to its initial position, just as observers made a saccade. We manipulated the onset and offset of the target and of distractors in various spatial relations to the target, and assessed their effect on performance and subjective confidence. Although the presence of the target after the saccade caused the strongest omission, the offset of spatially distant distractor stimuli upon saccade offset also impaired performance. The temporal properties of these two separate effects suggest that, in addition to masking, an independent effect of attentional distraction further accentuates perceptual omission of intra-saccadic motion streaks.

Generating surrogates from recurrences.

In this paper, we present an approach to recover the dynamics from recurrences of a system and then generate (multivariate) twin surrogate (TS) trajectories. In contrast to other approaches, such as the linear-like surrogates, this technique produces surrogates which correspond to an independent copy of the underlying system, i.e. they induce a trajectory of the underlying system visiting the attractor in a different way. We show that these surrogates are well suited to test for complex synchronization, which makes it possible to systematically assess the reliability of synchronization analyses. We then apply the TS to study binocular fixational movements and find strong indications that the fixational movements of the left and right eye are phase synchronized. This result indicates that there might be only one centre in the brain that produces the fixational movements in both eyes or a close link between the two centres.

Evaluation of Duraflo II heparin immobilized cardiopulmonary bypass circuits.

Cardiopulmonary bypass (CPB) involves extensive contact between blood and synthetic surfaces and may result in blood cell activation and plasma protein alterations. This study determines the effect of Duraflo II heparin treated CPB circuits (Bentley Laboratories, Irvine, CA) on calves under simulated clinical conditions. Calves were placed on CPB for 4 hr, and activated clotting times were maintained above 480 sec with systemic heparin. Better preserved platelet number and function, lower fibrinopeptide A levels, and lack of thrombus deposition were observed in the Duraflo II treated group, relative to the untreated control group, during the entire bypass period. The results suggest that despite high doses of circulating heparin in calves during CPB, the use of extracorporeal circuits with improved blood compatibility still provides measurable benefit.

Platelet loss on exposure of citrated blood to various foreign surfaces.

Citrated whole blood was rotated in tubes or closed loops of tubing and the percentage of platelets lost on exposure to the surface of the container was noted. Platelet loss in the presence of uncoated glass surfaces (mean loss 31%) was significantly less than in the presence of glass siliconed with two different reagents (82% and 86%). Platelets adhered to siliconed glass but not to uncoated glass. Other inert surfaces also resulted in a high degree of platelet loss: Teflon 90 per cent, silicone rubber 85 per cent, Parawax 84 per cent, polysytrene 82 per cent, polyethylene 79 per cent, polypropylene 60 per cent, and polycarbonate 58 per cent. One lot of polyvinyl chloride transfusion grade tubing resulted in only 2 per cent loss of platelets, but other lots varied between 35 and 84 per cent. Loss of platelets on exposure to the surface of plastic containers may have to be considered when evaluating new materials for preparation of blood components.