Anodal tDCS of the left inferior parietal cortex enhances memory for correct information without affecting recall of misinformation.

False memories during testimony are an enormous challenge for criminal trials. Exposure to post-event misinformation can lead to inadvertent creation of false memories, known as the misinformation effect. We investigated anodal transcranial direct current stimulation (tDCS) on the left inferior parietal lobe (IPL) during recall testing to enhance accurate recall while addressing the misinformation effect. Participants (N = 60) watched a television series depicting a fictional terrorist attack, then received an audio recording with misinformation, consistent information, and control information. During cued recall testing, participants received anodal or sham tDCS. Results revealed a robust misinformation effect in both groups, with participants falsely recalling on average 26.6% of the misinformed items. Bayesian statistics indicated substantial evidence in favour of the null hypothesis that there was no difference between groups in the misinformation effect. Regarding correct recall however, the anodal group exhibited significantly improved recall for items from the original video. Together, these results demonstrate that anodal tDCS of the left IPL enhances correct recall of the episodes from the original event without affecting false recall of misinformation. The findings support the IPL's role in recollection and source attribution of episodic memories.

Prestimulus alpha power signals attention to retrieval.

The human brain is in distinct processing modes at different times. Specifically, a distinction can be made between encoding and retrieval modes, which refer to the brain's state when it is storing new information or searching for old information, respectively. Recent research proposed the idea of a "ready-to-encode" mode, which describes a prestimulus effect in brain activity that signals (external) attention to encoding and predicts subsequent memory performance. Whether there is also a corresponding "ready-to-retrieve" mode in human brain activity is currently unclear. In this study, we examined whether prestimulus oscillations can be linked to (internal) attention to retrieval. We show that task cues to prepare for retrieval (or testing) in comparison with restudy of previously studied vocabulary word pairs led to a significant decrease of prestimulus alpha power just before the onset of word stimuli. Beamformer analysis localized this effect in the right secondary visual cortex (Brodmann area 18). Correlation analysis showed that the task cue-induced, prestimulus alpha power effect is positively related to stimulus-induced alpha/beta power, which in turn predicted participants' memory performance. The results are consistent with the idea that prestimulus alpha power signals internal attention to retrieval, which promotes the elaborative processing of episodic memories. Future research on brain-computer interfaces may find the findings interesting regarding the potential of using online measures of fluctuating alpha oscillations to trigger the presentation and sequencing of restudy and testing trials, ultimately enhancing instructional learning strategies.

Perception-Action Integration Is Altered in Functional Movement Disorders.

BACKGROUND: Although functional neurological movement disorders (FMD) are characterized by motor symptoms, sensory processing has also been shown to be disturbed. However, how the integration of perception and motor processes, essential for the control of goal-directed behavior, is altered in patients with FMD is less clear. A detailed investigation of these processes is crucial to foster a better understanding of the pathophysiology of FMD and can systematically be achieved in the framework of the theory of event coding (TEC). OBJECTIVE: The aim was to investigate perception-action integration processes on a behavioral and neurophysiological level in patients with FMD. METHODS: A total of 21 patients and 21 controls were investigated with a TEC-related task, including concomitant electroencephalogram (EEG) recording. We focused on EEG correlates established to reflect perception-action integration processes. Temporal decomposition allowed to distinguish between EEG codes reflecting sensory (S-cluster), motor (R-cluster), and integrated sensory-motor processing (C-cluster). We also applied source localization analyses. RESULTS: Behaviorally, patients revealed stronger binding between perception and action, as evidenced by difficulties in reconfiguring previously established stimulus-response associations. Such hyperbinding was paralleled by a modulation of neuronal activity clusters, including reduced C-cluster modulations of the inferior parietal cortex and altered R-cluster modulations in the inferior frontal gyrus. Correlations of these modulations with symptom severity were also evident. CONCLUSIONS: Our study shows that FMD is characterized by altered integration of sensory information with motor processes. Relations between clinical severity and both behavioral performance and neurophysiological abnormalities indicate that perception-action integration processes are central and a promising concept for the understanding of FMD. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Watching the Brain as It (Un)Binds: Beta Synchronization Relates to Distractor-Response Binding.

Human action control relies on event files, that is, short-term stimulus-response bindings that result from the integration of perception and action. The present EEG study examined oscillatory brain activities related to the integration and disintegration of event files in the distractor-response binding (DRB) task, which relies on a sequential prime-probe structure with orthogonal variation of distractor and response relations between prime and probe. Behavioral results indicated a DRB effect in RTs, which was moderated by the duration of the response-stimulus interval (RSI) between prime response and probe stimulus onset. Indeed, a DRB effect was observed for a short RSI of 500 msec but not for a longer RSI of 2000 msec, indicating disintegration of event files over time. EEG results revealed a positive correlation between individual DRB in the RSI-2000 condition and postmovement beta synchronization after both prime and probe responses. Beamformer analysis localized this correlation effect to the middle occipital gyrus, which also showed highest coherency with precentral and inferior parietal brain regions. Together, these findings suggest that postmovement beta synchronization is a marker of event file disintegration, with the left middle occipital gyrus being a hub region for stimulus-response bindings in the visual DRB task.

Electrophysiological correlates of saving-enhanced memory: Exploring similarities to list-method directed forgetting.

People regularly outsource parts of their memory onto external memory stores like computers or smartphones. Such cognitive offloading can enhance subsequent memory performance, as referred to the saving-enhanced memory effect (Storm & Stone, 2015). The cognitive mechanisms of this effect are not clear to date, however similarities to list-method directed forgetting (LMDF) have been stated. Here, we examined in 52 participants the electrophysiological (EEG) correlates of the saving-enhanced memory effect and compared our results to earlier LMDF findings (Hanslmayr et al., 2012). For this purpose, EEG alpha power and alpha phase synchrony during the encoding of two word lists were compared as a function of saving or no-saving. We hypothesised that if saving-enhanced memory was related to LMDF, saving in comparison to no-saving between lists should reduce alpha power and alpha phase synchrony during List 2 encoding, two effects that have been related to List 2 encoding benefits and List 1 inhibition in the earlier LMDF work. The results showed no statistically significant saving-enhanced memory effect and no significant effects in EEG alpha power or alpha phase synchrony. Possible explanations for and implications of these non-significant findings are discussed.

Transcranial direct current stimulation over the left anterior temporal lobe during memory retrieval differentially affects true and false recognition in the DRM task.

Transcranial direct current stimulation (tDCS) is a form of non-invasive brain stimulation that has been used to modulate human brain activity and cognition. One area which has not yet been extensively explored using tDCS is the generation of false memories. In this study, we combined the Deese-Roediger-McDermott (DRM) task with stimulation of the left anterior temporal lobe (ATL) during retrieval. This area has been shown to be involved in semantic processing in general and retrieval of false memories in the DRM paradigm in particular. During stimulation, 0.7 mA were applied via a 9 cm² electrode over the left ATL, with the 35 cm² return electrode placed over the left deltoid. We contrasted the effects of cathodal, anodal, and sham stimulation, which were applied in the recognition phase of the experiment on a sample of 78 volunteers. Results showed impaired recognition of true memories after both anodal and cathodal stimulation in comparison to sham stimulation, suggesting a reduced signal-to-noise ratio. In addition, the results revealed enhanced false recognition of concept lure items during cathodal stimulation compared to anodal stimulation, indicating a polarity-dependent impact of tDCS on false memories in the DRM task. The pathway by which tDCS modulated false recognition remains unclear: stimulation may have changed the activation of irrelevant lures or affected the weighting and monitoring of lure activations. Nevertheless, these results are a first step towards using brain stimulation to decrease false memories. Practical implications of the findings for real-life settings, for example, in the courtroom, need to be addressed in future work.

Target Amplification and Distractor Inhibition: Theta Oscillatory Dynamics of Selective Attention in a Flanker Task.

Selective attention is a key mechanism to monitor conflict-related processing and behaviour, by amplifying task-relevant processing and inhibiting task-irrelevant information. Conflict monitoring and resolution is typically associated with brain oscillatory power increase in the theta frequency range (3-8 Hz), as indexed by increased midfrontal theta power. We expand previous findings of theta power increase related to conflict processing and distractor inhibition by considering attentional target amplification to be represented in theta frequency as well. The present study (N = 41) examined EEG oscillatory activities associated with stimulus and response conflict in a lateralized flanker task. Depending on the perceptual (in)congruency and response (in)compatibility of distractor-target associations, resulting stimulus and response conflicts were examined in behavioural and electrophysiological data analyses. Both response and stimulus conflict emerged in RT analysis. Regarding EEG data, response-locked cluster analysis showed an increase of midfrontal theta power related to response conflict. In addition, stimulus-locked cluster analysis revealed early clusters with increased parietal theta power for nonconflicting compared to conflicting trials, followed by increased midfrontal theta power for both stimulus and response conflict. Our results suggest that conflict resolution in the flanker task relies on a combination of target amplification, depicted by parietal theta power increase, and distractor inhibition, indexed by midfrontal theta power increase, for both stimulus and response conflicts. Attentional amplification of sensory target features is discussed with regard to a domain-general conflict monitoring account.

It's the Other Way Around! Early Modulation of Sensory Distractor Processing Induced by Late Response Conflict.

Understanding the neural processes that maintain goal-directed behavior is a major challenge for the study of attentional control. Although much of the previous work on the issue has focused on prefrontal brain areas, little is known about the contribution of sensory brain processes to the regulation of attentional control. The present EEG study examined brain oscillatory activities invoked in the processing of response conflict in a lateralized Eriksen single-flanker task, in which target letters were presented at fixation and single distractor letters were presented either left or right to the targets. Distractors were response compatible, response incompatible, or neutral in relation to the responses associated with the targets. The behavioral results showed that responses to targets in incompatible trials were slower and more error prone than responses in compatible trials. The electrophysiological results revealed an early sensory lateralization effect in (both evoked and induced) theta power (3-6 Hz) that was more pronounced in incompatible than compatible trials. The sensory lateralization effect preceded in time a midfrontal conflict effect that was indexed by an increase of (induced) theta power (6-9 Hz) in incompatible compared with compatible trials. The findings indicate an early modulation of sensory distractor processing induced by response conflict. Theoretical implications of the findings, in particular with respect to the theory of event coding and theories relating to stimulus-response binding [Henson, R. N., Eckstein, D., Waszak, F., Frings, C., & Horner, A. Stimulus-response bindings in priming. Trends in Cognitive Sciences, 18, 376-384, 2014; Hommel, B., Müsseler, J., Aschersleben, G., & Prinz, W. The theory of event coding (TEC): A framework for perception and action planning. Behavioral and Brain Sciences, 24, 849-878, 2001], are discussed.

Bad things come easier to the mind but harder to the body: Evidence from brain oscillations.

An intriguing finding of research on emotional processing is a discrepancy between perception and behavior. Perceptually, a robust finding is that negative stimuli are processed faster and more efficiently than positive stimuli. Behaviorally, a similarly robust finding is that response times are slower for negative than for positive stimuli. We proposed and tested a novel account to explain this still unexplained discrepancy, on the basis of the assumption that negative valence narrows perceptual processes to the benefit of speeded perception, but broadens motor processes at the cost of slowed responding. Participants performed a valence judgment task in which they responded with their left or right hand to negative and positive stimuli that were presented on the left or right, and we measured the activation of relevant/deactivation of irrelevant perceptual and motor processes, as revealed by the lateralization of electroencephalographic brain oscillations. Stimulus-related lateralization of alpha activity (8-12 Hz) over perceptual areas was increased for negative stimuli, indicating more efficient perceptual processing. By contrast, response-related lateralization of beta activity (20-25 Hz) over motor areas was decreased for negative stimuli, indicating less efficient response activation. Consistent with our predictions, more detailed analyses showed that both lateralization effects were caused by dynamics at the level of inhibiting irrelevant processes. For negative as compared to positive stimuli, the inhibition of irrelevant perceptual processes was increased, but the inhibition of irrelevant motor processes was decreased. These findings indicate that the discrepancy between perception and behavior in emotional processing may stem from asymmetrical effects of emotional valence on the breadth of cortical activations in perceptual and motor networks.

Reversing the testing effect by feedback: Behavioral and electrophysiological evidence.

The testing effect refers to the finding that retrieval practice of previously studied information enhances its long-term retention more than restudy practice does. Recent work showed that the testing effect can be dramatically reversed when feedback is provided to participants during final recall testing (Storm, Friedman, Murayama, & Bjork, 2014). Following this prior work, in this study, we examined the reversal of the testing effect by investigating oscillatory brain activity during final recall testing. Twenty-six healthy participants learned cue-target word pairs and underwent a practice phase in which half of the items were retrieval practiced and half were restudy practiced. Two days later, two cued recall tests were administered, and immediate feedback was provided to participants in Test 1. Behavioral results replicated the prior work by showing a testing effect in Test 1, but a reversed testing effect in Test 2. Extending the prior work, EEG results revealed a feedback-related effect in alpha/lower-beta and retrieval-related effects in slow and fast theta power, with practice condition modulating the fast theta power effect for items that were not recalled in Test 1. The results indicate that the reversed testing effect can arise without differential strengthening of restudied and retrieval-practiced items via feedback learning. Theoretical implications of the findings, in particular with respect to the distribution-based bifurcation model of testing effects (Kornell, Bjork, & Garcia, 2011), are discussed.

List-method directed forgetting: Evidence for the reset-of-encoding hypothesis employing item-recognition testing.

In list-method directed forgetting (LMDF), people are cued to forget a previously studied item list (List 1) and to learn a new list of items (List 2) instead. Such cuing typically enhances memory for the List 2 items, in both recall and (sometimes) item-recognition testing. It has recently been hypothesized that the enhancement effect for List 2 items (partly) reflects the result of a reset-of-encoding process. The proposal is that encoding efficacy decreases with an increase in study material, but the forget cue can reset the encoding process to make the encoding of early List 2 items as effective as the encoding of early List 1 items. An experiment is reported that examined the reset-of-encoding hypothesis with item-recognition testing, examining influences of items' serial learning position on the effects of the forget cue. Item-recognition tests were conducted separately for the two lists. Consistent with the reset-of-encoding hypothesis, the results showed strong enhancement effects for early List 2 items, but hardly any enhancement effects for middle and late List 2 items. Like in previous item-recognition studies, no cuing effects were found for List 1 items. The results support two-mechanism accounts of LMDF, which assume a critical role for a reset-of-encoding process for List 2 enhancement.

Distinct slow and fast cortical theta dynamics in episodic memory retrieval.

Brain oscillations in the theta frequency band (3-8 Hz) have been shown to be critically involved in human episodic memory retrieval. In prior work, both positive and negative relationships between cortical theta power and retrieval success have been reported. This study examined the hypothesis that slow and fast cortical theta oscillations at the edges of the traditional theta frequency band are differentially related to retrieval success. Scalp EEG was recorded in healthy human participants as they performed a cued-recall episodic memory task. Slow (~3 Hz) and fast (~7 Hz) theta oscillations at retrieval were examined as a function of whether an item was recalled or not and as a function of the items' output position at test. Recall success typically declines with output position, due to increases in interference level. The results showed that slow theta power was positively related but fast theta power was negatively related to retrieval success. Concurrent positive and negative episodic memory effects for slow and fast theta oscillations were dissociable in time and space, showing different time courses and different spatial locations on the scalp. Moreover, fast theta power increased from early to late output positions, whereas slow theta power was unaffected by items' output position. Together with prior work, the results suggest that slow and fast theta oscillations have distinct functional roles in episodic memory retrieval, with slow theta oscillations being related to processes of recollection and conscious awareness, and fast theta oscillations being linked to processes of interference and interference resolution.

Judgments of Learning Reactively Improve Memory by Enhancing Learning Engagement and Inducing Elaborative Processing: Evidence from an EEG Study.

Making judgments of learning (JOLs) can reactively alter memory itself, a phenomenon termed the reactivity effect. The current study recorded electroencephalography (EEG) signals during the encoding phase of a word list learning task to explore the neurocognitive features associated with JOL reactivity. The behavioral results show that making JOLs reactively enhances recognition performance. The EEG results reveal that, compared with not making JOLs, making JOLs increases P200 and LPC amplitudes and decreases alpha and beta power. Additionally, the signals of event-related potentials (ERPs) and event-related desynchronizations (ERDs) partially mediate the reactivity effect. These findings support the enhanced learning engagement theory and the elaborative processing explanation to account for the JOL reactivity effect.

Dynamic adjustments of cognitive control: oscillatory correlates of the conflict adaptation effect.

It is a prominent idea that cognitive control mediates conflict adaptation, in that response conflict in a previous trial triggers control adjustments that reduce conflict in a current trial. In the present EEG study, we investigated the dynamics of cognitive control in a response-priming task by examining the effects of previous trial conflict on intertrial and current trial oscillatory brain activities, both on the electrode and the source level. Behavioral results showed conflict adaptation effects for RTs and response accuracy. Physiological results showed sustained intertrial effects in left parietal theta power, originating in the left inferior parietal cortex, and midcentral beta power, originating in the left and right (pre)motor cortex. Moreover, physiological analysis revealed a current trial conflict adaptation effect in midfrontal theta power, originating in the ACC. Correlational analyses showed that intertrial effects predicted conflict-induced midfrontal theta power in currently incongruent trials. In addition, conflict adaptation effects in midfrontal theta power and RTs were positively related. Together, these findings point to a dynamic cognitive control system that, as a function of previous trial type, up- and down-regulates attention and preparatory motor activities in anticipation of the next trial.

List-method directed forgetting can be selective: evidence from the 3-list and the 2-list tasks.

When people are cued to forget previously studied irrelevant information and study new information instead, such cuing typically leads to forgetting of the precue information. But what do people forget if, before the forget cue is provided, both irrelevant and relevant information have been encoded? Using relatively short item lists, we examined in a series of three experiments whether participants are able to selectively forget the irrelevant precue information, when relevant and irrelevant precue items were presented subsequently in two separate lists (3-list task) and when the two types of items were presented alternatingly within a single list (2-list task). Selective forgetting of the irrelevant precue items arose in the 3-list task, independent of modality of item presentation and level of discriminability of the precue lists, and it arose in the 2-list task. The findings suggest that, at least with relatively short precue lists, participants may well be able to selectively forget irrelevant precue information when cued to do so. Implications of the results for theoretical accounts of list-method directed forgetting are discussed.

The Forward Testing Effect Is Resistant to Acute Psychosocial Retrieval Stress.

The forward testing effect refers to the finding that testing of previously studied information improves memory for subsequently studied newer information. Recent research showed that the effect is immune to acute psychosocial encoding/retrieval stress, i.e., stress that is induced before initial encoding. The present study investigated whether the forward testing effect is also robust to acute psychosocial retrieval stress, i.e., stress that is induced after encoding but before retrieval of the critical item list. Participants (N = 128) studied three lists of words in anticipation of a final cumulative recall test. Participants were tested immediately on Lists 1 and 2 (testing condition) or restudied the two lists after initial study (restudy condition). After study of the critical List 3, psychosocial stress was induced in half of the participants (stress group), whereas no stress was induced in the other half (control group). The Trier Social Stress Test for Groups (TSST-G) was used for stress induction. Salivary cortisol, alpha amylase, and subjective stress were repeatedly measured. The results of the criterion test showed a generally detrimental effect of psychosocial retrieval stress on List 3 recall. Importantly, the forward testing effect was unaffected by retrieval stress. The findings are discussed with respect to current theories of the forward testing effect.

The oscillatory fingerprints of self-prioritization: Novel markers in spectral EEG for self-relevant processing.

Self-prioritization is a very influential modulator of human information processing. Still, little is known about the time-frequency dynamics of the self-prioritization network. In this EEG study, we used the familiarity-confound free matching task to investigate the spectral dynamics of self-prioritization and their underlying cognitive functions in a drift-diffusion model. Participants (N = 40) repeatedly associated arbitrary geometric shapes with either "the self" or "a stranger." Behavioral results demonstrated prominent self-prioritization effects (SPEs) in reaction time and accuracy. Remarkably, EEG cluster analysis also revealed two significant SPEs, one in delta/theta power (2-7 Hz) and one in beta power (19-29 Hz). Drift-diffusion modeling indicated that beta activity was associated with evidence accumulation, whereas delta/theta activity was associated with response selection. The decreased beta suppression of the SPE might indicate more efficient sensorimotor processing of self-associated stimulus-response features, whereas the increased delta/theta SPE might refer to the facilitated retrieval of self-relevant features across a widely distributed associative self-network. These novel oscillatory biomarkers of self-prioritization indicate their function as an associative glue for the self-concept.

Posterior delta/theta EEG activity as an early signal of Stroop conflict detection.

The conflict monitoring theory postulates that conflict detection is initiated in the anterior cingulate cortex (ACC), indexed by midfrontal theta oscillations in the electroencephalogram (EEG). Recent research suggested that distractor detection (in the Eriksen flanker task) can be initiated relatively early by attentional control processes in the occipital lobe. Whether attentional control is also involved in the detection of stimulus-response overlapping conflict in the Stroop task is yet unclear. In the present study, we analyzed EEG time-frequency data (N = 47) to investigate the contribution of early attentional control processes to the detection of response conflict and semantic conflict in a lateralized version of the color-word Stroop task. The behavioral results showed significant conflict effects in response times (RT). The EEG results showed a prominent midfrontal response conflict effect in total theta power (4-8 Hz). Importantly, detection of response conflict and semantic conflict was observed in posterior delta/theta power (2-8 Hz), which was lateralized depending on the presentation side of the irrelevant Stroop words. In explorative regression analysis, both the midfrontal and the posterior response conflict effects predicted the size of response conflict errors. These results suggest that attentional control processes in posterior areas contribute to the initiation of response-conflict detection in the Stroop task. The findings are consistent with the idea of a representational link between stimulus and response features, known as the common coding principle.

The relation between learning and stimulus-response binding.

Perception and action rely on integrating or binding different features of stimuli and responses. Such bindings are short-lived, but they can be retrieved for a limited amount of time if any of their features is reactivated. This is particularly true for stimulus-response bindings, allowing for flexible recycling of previous action plans. A relation to learning of stimulus-response associations suggests itself, and previous accounts have proposed binding as an initial step of forging associations in long-term memory. The evidence for this claim is surprisingly mixed, however. Here we propose a framework that explains previous failures to detect meaningful relations of binding and learning by highlighting the joint contribution of three variables: (a) decay, (b) the number of repetitions, and (c) the time elapsing between repetitions. Accounting for the interplay of these variables provides a promising blueprint for innovative experimental designs that bridge the gap between immediate bindings on the one hand and lasting associations in memory on the other hand. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Oscillatory correlates of controlled speed-accuracy tradeoff in a response-conflict task.

In making decisions, people have to balance between the competing demands of speed and accuracy, a balance generally referred to as the speed-accuracy tradeoff (SAT). In this study, we investigated the role of controlled SAT in a two-choice task in which manual responses were either validly or invalidly cued. Examining electrophysiological measurements of oscillatory brain activity, theta power in the anterior cingulate cortex (ACC), alpha power in the occipital cortex, and beta power in the motor cortex were found to be related to SAT. Because oscillatory effects of SAT were found to emanate from the SAT baseline interval preceding the two-choice task, the results indicate that SAT is modulated by a change of visuo-motor baseline activities rather than a change of response threshold. Moreover, in the two-choice task, conflict-induced theta power in the ACC was found to be more pronounced in speed than in accuracy trials, whereas priming-related beta power dynamics in the motor cortex were unaffected by SAT. These results indicate that conflict processing, but not response priming, depends on SAT.