Top-down processing modulates older adults' susceptibility to noise.

The present study examined older and younger adults' ability to use top-down processes to mitigate the effects of display noise during simple feature, visual search. As display noise levels increased, older adults (age 60-74 years, n = 32) exhibited greater top-down search reaction time (RT) benefits (bottom-up minus top-down search RT), compared to younger adults (age 18-27, n = 32). Older adults' ability to mitigate the effects of noise was further assessed with RT variability, as measured by intra-individual standard deviations across trials. Older adults again exhibited larger top-down benefits (i.e., less RT variability) compared to younger adults, and more so when display noise was present vs. absent. These results suggest a sparing of top-down processes with age (Madden, Whiting, Spaniol, & Bucur, 2005; Psychology and Aging, 20, 317), and that top-down processes in older adults enhance search efficiency by optimizing signal-to-noise ratios.

A polymethylpentene fiber gas exchanger for long-term extracorporeal life support.

A polymethylpentene (PMP) fiber gas exchange device was evaluated in healthy sheep (35-42 kg) to characterize its performance and potential use in clinical extracorporeal life support (ECLS). Five PMP devices (1.3 m2) were compared with five silicone rubber membrane lung (SRML) devices (1.5 m2) that were supported on venovenous ECLS for 72 hours. The two device groups were compared for differences in gas exchange, device pressure gradient, hematology, blood biochemistry, and pathology. The results showed superiority in the PMP devices in both oxygen and CO2 exchange when compared at similar blood flow rates. Platelet consumption and the device pressure gradient were significantly less when using the PMP device. The device pressure gradient across the PMP devices was < 20 mm Hg as compared with > 150 mm Hg for the SRML devices at all blood flow rates. Changes in plasma hemoglobin levels, leukocyte counts, blood chemistry results, and pathologic findings were not significantly different between the two device groups. Plasma leakage or device failure did not occur in any of the test devices. These data support the use of the PMP device for extended circulatory support. Patients may fare better because of improved preservation of platelets, and the low resistance may allow for wider use of centrifugal-style pumps or the use of the device in a pumpless arteriovenous mode.