Visual Field Dependence Is Associated with Reduced Postural Sway, Dizziness and Falls in Older People Attending a Falls Clinic.

Moving visual fields can have strong destabilising effects on balance, particularly when visually perceived motion does not correspond to postural movements. This study investigated relationships between visual field dependence (VFD), as assessed using the roll vection test, and reported dizziness, falls and sway under eyes open, eyes closed and optokinetic conditions. Ninety five falls clinic attendees undertook the roll vection test (i.e. attempted to align a rod to the vertical while exposed to a rotating visual field). Sway was assessed under different visual conditions by centre of pressure movement. Participants also completed questionnaires on space and motion discomfort, fear of falling, depression and anxiety. Thirty four (35.8%) participants exhibited VFD, i.e. had an error > 6.5º in the roll vection test. Compared to participants without VFD, participants with VFD demonstrated less movement of the centre of pressure across all visual conditions, were more likely to report space and motion discomfort and to have suffered more multiple falls in the past year. VFD was independent of fear of falling, anxiety and depression. VFD in a falls clinic population is associated with reduced sway possibly due to a stiffening strategy to maintain stance, dizziness symptoms and an increased risk of falls

Home on the Range: Factors Explaining Partial Migration of African Buffalo in a Tropical Environment

Partial migration (when only some individuals in a population undertake seasonal migrations) is common in many species and geographical contexts. Despite the development of modern statistical methods for analyzing partial migration, there have been no studies on what influences partial migration in tropical environments. We present research on factors affecting partial migration in African buffalo (Syncerus caffer) in northeastern Namibia. Our dataset is derived from 32 satellite tracking collars, spans 4 years and contains over 35,000 locations. We used remotely sensed data to quantify various factors that buffalo experience in the dry season when making decisions on whether and how far to migrate, including potential man-made and natural barriers, as well as spatial and temporal heterogeneity in environmental conditions. Using an information-theoretic, non-linear regression approach, our analyses showed that buffalo in this area can be divided into 4 migratory classes: migrants, non-migrants, dispersers, and a new class that we call “expanders”. Multimodel inference from least-squares regressions of wet season movements showed that environmental conditions (rainfall, fires, woodland cover, vegetation biomass), distance to the nearest barrier (river, fence, cultivated area) and social factors (age, size of herd at capture) were all important in explaining variation in migratory behaviour. The relative contributions of these variables to partial migration have not previously been assessed for ungulates in the tropics. Understanding the factors driving migratory decisions of wildlife will lead to better-informed conservation and land-use decisions in this area

The emergence of educational technology

10.1007/978-0-387-09657-5_6IFIP International Federation for Information Processing26999-11