Cerebellar Complex Spike Firing Is Suitable to Induce as Well as to Stabilize Motor Learning

SummaryBackgroundCerebellar Purkinje cells (PC) generate two responses: the simple spike (SS), with high firing rates (>100 Hz), and the complex spike (CS), characterized by conspicuously low discharge rates (1–2 Hz). Contemporary theories of cerebellar learning suggest that the CS discharge pattern encodes an error signal that drives changes in SS activity, ultimately related to motor behavior. This then predicts that CS will discharge in relation to the error and at random once the error has been nulled by the new behavior.ResultsWe tested this hypothesis with saccadic adaptation in macaque monkeys as a model of cerebellar-dependent motor learning. During saccadic adaptation, error information unconsciously changes the endpoint of a saccade prompted by a visual target that shifts its final position during the saccade. We recorded CS from PC of the posterior vermis before, during, and after saccadic adaptation. In clear contradiction to the “error signal” concept, we found that CS occurred at random before adaptation onset, i.e., when the error was maximal, and built up to a specific saccade-related discharge profile during the course of adaptation. This profile became most pronounced at the end of adaptation, i.e., when the error had been nulled.ConclusionsWe suggest that CS firing may underlie the stabilization of a learned motor behavior, rather than serving as an electrophysiological correlate of an error

Spectroscopy of the 1S0−3P0^1S_0-{}^3P_0 Clock Transition of 87^{87}Sr in an Optical Lattice

We report on the spectroscopy of the $5s^2 {}^1S_0 (F=9/2) \to 5s5p {}^3P_0 (F=9/2)$ clock transition of ${}^{87}{\rm Sr}$ atoms (natural linewidth of 1 mHz) trapped in a one-dimensional optical lattice. Recoilless transitions with a linewidth of 0.7 kHz as well as the vibrational structure of the lattice potential were observed. By investigating the wavelength dependence of the carrier linewidth, we determined the magic wavelength, where the light shift in the clock transition vanishes, to be $813.5\pm0.9$ nm.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Lett. (09/May/2003

Effect of age, female mating status and density on the banana weevil response to aggregation pheromone

The banana ( Musa spp.) weevil ( Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae) is a major pest in East Africa causing yield losses of up to 14 metric tonnes per hectare annually. Laboratory and field experiments were conducted to determine whether the response of the banana weevil, Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae) to its aggregation pheromone was influenced by age, female mating status and weevil density. Laboratory bioassays were conducted using a double pitfall olfactometer, while a bucket pitfall trap was used in field experiments. There was no significant (P>0.05) difference in response to pheromone between immature and mature weevils (males and females) in laboratory bioassays. Forty-day-old weevils had a stronger response to the pheromone than 10-day-old ones under field conditions. The response of unmated weevils to the pheromone was stronger than that of mated weevils, both in the laboratory and field. The percentage of unmated and mated weevils recaptured from 0 and 3 m were similar but significantly different from 6 m way from the pheromone baited trap. The response of the weevils to the pheromone was not significantly (P>0.05) influenced by its previous density

Cross-cultural generalizability of social and dimensional comparison effects on reading, math, and science self-concepts for primary school students using the combined PIRLS and TIMSS data

Previous cross-cultural studies of social and dimensional comparison processes forming academic self-concepts (the big-fish-little-pond effect (BFLPE) and Internal-external frame-of-reference (I/E) models) have mostly been based on high-school students and two subject domains. Our study is the first to test the cross-cultural generalizability of both comparison processes across reading, mathematics, and science by combining of the TIMSS and PIRLS 2011 databases (15 OECD countries, 67,386 fourth-graders). Consistent with the I/E model, high achievement in mathematics/reading had positive effects on self-concept in the matching domain but negative effects in the non-matching domain. Extending the I/E model, students engaged in assimilating comparisons between science and reading (i.e., achievement in one subject had positive effects on self-concept in the other) but contrasting comparisons between mathematics and science. Strong BFLPEs (negative effects of class-average achievement on self-concept) were found for mathematics but were smaller for reading and science. The results generalized well across all countries

Effect of mulching on banana weevil movement relative to pheromone traps

Banana weevil (Cosmopolites sordidus) is a major pest in East Africa causing yield losses of up to 14 metric tonnes per hectare annually. A study was conducted in Uganda to determine the effect of mulching on banana (Musa spp. L.) weevil, Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae), movement relative to pheromone-baited traps. Three treatments were used to create different mulching levels: banana without mulch (control), banana with thin mulch (< 6 cm thick), and banana with thick mulch (15 cm thick). Pheromone trapswere placed in the plots and weevil trap catches were monitored. Weevil catches in pheromone traps from both mulched and unmulched plots were generally similar. The mulching level had no effect on the ratio of males to females recaptured. The numbers of weevils captured in pheromone traps were lower than in the wet season andwas not influenced by mulch levels. Mulching levels had a limited influence on the numbers of weevils recaptured from different directions. The results generally indicate that mulching has no effect on weevil catches in pheromone traps

The subjective visual vertical in a nonhuman primate

We perceive the visual world as upright as our visual system used information on the orientation of the body to update the internal representation of the visual scene. In humans, this updating is not perfect, thus leading to distortions of the subjective visual vertical. For small roll-tilt angles (G60-), subjects overestimate the body tilt (E-effect), whereas for larger angles they underestimate it (A-effect). We wanted to know if monkeys show comparable perceptual distortions as they might help to identify the neural basis of a tilt-independent representation of visual objects at the level of single neurons. In order to answer this question, we trained two monkeys to align an arrow with an upright world-centered reference line whose visibility was varied between trials. Trials were performed at roll-tilt angles chosen from j90-to 90-. The monkeys&apos; responses were precise for trials in which the reference line was visible. However, for the trials in which there was no reference line, their responses reflected an overestimation of body tilt (E-effect-like) very similar to humans. Our ability to demonstrate similar visuo-vestibular illusions in monkeys and man is an important step towards understanding the neural mechanism responsible for the perception of an upright visual world

Generation of scalar-tensor gravity effects in equilibrium state boson stars

Boson stars in zero-, one-, and two-node equilibrium states are modeled numerically within the framework of Scalar-Tensor Gravity. The complex scalar field is taken to be both massive and self-interacting. Configurations are formed in the case of a linear gravitational scalar coupling (the Brans-Dicke case) and a quadratic coupling which has been used previously in a cosmological context. The coupling parameters and asymptotic value for the gravitational scalar field are chosen so that the known observational constraints on Scalar-Tensor Gravity are satisfied. It is found that the constraints are so restrictive that the field equations of General Relativity and Scalar-Tensor gravity yield virtually identical solutions. We then use catastrophe theory to determine the dynamically stable configurations. It is found that the maximum mass allowed for a stable state in Scalar-Tensor gravity in the present cosmological era is essentially unchanged from that of General Relativity. We also construct boson star configurations appropriate to earlier cosmological eras and find that the maximum mass for stable states is smaller than that predicted by General Relativity, and the more so for earlier eras. However, our results also show that if the cosmological era is early enough then only states with positive binding energy can be constructed.Comment: 20 pages, RevTeX, 11 figures, to appear in Class. Quantum Grav., comments added, refs update

Non-Metric Gravity I: Field Equations

We describe and study a certain class of modified gravity theories. Our starting point is Plebanski formulation of gravity in terms of a triple B^i of 2-forms, a connection A^i and a ``Lagrange multiplier'' field Psi^ij. The generalization we consider stems from presence in the action of an extra term proportional to a scalar function of Psi^ij. As in the usual Plebanski general relativity (GR) case, a certain metric can be constructed from B^i. However, unlike in GR, the connection A^i no longer coincides with the self-dual part of the metric-compatible spin-connection. Field equations of the theory are shown to be relations between derivatives of the metric and components of field Psi, as well as its derivatives, the later being in contrast to the GR case. The equations are of second order in derivatives. An analog of the Bianchi identity is still present in the theory, as well as its contracted version tantamount to energy conservation equation.Comment: 21 pages, no figures (v2) energy conservation equation simplified, note on reality conditions added (v3) minor change