Binocular vision disorders (BVD) are quite common in subjects with cerebellar dysfunctions. Also individuals with strabismus often suffer from many motor deficits, such as impaired body balance and walking. It is known that the cerebellum is necessary to maintain proper body posture but also to learn motor skills. It is conceivable that subjects with BVD would also have deficits in procedural (implicit) motor learning, one of the primary cerebellar functions. The primary aim of this study was to explore motor learning abilities in subjects with BVD (strabismic group, SG). Modified versions of a single reaction time task were used in the scheme proposed by Molinari et al. in 1997. A set of three different tasks (Experiment 1) were performed under dominant eye viewing to investigate (a) procedural (implicit) motor learning, (b) declarative (explicit) learning, and (c) simple stimulus-response associative learning. Because each task examined different aspects of motor learning abilities, it could be revealed which motor learning pathway is impaired in SG. Results showed that the SG had slower reaction times in all three tasks and demonstrated poor implicit motor learning ability compared to controls. To verify if these results were caused by reduced binocular vision or cerebellar deficits, per se, a nonstrabismic binocular anomalies group (NSG) was introduced, and all the same tests were performed (Experiment 2). These results revealed that there were no differences between the NSG and the control group with good binocularity. To conclude, the poor procedural learning ability and slower reaction times in strabismic subjects should not be explained as an effect of incomplete binocular vision that influences the maturity of the visual cortex and transformation of visual information into a motor program because binocular anomaly individuals without strabismus have motor learning abilities close to the controls. Some cerebellar deficits appear to be the origin of observed anomalies.

No abstract

We investigate the dynamical stabilization of the initial state of a one-dimensional Rydberg atom subjected to a periodic train of half-cycle pulses. A survival probability of the initial state as a function of pulse repetition frequency is presented for different values of momentum transferred to the electron. This survival probability exhibits a broad maximum at train repetition frequencies close to the classical orbital frequency provided that the momentum is negative. There is no such behaviour for positive momentum transferred to the electron.

We discuss a protocol for efficient and quick transfer of population between nearly one-dimensional Rydberg states by a chirped train of half-cycle pulses. The chirp refers both to the time interval and relative strength between subsequent pulses. The most spectacular result obtained by the use of this protocol is the transfer of over 10% of the initial population from the high-Rydberg state of n = 50, 80 to much lower ones of nЈ Ϸ 10 in a short time of the order of 1 ns.

Geometrically frustrated quantum spin systems, with competing antiferromagnetic couplings, show the Kahn degenerate frustration for some specific values of Heisenberg Hamiltonian parameters. It has been recently shown for rings with a defect bond and centered rings. In the case of classical counterparts of these systems, degenerated configurations with the lowest energy are present for the energy function parameter greater than a certain threshold. In these domains such configurations are planar but non-collinear with continuous changes of the net magnetic moment with respect to the Hamiltonian parameter. Outside these domains there is unique collinear ground state configuration (neglecting choice of the net magnetic moment direction). However, these collinear configurations are the same in both non-frustrated and geometrically frustrated domains. Numerically exact calculations for quantum systems strongly confirm that determined properties of their classical counterparts realize the classical limit s Ñ 8.