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.     

Is cross-modal integration of emotional expressions independent of attentional resources?

In this study, we examined whether integration of visual and auditory information about emotions requires limited attentional resources. Subjects judged whether a voice expressed happiness or fear, while trying to ignore a concurrently presented static facial expression. As an additional task, the subjects had to add two numbers together rapidly (Experiment 1), count the occurrences of a target digit in a rapid serial visual presentation (Experiment 2), or judge the pitch of a tone as high or low (Experiment 3). The visible face had an impact on judgments of the emotion of the heard voice in all the experiments. This cross-modal effect was independent of whether or not the subjects performed a demanding additional task. This suggests that integration of visual and auditory information about emotions may be a mandatory process, unconstrained by attentional resources.     

Root nonfinite and finite utterances in child language and agrammatic speech

Root nonfinite structures are frequent in both child language and agrammatic speech. Moreover, root nonfinites seem to have quite similar properties in both types of speech. Although many accounts are available for child language this is not the case for agrammatic speech. I present data of a Dutch agrammatic patient in this paper. The properties of her root nonfinites are best accounted for by the assumption of an underspecified Tense Phrase licensed by an empty element. In her finite sentences a dummy Tense element shows up. The use of either an empty or a dummy Tense element is a way of reducing the processing load of the utterance. The speech of this patient shows a dissociation between the verbal and the nominal domain.     

Hallucinatory predisposition and vividness of auditory imagery: self-report and behavioral indices.

This study examined the relation between a subjective and a behavioral measure of the vividness of auditory imagery as well as the disposition towards hallucination in normal subjects. In addition to the Launay-Slade Hallucination Scale, subjects (57 university students) completed the Betts questionnaire in which they rated the vividness of their experienced mental images and performed a behavioral task aimed at measuring auditory imagery. The task consisted of a perception and an imagery condition in which subjects had to indicate the odd one of three everyday sounds. Performance on the behavioral task did not correlate with the auditory or scores on the Visual subscale of the Betts. In addition, neither scores on the behavioral measure nor the Auditory subscale of the Betts correlated significantly with hallucinatory predisposition as rated on the Launay-Slade Hallucination Scale. In contrast, the Visual subscale of the Betts did correlate with scores on the Launay-Slade Hallucination Scale, consistent with previous research. We conclude that there is no straightforward relationship between imagery vividness and hallucinatory experiences and that subjective and objective indices of imagery vividness measure different aspects of mental function.     

Work and Individual Determinants of Intrinsic Work Motivation, Emotional Exhaustion, and Turnover Intention: A Multi-Sample Analysis

This study tested the influence of personal characteristics on a pattern of specific relationships between work characteristics and psychological outcomes. The study hypotheses were: (1) Growth Need Strength has a direct effect on intrinsic work motivation and moderates the relationship between task characteristics and intrinsic work motivation; (2) Negative Affectivity has a direct effect on emotional exhaustion and moderates the relationships between workload and social support on the one hand and emotional exhaustion on the other; and (3) Upward Striving has a direct effect on turnover intention and moderates the relationship between unmet career expectations and turnover intention. These hypotheses were tested in two samples (bank employees and teachers) using Multi-Sample Analysis. The results showed that, generally, personal characteristics had a direct effect on the outcomes as hypothesized. We only found one moderating effect: Upward Striving moderated the relationship between unmet career expectations and turnover intention.