Reversal of Relative Thresholds for Synaptic Facilitation and Increased Excitability Induced by Serotonin and Tail Nerve Stimulation inAplysiaSensory Neurons

Tail shock induces reflex sensitization inAplysiaand, in parallel, induces a number of modulatory effects in central neurons, such as increased excitability in tail sensory neurons (SNs) and facilitation of synaptic transmission from SNs to motor neurons. Both of these modulatory effects are mimicked by exogenous application of serotonin (5HT) or electrical stimulation of the tail nerve P9. In the present study we examined the activation thresholds for increased excitability and synaptic facilitation induced by either 5HT or P9 stimulation. We found that the concentration of 5HT sufficient to produce a significant increase in excitability produced no significant synaptic facilitation and, conversely, that the intensity of nerve stimulation sufficient to produce significant synaptic facilitation produced no excitability changes. This reversal of relative thresholds for these modulatory effects may reflect the differential access of exogenous 5HT and endogenous 5HT (released by tail nerve stimulation) to the SN cell body and synaptic terminals, respectively.     

Flexibility of Labor, Well-Being, and Stress

After a short introduction into the changing nature of our society and organizations, we outline two kinds of flexibility of labor: qualitative flexibility, that is the degree to which people who work in or for a certain organization can and do perform different tasks, and quantitative flexibility, that is, varying the quantity of personnel and their working hours. Then, the different ways in which we organize our work and organizations are dealt with in terms of quantitative and qualitative flexibility. Next, we survey these ways of organizing on the degree to which they moderate the positive individual outcomes, or individual goals, of work. It can be concluded that quantitatively flexible work, besides some minor positive consequences, may have serious negative consequences for one's well-being, health, and personal development, while qualitative flexibility may have many more advantages, though it may lead to a devastating task overload. Last, we explore some ways to alleviate these negative effects.     

Language-specific listening

Languages differ in their phonological structure and physcholinguists have begun to explore the conseqence, of this fact for speech perception. We review research documenting that listeners attune their perceptual processes finaly to exploit the phonological regularities of their nativ language. As a consequence, these perceptual process are fill-adapted to listening to languages that do not display such, regularities. Thus, not only do late language-learners have trouble speaking a second language, also they do not hear it as native speakers do; worse, they apply their native language listening prosedures which may actually interfere with successful processing of the non-native input. We also present data from studies on infants showing that the initial attuning occurs early in life; very yong infants are sensitive to the relevant phonological regularities which distinguish different languages, and quickly distinguish the native language of their environment from languages with different regularities.     

A program for parsing mouse movements into component submovements

Most current movement control theories include the idea that movement toward a target can be broken into several submovements. The complexity of analyzing a movement into its constituent submovement structure and the additional complexity imposed by the problem of noise in the data and hand tremor seem to be daunting to researchers. This paper discusses a program that can ameliorate both of these problems and parse movements into their constituent submovements. It also contains a graphing feature that is useful as a visual tool for analyzing submovement structure. The programs are easily modifiable, so that researchers can specify their own parsing rules on the basis of different assumptions about movement control and use the parser for data from different experimental tasks.     

Spline smoothing with model-based penalties

Nonparametric regression techniques, which estimate functions directly from noisy data rather than relying on specific parametric models, now play a central role in statistical analysis. We can improve the efficiency and other aspects of a nonparametric curve estimate by using prior knowledge about general features of the curve in the smoothing process. Spline smoothing is extended in this paper to express this prior knowledge in the form of a linear differential operator that annihilates a specified parametric model for the data. Roughness in the fitted function is defined in terms of the integrated square of this operator applied to the fitted function. A fastO(n) algorithm is outlined for this smart smoothing process. Illustrations are provided of where this technique proves useful.     

Opportunities For Learning: Course Sequences and Positional Advantages

Course sequences are strands of courses in particular content areas that span a student's educational career. Courses that are differentiated and sequentially organized, such as mathematics and science course sequences, create opportunities for positional advantages in a school's curricular structure. When students make a nonroutine change of schools – that is, transferring to a school outside of the regular attendance zone – they are at risk of changing their positional advantage. Using data from the National Education Longitudinal Study of 1988–94 (NELS:88–94), we examine the educational outcomes of sequences and explore curricular dislocations within the context of school choice. We find that the strongest predictors of 12th-grade mathematics and science course sequences are a student's course sequences at 10th grade. With regard to outcomes, students in higher mathematics and science sequences show greater achievement gains. Furthermore, students in higher mathematics sequences are less likely to have behavior problems and are more likely to graduate from high school and attend college. Students who make a nonroutine change of schools are more likely to be in lower course sequences than students who do not transfer. Thus, course sequences in mathematics and science are tangible experiences with real consequences for students' lives during and beyond high school and are sensitive to transitions which disrupt the continuity of students' high school careers.     

The organization of multidimensional selection on the basis of color and shape: An event-related brain potential study

In this paper, we examine whether color and shape, tied to a single object in space, (1) are identified and selected in series or in parallel, (2) are identified and selected in a dependent, self-terminating manner or in an independent and exhaustive manner, and (3) are conjoined by a feature integration process before or only after an initial stage of separate attribute analyses has finished. We measured response time and the selection negativity (SN) derived from event-related brain potentials when participants responded to a unique conjunction of color and shape in a go/no-go target detection task. The discriminability of the color and the shape of the conjunction was manipulated in three conditions. When color and shape were easy to discriminate, the SNs to color and shape started at the same time. When one attribute was less discriminable, the SN to that attribute started later, but not the SN to the complementary attribute. This suggests that color and shape are identified and selected in parallel. In all three discriminability conditions, the SNs to color and shape were initially independent but later interacted. This suggests that color and shape are initially selected independently and exhaustively, after which their conjunction is analyzed. The SN to local shape features started later than that to the conjunction of color and global shape features, which suggests that feature integration can start before the analyses of the separate attributes have finished.     

The perception of shape and curvedness from binocular stereopsis and structure from motion

The integration of binocular stereopsis and kinetic depth was measured for two distinct aspects of 3-Dstructure: (1)shape index, which is a measure of scale-independent structure, and (2)curvedness, which is a measure of scale-dependent structure. We found that motion contributes significantly more to judged shape index than it does to judged curvedness, and stereo contributes significantly more to judged curvedness than it does to judged shape index. This suggests that the differences in the relative contribution of motion and stereo reported here occurred because these two sources do not equally specify the scale-dependent and scale-independent aspects of surface structure. Furthermore, these results seem to be inconsistent with integration models in which the different visual cues all initially contribute to the same single representation of 3-Dstructure.