Bernhard Pastötter

Bio: Bernhard Pastötter is an academic researcher from University of Trier. The author has contributed to research in topics: Recall & Forgetting. The author has an hindex of 20, co-authored 45 publications receiving 1665 citations. Previous affiliations of Bernhard Pastötter include Stony Brook University & University of Regensburg.

The electrophysiological dynamics of interference during the stroop task

Abstract: If subjects are required to name the color of the word red printed in blue ink, interference between word meaning and ink color occurs, which slows down reaction time. This effect is well known as the Stroop effect. It is still an unresolved issue how the brain deals with interference in this type of task. To explore this question, an electroencephalogram (EEG) study was carried out. By analyzing several measures of EEG activity, two main findings emerged. First, the event-related potential (ERP) showed increased fronto-central negativity in a time window around 400 msec for incongruent items in contrast to congruent and neutral items. Source localization analysis revealed that a source in the anterior cingulate cortex (ACC) contributed most to the difference. Second, time-frequency analysis showed that theta oscillations (4--7 Hz) in the ACC increased linearly with increasing interference and that phase coupling between the ACC and the left prefrontal cortex was longer persistent for incongruent items compared to congruent and neutral items. These effects occurred at a time window around 600 msec. We conclude that interference between color naming and word meaning in the Stroop task manifests itself at around 400 msec and mainly activates the ACC. Thereafter, sustained phase coupling between the ACC and the prefrontal cortex occurs, which most likely reflects the engagement of cognitive control mechanisms.

Retrieval during learning facilitates subsequent memory encoding.

Abstract: In multiple-list learning, retrieval during learning has been suggested to improve recall of the single lists by enhancing list discrimination and, at test, reducing interference. Using electrophysiological, oscillatory measures of brain activity, we examined to what extent retrieval during learning facilitates list encoding. Subjects studied five lists of items in anticipation of a final cumulative recall test and did either a retrieval or a noretrieval task between study of the lists. Retrieval was from episodic memory (recall of the previous list), semantic memory (generation of exemplars from an unrelated category), or short-term memory (2-back task). Behaviorally, all three forms of retrieval enhanced recall of both previously and subsequently studied lists. Physiologically, the results showed an increase of alpha power (8-14 Hz) from List-1 to List-5 encoding when no retrieval activities were interpolated, but no such increase when any of the three retrieval activities occurred. Brain-behavior correlations showed that alpha-power dynamics from List-1 to List-5 encoding predicted subsequent recall performance. The results suggest that, without intermittent retrieval, encoding becomes ineffective across lists. In contrast, with intermittent retrieval, there is a reset of the encoding process for each single list that makes encoding of later lists as effective as encoding of early lists.

Retrieval practice enhances new learning: the forward effect of testing.

Abstract: In the last couple of years, there has been a dramatic increase in laboratory research examining the benefits of recall testing on long-term learning and retention. This work was largely on the backward effect of testing, which shows that retrieval practice on previously studied information, compared to restudy of the same material, renders the information more likely to be remembered in the future. Going beyond this prominent work, more recent laboratory research provided evidence that there is also a forward effect of testing, which shows that recall testing of previously studied information can enhance learning of subsequently presented new information. Here, we provide a review of research on this forward effect of testing. The review shows that the effect is a well replicated phenomenon in laboratory studies that has been observed for both veridical information and misinformation. In particular, the review demonstrates that the effect may be applied to educational and clinical settings, enhancing learning in students and reducing memory deficits in clinical populations. The review discusses current theoretical explanations of the forward effect of testing and provides suggestions for future research directions.

Beta-band oscillations--signalling the status quo?

Abstract: In this review, we consider the potential functional role of beta-band oscillations, which at present is not yet well understood. We discuss evidence from recent studies on top-down mechanisms involved in cognitive processing, on the motor system and on the pathophysiology of movement disorders that suggest a unifying hypothesis: beta-band activity seems related to the maintenance of the current sensorimotor or cognitive state. We hypothesize that beta oscillations and/or coupling in the beta-band are expressed more strongly if the maintenance of the status quo is intended or predicted, than if a change is expected. Moreover, we suggest that pathological enhancement of beta-band activity is likely to result in an abnormal persistence of the status quo and a deterioration of flexible behavioural and cognitive control.

Prelude to and resolution of an error: EEG phase synchrony reveals cognitive control dynamics during action monitoring

Abstract: Error-related activity in the medial prefrontal cortex (mPFC) is thought to work in conjunction with lateral prefrontal cortex (lPFC) as a part of an action-monitoring network, where errors signal the need for increased cognitive control. The neural mechanism by which this mPFC-lPFC interaction occurs remains unknown. We hypothesized that transient synchronous oscillations in the theta range reflect a mechanism by which these structures interact. To test this hypothesis, we extracted oscillatory phase and power from current-source-density-transformed electroencephalographic data recorded during a Flanker task. Theta power in the mPFC was diminished on the trial preceding an error and increased immediately after an error, consistent with predictions of an action-monitoring system. These power dynamics appeared to take place over a response-related background of oscillatory theta phase coherence. Theta phase synchronization between FCz (mPFC) and F5/6 (lPFC) sites was robustly increased during error trials. The degree of mPFC-lPFC oscillatory synchronization predicted the degree of mPFC power on error trials, and both of these dynamics predicted the degree of posterror reaction time slowing. Oscillatory dynamics in the theta band may in part underlie a mechanism of communication between networks involved in action monitoring and cognitive control.