Top-down processes in object identification: evidence from experimental psychology,neuropsychology and functional anatomy.

Many models of object identification are bottom-up and serial in nature; processing at a first stage needs to be complete before it is passed on to a subsequent stage, and there is no top-down feedback from the later to the earlier stages. However, data on picture identification in normal observers contradict a strict serial account of processing, since effects of variables on early and late stages of object identification combine in an interactive rather than an additive manner. Recent neuropsychological and functional anatomical data also indicate that object identification involves top-down activation of earlier stages of visual processing. In neuropsychological patients, subtle perceptual deficits can produce naming problems, even when there is good access to associated semantic knowledge; in functional activation studies, there is increased activity in visual processing areas when conditions require object naming relative to object recognition. These studies provide evidence that increased visual processing occurs in identification tasks, suggesting that there is re-current feedback during the identification process.     

Quantifying the Hydroregime of a Temporary Pool Habitat: A Modelling Approach for Ephemeral Rock Pools in SE Botswana

Ecological and evolutionary processes in temporary rock pools operate within constraints imposed by their hydrologic regimes. These shallow pools flood when seasonal rains accumulate on impermeable substrates. Despite the ecological importance of hydrologic conditions for these ecosystems, we typically lack tools and empirical data required to understand the implications of hydrologic variability and climate change for biotic populations and communities in these habitats. In this study, we developed a hydrologic model to simulate rock pool hydrologic regimes based on rainfall, evapotranspiration, and basin geometry. The model was used to investigate long-term patterns of seasonal and inter-annual variation in hydroregime. In addition, hydrologic conditions associated with potential climate change scenarios were simulated and evaluated with respect to the biological requirements of the anostracan Branchipodopsis wolfi. The model’s output for daily inundation matched with field observations with an overall accuracy of 85% and correctly estimated complete hydroperiods with an overall accuracy of 70%. Simulations indicate large variation in individual hydroperiods (76–115%) as well as in the number of hydroperiods per year (19–23%). Furthermore, this study suggests that climate change may significantly alter the rock pool hydroregime. These findings confirm the hydrologic sensitivity of these ephemeral habitats to precipitation patterns, and their potential sensitivity to future climate change. Modelling indicates that the suitability of average inundation conditions for B. wolfi deteriorates significantly under future climate predictions. High levels of spatial and temporal variation in hydrologic conditions are dominant features of these habitats and an essential consideration for understanding population and community-level ecological processes.     

When connectedness increases hemispatial neglect

Patients with left neglect were tested with "chimeric" figures composed of the right and left halves of two different objects. The connectivity relation was modulated between the two half figures. For some displays, the two chimeric halves were separated by a small gap, while in others, the separate halves were connected by a line segment. In line with previous reports, performance on reporting the left half improved when the chimera were separated; but when a line connected the two separated halves the advantage was lost. If the connecting line was broken, the performance was again enhanced. The results suggest an important role for connectedness in the representation of perceptual objects and in the distribution of attention in neglect.     

Temporary pools are not `enemy-free'

Temporary pools are traditionally considered as refuges where the conspicuous anostracans are protected from predation. While this is true for the size-selective predation by fish, there is compelling evidence that invertebrate predation is an important biotic stress regulating temporary pool communities. In rock pools in southeastern Botswana, we studied the impact of some suspected invertebrate predators on populations of the freshwater anostracan Branchipodopsis wolfi by means of observations and manipulative experiments. In a survey of 45 pools, the relationship between B. wolfi natural population sizes and the abundance of suspected predators were never negative for turbellarians and mosquito larvae. When dragonfly larvae, notonectids or tadpoles were present, the anostracan populations were generally non-existent or very small. In enclosure experiments with turbellarians, there was a significant effect of predation within one hour of the start; the average daily predation rate was about 1/4 anostracan per turbellarian. Anostracans from a pool with few turbellarians were slightly less vulnerable than those from a turbellarian-rich pool. Furthermore, there was an indication of males being predated on more than females. With dragonfly larvae and notonectids, the predation effect was marked with all six anostracans in an experiment eaten in less than one day by a single predator (predation rate: about one anostracan every 2 h per predator). In a behavioral study, both sexes of B. wolfi avoided swimming above sediment that held more turbellarians than the open patches; there was no evidence for chemical communication with respect to this behavior.     

Changes in functional properties of the caffeine-sensitive Ca2+ store during differentiation of human SH-SY5Y neuroblastoma cells

We have used single cell fluorescence imaging techniques to examine how functional properties of the caffeine-sensitive Ca(2+) store change during differentiation of a sub-population of caffeine-sensitive SH-SY5Y cells. Application of caffeine (30 mM) 1-10.5 min after a 'priming' depolarisation pulse of 55 mM K(+) revealed that the caffeine-sensitive store in undifferentiated cells remained replete, whereas that in 9-cis retinoic acid (9cRA)-differentiated cells spontaneously dissipated with a t(1/2) of 2.8 min, and was essentially completely depleted approximately 10 min after priming. In 9cRA-differentiated cells that were stimulated with methacholine (10 microM) 1 min after priming, the amplitude, rate of rise and propagation velocity of the Ca(2+) wave in the neurites were all constant, whereas these kinetic parameters all progressively decreased as the wave travelled along the neurites in cells that were stimulated 10 min after priming. Use-dependent block with ryanodine inhibited the global Ca(2+) signal in 9cRA-differentiated cells stimulated with methacholine 1 min after priming (71+/-8%) but not 10 min after priming. Depolarisation was more effective at priming the caffeine-sensitive Ca(2+) store in 9cRA-differentiated cells, which lack a functional store-operated Ca(2+) entry pathway. We conclude that differentiation of caffeine-sensitive SH-SY5Y cells is accompanied by an increase in lability of the caffeine-sensitive Ca(2+) store, and that spontaneous dissipation of Ca(2+) from the store limits the time course of its molecular 'memory' during which it can amplify the hormone-induced Ca(2+) signal by Ca(2+)-induced Ca(2+) release.     

Early life determinants of physical activity in 11 to 12 year olds: cohort study

Objective To examine factors in early life (up to age 5 years) that are associated with objectively measured physical activity in 11-12 year olds.Design Prospective cohort study.Setting Avon longitudinal study of parents and children, United Kingdom. Participants Children aged 11-12 years from the Avon longitudinal study of parents and children.Main outcome measure Physical activity levels in counts per minute (cpm) and minutes of moderate to vigorous physical activity for seven days measured with a uniaxial actigraph accelerometer.Results Valid actigraph data, defined as at least three days of physical activity for at least 10 hours a day, were collected from 5451 children. Several factors were associated with physical activity at ages 11-12 years. Regression coefficients are compared with the baseline of “none” for categorical variables: maternal brisk walking during pregnancy (regression coefficient 5.0, 95% confidence interval −8.5 to 18.5; cpm for <1 h/wk and ≥2 h/wk of physical activity 17.7, 5.3 to 30.1), maternal swimming during pregnancy (21.5, 10.9 to 32.1 and cpm for <1 h/wk and ≥2 h/wk of physical activity 24.2, 7.8 to 40.7), parents’ physical activity when the child was aged 21 months (28.5, 15.2 to 41.8 and cpm of physical activity for either parent active and both parents active 33.5, 17.8 to 49.3), and parity assessed during pregnancy (2.9, −7.6 to 13.4 and cpm of physical activity for 1 and ≥2 parity 21.2, 7.1 to 35.3).Conclusions Few factors in early life predicted later physical activity in 11-12 year olds. Parents’ physical activity during pregnancy and early in the child’s life showed a modest association with physical activity of the child at age 11-12 years, suggesting that active parents tend to raise active children. Helping parents to increase their physical activity therefore may promote children’s activity.