Improvement of obstacle avoidance on a compliant surface during transfer to a novel visual task after variable practice under unusual visual conditions.

Previous work has shown that variable practice facilitates adaptation to novel visuomotor changes during throwing tasks and obstacle avoidance on a solid floor. To assess whether locomotor skill on an obstacle-avoidance task performed on a compliant surface and in a novel visuomotor environment improved after training with variable practice, 61 normal adults practiced traversing the obstacle course. Half the trials were performed with no visual changes and half with either sham lenses or visually distorting lenses; the latter were either single or multiple lenses. On transfer tests on the obstacle course while wearing novel lenses, scores were significantly better with multiple lenses than sham; the single-lens group did not differ from sham or multiple-lens groups. Thus, performance in a novel visual environment on a compliant surface improved most with variable practice.

Short-duration space flight and hearing loss.

OBJECTIVES: The study goal was to determine whether a single Space Shuttle mission can induce decrements in astronaut hearing. Study design We retrospectively compared audiogram information obtained from Space Shuttle astronauts at 10 days preflight, day of return (R + 0), 3 days after landing return (R + 3), and at a mean delayed postflight follow-up of 8 months. RESULTS: Temporary threshold shift (mean, 4.6 dB) was noted in R + 0 versus preflight conditions (P < 0.01). Small permanent threshold shifts (mean, 0.83 dB) were found at R + 3 and postflight follow-up compared with preflight in the lower frequencies (500 to 2000 Hz), and corresponding pure tone average (P < 0.001). Conclusions and significance The data indicate that a single Shuttle flight can induce a substantial temporary threshold shift and a small but statistically significant permanent threshold shift, particularly in the frequencies involved in speech reception. Although single-mission effects are small, cumulative effects over several missions may ultimately produce clinically significant hearing loss.

Effects of normal aging on visuo-motor plasticity.

Normal aging is associated with declines in neurologic function. Uncompensated visual and vestibular problems may have dire consequences including dangerous falls. Visuo-motor plasticity is a form of behavioral neural plasticity, which is important in the process of adapting to visual or vestibular alteration, including those changes due to pathology, pharmacotherapy, surgery or even entry into microgravity or an underwater environment. To determine the effects of aging on visuo-motor plasticity, we chose the simple and easily measured paradigm of visual-motor rearrangement created by using visual displacement prisms while throwing small balls at a target. Subjects threw balls before, during and after wearing a set of prisms which displace the visual scene by twenty degrees to the right. Data obtained during adaptation were modeled using multilevel modeling techniques for 73 subjects, aged 20 to 80 years. We found no statistically significant difference in measures of visuo-motor plasticity with advancing age. Further studies are underway examining variable practice training as a potential mechanism for enhancing this form of behavioral neural plasticity.