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Accessed 27 Apr Download references. Department of Intervention Research in Exercise Training, German Sport University Cologne, Cologne, Germany. Faculty of Education and Health Sciences, University of Limerick, Limerick, Ireland.

You can also search for this author in PubMed Google Scholar. Correspondence to Kechi Anyadike-Danes. All authors declare that they have no conflicts of interest that are directly relevant to the content of this article.

All data are stored on institutional servers of the corresponding author and are available in the supplementary file. The study was designed and developed by KAD.

Data was collected, analysed and prepared for the first draft by KAD. The manuscript was critically revised by JK, and LD. All authors approved of the final version to be published and agree to be accountable for any part of the work.

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Reprints and permissions. Anyadike-Danes, K. Participants were included, if they had completed more than 10 training sessions. The mean number of completed sessions was 15 SD: 1. Each training session consisted of a flanker task training block and a n-back task training block, each lasting approximately 10—15 minutes depending on individual response times and difficulty level adding up to a total duration of 20—30 minutes.

Task order was alternated every day. In the n-back task, numbers were presented consecutively on the screen. Targets were defined as reoccurrence of a number previously presented n trials before i. one trial before in the 1-back condition, two trials before in the 2-back condition, etc.

In the flanker tasks compatible target and flanker arrows pointed in the same direction and incompatible target and flanker arrows pointed in opposite directions were presented and participants were instructed to respond as quickly and accurately as possible to the direction of the central arrow by pressing the left or right arrow key.

On each difficulty level, three different cognitive load conditions were presented. Variability of cognitive load conditions within each difficulty level was implemented, since deficits in executive functions are often not only characterized by reduced overall performance levels, but also by reduced cognitive flexibility.

By applying variations within each difficulty level, we aimed to enhance flexible adaptation to environmental demands. Difficulty was increased in a step-wise fashion by a combination of maximal cognitive load and time pressure. Time pressure was increased by shortening the inter-stimulus-interval by ms.

Difficulty levels were adapted independently for the two tasks with twelve levels within each task. If participants reached the maximum difficulty level before completing the training procedure, difficulty stayed on maximum for the remaining training sessions.

Each block comprised trials. Each block comprised 24 trials, containing six targets. Block order was pseudo-randomly varied within each session.

Interstimulusinterval ISI is reported in ms. Participants completed their training on their home computers. At the end of each session, a logfile containing response times, hit rates and difficulty level for both tasks was automatically transferred to the study coordinators. If the participants failed to complete at least five trainings sessions within one week, they were contacted by e-mail by the study coordinators and reminded to train regularly.

Participants reached a mean difficulty level of 9 SD: 3. EEG and electroocculographic EOG activity were recorded continuously with 64 Ag-AgCl electrodes including Cz as recording reference.

Electrodes were mounted with an EasyCap electrode system Falk Minow Services, Munich, Germany based on an equidistant electrode position system. Additional electrodes were placed on five external locations: IO1, IO2, Nz, neck and cheek.

The electrode on the cheek served as ground. Electrode impedances were kept below 5 kΩ. The EEG was recorded with a sampling rate of Hz and a band pass filter of 0.

EEG data were processed with the Brain Vision Analyzer 2 Brain Products, Munich, Germany. Eye-movement artifacts were corrected using an automatic ocular correction independent component analysis.

Continuous EEG signals were filtered with a high-pass filter of 0. For N2 analysis, stimulus-locked epochs with a duration of ms including ms pre-stimulus interval were extracted.

The interval from ms to 0 ms prior to the stimulus served as a baseline. For CRN analysis, response-locked epochs with a duration of ms including ms pre-response interval were extracted.

The interval from ms to 0 ms prior to the response served as a baseline. Epochs containing artifacts exceeding ± μV in amplitude, voltage steps of more than 40 μV between consecutive data points or a minimal overall activity below 0.

Flanker stimulus-locked averages for the N2 analysis and response-locked averages for the CRN analysis included only correct trials and were computed separately for each participant, for each test session pre- and post-training , for compatible and incompatible trials, for each conflict frequency condition FC, FI and for each picture type neutral, negative.

Grand averages were filtered with a 15 Hz low-pass filter for visual presentation. Statistical analyses were conducted with SPSS Version Repeated-measurement analyses of variance ANOVA were used for statistical analyses of performance and ERP measures.

Correct response times were analyzed using a 2 x 2 x 2 x 2 ANOVA including the factors time pre-training, post-training , conflict frequency FC, FI , compatibility compatible, incompatible and picture type neutral, negative. Error response times and error rates in incompatible trials were analyzed using a 2 x 2 x 2 ANOVA including the factors time pre-training, post-training , conflict frequency FC, FI and picture type neutral, negative.

N2 and CRN amplitudes were analyzed using a 3 x 2 x 2 x 2 x 2 ANOVA with the factors electrode Fz, FCz, Cz , time pre-training, post-training , conflict frequency FC, FI , compatibility compatible, incompatible and picture type neutral, negative.

For all significant main effects or interactions, post-hoc comparisons were conducted using paired-samples t-tests. Error rates and response times are presented in Table 2 and in Fig 2. Bars represent standard errors. Error rates in incompatible trials were lower in the FI than in the FC block.

ERPs are depicted in Fig 3 and amplitude values are presented in Table 3. ERPs illustrating the proportion congruency effect are presented in the supplemental material S2 in S1 File.

Grand Averages of the N2 in incompatible upper panel and compatible trials middle panel with neutral and negative pictures in the FC and FI condition at pre- T1 and post-training T2 at electrode FCz.

The lower panel presents the CRN amplitude in each condition. The ANOVA yielded several effects involving the factor picture type. Additionally, the reduction after negative pictures was stronger after training than before training. ERPs are depicted in Fig 4 and amplitude values are presented in Table 3.

ERPs illustrating the proportion congruency effect are presented in S1 Fig in S1 File. The lower panel presents the N2 amplitude in each condition. In the present study, we investigated near-transfer effects of an adaptive executive control training to two domains, namely adaptation to task difficulty and inhibition of emotional interference.

Several psychological disorders are associated with alterations in interference control. As these alterations may be further characterized by reduced adaptation to task requirements and impaired inhibition of emotional interference, executive training procedures targeting these domains might be especially promising for clinical application.

We applied an adaptive three-week executive control training, that targets interference control flanker task and working memory components n-back task and has previously been shown to successfully enhance interference control on the behavioral and ERP level [ 76 ].

At baseline, a typical proportion congruency effect was observed for error rates, which were lower in the FI than in the FC condition, indicating increased interference control in the FI condition.

Furthermore, a typical proportion congruency effect was observed for the CRN, with decreased amplitudes of the incompatible CRN and increased amplitudes of the compatible CRN in the FI condition. However, in contrast to previous studies, the modulation of response times and N2 amplitudes was more pronounced for compatible than for incompatible trials.

For the N2 in incompatible trials, an unusual pattern of higher N2 amplitudes in the FC than in the FI condition was observed. Taken together, the pattern of proportion congruency effect was less consistent than in previous studies. It appears plausible, that this might be related to the unpredictable picture presentation.

As picture valence was randomized across trials, participants could not anticipate which picture type would be presented on each trial. Unpredictable threat has high evolutionary relevance and leads to increased defensive activation, as indexed by increased fear-potentiated startle [ 82 — 84 ], and hypervigilance, as indexed by increased recruitment of attention networks [ 85 — 89 ].

Thus, the unpredictable threat induced by the random picture presentation may have resulted in altered activation of attentional processes, thereby obscuring typical proportion congruency adaptations.

Furthermore, the current results illustrate that although the proportion congruency effect usually creates a complementary modulation of the N2 and CRN [ 10 , 11 , 16 ], and these opposing modulations have previously been found to be correlated on the inter- and intra-individual level [ 10 ], these modulations are not necessarily directly coupled and can also occur independently of each other as in the present study.

Regarding the primary training effect, results confirmed that the adaptive executive control training resulted in increased interference control as evident in reduced response times and reduced error rates after training. These behavioral effects were accompanied by increased N2 amplitudes and decreased CRN amplitudes, reflecting increased stimulus-locked interference control and decreased response-locked strategy adaptation.

As previously described, these effects were specific to incompatible trials [ 76 ]. Please note that as the samples were overlapping and the modified flanker task contains elements of the standard flanker task analyzed in our previous report, this should not be valued as an independent replication.

Still, these results illustrate, that the training successfully enhanced the targeted executive control functions. Contrary to our expectation, the training did not produce near-transfer effects on adaptation to task difficulty as reflected in the proportion congruency effect.

Thus, participants were required to continuously adapt their behavior to changing task requirements. This information was implemented to facilitate adaptation to task requirements by recruiting explicit, conscious adaptation mechanisms in addition to implicit mechanisms, thus possible strengthening training effects.

Nevertheless, significant training-related changes in difficulty adaptation were not observed, neither for the behavioral nor for the ERP level.

This lack of effect may be related to several factors. First of all, the current pilot study investigated a sample of healthy young adults without a diagnosis of psychological disorders.

Previous studies have demonstrated that this group usually shows fast, flexible and efficient adaptation to task requirements [ 9 — 11 , 16 , 18 — 23 ]. As the training was designed to alleviate adaptation deficits in clinical populations, the lack of modulation may be due to a ceiling effect in the healthy study sample.

Thus, the training may yield effects on difficulty adaptation in populations exhibiting pre-training deficits. Furthermore, the training incorporated explicit information about the upcoming difficulty before each block.

This information was not presented in the transfer task before and after training. Consequently, the training may predominantly have enhanced conscious difficulty adaptation strategies that, due to the lack of cues, could not be applied in the transfer task.

However, the training modulated the susceptibility to emotional interference on the ERP level. Specifically, the training changed the time-point at which task processing is affected by emotional interference. For both ERP components a significant modulation of the emotional interference effect by the factor time was observed.

For the CRN, emotional interference was stronger before training than after training. For the N2, the opposite pattern was observed. Here, emotional interference was stronger after training than before training.

Interestingly, this mirrors the main effect of the training on these two components: After training, the N2 was increased, while the CRN was reduced. As both components share a similar topography it has been argued that they are generated by the same brain region and reflect similar functional processes [ 8 , 10 , 11 , 14 — 17 , 26 ].

In this line of thought, complementary modulation of these two ERP components may reflect a shift in the primary time-point of control application. Improved task processing after training appears to be characterized by enhanced stimulus-locked application of interference control, as reflected in the N2, and reduced response monitoring and reactive trial-to-trial strategy adaptation, as reflected in the CRN.

The present data indicates, that emotional interference manifests in the predominant time-window of control application, which is shifted after training. Altered cognitive control in internalizing disorders mainly affects response-locked processes i.

the CRN and ERN and appears to be strongly linked to emotional processes such as subjective error salience and threat sensitivity [ 90 ]. Thus, the training procedure may be applied to target these alterations by reducing both the overall magnitude of and the susceptibility to emotional influence of post-response control application.

It is important to note that, contradicting our expectations, the training did not result in a general reduction of emotional interference on the behavioral level. An increased error rate after negative pictures was observed before training, but this effect was not significantly modulated by the training.

Still, the numerical values indicate a reduction of the emotional interference effect in the FC condition after training Δ negative-neutral before training: 4. This is in accordance with the dual mechanisms of control model [ 68 ] that postulates that interference is stronger under conditions with low executive control and indicates that after training interference control is generally increased irrespective of conflict frequency condition.

Additionally, in accordance with previous studies in healthy participants, emotional interference effects at baseline were rather smaller [ 16 ]. Thus, possible training effects might again be obscured by ceiling effects and should be further explored in clinical population exhibiting stronger baseline deficits.

Some limitations need to be considered. The current design did not comprise a control condition, thus the observed changes may be partly caused by unspecific mechanisms. However, in a previous study [ 76 ], the adaptive training program was shown to create superior effects on interference control compared to a control condition non-adaptive training and the current study investigated the transfer effects of the previously established procedure.

Due to practical reasons, both transfer effects difficulty adaptation, emotional interference were assessed in a single task. As the current data indicates that picture presentation may have reduced difficulty adaptation, transfer effects should preferably be assessed separately in future studies.

Furthermore, the current design did not include trials without pictures. Thus, the interference effect created by general picture presentation irrespective of valence cannot be quantified. Finally, as participants were recruited from psychology students, they were comparably young and the majority was female.

Thus, the generalizability of the findings may be limited. Since women have been shown to react more strongly to IAPS pictures [ 91 — 93 ], the effects might be smaller in male participants. The current study replicates in a partially overlapping sample that a three-week executive control training increases interference control as reflected in decreased response times and error rates, decreased CRN and increased N2 amplitudes in incompatible trials.

Near transfer effects to difficulty adaptation were not observed, but might have been limited by a ceiling effect in the healthy study sample. The training modulated the time-point of emotional interference: Before training, emotional interference mainly affected response-locked control processes CRN , after training it manifested on stimulus-locked interference control N2.

These effects illustrate, that improved behavioral performance after training is accompanied by a change in processing mode in which response-locked processes lose importance in favor of stimulus-locked processes.

As alterations of cognitive control in internalizing disorders mainly manifest in an increased magnitude of and increased susceptibility to emotional processes of response-locked control CRN, ERN , the current training procedure may be helpful in alleviating these deficits by shifting the primary time-point of control application to the stimulus-locked time-window.

The authors thank Rainer Kniesche, Thomas Pinkpank and Ulrike Bunzenthal for technical assistance. The authors also thank Marie Bartossek, Franziska Jüres, Jacqueline Kimm, Marlene Reissing, Janika Wolter-Weging and Maria Zadorozhnaya for assistance in data collection.

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Abstract Intact executive functions are characterized by flexible adaptation to task requirements, while these effects are reduced in internalizing disorders. Introduction Executive functions are essential to intentional behavior and cognitive control. Methods 2.

Download: PPT. Fig 1. Experimental design of the flanker task: Flanker stimuli were presented superimposed on neutral or negative IAPS pictures or OCD-related pictures. Table 1. Difficulty levels in the flanker and nback task in the adaptive training procedure.

Results 3. Fig 2. Behavioral data error rates in incompatible trials, response times in compatible and incompatible trials in trials with negative and neutral pictures in the FC and FI condition before and after training.

Table 2. Response times for correct responses in compatible and incompatible trials and error rates and error response times in incompatible trials after neutral and negative pictures in the FC and FI condition before and after training.

Table 3. Amplitudes in μV of the N2 and CRN in compatible and incompatible trials after neutral and negative pictures in the FC and FI condition before and after training at electrode Fz, FCz and Cz.

Fig 4. Grand Averages of the CRN in incompatible upper panel and compatible trials middle panel with neutral and negative pictures in the FC and FI condition at pre- T1 and post-training T2 at electrode FCz.

Discussion In the present study, we investigated near-transfer effects of an adaptive executive control training to two domains, namely adaptation to task difficulty and inhibition of emotional interference. Supporting information. S1 File.

s DOCX. Acknowledgments Author notes The authors thank Rainer Kniesche, Thomas Pinkpank and Ulrike Bunzenthal for technical assistance. References 1. Diamond A. Executive functions. Annu Rev Psychol. Miyake A, Friedman NP.

The Nature and Organization of Individual Differences in Executive Functions: Four General Conclusions. Curr Dir Psychol Sci. Malloy-Diniz LF, Miranda DM, Grassi-Oliveira R. Editorial: Executive Functions in Psychiatric Disorders. Frontiers in Psychology. Miyake A, Friedman NP, Emerson MJ, Witzki AH, Howerter A, Wager TD.

The unity and diversity of executive functions and their contributions to complex "Frontal Lobe" tasks: a latent variable analysis. Cogn Psychol. Baddeley A. Working memory. Conversely, a training load that stimulates adaptations for a more advanced athlete will be excessive when applied to novice athletes and result in a significant increase in injury risk and occurrences of overtraining responses.

Ultimately, the primary objective of the training process is to systematically and progressively implement overload as part of the training process.

This process is often referred to as progressive overload , in which the athlete is exposed to higher training loads to overcome the threshold of adaptation figure 1.

To be effective, these loads need to be implemented into the training plan in a progressive manner because significant increases or spikes in training have been associated with increased injury risk 57, 58, , For example, Gabbett et al. There are, however, scenarios in which a sharp spike in training, or what is termed overreaching , is warranted; if programmed correctly, these increased periods of training can be powerful tools for inducing adaptation and performance gains in subsequent training periods Based on these data, it is recommended that variations in training loads be carefully planned to minimize the risk of injuries associated with significant spikes in training loads.

As athletes become more trained, they require greater training stimuli to continue to adapt and elevate their performance capacity closer to their genetic ceilings.

Therefore, the athlete needs to be exposed to progressively increasing training loads in order to continue to stimulate adaptation and elevate performance 39, , This is most evident in the progression of the athlete through their long-term athlete development plan 50, , , in which training focus and loads are varied to continue to stimulate adaptive responses and performance gains.

For example, athletes who have the alpha-actinin-3 ACTN3 R allele exhibit an enhanced response to resistance training, whereas those with the ACTN3 XX genotype display a reduced responsiveness to resistance training Previous Next.

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