Interaction between transient change in local muscle structure and segmented leg motor responses

We investigated the interaction between transient change in the local structure of gastrocnemius muscle fibers and the segmented leg motor responses elicited by toes-up rotation of the support surface. The gastrocnemius muscle in healthy young subjects underwent a sustained 2-min, isometric stretch (Prestretch group), followed immediately by the rotations. Analysis showed that the prestretch affected the amplitude of the monosynaptic but not the automatic components of the medial gastrocnemius muscle responses (monosynaptic response: 93 +/- 20% of the mean of the last three rotations in the Prestretch group compared to 174 +/- 42% in the Control group; automatic response: 128 +/- 18% in the Prestretch group versus 123 +/- 31% in the Control group). The shortened tibialis anterior muscle response and the onset latencies of responses were not affected by prestretching the gastrocnemius muscle. The prestretch effect on the amplitude of the monosynaptic (mediated by group Ia afferents) but not the automatic gastrocnemius muscle response (mediated by group II afferents) suggests that the automatic component of the muscle response to platform rotations has a stronger supraspinal influence than the monosynaptic response and is thus less affected by local events such as prolonged stretching.     

Commitment Shift during Organizational Upheaval: Physicians' Transitions from Private Practitioner to Employee

This longitudinal study examines the individual transition journeys of physicians as their private medical practices are acquired by a large integrated health care system. We test the proposition that transition patterns (trends in an individual's commitments to organization and profession over time) are a function of individual differences in years in profession and perceived organizational enabling characteristics (change involvement, openness to ideas, and work discretion). Three years of survey data were obtained from a panel of 48 physicians who transitioned through an organizational change process. Results challenge traditional assumptions that tenure reinforces commitment and cast doubt on the effectiveness of current medical school curricula in preparing medical graduates to practice in an administrative environment. In addition, results strongly suggest that enabling characteristics of organizational change are critical for compatibility between the organizational and professional attachments of transitioning physicians.     

The processing and representation of Dutch and English compounds: peripheral morphological and central orthographic effects

In this study, we use the association between various measures of the morphological family and decision latencies to reveal the way in which the components of Dutch and English compounds are processed. The results show that for constituents of concatenated compounds in both languages, a position-related token count of the morphological family plays a role, whereas English open compounds show an effect of a type count, similar to the effect of family size for simplex words. When Dutch compounds are written with an artificial space, they reveal no effect of type count, which shows that the differential effect for the English open compounds is not superficial. The final experiment provides converging evidence for the lexical consequences of the space in English compounds. Decision latencies for English simplex words are better predicted from counts of the morphological family that include concatenated and hyphenated but not open family members.     

Promoting perspective coordination by dilemma discussion. The effectiveness of classroom group discussion on interpersonal negotiation strategies of 12-year-old students

Promoting social competence and social cognition is an important aim of education and socialization. According to theories of social cognitive and moral development, social cognition may be promoted by adolescent peer interaction. In this study, social cognition is theoretically conceptualized by the interpersonal negotiation strategies model of Selman which distinguishes levels of perspective coordination and steps of information processing (identification of a problem, generating negotiation strategies, selection of a strategy, evaluation). In a pre-post control group design this study investigated whether dilemma discussions among peers lead to higher individual levels of perspective coordination compared to an individualistic condition. Members of the discussion-condition exhibited higher gain scores in perspective coordination compared to the control group regarding the information processing steps generating strategies and strategy selection. In order to analyze verbal interaction in the discussion groups, an integrative coding schedule was developed. In addition, trait-like argumentative motives of the participants were assessed. The results of multilevel analyses suggest that progress in posttest-perspective coordination is mediated by the groups consensual solution of the dilemma as well as by an explanation-oriented discussion style, but only if the latter is accompanied by a trait-like subject- and consensus-oriented argumentative motive. Theoretical and practical conclusions are drawn.     

Non-invasive estimation of local field potentials for neuroprosthesis control

Recent experiments have shown the possibility of using the brain electrical activity to directly control the movement of robots or prosthetic devices in real time. Such neuroprostheses can be invasive or non-invasive, depending on how the brain signals are recorded. In principle, invasive approaches will provide a more natural and flexible control of neuroprostheses, but their use in humans is debatable given the inherent medical risks. Non-invasive approaches mainly use scalp electroencephalogram (EEG) signals and their main disadvantage is that these signals represent the noisy spatiotemporal overlapping of activity arising from very diverse brain regions, i.e., a single scalp electrode picks up and mixes the temporal activity of myriads of neurons at very different brain areas. In order to combine the benefits of both approaches, we propose to rely on the non-invasive estimation of local field potentials (LFP) in the whole human brain from the scalp measured EEG data using a recently developed inverse solution (ELECTRA) to the EEG inverse problem. The goal of a linear inverse procedure is to de-convolve or un-mix the scalp signals attributing to each brain area its own temporal activity. To illustrate the advantage of this approach we compare, using an identical set of spectral features, classification of rapid voluntary finger self-tapping with left and right hands based on scalp EEG and non-invasively estimated LFP on two subjects using a different number of electrodes.

The conflict adaptation effect: It’s not just priming

Analyses of trial sequences in flanker tasks have revealed cognitive adaptation, reflected in a reduced interference effect following incompatible trials (Gratton, Coles, & Donchin, 1992). These effects have been explained on the basis of the response conflict monitoring model of Botvinick, Braver, Barch, Carter, and Cohen (2001), who proposed that preceding response conflict triggers stronger topdown control, leading to performance improvements on subsequent trials of similar context. A recent study (Mayr, Awh, & Laurey, 2003) has challenged this account, suggesting that the behavioral adaptations are confined to trial sequences of exact trial repetitions and can therefore be explained by repetition priming. Here, we present two experiments in which the sequential dependency effect was present even on trial sequences that did not involve stimulus repeats. We discuss the data with respect to the conflict-monitoring and repetition-priming accounts.     

Efficiently measuring recognition performance with sparse data

We examine methods for measuring performance in signal-detection-like tasks when each participant provides only a few observations. Monte Carlo simulations demonstrate that standard statistical techniques applied to ad’ analysis can lead to large numbers of Type I errors (incorrectly rejecting a hypothesis of no difference). Various statistical methods were compared in terms of their Type I and Type II error (incorrectly accepting a hypothesis of no difference) rates. Our conclusions are the same whether these two types of errors are weighted equally or Type I errors are weighted more heavily. The most promising method is to combine an aggregated’ measure with a percentile bootstrap confidence interval, a computerintensive nonparametric method of statistical inference. Researchers who prefer statistical techniques more commonly used in psychology, such as a repeated measurest test, should useγ (Goodman & Kruskal, 1954), since it performs slightly better than or nearly as well asd’. In general, when repeated measurest tests are used,γ is more conservative thand’: It makes more Type II errors, but its Type I error rate tends to be much closer to that of the traditional .05 α level. It is somewhat surprising thatγ performs as well as it does, given that the simulations that generated the hypothetical data conformed completely to thed’ model. Analyses in which H—FA was used had the highest Type I error rates. Detailed simulation results can be downloaded fromwww.psychonomic.org/archive/Schooler-BRM-2004.zip.