Choice Reaction Time Task Research Articles

Dysfunction of the Prefrontal Cortex in Betel-Quid-Dependent Chewers.

Betel quid is the fourth most popular psychoactive agent worldwide. Imaging studies have found altered brain structure in prefrontal cortex (PFC) in betel-quid dependent (BQD) chewers. However, the brain function in PFC associated with BQ use still remains unclear. The present study aimed to examine brain functional activity in PFC in individuals with BQD. This study recruited 48 participants with BQD and 22 normal controls (NCs). Both BQ-specific cue reactivity and Go/NoGo tasks were administered with functional magnetic resonance imaging (fMRI). Behavioral results showed a deficit in the choice reaction time task in BQD group. The fMRI results of the cue reactivity task suggested that, individuals with BQD exhibited responses in right ventromedial PFC, left posterior cingulate cortex (PCC), left lateral parietal lobe (LPL), left middle temporal gyrus and left visual cortex, when seeing BQ images compared with control images. In the Go/NoGo task, relative to NCs group, individuals with BQD showed higher activity in right dorsolateral PFC, right PCC and bilateral LPL between NoGo and Go trials. Across these two tasks, we consistently found disrupted function in PFC in individuals with BQD, which might lead to impaired craving and response inhibition in BQ addiction. Results of current study might shed light on the neural mechanisms involved in BQ use, which could be used as potential guidelines for diagnosis and treatment of BQ dependence.

Hidden wounds of violence: Abnormal motor oscillatory brain activity is related to posttraumatic stress symptoms

Victims of urban violence are at risk of developing Posttraumatic Stress Disorder (PTSD), one of the most debilitating consequences of violence. Considering that PTSD may be associated with inefficient selection of defensive responses, it is important to understand the relation between motor processing and PTSD. The present study aims to investigate the extent to which the severity of posttraumatic stress symptoms (PTSS) is related to motor preparation against visual threat cues in victims of urban violence. Participants performed a choice reaction time task while ignoring a picture that could be threating or neutral. The EEG indices extracted were the motor-related amplitude asymmetry (MRAA) in the alpha frequency range, and the lateralized readiness potential (LRP). We observed a linear relation between longer LRP latency and a slower reaction time, selectively during threat processing (compared to neutral) in low PTSS, but not in high PTSS participants. Alpha MRAA suppression and the PTSS were also linearly related: the smaller the alpha MRAA suppression in the threat condition relative to neutral, the greater the PTSS. These results provide evidence that threatening cues affect motor processing that is modulated by the severity of PTSS in victims of urban violence.

Top-Down Processing of Drug Names Can Induce Errors in Discriminating Similar Pseudo-Drug Names by Nurses.

One factor that could cause medical errors is confusing medicines with similar names. A previous study showed that nurses who have knowledge about drugs faced difficulty in discriminating a drug name from similar pseudo-drug names. To avoid such errors, finger-pointing and calling (FPC) has been recommended in Japan. The present study had two aims. The first was to determine whether such difficulty was due to top-down processing, rather than bottom-up processing, being applied even for pseudo-names. The other was to investigate whether FPC affected error prevention for similar drug names. In two experiments, nurses and non-health care professionals performed a choice reaction time task for drug names and common words, with or without FPC. Error rate and reaction time were analyzed. When drug names were used, nurses showed difficulty discriminating target names from distractors. Furthermore, the error prevention effect of FPC was marginally significant for drug names. However, nurses showed no significant differences when similar drug names were used. There was no significant difference regarding the error rate for words. Nurses' knowledge of drug names activates top-down processing. As a result, the processing of drug names was not as accurate and quick as that for words for nurses, which caused difficulty in discriminating similar names. FPC may be applicable to reduce confusion errors, possibly by leading individuals to process drug names using bottom-up processing. The present study advances current knowledge about error tendencies with similar drug names and the effects of FPC on error prevention.

Self-reported impulsivity does not predict response caution

The broad construct of impulsivity is one that spans both personality and cognitive ability. Despite a common overarching construct, previous research has found no relationship between self-report measures of impulsivity and people's ability to inhibit pre-potent responses. Here, we use evidence accumulation models of choice reaction time tasks to extract a measure of “response caution” (boundary separation) and examine whether this correlates with self-reported impulsivity as measured by the UPPS-P questionnaire. Response caution reflects whether an individual makes decisions based on more (favouring accuracy) or less (favouring speed) evidence. We reasoned that this strategic dimension of behaviour is conceptually closer to the tendencies that self-report impulsivity measures probe than what is traditional measured by inhibition tasks. In a meta-analysis of five datasets (total N = 296), encompassing 19 correlations per subscale, we observe no evidence that response caution correlates with self-reported impulsivity. Average correlations between response caution and UPPS-P subscales ranged from rho = −0.02 to −0.04. While the construct of response caution has demonstrated value in understanding individual differences in cognition, brain functioning and aging; the factors underlying what has been called “impulsive information processing” appear to be distinct from the concept of impulsivity derived from self-report.

Considering Motor Excitability During Action Preparation in Gambling Disorder: A Transcranial Magnetic Stimulation Study.

A lack of inhibitory control appears to contribute to the development and maintenance of addictive disorders. Among the mechanisms thought to assist inhibitory control, an increasing focus has been drawn on the so-called preparatory suppression, which refers to the drastic suppression observed in the motor system during action preparation. Interestingly, deficient preparatory suppression has been reported in alcohol use disorders. However, it is currently unknown whether this deficit also concerns behavioral, substance-free, addictions, and thus whether it might represent a vulnerability factor common to both substance and behavioral addictive disorders. To address this question, neural measures of preparatory suppression were obtained in gambling disorder patients (GDPs) and matched healthy control subjects. To do so, single-pulse transcranial magnetic stimulation was applied over the left and the right motor cortex to elicit motor-evoked potentials (MEPs) in both hands when participants were performing a choice reaction time task. In addition, choice and rapid response impulsivity were evaluated in all participants, using self-report measures and neuropsychological tasks. Consistent with a large body of literature, the MEP data revealed that the activity of the motor system was drastically reduced during action preparation in healthy subjects. Surprisingly, though, a similar MEP suppression was observed in GDPs, indicating that those subjects do not globally suffer from a deficit in preparatory suppression. By contrast, choice impulsivity was higher in GDPs than healthy subjects, and a higher rapid response impulsivity was found in the more severe forms of GD. Altogether, those results demonstrated that although some aspects of inhibitory control are impaired in GDPs, these alterations do not seem to concern preparatory suppression. Yet, the profile of individuals suffering of a GD is very heterogeneous, with only part of them presenting an impulsive disposition, such as in patients with alcohol use disorders. Hence, a lack of preparatory suppression may be only shared by this sub-type of addicts, an interesting issue for future investigation.

Association between cardiorespiratory fitness and social cognition in healthy adults

Whereas there is compelling evidence for an association between cardiorespiratory fitness (CRF) and executive function and attention, its relation with social cognition has not been investigated yet. However, social cognition is linked with mental health and career success in jobs with high demands on social interaction. The present study aims to examine the association between CRF and the facial emotion recognition aspect of social cognition in police officers. The study utilized a cross-sectional design. 198 male and female participants (aged 38.3±1.3years) completed the Åstrand submaximal bicycle ergometer test and their CRF was estimated using the Åstrand-Rhyming nomogram. Additionally, a 2-choice reaction time task and two facial emotion recognition tasks (labeling and matching) with low (emotion recognition from faces) and high (emotion recognition from eyes) difficulty trials were administered for the assessment of attention and social cognition. Adjusting for age, gender, education, and attention, hierarchical regression supported higher CRF to be related to higher performance on overall performance on the facial emotion labeling and matching tasks, Beta=0.141, P=.046. With regard to difficulty levels, a similar association between CRF and task performance was found for the faces condition, Beta=0.147, P=.043, but not for the eyes condition, Beta=0.105, P=.132. Social cognition appears to differ as a function of adults' CRF level. The present findings have a high relevance for police officers, because they need to rely on this cognitive domain for many decisions in their work-life.

Electrophysiological Evidence for Distinct Proactive Control Mechanisms in a Stop-Signal Task: An Individual Differences Approach.

Proactive control reflects a sustained, top-down maintenance of a goal representation prior to task-related events, whereas reactive control reflects a transient, bottom-up goal reactivation in response to them. We designed a manual stop-signal task to isolate electrophysiological signals specifically involved in proactive control. Participants performed a simple choice reaction time task but had to withhold their response to an infrequent stop signal, resulting in go- and stop-signal trials. We manipulated the stop-signal probability (30% vs. 10%) over different blocks of trials so that different proactive control levels were sustained within each block. The behavioral results indicated that most participants proactively changed their behaviors. The reaction times in the go trials increased and the number of response errors in the stop-signal trials decreased. However, those two behavioral measures did not correlate: individuals with an increased delayed reaction did not necessarily manifest a higher decrease in response errors in the stop-signal trials. To isolate the proactive control signal, we obtained event-related potentials (ERPs) locked to an uninformative fixation onset and compared the signals between the two stop-signal probability conditions. We found that the ERPs at the left hemisphere were more negatively shifted with the increasing stop-signal probability. Moreover, ERP differences obtained from a set of electrodes in the left hemisphere accounted for the changes in response errors in the stop-signal trials but did not explain the changes in reaction times of the go trials. Together, the behavioral and electrophysiological results suggest that proactive control mechanisms reducing erroneous responses of the stop-signal trials are different from mechanisms slowing reaction times of the go trials.

Bilingualism and Processing Speed in Typically Developing Children and Children With Developmental Language Disorder.

Purpose The aim of the current study was to investigate whether dual language experience modulates processing speed in typically developing (TD) children and in children with developmental language disorder (DLD). We also examined whether processing speed predicted vocabulary and sentence-level abilities in receptive and expressive modalities. Method We examined processing speed in monolingual and bilingual school-age children (ages 8-12 years) with and without DLD. TD children (35 monolinguals, 24 bilinguals) and children with DLD (17 monolinguals, 10 bilinguals) completed a visual choice reaction time task. The Clinical Evaluation of Language Fundamentals, the Peabody Picture Vocabulary Test, and the Expressive Vocabulary Test were used as language measures. Results The children with DLD exhibited slower response times relative to TD children. Response time was not modified by bilingual experience, neither in children with typical development nor children with DLD. Also, we found that faster processing speed was related to higher language abilities, but this relationship was not significant when socioeconomic status was controlled for. The magnitude of the association did not differ between the monolingual and bilingual groups across the language measures. Conclusions Slower processing speed is related to lower language abilities in children. Processing speed is minimally influenced by dual language experience, at least within this age range. Supplemental Material https://doi.org/10.23641/asha.12210311.

Contingent negative variation: a biomarker of abnormal attention in functional movement disorders.

Background and purposeContingent negative variation (CNV) is a negative cortical wave that precedes a pre‐cued imperative stimulus requiring a quick motor response. It has been related to motor preparation and anticipatory attention. The aim was to ascertain whether the clinical improvement of functional movement disorders after physiotherapy would be associated with faster reaction times and modulation of CNV.MethodsMotor performance and CNV were analysed during a pre‐cued choice reaction time task with varying cue validity. Twenty‐one patients with functional movement disorders and 13 healthy controls at baseline were compared. Patients then underwent physiotherapy. At follow‐up after physiotherapy, patients were categorized as clinically improved (responders) or not improved (non‐responders) and retested.ResultsAt baseline, patients did not generate CNV, contrary to controls [mean amplitude (µV) at the end of preparation to move: patients −0.47 (95% CI −1.94, 1.00) versus controls −2.59 (95% CI −4.46, −0.72)]. Responders performed faster after physiotherapy [mean natural logarithm (ln) reaction time (RT) (ms): follow‐up 6.112 (95% CI 5.923, 6.301) versus baseline 6.206 (95% CI 6.019, 6.394), P = 0.010], contrary to non‐responders. Simultaneously, responders showed a recovery of CNV after physiotherapy [follow‐up −1.95 (95% CI −3.49, −0.41) versus baseline −0.19 (95% CI −1.73, 1.35), P < 0.001], contrary to non‐responders [follow‐up −0.32 (95% CI −1.79, 1.14) versus baseline −0.72 (95% CI −2.19, 0.75), P = 0.381].ConclusionsClinical improvement of functional movement disorders after physiotherapy was associated with faster reaction times and normalization of CNV, which was absent at baseline. These findings suggest that CNV may constitute a useful neurophysiological biomarker related to abnormal attention in functional movement disorders.

Allometrically scaled explosive strength, but not static strength or maximal oxygen uptake is associated with better central processing time in young males.

We aimed to examine the associations of cardiorespiratory fitness (CRF), static strength and explosive strength with cognitive functions in young males. Eighty-six young males (age 16-24 years) participated in the study and took part in a number of tests including: static strength (grip strength test), explosive strength (Sargent jump test), and CRF (via direct measure of maximal oxygen uptake [VO2max]). Static strength and explosive strength were scaled by allometrically modeled skeletal muscle mass (SMM) and height while VO2max was scaled by SMM and body mass (BM). Cognition was assessed by inhibitory control, simple and choice reaction time tasks using computerized Cambridge Neuropsychological Test Battery (CANTAB). Central processing time was measured by surface electromyography changes in isometric contraction response to an audio stimulus. VO2max scaled by BM (but not SMM), was associated with better central processing time and stop-signal reaction time (SSRT). Explosive strength was also associated with better central processing time independent of VO2max. However, static strength was not associated with cognition. The results suggest that explosive strength is a better predictor of central processing than static strength or VO2max in young males. Longitudinal studies are needed to examine whether explosive strength training in youth would improve central processing time.

The Impact of Voice Leading and Harmony on Musical Expectancy

In Western tonal music, voice leading (VL) and harmony are two central concepts influencing whether a musical sequence is perceived as well-formed. However, experimental studies have primarily focused on the effect of harmony on the cognitive processing of polyphonic music. The additional effect of VL remains unknown, despite music theory suggesting VL to be tightly connected to harmony. Therefore, the aim of this study was to investigate and compare the effects of both VL and harmony on listener expectations. Using a priming paradigm and a choice reaction time task, participants (N = 34) were asked to indicate whether the final chord in a sequence had a different timbre than the preceding ones (cover task), with the experimental conditions being good and poor VL or harmony, respectively. An analysis with generalised mixed effects models revealed a significant influence of both VL and harmony on reaction times (RTs). Moreover, pairwise comparison showed significantly faster RTs when VL was good as compared to both VL and harmony being poor, which was not the case when only harmony was good. This study thus provides evidence for the additional importance of VL for the processing of Western polyphonic music.

Understanding the influence of a cognitively demanding task on motor response times and subjective mental fatigue/boredom

BACKGROUND: Several methods are used to induce mental fatigue; predominantly the modified Stroop task, which arguably has little relation to daily lifestyle tasks.&#x0D; AIM: To investigate the influence of the modified Stroop task on mental fatigue, boredom and motor response times.&#x0D; METHOD: 15 subjects (24.3±2.3 years) completed a 30-min modified Stroop task (control condition: 30-min reading) and completed PRE, POST and POST 5-min subjective ratings of mental fatigue, mental effort and boredom. Participants' ability to use congruent and inhibit incongruent precues in a choice reaction time task (CRTT) was measured pre- and post- Stroop and control.&#x0D; RESULTS: Significantly higher subjective ratings of pre-post condition mental fatigue (pre:2.43±1.31 AU, post: 6.42±2.08 AU,p&lt;0.01) and boredom (PRE: 1.65±1.49 AU, POST: 5.03±2.92 AU,p&lt;0.01) were reported following the modified Stroop task condition compared to the control condition mental fatigue (PRE: 1.62±1.17 AU, POST: 2.10±0.92 AU,p&gt;0.05) and boredom (PRE: 1.94±1.52 AU, POST: 3.32 ± 1.66 AU,p&gt;0.05). No significant differences were found between conditions for the extent to which participants’ response times were affected by congruent (p=0.481) or incongruent (p=0.225) precues.&#x0D; CONCLUSION: Future research must adopt cognitive activities with higher contextual interference for greater ecological validity, and elucidate the impact of rest on recovery from mental fatigue.

Heterogeneous Indicators of Cognitive Performance and Performance Variability Across the Lifespan.

Reaction time (RT) and RT variability are core components of cognitive performance that can be captured through brief and easy-to-administer tasks of simple RT and choice RT. The current study aims to describe age-related differences in cognitive performance, toward better characterizing normative performance across the lifespan. We examined mean and variability of response times on a simple RT and choice RT tasks in a large and diverse web-based sample (10,060 visitors to TestMyBrain.org). We also examined lifespan-related differences in response time variability using multiple different approaches (raw variability, mean scaled variability, and mean residualized variability). These analyses revealed significant heterogeneity in the patterns of age-related differences in performance, across metrics and within different estimates of the same metric. Based on segmented regression analysis, age of peak performance differed significantly across metrics, with young adults having the best performance based on measures of median RT, middle age adults at peak on certain measures of RT variability (standard deviation and coefficient of variability), and older adults showing the best performance based on accuracy and mean-corrected RT variability. Our results indicate that no single measure of cognitive performance and performance variability produces the same findings with respect to age related change, with further work needed to establish the validity of particular metrics for different applications.

Three consecutive nights of sleep loss: Effects of morning caffeine consumption on subjective sleepiness/alertness, reaction time and simulated driving performance

Caffeinated products are often consumed as a popular countermeasure to the effects of sleep loss. However, the efficacy of caffeine to exert these effects after consecutive nights of sleep loss is poorly understood. The aim of this study was to investigate the effects of three consecutive nights of restricted sleep and morning caffeine consumption on subjective ratings of sleepiness/alertness, reaction time, and simulated driving performance. Twenty healthy, habitual caffeine consumers (11 females; age: 23.3 ± 5.7 y; BMI: 22.3 ± 3.5 kg⋅m−2; caffeine intake: 204 ± 89 mg⋅day−1; Mean ± SD) who had normal sleeping patterns (≥8 h⋅night−1) participated in this double-blind, placebo-controlled, randomised study. Following one night of normal sleep (≥8 h time in bed (TIB)), participants underwent three consecutive nights of restricted sleep (5 h TIB). Participants received caffeine (200 mg; n = 10) or placebo (n = 10) capsules each morning and all participants received caffeine (100 mg) capsules each afternoon. Subjective ratings of alertness, concentration and tiredness were measured before and 1 h after morning capsule administration. Choice Reaction Time (CRT) was examined 1 h after morning capsule administration, with response speed and accuracy as outcome variables. Driving performance was assessed using a 30 min simulated driving task, with lateral (standard deviation of lane position [SDLP]; total number of line crossings [LC]) and longitudinal (standard deviation of speed [SDSP]) measures of vehicle control as outcome variables. Alertness and concentration significantly decreased, and tiredness increased across the three days of sleep loss. Caffeine only marginally alleviated these effects. No differences were observed between treatments or across trial days for response speed and accuracy on the CRT task. Likewise, no significant differences were observed between groups or across trial days for any measures of simulated driving performance. Overall, results from this study indicate that three consecutive days of sleep loss influence subjective ratings of alertness, concentration and tiredness, but does not alter CRT or simulated driving performance. Caffeine may alleviate some of the negative subjective effects imposed by restricted sleep, but the efficacy of caffeine to attenuate performance changes in CRT and driving performance were unable to be observed.

The rise and fall of executive functions in high-level football players

IntroductionExecutive functions are higher-level cognitive functions. Despite being relevant to many aspects of everyday life, it is contentious whether executive functions are important for high performing athletes. Executive functions increase throughout the career of an athlete, yet it remains unknown what are the main contributors. Therefore, this study examined the effect of age and experience on executive functions in a cohort of high performing football players. MethodsData were collected over three seasons, resulting in a mixed longitudinal sample of 1018 observations in 343 male players (1–5 observations/player, age: 10.34–34.72 years; playing experience: 5–22 years) from the U12-Senior age groups of a professional German football club. Players participated in four cognitive tasks aimed at measuring higher-level cognitive functioning: a precued choice reaction-time task, a stop-signal reaction-time task, a sustained attention task, and a multiple-object tracking task, from which a total of eight dependent variables related to response time and/or accuracy were derived. ResultsLinear and non-linear mixed effects regressions were used to investigate the relationship between age, experience and executive functions. A second order polynomial revealed that, generally, a negatively accelerated curve best described the relationship between age, experience and executive functions. An increasingly smaller difference in executive functioning was generally observed between subsequent age groups, with a performance plateau evident around adulthood (~21 years old). Age and experience only explained a very low to moderate proportion of the variance in executive functions (marginal explained variance ranged between 2 and 57%). A significant age by field position interaction effect was only observed for the sustained attention task’s accuracy and response time components (p < 0.001). ConclusionsBoth age and experience showed a negatively accelerated relationship with executive functions in youth football players, and this relationship was generally field position-independent. These negatively accelerated curves seem to reflect those observed in general populations, where a plateau phase in the development of higher-level cognitive functioning is also observed around 21 years, reflecting the maturation of the central nervous system in normally developing individuals. Therefore, this study challenges the assumption surrounding the use and validity of executive functions as a measure of football performance potential in high performing athletes.

Window view of nature after brief exercise improves choice reaction time and heart rate restoration

Research indicates that natural environments induce restorative effects on cognitive capacity and autonomic arousal. The present study investigates differences in choice reaction time (CRT) and heart rate responses in students (n = 9) resting with or without a window view of a modest natural environment after a physical exertion. Subjects performed a CRT-task before pedaling a spinning bike, followed by resting in a chair with either a window view of a natural environment, or no view. Heart rate was obtained during the rest-period, and the CRT task was performed again immediately after resting.Results indicated that subjects elicited significantly larger improvement in CRTs and more efficient heart rate restoration after resting with a window view, compared to resting without a view. Resting with a modest view of a natural environment after brief exercise demonstrated both a greater effect of cognitive enhancement and more efficient physiological restoration compared to resting without a view. These findings advance prior research by demonstrating both cognitive and physiological benefits from resting in a modest natural environment.

The therapeutic effect of progranulin derived Pcgin on neuronopathic Gaucher disease

Executive functions are higher-level cognitive functions. Despite being relevant to many aspects of everyday life, it is contentious whether executive functions are important for high performing athletes. Executive functions increase throughout the career of an athlete, yet it remains unknown what are the main contributors. Therefore, this study examined the effect of age and experience on executive functions in a cohort of high performing football players.Data were collected over three seasons, resulting in a mixed longitudinal sample of 1018 observations in 343 male players (1–5 observations/player, age: 10.34–34.72 years; playing experience: 5–22 years) from the U12-Senior age groups of a professional German football club. Players participated in four cognitive tasks aimed at measuring higher-level cognitive functioning: a precued choice reaction-time task, a stop-signal reaction-time task, a sustained attention task, and a multiple-object tracking task, from which a total of eight dependent variables related to response time and/or accuracy were derived.Linear and non-linear mixed effects regressions were used to investigate the relationship between age, experience and executive functions. A second order polynomial revealed that, generally, a negatively accelerated curve best described the relationship between age, experience and executive functions. An increasingly smaller difference in executive functioning was generally observed between subsequent age groups, with a performance plateau evident around adulthood (~21 years old). Age and experience only explained a very low to moderate proportion of the variance in executive functions (marginal explained variance ranged between 2 and 57%). A significant age by field position interaction effect was only observed for the sustained attention task’s accuracy and response time components (p < 0.001).Both age and experience showed a negatively accelerated relationship with executive functions in youth football players, and this relationship was generally field position-independent. These negatively accelerated curves seem to reflect those observed in general populations, where a plateau phase in the development of higher-level cognitive functioning is also observed around 21 years, reflecting the maturation of the central nervous system in normally developing individuals. Therefore, this study challenges the assumption surrounding the use and validity of executive functions as a measure of football performance potential in high performing athletes.

A TMS study of preparatory suppression in binge drinkers

Binge drinking consists in a pattern of consumption characterised by the repeated alternation between massive alcohol intakes and abstinence periods. A continuum hypothesis suggests that this drinking endeavour represents an early stage of alcohol dependence rather than a separate phenomenon. Among the variety of alterations in alcohol-dependent individuals (ADIs), one has to do with the motor system, which does not show a normal pattern of activity during action preparation. In healthy controls (HCs), motor-evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) over primary motor cortex (M1) show both facilitation and suppression effects, depending on the time and setting of TMS during action preparation. A recent study focusing on the suppression component revealed that this aspect of preparatory activity is abnormally weak in ADIs and that this defect scales with the risk of relapse. In the present study, we tested whether binge drinkers (BDs) present a similar deficit. To do so, we recorded MEPs in a set of hand muscles applying TMS in 20 BDs and in 20 matched HCs while they were preparing index finger responses in an instructed-delay choice reaction time task. Consistent with past research, the MEP data in HCs revealed a strong MEP suppression in this task. This effect was evident in all hand muscles, regardless of whether they were relevant or irrelevant in the task. BDs also showed some preparatory suppression, yet this effect was less consistent, especially in the prime mover of the responding hand. These findings suggest abnormal preparatory activity in BDs, similar to alcohol-dependent patients, though some of the current results also raise new questions regarding the significance of these observations.

Task-related measures of short-interval intracortical inhibition and GABA levels in healthy young and older adults: A multimodal TMS-MRS study

Establishing the associations between magnetic resonance spectroscopy (MRS)-assessed gamma-aminobutyric acid (GABA) levels and transcranial magnetic stimulation (TMS)-derived ‘task-related’ modulations in GABAA receptor-mediated inhibition and how these associations change with advancing age is a topic of interest in the field of human neuroscience. In this study, we identified the relationship between GABA levels and task-related modulations in GABAA receptor-mediated inhibition in the dominant (left) and non-dominant (right) sensorimotor (SM) cortices. GABA levels were measured using edited MRS and task-related GABAA receptor-mediated inhibition was measured using a short-interval intracortical inhibition (SICI) TMS protocol during the preparation and premotor period of a choice reaction time (CRT) task in 25 young (aged 18–33 years) and 25 older (aged 60–74 years) adults. Our results demonstrated that GABA levels in both SM voxels were lower in older adults as compared to younger adults; and higher SM GABA levels in the dominant as compared to the non-dominant SM voxel pointed to a lateralization effect, irrespective of age group. Furthermore, older adults showed decreased GABAA receptor-mediated inhibition in the preparation phase of the CRT task within the dominant primary motor cortex (M1), as compared to young adults. Finally, results from an exploratory correlation analysis pointed towards positive relationships between MRS-assessed GABA levels and TMS-derived task-related SICI measures. However, after correction for multiple comparisons none of the correlations remained significant.

Three consecutive nights of restricted sleep: effects of morning caffeine consumption on mood, reaction time and simulated driving performance

Introduction: Sleep is a fundamental biological requirement, essential for optimal health. Individuals unable to achieve adequate amounts of sleep may experience a range of negative behavioural and psychological consequences (e.g. increased daytime sleepiness, altered mood, reduced cognitive performance, driving impairment). Caffeinated products are often consumed as a popular countermeasure to reduce sleepiness, enhance mood, and improve cognitive functioning. However, the efficacy of caffeine to exert these effects after consecutive nights of restricted sleep is poorly understood, particularly in relation to performance on complex applied tasks (e.g. driving a motor vehicle). Therefore, the aim of this study was to investigate the effects of three consecutive nights of restricted sleep on subjective ratings of mood, cognitive function, and simulated driving performance and assess the ability of a morning dose of caffeine to attenuate any effects associated with sleep restriction. Materials and methods: Twenty healthy habitual caffeine consumers (11 females; age: 23.3±5.7 y; BMI: 22.3±3.5 kg·m-2; caffeine intake: 204±89 mg·day-1; Mean±SD) who had normal sleeping patterns (≥8 h sleep/night) participated in this double-blind, placebo-controlled, randomised study. Following one night of normal sleep (Day 0: ≥8 h time in bed (TIB)), participants underwent three consecutive nights of restricted sleep (Day 1, 2, 3: 5 h TIB). Participants received caffeine (200 mg; n=10) or placebo (n=10) capsules, together with a decaffeinated coffee and standardised breakfast each morning. All participants received caffeine (100 mg) capsules to consume in the afternoon of each trial day. On Day 0, 1 and 3, participants completed visual analog scales to measure subjective ratings of alertness, concentration and tiredness, before and 1 h after capsule administration. Cognitive function was examined 1 h after capsule administration using a computerised Choice Reaction Time (CRT) task. Response speed and accuracy were the outcome variables. Analysis of response speed was conducted using both traditional central tendency measures (comparing mean and variance) and ex-Gaussian distributional analysis. Driving performance was assessed using a 30 min simulated driving task. Lateral (standard deviation of lane position [SDLP] and total number of line crossings [LC]) and longitudinal (standard deviation of speed [SDSP]) measures of vehicular control were the outcome variables. Results: Alertness and concentration significantly decreased, and tiredness increased across the three days of sleep restriction (all p's< 0.001). Caffeine only marginally alleviated these effects. No differences were observed between treatments or across trial days for response speed and accuracy on the CRT task, irrespective of the analytical approach employed. Likewise, no significant differences were observed between groups or across trial days for lateral (SDLP, LC) and longitudinal (SDSP) measures of simulated driving performance. Conclusion: Overall, results from this study indicate that three consecutive days of sleep restriction may influence subjective ratings of alertness, concentration and tiredness, but does not appear to impact CRT or simulated driving performance. Caffeine may alleviate some of the negative subjective effects imposed by restricted sleep, but the efficacy of caffeine to attenuate performance changes in cognitive function and driving performance were unable to be observed in this study.