A lack of timing-dependent effects of transcranial direct current stimulation (tDCS) on the performance of a choice reaction time task

Anodal transcranial direct current stimulation (tDCS) can enhance the retention of a previously practiced motor skill. However, the effects of tDCS on the performance of the choice reaction time task are not fully understood. We examined the effects of anodal tDCS over the left primary motor cortex (M1) on the retention of a 4-choice visual-motor reaction time task (4-ChRT). Right-handed healthy participants (n = 100) were randomly assigned to five groups: three groups received anodal tDCS: before (tDCSbefore), during (tDCSduring), or after (tDCSafter) motor practice. In addition, there were two control groups: with (CONmp) and without (CON) motor practice. We evaluated the speed and precision of the 4-ChRT task before (PRE), during, and 24 h (POST) after the interventions. All groups, including the non-stimulation (CONmp) and non-practice groups (CON), improved (p < 0.05) motor retention (Δ4-ChRT: 35.8 ± 36.0 ms). These findings suggest that the tDCS effects over M1 may differ for serial versus choice RT tasks, perhaps due to the different brain areas involved in each motor task

Oscillations in the basal ganglia in Parkinson's disease patients and their influence on the cerebral cortex and behavioural performance

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Implicit versus explicit local contextual processing.

We investigated the effects of implicit local contextual processing using behavioral and electrophysiological measures. EEG recording blocks consisted of targets preceded by either randomized sequences of standards or by sequences including a predictive sequence signaling the occurrence of a target event. Subjects performed two sessions: in the first the regularity of the predictive sequence was implicit, while in the second this regularity was made explicit. Subjects pressed a button in response to targets. Both the implicit and explicit sessions showed shorter reaction times and peak P3b latencies for predicted versus random targets, although to a greater extent in the explicit session. In both sessions the middle and last most-informative stimuli of the three-standard predictive sequence induced a significant larger P3b compared with randomized standards. The findings show that local contextual information is processed implicitly, but that this modulation was significantly greater when subjects were explicitly instructed to attend to target-predictive contextual information. The findings suggest that top-down attentional networks have a role in modulating the extent to which contextual information is utilized

Grand average at CPz for the three stimuli comprising the predictive sequence.

<p>The first least-informative (n-3), the middle (n-2) and last most informative (n-1); and for random preceding standards (Standard) for implicit (A) and explicit (B) sessions. Vertical dotted lines indicate time of stimulus presentation onset.</p

P3b amplitudes at CPz for the three stimuli comprising the predictive sequence.

<p>The first least-informative (n-3), the middle (n-2), and last most informative (n-1); and for the corresponding three standards presented randomly (Standards) for implicit and explicit sessions.</p

Grand average at CPz for the 4 conditions: targets after random non predictive (Random) and predictive sequences (Predicted), the last most informative standard comprising the predicting sequence (n-1) and random preceding standards (Standard); and the topographic maps of predicted, random targets and n-1, for implicit (A) and explicit (B) sessions.

<p>Vertical dotted lines indicate time of stimulus presentation onset.</p

Task timeline.

<p>Stimuli presented in the sessions. Sequences of standards S1, S2 and S3 with a predicted sequence (top) and in randomized order (bottom) preceding the target (T). The predictive sequence is always S1 followed by S2 and then S3 (n-1). Inter-trial intervals, including duration of stimulus presentation (150 ms) are displayed. Each block consisted of 6 different randomized sequences of standards (3–8 standards long) preceding the target; and 6 sequences of standards (3–8 standards long) with the predictive sequence preceding the target in each.</p

Local contextual processing of abstract and meaningful real-life images in professional athletes

We investigated the effect of abstract versus real-life meaningful images from sports on local contextual processing in two groups of professional athletes. Local context was defined as the occurrence of a short predictive series of stimuli occurring before delivery of a target event. EEG was recorded in 10 professional basketball players and 9 professional athletes of individual sports during three sessions. In each session, a different set of visual stimuli were presented: triangles facing left, up, right, or down; four images of a basketball player throwing a ball; four images of a baseball player pitching a baseball. Stimuli consisted of 15 % targets and 85 % of equal numbers of three types of standards. Recording blocks consisted of targets preceded by randomized sequences of standards and by sequences including a predictive sequence signaling the occurrence of a subsequent target event. Subjects pressed a button in response to targets. In all three sessions, reaction times and peak P3b latencies were shorter for predicted targets compared with random targets, the last most informative stimulus of the predictive sequence induced a robust P3b, and N2 amplitude was larger for random targets compared with predicted targets. P3b and N2 peak amplitudes were larger in the professional basketball group in comparison with professional athletes of individual sports, across the three sessions. The findings of this study suggest that local contextual information is processed similarly for abstract and for meaningful images and that professional basketball players seem to allocate more attentional resources in the processing of these visual stimuli

Schizophrenia detection and classification by advanced analysis of EEG recordings using a single electrode approach.

Electroencephalographic (EEG) analysis has emerged as a powerful tool for brain state interpretation and diagnosis, but not for the diagnosis of mental disorders; this may be explained by its low spatial resolution or depth sensitivity. This paper concerns the diagnosis of schizophrenia using EEG, which currently suffers from several cardinal problems: it heavily depends on assumptions, conditions and prior knowledge regarding the patient. Additionally, the diagnostic experiments take hours, and the accuracy of the analysis is low or unreliable. This article presents the "TFFO" (Time-Frequency transformation followed by Feature-Optimization), a novel approach for schizophrenia detection showing great success in classification accuracy with no false positives. The methodology is designed for single electrode recording, and it attempts to make the data acquisition process feasible and quick for most patients