Acute effects of continuous and high‐intensity interval exercise on executive function

The purpose of this study was to examine the acute effects of 20‐min of cycling exercise at varying exercise intensities on executive function performance. Participants (N = 107) completed a baseline measure of executive function (Stroop task [ST]) and a graded cardiovascular exercise test during Visit 1. During Visit 2, participants were randomized to groups and completed 20 min of activity involving: high‐intensity interval exercise, high‐, moderate‐ or very‐light intensity continuous exercise, or no‐exercise (control). The ST was performed immediately following the exercise/control manipulation and at 10‐min post‐manipulation. Results showed exercise positively influenced executive function immediately after exercising in all groups with the exception of the very‐light intensity exercise group, while all groups showed significant improvements at 10‐min post‐exercise. Findings also revealed a significant difference between the moderate‐intensity exercise group in comparison to the very‐light intensity exercise group immediately post‐exercise. Among the exercise stimuli investigated, results suggest moderate‐intensity exercise provides the greatest beneficial effects on executive function immediately following exercise. Future research should focus on mechanisms that would account for enhanced executive function performance following acute exercise and dose–response effects.     

The effect of acute treadmill walking on cognitive control and academic achievement in preadolescent children

The effect of an acute bout of moderate treadmill walking on behavioral and neuroelectric indexes of the cognitive control of attention and applied aspects of cognition involved in school-based academic performance were assessed. A within-subjects design included 20 preadolescent participants (age=9.5±0.5 years; eight female) to assess exercise-induced changes in performance during a modified flanker task and the Wide Range Achievement Test 3. The resting session consisted of cognitive testing followed by a cardiorespiratory fitness assessment to determine aerobic fitness. The exercise session consisted of 20 min of walking on a motor-driven treadmill at 60% of estimated maximum heart rate followed by cognitive testing once heart rate returned to within 10% of pre-exercise levels. Results indicated an improvement in response accuracy, larger P3 amplitude, and better performance on the academic achievement test following aerobic exercise relative to the resting session. Collectively, these findings indicate that single, acute bouts of moderately-intense aerobic exercise (i.e. walking) may improve the cognitive control of attention in preadolescent children, and further support the use of moderate acute exercise as a contributing factor for increasing attention and academic performance. These data suggest that single bouts of exercise affect specific underlying processes that support cognitive health and may be necessary for effective functioning across the lifespan.     

Quick benefits of interval training versus continuous training on bone: a dual‐energy X‐ray absorptiometry comparative study

To delay age‐related bone loss, physical activity is recommended during growth. However, it is unknown whether interval training is more efficient than continuous training to increase bone mass both quickly and to a greater extent. The aim of this study was to compare the effects of a 10‐week interval training regime with a 14‐week continuous training regime on bone mineral density (BMD). Forty‐four male Wistar rats (8 weeks old) were separated into four groups: control for 10 weeks (C10), control for 14 weeks (C14), moderate interval training for 10 weeks (IT) and moderate continuous training for 14 weeks (CT). Rats were exercised 1 h/day, 5 day/week. Body composition and BMD of the whole body and femur respectively were assessed by dual‐energy X‐ray absorptiometry at baseline and after training to determine raw gain and weight‐normalized BMD gain. Both trained groups had lower weight and fat mass gain when compared to controls. Both trained groups gained more BMD compared to controls when normalized to body weight. Using a 30% shorter training period, the IT group showed more than 20% higher whole body and femur BMD gains compared to the CT. Our data suggest that moderate IT was able to produce faster bone adaptations than moderate CT.     

EEG delta oscillations index inhibitory control of contextual novelty to both irrelevant distracters and relevant task‐switch cues

Delta oscillations contribute to the human P300 event‐related potential evoked by oddball targets, although it is unclear whether they index contextual novelty (event oddballness, novelty P3, nP3), or target‐related processes (event targetness, target P3b). To examine this question, the electroencephalogram (EEG) was recorded during a cued task‐switching version of the Wisconsin card‐sorting test. Each target card was announced by a tone cueing either to switch or repeat the task. Novel sound distracters were interspersed among trials. Time‐frequency EEG analyses revealed bursts of delta (2–4 Hz) power associated with enhanced nP3 amplitudes to both task‐switch cues and novel distracters—but no association with target P3b. These findings indicate that the P300‐delta response indexes contextual novelty regardless of whether novelty emanates from endogenous (new task rules) or exogenous (novel distracters) sources of information.     

Uniqueness of interval and continuous training at the same maintained exercise intensity

Summary The present study sought to evaluate the inconsistencies previously observed regarding the predominance of continuous or interval training for improving fitness. The experimental design initially equated and subsequently maintained the same relative exercise intensity by both groups throughout the program. Twelve subjects were equally divided into continuous (CT, exercise at 50% maximal work) or interval (IT, 30 s work, 30 s rest at 100% maximal work) training groups that cycled 30 min day^–1, 3 days week^–1, for 8 weeks. Following training, aerobic power (VO_2max), exercising work rates, and peak power output were all higher (9–16%) after IT than after CT (5–7%). Vastus lateralis muscle citrate synthase activity increased 25% after CT but not after IT. A consistent increase in adenylate kinase activity (25%) was observed only after IT. During continuous cycling testing the CT group had reduced blood lactate (1a_b) levels and respiratory quotient at both the same absolute and relative (70% VO_2max) work rates after training, while the IT group displayed similar changes only at the same absolute work rates. By contrast, both groups responded similarly during intermittent cycling testing with lower 1a_b concentrations seen only at absolute work rates. These results show that, of the two types of training programs currently employed, IT produces higher increases in VO_2max and in maximal exercise capacity. Nevertheless, CT is more effective at increasing muscle oxidative capacity and delaying the accumulation of 1a_b during continuous exercise.     

Cardiorespiratory fitness and acute aerobic exercise effects on neuroelectric and behavioral measures of action monitoring

Cardiorespiratory fitness and acute aerobic exercise effects on cognitive function were assessed for 28 higher- and lower-fit adults during a flanker task by comparing behavioral and neuroelectric indices of action monitoring. The error-related negativity, error positivity, and N2 components, as well as behavioral measures of response speed, accuracy, and post-error slowing were measured following a 30-minute acute bout of treadmill exercise or following 30-minutes of rest. A graded maximal exercise test was used to measure cardiorespiratory fitness by assessing maximal oxygen uptake. Results indicated that higher-fit adults exhibited reduced error-related negativity amplitude, increased error positivity amplitude, and increased post-error response slowing compared with lower-fit adults. However, acute exercise was not related to any of the dependent measures. These findings suggest that cardiorespiratory fitness, but not acute aerobic exercise, may be beneficial to behavioral and neuroelectric indices of action monitoring following errors of commission by increasing top-down attentional control.     

How inappropriate high‐pass filters can produce artifactual effects and incorrect conclusions in ERP studies of language and cognition

Although it is widely known that high‐pass filters can reduce the amplitude of slow ERP components, these filters can also introduce artifactual peaks that lead to incorrect conclusions. To demonstrate this and provide evidence about optimal filter settings, we recorded ERPs in a typical language processing paradigm involving syntactic and semantic violations. Unfiltered results showed standard N400 and P600 effects in the semantic and syntactic violation conditions, respectively. However, high‐pass filters with cutoffs at 0.3 Hz and above produced artifactual effects of opposite polarity before the true effect. That is, excessive high‐pass filtering introduced a significant N400 effect preceding the P600 in the syntactic condition, and a significant P2 effect preceding the N400 in the semantic condition. Thus, inappropriate use of high‐pass filters can lead to false conclusions about which components are influenced by a given manipulation. The present results also lead to practical recommendations for high‐pass filter settings that maximize statistical power while minimizing filtering artifacts.     

Detection of deception: Event‐related potential markers of attention and cognitive control during intentional false responses

Successful deception requires the coordination of multiple mental processes, such as attention, conflict monitoring, and the regulation of emotion. We employed a simple classification task, assessing ERPs to further investigate the attentional and cognitive control components of (instructed) deception. In Experiment 1, 20 participants repeatedly categorized visually presented names of five animals and five plants. Prior to the experiment, however, each participant covertly selected one animal and one plant for deliberate misclassification. For these critical items, we observed significantly increased response times (RTs), error rates, and amplitudes of three ERP components: anterior P3a indicating the processing of task relevance, medial‐frontal negativity reflecting conflict monitoring, and posterior P3b indicating sustained visual attention. In a blind identification of the individual critical words based on a priori defined criteria, an algorithm using two behavioral and two ERP measures combined showed a sensitivity of 0.73 and a specificity of 0.95, thus performing far above chance (0.2/0.2). Experiment 2 used five clothing and five furniture names and successfully replicated the findings of Experiment 1 in 25 new participants. For detection of the critical words, the algorithm from Experiment 1 was reused with only slight adjustments of the ERP time windows. This resulted in a very high detection performance (sensitivity 0.88, specificity 0.94) and significantly outperformed an algorithm based on RT alone. Thus, at least under controlled laboratory conditions, a highly accurate detection of instructed lies via the attentional and cognitive control components is feasible, and benefits strongly from combined behavioral and ERP measures.     

Testing food‐related inhibitory control to high‐ and low‐calorie food stimuli: Electrophysiological responses to high‐calorie food stimuli predict calorie and carbohydrate intake

Maintaining a healthy diet has important implications for physical and mental health. One factor that may influence diet and food consumption is inhibitory control—the ability to withhold a dominant response in order to correctly respond to environmental demands. We examined how N2 amplitude, an ERP that reflects inhibitory control processes, differed toward high‐ and low‐calorie food stimuli and related to food intake. A total of 159 participants (81 female; M age = 23.5 years; SD = 7.6) completed two food‐based go/no‐go tasks (one with high‐calorie and one with low‐calorie food pictures as no‐go stimuli) while N2 amplitude was recorded. Participants recorded food intake using the Automated Self‐Administered 24‐hour Dietary Recall system. Inhibiting responses toward high‐calorie stimuli elicited a larger (i.e., more negative) no‐go N2 amplitude; inhibiting responses toward low‐calorie stimuli elicited a smaller no‐go N2 amplitude. Participants were more accurate during the high‐calorie than low‐calorie task, but took longer to respond on go trials toward high‐calorie rather than low‐calorie stimuli. When controlling for age, gender, and BMI, larger high‐calorie N2 difference amplitude predicted lower caloric intake (β = 0.17); low‐calorie N2 difference amplitude was not related to caloric intake (β = −0.03). Exploratory analyses revealed larger high‐calorie N2 difference amplitude predicted carbohydrate intake (β = 0.22), but not protein (β = 0.08) or fat (β = 0.11) intake. Results suggest that withholding responses from high‐calorie foods requires increased recruitment of inhibitory control processes, which may be necessary to regulate food consumption, particularly for foods high in calories and carbohydrates.     

Effects of high‐intensity intermittent swimming on PGC‐1α protein expression in rat skeletal muscle

Aim: The aim of the present investigation was to elucidate the effects of exercise intensity on exercise‐induced expression of peroxisome proliferator‐activated receptor γ coactivator‐1α (PGC‐1α) protein in rat skeletal muscle. Methods: We measured PGC‐1α content in the skeletal muscles of male Sprague–Dawley rats (age: 5–6 weeks old; body weight: 150–170 g) after a single session of high‐intensity intermittent exercise (HIE) or low‐intensity prolonged swimming exercise (LIE). During HIE, the rats swam for fourteen 20‐s periods carrying a weight (14% of body weight), and the periods of swimming were separated by a 10‐s pause. LIE rats swam with no load for 6 h in two 3‐h sessions, separated by 45 min of rest. Results: After HIE, the PGC‐1α protein content in rat epitrochlearis muscle had increased by 126, 140 and 126% at 2, 6 and 18 h, respectively, compared with that of the age‐matched sedentary control rats’ muscle. Immediately, 6 and 18‐h after LIE, the PGC‐1α protein content in the muscle was significantly elevated by 84, 95 and 67% respectively. The PGC‐1α protein content observed 6 h after HIE tended to be higher than that observed after LIE. However, there was no statistically significant difference between the two values (P = 0.12). Conclusion: The present investigation suggests that irrespective of the intensity of the exercise, PGC‐1α protein content in rat skeletal muscle increases to a comparable level when stimuli induced by different protocols are saturated. Further, HIE is a potent stimulus for enhancing the expression of PGC‐1αprotein, which may induce mitochondrial biogenesis in exercise‐activated skeletal muscle.     

The distribution of rest periods affects performance and adaptations of energy metabolism induced by high‐intensity training in human muscle

The effect of the distribution of rest periods on the efficacy of interval sprint training is analysed. Ten male subjects, divided at random into two groups, performed distinct incremental sprint training protocols, in which the muscle load was the same (14 sessions), but the distribution of rest periods was varied. The `short programme' group (SP) trained every day for 2 weeks, while the `long programme' group (LP) trained over a 6‐week period with a 2‐day rest period following each training session. The volunteers performed a 30‐s supramaximal cycling test on a cycle ergometer before and after training. Muscle biopsies were obtained from the vastus lateralis before and after each test to examine metabolites and enzyme activities. Both training programmes led to a marked increase (all significant, P < 0.05) in enzymatic activities related to glycolysis (phosphofructokinase – SP 107%, LP 68% and aldolase – SP 46%, LP 28%) and aerobic metabolism (citrate synthase – SP 38%, LP 28.4% and 3‐hydroxyacyl‐CoA dehydrogenase – SP 60%, LP 38.7%). However, the activity of creatine kinase (44%), pyruvate kinase (35%) and lactate dehydrogenase (45%) rose significantly (P < 0.05) only in SP. At the end of the training programme, SP had suffered a significant decrease in anaerobic ATP consumption per gram muscle (P < 0.05) and glycogen degradation (P < 0.05) during the post‐training test, and failed to improve performance. In contrast, LP showed a marked improvement in performance (P < 0.05) although without a significant increase in anaerobic ATP consumption, glycolysis or glycogenolysis rate. These results indicate that high‐intensity cycling training in 14 sessions improves enzyme activities of anaerobic and aerobic metabolism. These changes are affected by the distribution of rest periods, hence shorter rest periods produce larger increase in pyruvate kinase, creatine kinase and lactate dehydrogenase. However, performance did not improve in a short training programme that did not include days for recovery, which suggests that muscle fibres suffer fatigue or injury.     

The effects of response sharing and stimulus presentation frequency on event‐related potentials in an auditory oddball paradigm

An experimental model for investigating the processes involved in reacting to unpredictable events is the oddball paradigm. We investigated how the commonality or independence of response options (i.e., many‐to‐one vs. one‐to‐one stimulus‐response mappings) influences processing in an auditory oddball paradigm. Participants performed a discrimination task with two one‐to‐one and one two‐to‐one mappings. The pattern of conflict‐ and oddball‐related N2 event‐related potentials suggest that information that would allow correct responding is represented at the latency of the N2. Integration of this information takes place only by the latency of P3b, and longer reaction times to rare stimuli are probably due to processes preventing the utilization of this information. We also suggest that, in the given task context, conflict‐related N2 may reflect the number of alternative stimuli leading to alternative response options.     

Electrophysiological correlates of prediction formation in anticipation of reward‐ and punishment‐related feedback signals

Feedback processing during decision making involves comparing anticipated and actual outcome. Although effects on ERPs of valence, magnitude, expectancy, and context during feedback processing have been extensively investigated, the electrophysiological processes underlying prediction formation in anticipation of feedback signals have received little attention. The aim of the present study was to explore these processes of prediction formation and their influence on subsequent feedback signals. Twenty healthy, right‐handed volunteers performed a forced‐choice task in which they had to indicate which of two presented objects was more expensive. After the volunteer's choice, an expert cue, which was accurate in 80% of trials, was presented to manipulate prediction formation about future reward and punishment. ERPs were recorded during presentation of the expert cue and during feedback. Results revealed that prediction formation of future rewards and punishments is accompanied by differences in the P2 component and a subsequent delay period. During feedback processing, the prediction‐related P2 was associated with the processing of valence reflected in the feedback‐related P2. Furthermore, the prediction‐related difference in the delay period was associated with error processing in feedback‐related medial frontal negativity. These findings suggest that prediction signals prior to feedback contain information about whether a prediction is correct or wrong (expectancy) and if the outcome will be a reward or punishment (valence).     

The effects of aerobic interval training on the left ventricular morphology and function of VLCAD-deficient mice

This study examined the effect of aerobic interval training on cardiac adaptations in VLCAD-deficient mice and determined the effects of the deficiency on the morphology and function of the left ventricle among 53 knockout homozygous VLCAD−/−, 28 heterozygous VLCAD±, and 39 controls VLCAD+/+ male mice (129 SvJ/C57BL6). Echocardiographic images were used to determine the left ventricular (LV) wall thicknesses, during systole and diastole, acquired at a depth setting of 20 mm. Cardiac hypertrophy (as evidenced by increased wall thickness, and decreased left ventricular dimension in diastole and systole) appeared to be a major finding in the VLCAD−/− mouse with, however, normal %FS. The trained mice from all three genotypes exhibited lower body weight compared with their controls. The echocardiographic data of this study demonstrated structural but not functional differences among the three genotypes. This study demonstrated that VLCAD± deficient mice handled interval training similarly to the non-deficient mice. Four VLCAD−/− deficient mice died unexpectedly on the treadmill during the early stages of training. The VLCAD−/− deficient mice that survived adapted to the aerobic interval training similarly to the non-deficient mice. It is unclear whether aerobic interval training is an appropriate training tool for the VLCAD-deficient humans.     

The independency of the Bereitschaftspotential from previous stimulus‐locked P3 in visuomotor response tasks

The Bereitschaftspotential (BP) and the P3 are well‐known ERPs usually observed during self‐paced and externally triggered tasks. Recently, the BP was also detected in externally triggered tasks before stimulus onset. However, doubts have been raised about the authenticity of the BP in these tasks due to possible overlaps with the previous trial P3 (hereinafter s‐1 P3). Here, we aim to test the authenticity of the BP in externally triggered tasks by comparing ERPs obtained during two visuomotor response tasks with different interstimulus intervals (ISIs) allowing (short‐ISI; 1,000–2,000 ms) or not (long‐ISI; 2,000–4,000 ms) P3‐BP overlaps. In line with previous research, we hypothesize that BP and the s‐1 P3 contribute independently to the scalp‐detected activities during these tasks. ERPs were recorded from 14 healthy participants during the short‐ISI and long‐ISI visuomotor response tasks. Amplitudes and latencies of pre‐ (BP and pN) and poststimulus ERP components (P1, pN1, pP1, N1, pP2, dpP2, N2, P3) were compared between conditions. No effect of ISI was found on the amplitude of any pre‐ and poststimulus components. In contrast, longer ISI is associated with earlier onsets of the BP and pN components. In visuomotor response tasks, the BP is independent from the P3 elicited by the previous trial (s‐1 P3), even using relatively short ISI. Since the different ISIs did not affect the amplitude of the BP and the P3 components, we conclude that also a short ISI can be adopted safely and conveniently to keep a reasonable duration of the overall experiment.     

Teasing apart the anticipatory and consummatory processing of monetary incentives: An event‐related potential study of reward dynamics

The monetary incentive delay (MID) task has been widely used in fMRI studies to investigate the neural networks involved in anticipatory and consummatory reward processing. Previous efforts to adapt the MID task for use with ERPs, however, have had limited success. Here, we sought to further decompose reward dynamics using a comprehensive set of anticipatory (cue‐N2, cue‐P3, contingent negative variation [CNV]) and consummatory ERPs (feedback negativity [FN], feedback P3 [fb‐P3]). ERP data was recorded during adapted versions of the MID task across two experiments. Unlike previous studies, monetary incentive cues modulated the cue‐N2, cue‐P3, and CNV; however, cue‐related ERPs and the CNV were uncorrelated with one another, indicating distinct anticipatory subprocesses. With regard to consummatory processing, FN amplitude primarily tracked outcome valence (reward vs. nonreward), whereas fb‐P3 amplitude primarily tracked outcome salience (uncertain vs. certain). Independent modulation of the cue‐P3 and fb‐P3 was observed, indicating that these two P3 responses may uniquely capture the allocation of attention during anticipatory and consummatory reward processing, respectively. Overall, across two samples, consistent evidence of both anticipatory and consummatory ERP activity was observed on an adapted version of the MID paradigm, demonstrating for the first time how these ERP components may be integrated with one another to more fully characterize the time course of reward processing. This ERP‐MID paradigm is well suited to parsing reward dynamics, and can be applied to both healthy and clinical populations.     

The effects of inhibitory control training on alcohol consumption,implicit alcohol-related cognitions and brain electrical activity

This study aimed to replicate findings that alcohol consumption and positive implicit beer-related cognitions can be reduced using inhibitory control (IC) training, with the addition of an active training control. Frontal EEG asymmetry, an objective psychophysiological index of approach motivation, was used as a dependent measure to examine training outcomes. Participants were randomly assigned to one of two IC training conditions (Beer NoGo or Beer Go) or a Brief Alcohol Intervention (BAI) (i.e. the active training control). The IC training tasks consistently paired a stimulus that required a response with images of water (Beer NoGo) or images of beer (Beer Go). Alcohol consumption and implicit beer-related cognitions were measured at pre-training, post-training and at one week follow-up. Frontal EEG asymmetry was recorded during a passive image viewing task that presented neutral, healthy, and beer stimuli — at pre-training, post-training and follow-up. Participants in the Beer NoGo and BAI conditions consumed less beer in a taste test immediately after training than Beer Go participants, suggesting that IC training may be as effective as the already established BAI. The taste test findings were in line with the frontal EEG asymmetry data, which indicated that approach motivation for beer stimuli was altered in the expected directions. However, the positive correlation between post-training frontal EEG asymmetry data and taste test consumption was not significant. While there were no significant changes in implicit beer-related cognitions following training, a trending positive relationship between implicit beer-related cognitions at post-training and taste test consumption was reported. Further exploration addressing the limitations of the current study is required in order to clarify the implications of these findings.     

Influence of acute stress on response inhibition in healthy men: An ERP study

The current study investigated the influence of acute stress and the resulting cortisol increase on response inhibition and its underlying cortical processes, using EEG. Before and after an acute stressor or a control condition, 39 healthy men performed a go/no‐go task while ERPs (N2, P3), reaction times, errors, and salivary cortisol were measured. Acute stress impaired neither accuracy nor reaction times, but differentially affected the neural correlates of response inhibition; namely, stress led to enhanced amplitudes of the N2 difference waves (N2d, no‐go minus go), indicating enhanced response inhibition and conflict monitoring. Moreover, participants responding to the stressor with an acute substantial rise in cortisol (high cortisol responders) showed reduced amplitudes of the P3 of the difference waves (P3d, no‐go minus go) after the stressor, indicating an impaired evaluation and finalization of the inhibitory process. Our findings indicate that stress leads to a reallocation of cognitive resources to the neural subprocesses of inhibitory control, strengthening premotor response inhibition and the detection of response conflict, while concurrently diminishing the subsequent finalization process within the stream of processing.