Dissociable effects of positive feedback on the capture and inhibition of impulsive behavior in adolescents with ADHD versus typically developing adolescents.

The present study investigated how enhancing motivation by delivering positive feedback (a smiley) after a successful trial could affect interference control in adolescents with Attention Deficit Hyperactivity Disorder (ADHD) and in their typically developing (TD) peers. By using a Simon task within the theoretical framework of the "activation-suppression" model, we were able to separately investigate the expression and the inhibition of impulsive motor behavior. The experiment included 19 adolescents with ADHD and 20 TD adolescents in order to explore whether data found in adolescents with ADHD were similar to those found in TD adolescents.

The effect of reducing attentional resources on selective suppression in the Simon task.

Studies using reaction times (RTs) distribution methods find that the Simon effect is greater for fast RTs and becomes smaller or reversed for slow RTs. However, the exact mechanisms responsible for this reduction are under debate. This study addressed the issue of whether attentional resources play a role in reduction of the Simon effect over time by investigating whether it is influenced by attentional constraints in a dual-task paradigm.

Two sides of the same coin: ADHD affects reactive but not proactive inhibition in children.

Children with attention-deficit/hyperactivity disorder (ADHD) present a deficit in inhibitory control. Still, it remains unclear whether it comes from a deficit in reactive inhibition (ability to stop the action in progress), proactive inhibition (ability to exert preparatory control), or both.We compared the performance of 39 children with ADHD and 42 typically developing children performing a Simon choice reaction time task.

Stronger impulse capture and impaired inhibition of prepotent action in children with ADHD performing a Simon task: An electromyographic study.

Objective: A deficit in interference control is commonly reported in children with attention deficit hyperactivity disorder (ADHD). This has mainly been interpreted as a difficulty in inhibiting inappropriate responses. However, it could be due to at least two distinct and independent processes, which are often confounded: The activation or suppression of impulsive responses.

Differential response to pharmacological intervention in ADHD furthers our understanding of the mechanisms of interference control.

The deficit in "interference control" found in children with Attention Deficit Hyperactivity Disorder (ADHD) could be due to two distinct processes, which are not disentangled in most studies: a larger susceptibility to activating prepotent response impulses and a deficit in suppressing them. Here, we investigated the effect of 1/ADHD and 2/ methylphenidate (MPH), on these two components of interference control. We compared interference control between untreated children with ADHD, children with ADHD under MPH, and typically developing children performing a Simon task.

How Is Temporal Processing Affected in Children with Attention-deficit/hyperactivity Disorder?

We compared the performance of children with ADHD and typically developing children on two temporal tasks, a bisection task and a reproduction task, in auditory and visual modalities. Children with ADHD presented a larger variability when performing auditory and visual temporal tasks. Moreover, they overestimated the durations in bisection tasks and underproduced duration intervals in the visual reproduction task.

The effect of zolpidem on cognitive function and postural control at high altitude.

Study Objectives: Sleep is altered at high altitude leading many mountaineers to use hypnotics in order to improve sleep efficiency. While after a full night at altitude the short-acting hypnotic zolpidem does not appear to alter cognitive function, residual adverse effects should be considered following early waking-up as performed by mountaineers. We hypothesized that zolpidem intake at high altitude would alter cognitive function 4 hours after drug intake.

Cognitive Performance Enhancement Induced by Caffeine, Carbohydrate and Guarana Mouth Rinsing during Submaximal Exercise.

The aim of this study was to investigate the influence of serial mouth rinsing (MR) with nutritional supplements on cognitive performance (i.e., cognitive control and time perception) during a 40-min submaximal exercise.

It's about time: revisiting temporal processing deficits in dyslexia.

Temporal processing in French children with dyslexia was evaluated in three tasks: a word identification task requiring implicit temporal processing, and two explicit temporal bisection tasks, one in the auditory and one in the visual modality. Normally developing children matched on chronological age and reading level served as a control group. Children with dyslexia exhibited robust deficits in temporal tasks whether they were explicit or implicit and whether they involved the auditory or the visual modality.

Cognitive functions and cerebral oxygenation changes during acute and prolonged hypoxic exposure.

The present study aimed to assess specific cognitive processes (cognitive control and time perception) and hemodynamic correlates using functional near-infrared spectroscopy (fNIRS) during acute and prolonged high-altitude exposure. Eleven male subjects were transported via helicopter and dropped at 14 272 ft (4 350 meters) of altitude where they stayed for 4 days. Cognitive tasks, involving a conflict task and temporal bisection task, were performed at sea level the week before ascending to high altitude, the day of arrival (D0), the second (D2) and fourth (D4) day at high altitude.

The Influence of Odors on Time Perception.

The effect of an olfactory stimulation on the perception of time was investigated through two different experiments based on temporal bisection tasks. In experiment 1, the durations to be classified as either short or long were centered on 400 ms while in Experiment 2 there were centered on 2000 ms. The participants were different in the two experiments (36 subjects in each one).

Online extraction and single trial analysis of regions contributing to erroneous feedback detection.

Understanding how the brain processes errors is an essential and active field of neuroscience. Real time extraction and analysis of error signals provide an innovative method of assessing how individuals perceive ongoing interactions without recourse to overt behaviour. This area of research is critical in modern Brain-Computer Interface (BCI) design, but may also open fruitful perspectives in cognitive neuroscience research.

Spatial and temporal resolutions of EEG: Is it really black and white? A scalp current density view.

Among the different brain imaging techniques, electroencephalography (EEG) is classically considered as having an excellent temporal resolution, but a poor spatial one. Here, we argue that the actual temporal resolution of conventional (scalp potentials) EEG is overestimated, and that volume conduction, the main cause of the poor spatial resolution of EEG, also distorts the recovered time course of the underlying sources at scalp level, and hence degrades the actual temporal resolution of EEG. While Current Source Density (CSD) estimates, through the Surface Laplacian (SL) computation, are well known to dramatically reduce volume conduction effects and hence improve EEG spatial resolution, its positive impact on EEG temporal resolution is much less recognized.

Linking EEG signals, brain functions and mental operations: Advantages of the Laplacian transformation.

Electroencephalography (EEG) is a very popular technique for investigating brain functions and/or mental processes. To this aim, EEG activities must be interpreted in terms of brain and/or mental processes. EEG signals being a direct manifestation of neuronal activity it is often assumed that such interpretations are quite obvious or, at least, straightforward.

A dual-task paradigm to study the interference reduction in the Simon task.

Analyzing RT distributions in the Simon task reveals that congruency effects decrease for the longest RTs. Four experiments were carried out to examine whether this decrease of the congruency effect with response speed was under a top-down control or due to bottom-up mechanisms. We specifically manipulated the availability of attentional resources by requiring participants to perform a Simon task concurrently to different secondary tasks.

The cognitive structure of time estimation impairments in adults with attention deficit hyperactivity disorder.

We compared the performance of 15 adults with attention deficit hyperactivity disorder (ADHD) and a group of 16 control adults on a temporal bisection task in auditory and visual modalities. The point of subjective equality (PSE) and the difference limen (DL) were computed to analyse performance. The main findings were that (a) individuals with ADHD overestimated the duration of both the auditory and visual stimuli in comparison to the control group, as evidenced by a shift in their mean PSE; (b) individuals with ADHD also showed less precision in their estimates than did the control group as evidenced by flatter psychometric functions; and (c) the degrees of overestimation and imprecision in subjects with ADHD were comparable across modalities.

How does one night of sleep deprivation affect the internal clock?

Twelve subjects performed two temporal tasks, one explicit (Experiment 1) and one implicit (Experiment 2) after one night of sleep deprivation and after one night of normal rest. Experiment 1 involved a 1100-ms duration production task, and in Experiment 2 subjects performed a word identification task requiring implicit estimation of vowel duration (around 150 ms). One night of sleep deprivation had the same pattern of effect on explicit timing in the suprasecond range and implicit timing in the millisecond range.

Speech perception engages a general timer: evidence from a divided attention word identification task.

Time is essential to speech. The duration of speech segments plays a critical role in the perceptual identification of these segments, and therefore in that of spoken words. Here, using a French word identification task, we show that vowels are perceived as shorter when attention is divided between two tasks, as compared to a single task control condition.

Relationship between the velocity of illusory hand movement and strength of MEG signals in human primary motor cortex and left angular gyrus.

We studied the relationship between the velocity of movement illusion and the activity level of primary motor area (M1) and of the left angular gyrus (AG) in humans. To induce illusory movement perception, we applied co-vibration at different frequencies on tendons of antagonistic muscle groups. Since it is well established that the velocity of illusory movement is related to the difference in vibration frequency applied to two antagonistic muscles, we compared magnetoencephalography (MEG) signals recorded in two conditions of co-vibration: in the "fast illusion" condition a frequency difference of 80 Hz was applied on the tendons of the right wrist extensor and flexor muscle groups, whereas in the "slow illusion" condition a frequency difference of 40 Hz was applied on the same muscle groups.

Cortical correlates of illusory hand movement perception in humans: a MEG study.

The present study aimed to investigate cortical activity associated with perception of illusory hand movements elicited by tendon vibration using magnetoencephalography (MEG) in humans. We compared MEG responses in two conditions of stimulation, "illusion" and "no illusion". In the "illusion" condition, covibration at different frequencies applied on the tendons of the right wrist flexor and extensor muscle groups evoked illusory movements of the hand.

Motor and parietal cortical areas both underlie kinaesthesia.

Tendon vibration has long been known to evoke perception of illusory movements through activation of muscle spindle primary endings. Few studies, however, have dealt with the cortical processes resulting in these kinaesthetic illusions. We conceived an fMRI experiment to investigate the cortical structures taking part in these illusory perceptions.