Predictive eye movements in natural vision.

In the natural world, the brain must handle inherent delays in visual processing. This is a problem particularly during dynamic tasks. A possible solution to visuo-motor delays is prediction of a future state of the environment based on the current state and properties of the environment learned from experience. Prediction is well known to occur in both saccades and pursuit movements and is likely to depend on some kind of internal visual model as the basis for this prediction. However, most evidence comes from controlled laboratory studies using simple paradigms. In this study, we examine eye movements made in the context of demanding natural behavior, while playing squash. We show that prediction is a pervasive component of gaze behavior in this context. We show in addition that these predictive movements are extraordinarily precise and operate continuously in time across multiple trajectories and multiple movements. This suggests that prediction is based on complex dynamic visual models of the way that balls move, accumulated over extensive experience. Since eye, head, arm, and body movements all co-occur, it seems likely that a common internal model of predicted visual state is shared by different effectors to allow flexible coordination patterns. It is generally agreed that internal models are responsible for predicting future sensory state for control of body movements. The present work suggests that model-based prediction is likely to be a pervasive component in natural gaze control as well.

High magnetic shear gain in a liquid sodium stable Couette flow experiment: a prelude to an α-Ω dynamo.

The Ω phase of the liquid sodium α-Ω dynamo experiment at New Mexico Institute of Mining and Technology in cooperation with Los Alamos National Laboratory has demonstrated a high toroidal field B(ϕ) that is ≃8×B(r), where B(r) is the radial component of an applied poloidal magnetic field. This enhanced toroidal field is produced by the rotational shear in stable Couette flow within liquid sodium at a magnetic Reynolds number Rm≃120. Small turbulence in stable Taylor-Couette flow is caused by Ekman flow at the end walls, which causes an estimated turbulence energy fraction of (δv/v)(2)∼10(-3).

Alterations in voiding frequency and cystometry in the clomipramine induced model of endogenous depression and reversal with fluoxetine.

PURPOSE: Because serotonin (5-HT) in the central nervous system may inhibit bladder activity, we postulated that depression associated with altered 5-HT function might be associated with overactive bladder (OAB). We examined a rat model of endogenous depression caused by lowering 5-HT for effects on voiding frequency (VF) and awake cystometry (CMG), and examined the effect of reversal using the selective serotonin reuptake inhibitor fluoxetine. MATERIALS AND METHODS: Wistar rat pups were divided into 2 groups, namely clomipramine treated (CL) and saline control (SC). From postnatal days 8 to 21 each pup was injected with CL hydrochloride (22.5 mg/kg body weight) or an equal volume of saline. VF was assessed at 10 and 15 weeks. Behavioral correlates of depression were assessed using the forced swim test. At age 15 weeks CMG was performed. Fluoxetine (20 mg/kg daily) was administrated to a subset of SC/CL rats, and VF and CMG were repeated. RESULTS: In CL rats immobility was increased when rats were submitted to the forced swim test, indicating depression. CL rats voided more frequently than the SC group at 10 and 15 weeks but the difference was significant only in females. CMG of female CL group showed decreased bladder capacity, micturition volume and intermicturition contractions compared with the SC group. Treatment with fluoxetine reversed these changes, as in SC rats. CONCLUSIONS: These results support the hypothesis that OAB in a subgroup of depressed individuals may be associated with altered 5-HT function. It may explain reports of an association between depression and OAB.