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The popularity and spread of health-related pseudoscientific practices is a worldwide problem. Despite being counteracted by competent agents of our societies, their prevalence and spread are still growing. Current research has focused on identifying which characteristics make us more likely to hold beliefs in favor of pseudoscience. However, how we hold these beliefs despite all the available information against them is a question that remains unanswered. We here aimed to assess if the development of health-related pseudoscience beliefs could be driven by a positive bias in belief updating. Additionally, we aimed to explore whether this bias could be exacerbated depending on source credibility. In this study, participants (N = 116 adult university students) underwent a belief updating task where they offered their agreement with various health-related pseudoscientific statements before and after receiving supporting and discrediting feedback from (a) experts (doctors) (b) peers or (c) a random number generator. Our results suggest that when receiving feedback from experts (but not from peers or random feedback) participants preferentially integrated supporting relative to discrediting information about health-related pseudoscientific proposals. We discuss the implications of this biased belief updating pattern on health-related pseudoscience research and suggest new strategies for intervention focused on increasing awareness, training, and consensus among healthcare practitioners.

Much work in rodents and in humans has provided evidence that post-encoding reinstatement plays an important role in stabilizing memory beyond initial learning processes. However, it remains unclear whether memory reinstatement is important for the rapid - one-shot - learning of an unfolding episode. Here, we asked whether the reinstatement of an episode may occur preferentially post-encoding, when an individual perceives a meaningful event to be concluded. We asked human participants (male and female) to encode sequences of pictures depicting unique episodic-like events. We used representational similarity analysis of scalp electroencephalography recordings during encoding and found evidence for memory reactivation of the just encoded sequence of elements at the offset of the episode. Importantly, memory reinstatement was not observed between successive elements within an episode, indicating memory reactivation was specifically induced once participants perceived the unfolding episode to be completed. We also found that memory reinstatement predicted memory recollection of an encoded episode and that offset memory reinstatement was not present when participants encoded sequences of pictures that were not perceived as meaningful episodes. These results indicate that memory reinstatement at episode offsets is a mechanism selectively engaged to support rapid memory formation of single events.

Autobiographical memory (AM) has been largely investigated as the ability to recollect specific events that belong to an individual's past. However, how we retrieve real-life routine episodes and how the retrieval of these episodes changes with the passage of time remain unclear. Here, we asked participants to use a wearable camera that automatically captured pictures to record instances during a week of their routine life and implemented a deep neural network-based algorithm to identify picture sequences that represented episodic events. We then asked each participant to return to the lab to retrieve AMs for single episodes cued by the selected pictures 1 week, 2 weeks and 6–14 months after encoding while scalp electroencephalographic (EEG) activity was recorded. We found that participants were more accurate in recognizing pictured scenes depicting their own past than pictured scenes encoded in the lab, and that memory recollection of personally experienced events rapidly decreased with the passing of time. We also found that the retrieval of real-life picture cues elicited a strong and positive ‘ERP old/new effect’ over frontal regions and that the magnitude of this ERP effect was similar throughout memory tests over time. However, we observed that recognition memory induced a frontal theta power decrease and that this effect was mostly seen when memories were tested after 1 and 2 weeks but not after 6–14 months from encoding. Altogether, we discuss the implications for neuroscientific accounts of episodic retrieval and the potential benefits of developing individual-based AM exploration strategies at the clinical level., This work was supported by Ministerio de Ciencia e Innovación, which is part of Agencia Estatal de Investigación, through the project PSI2016-80489-P and PID2019-111199GB-I00 (Co-funded by European Regional Development Fund. ERDF, a way to build Europe) and by ICREA Academia, to L.F. P.R. is supported by TIN2018-095232-B-C21, SGR-2017 1742, Greenhabit EIT Digital program. We thank CERCA Programme/Generalitat de Catalunya for institutional support. We thank the Editor and two anonymous reviewers for their constructive criticisms, remarks and advices.

The aim of the present research was to test whether involvement in a 14-days training program in the performing arts could reduce implicit biases. We asked healthy participants to complete an Implicit Association Test (IAT) to assess biased attitudes to physical illness in two separate sessions, before and after the training program. Two separate control groups matched by age, gender and educational level completed the two IAT sessions, separated by same number of days, without being involved in the training program. Results showed that participants who were involved in the training program reduced their implicit bias toward illness measured through IAT in the second session. This reduction in IAT measures was not observed in the control samples, despite the two IAT measures being matched in temporal delay with the experimental group. These findings suggest that an interventional program based on the performing arts could be effective in reducing levels of implicit biases among the general population.

How does one retrieve real-life episodic memories? Here, we tested the hypothesis, derived from computational models, that successful retrieval relies on neural dynamics patterns that rapidly shift towards stable states. We implemented cross-temporal correlation analysis of electroencephalographic (EEG) recordings while participants retrieved episodic memories cued by pictures collected with a wearable camera depicting real-life episodes taking place at “home” and at “the office”. We found that the retrieval of real-life episodic memories is supported by rapid shift towards brain states of stable activity, that the degree of neural stability is associated with the participants’ ability to recollect the episodic content cued by the picture, and that each individual elicits stable EEG patterns that were not shared with other participants. These results indicate that the retrieval of autobiographical memory episodes is supported by rapid shifts of neural activity towards stable states.

Sleep is thought to play a complementary role in human memory processing: sleep loss impairs the formation of new memories during the following awake period and, conversely, normal sleep promotes the strengthening of the already encoded memories. However, whether sleep can strengthen deteriorated memories caused by insufficient sleep remains unknown. Here, we showed that sleep restriction in a group of participants caused a reduction in the stability of EEG activity patterns across multiple encoding of the same event during awake, compared with a group of participants that got a full night’s sleep. The decrease of neural stability patterns in the sleep-restricted group was associated with higher slow oscillation-spindle coupling during a subsequent night of normal sleep duration, thereby suggesting the instantiation of restorative neural mechanisms adaptively supporting cognition and memory. Importantly, upon awaking, the two groups of participants showed equivalent retrieval accuracy supported by subtle differences in the reinstatement of encoding-related activity: it was longer lasting in sleep-restricted individuals than in controls. In addition, sustained reinstatement over time was associated with increased coupling between spindles and slow oscillations. Taken together, these results suggest that the strength of prior encoding might be an important moderator of memory consolidation during sleep. Supporting this view, spindles nesting in the slow oscillation increased the probability of correct recognition only for weakly encoded memories. Current results demonstrate the benefit that a full night’s sleep can induce to impaired memory traces caused by an inadequate amount of sleep.

Integrating new information into existing schematic structures of knowledge is the basis of learning in our everyday life activity as it enables structured representation of information and goal-directed behaviour in an ever-changing environment. However, how schematic mnemonic structures aid the integration of novel elements remains poorly understood. Here, we showed that the ability to integrate novel picture information into learn structures of picture associations that overlap by the same picture scene (associative network) or by the conceptually related scene information (schematic network) is hippocampus-dependent, as patients with lesions at the medial temporal lobe (including the hippocampus) were impaired in inferring novel relations between elements within these mnemonic networks but not in retrieving individual pictures in a subsequent memory test. In addition, we observed more persistent and widespread scalp electroencephalographic (EEG) theta oscillatory pattern (3-6Hz) while healthy participants encoded novel pictures related to schematic memory networks, suggesting that theta may reflect distances between elements within a representational network space. Finally, we found high similarity values for neural activity patterns elicited by novel and related events only within associative networks, thereby suggesting that neural reactivation may promote the integration of new information into existing memory networks only when direct associations within the network link their elements. These findings have important implications for our understanding of the neural mechanisms that support the development and organization of structures of knowledge.

Integrating new information into existing schematic structures of knowledge is the basis of learning in our everyday life activity as it enables structured representation of information and goal-directed behaviour in an ever-changing environment. However, how schematic mnemonic structures aid the integration of novel elements remains poorly understood. Here, we showed that the ability to integrate novel picture information into learn structures of picture associations that overlap by the same picture scene (associative network) or by the conceptually related scene information (schematic network) is hippocampus-dependent, as patients with lesions at the medial temporal lobe (including the hippocampus) were impaired in inferring novel relations between elements within these mnemonic networks but not in retrieving individual pictures in a subsequent memory test. In addition, we observed more persistent and widespread scalp electroencephalographic (EEG) theta oscillatory pattern (3-6Hz) while healthy participants encoded novel pictures related to schematic memory networks, suggesting that theta may reflect distances between elements within a representational network space. Finally, we found high similarity values for neural activity patterns elicited by novel and related events only within associative networks, thereby suggesting that neural reactivation may promote the integration of new information into existing memory networks only when direct associations within the network link their elements. These findings have important implications for our understanding of the neural mechanisms that support the development and organization of structures of knowledge.

The subjective sense of recollecting events from one's past is an essential feature of episodic memory, but the neural mechanisms supporting this capacity are poorly understood. We examined the role of large-scale patterns of neural synchrony using whole-head MEG recordings in healthy adults and S.M., who has severely deficient autobiographical memory (SDAM; Palombo et al., 2015), a syndrome in which autobiographical recollection is absent but other functions (including other mnemonic functions), are normal. MEG was conducted while participants listened to prospectively collected recordings documenting unique personal episodes (PE) that normally evoke rich recollection, as well as a condition including general semantic information that is non-specific in place or time (GS; Levine et al., 2004). We predicted that PE (and not GS) would be associated with changes in patterns of large-scale neural synchrony in comparison subjects. We found large-scale neural synchrony, specifically in the gamma frequency ranges (i.e., 27–45 Hz), specific to PE and not GS. These synchrony differences between PE and GS were not apparent in S.M. Our findings provide empirical evidence for the supporting role of large-scale gamma neural synchrony underlying autobiographical recollection.

The medial temporal lobe drives semantic congruence dependent memory formation. However, the exact roles of hippocampal subfields and surrounding brain regions remain unclear. Here, we used an established paradigm and high-resolution functional magnetic resonance imaging of the medial temporal lobe together with cytoarchitectonic probability estimates in healthy humans. Behaviorally, robust congruence effects emerged in young and older adults, indicating that schema dependent learning is unimpaired during healthy aging. Within the medial temporal lobe, semantic congruence was associated with hemodynamic activity in the subiculum, CA1, CA3 and dentate gyrus, as well as the entorhinal cortex and laterobasal amygdala. Importantly, a subsequent memory analysis showed increased activity for later remembered vs. later forgotten congruent items specifically within CA3, and this subfield showed enhanced functional connectivity to the laterobasal amygdala. As such, our findings extend current models on schema dependent learning by pinpointing the functional properties of subregions within the medial temporal lobe.

Summary Memory retrieval involves the reactivation of memory traces distributed throughout the brain. New research suggests that these memory reactivations have an oscillatory nature and that they are coupled to preferential stages of the hippocampal theta cycle.

Long-term memory can improve when incoming information is congruent with known semantic information. This so-called congruence effect has widely been shown in younger adults, but age-related changes and neural mechanisms remain unclear. Here, congruence improved recognition memory in younger and older adults (i.e. congruence effect), with only weak evidence for age-related decline in one behavioral study. In an EEG study, however, no significant behavioral differences in the congruence effect could be observed between age-groups. In line with this observation, electroencephalography data show that, in both groups, congruence led to widespread differences in Event-Related Potentials (ERPs), starting at around 400 ms after stimulus onset, and theta, alpha and beta oscillations (4–20 Hz). Importantly, these congruence-related ERPs were associated to increases in memory performance for congruent items, in both age groups. Finally, the described ERPs and neural oscillations in the theta-alpha range (5–13 Hz) were less pronounced in the elderly despite a preserved congruence effect. Together, semantic congruence increases long-term memory across the lifespan, and, at the neural level, this could be linked to neural oscillations in the theta, alpha and beta range, as well as ERPs that were previously associated with semantic processing.

Segmentation of continuous experience into discrete events is driven by rapid fluctuations in encoding stability at context shifts (i.e., event boundaries), yet the mechanisms underlying the online formation of event memories are poorly understood. We investigated the neural per-time point spatial similarity patterns of the scalp electrophysiological (EEG) activity of 30 human participants (male and female) watching a 50 min movie and found that event boundaries triggered the rapid reinstatement of the just-encoded movie event EEG patterns. We also found that the onset of memory reinstatement at boundary onset was accompanied by a left-lateralized anterior negative ERP effect, which likely reflects the detection of a shift in the narrative structure of the movie. A data-driven approach based on Hidden Markov modeling allowed us to detect event boundaries as shifts between stable patterns of brain EEG activity during encoding, and to identify their reactivation during a free recall task. These results provide the first neurophysiological underpinnings for how the memory systems segment a continuous long stream of experience into episodic events.SIGNIFICANCE OF STATEMENTMemory for specific episodic events are the building blocks of our autobiographical memory. However, it is still unclear how the memory systems structure the unfolding experience into discrete event units that can be understood and remembered at the long-term. Here, we show that the detection of context shifts, or event boundaries, during a 50 min movie viewing triggers the rapid memory reactivation of the just-encoded event to promote its successful encoding into long-term memory. By finding that memory reactivation, a neural mechanism critical for episodic memory formation and consolidation, takes place under these ecologically valid experimental circumstances, our results provide valuable insights into how the brain shapes the ongoing experience into episodic memories in the real-life.

Introduction It has long been posited that threat learning operates and forms under an affective and a cognitive learning system that is supported by different brain circuits. A primary drawback in exposure‐based therapies is the high rate of relapse that occurs when higher order areas fail to inhibit responses driven by the defensive circuit. It has been shown that implicit exposure of fearful stimuli leads to a long‐lasting reduction in avoidance behavior in patients with phobia. Despite the potential benefits of this approach in the treatment of phobias and posttraumatic stress disorder, implicit extinction is still underinvestigated. Methods Two groups of healthy participants were threat conditioned. The following day, extinction training was conducted using a stereoscope. One group of participants was explicitly exposed with the threat‐conditioned image, while the other group was implicitly exposed using a continuous flash suppression (CFS) technique. On the third day, we tested the spontaneous recovery of defensive responses using explicit presentations of the images. Results On the third day, we found that only the implicit extinction group showed reduced spontaneous recovery of defensive responses to the threat‐conditioned stimulus, measured by threat‐potentiated startle responses but not by the electrodermal activity. Conclusion Our results suggest that implicit extinction using CFS might facilitate the modulation of the affective component of fearful memories, attenuating its expression after 24 hr. The limitations of the CFS technique using threatful stimuli urge the development of new strategies to improve implicit presentations and circumvent such limitations. Our study encourages further investigations of implicit extinction as a potential therapeutic target to further advance exposure‐based psychotherapies.

It has long been posited that threat learning operates and forms under an affective and a cognitive learning system that are supported by different brain circuits. A primary drawback in exposure-based therapies is the high rate of relapse when higher order inhibitory structures failed to inhibit the emotional responses driven by the defensive circuit. It has been shown that implicit exposure of fearful stimuli leads to a long-lasting reduction of avoidance behavior in patients with phobia through the facilitation of fear processing areas in the absence of subjective fear. Despite the potential benefits of this approach in the treatment of phobias and PTSD, implicit exposure to fearful stimuli is still under-investigated. Here, we used unconscious presentation of threat-conditioned stimuli in healthy humans, using a continuous flash suppression technique. We found that implicit exposure of a conditioned stimulus reduced, on the following day, defensive responses to the conditioned stimulus measured by threat-potentiated startle responses but not by the electrodermal activity. Our results suggest that implicit exposure using CFS might facilitate the modulation of the affective component of fearful memories, representing an important therapeutic target to further advance exposure-based psychotherapies.

Temporal lobe epilepsy (TLE) is the most common form of focal epilepsy. The most frequent pathologic finding in this condition is hippocampal sclerosis (HS). In addition, in a small proportion (14-23%) of refractory TLE patients, the presence of HS is bilateral. TLE involves grey matter (GM) and white matter (WM) abnormalities in a wide cortico-subcortical network. However, the impact of neuronal loss on specific WM fiber pathways and associated functional systems as well as seizure propagation pathways remains unclear. There is still much controversy regarding the role of the commissures (corpus callosum, hippocampal commissure and anterior commissure) in interhemispheric seizure propagation. This study aimed to investigate the integrity of WM interhemispheric connectivity in a singular sample of patients with TLE and bilateral HS using structural magnetic resonance imaging (MRI). We performed multimodal structural MRI [high resolution T1-weighted and diffusion tensor imaging (DTI)] analyses of seven patients with medically refractory TLE with bilateral HS, fourteen unilateral left TLE patients and fifteen matched healthy individuals. Whole-brain voxel-wise analysis techniques were used. These patients evidenced WM derangement [reduced fractional anisotropy (FA), increased mean diffusivity (MD) or reduced WM volume] in temporal and extratemporal tracks, but also in commissural pathways, compared to the unilateral left TLE patients and the control group. Presence of reduced FA or increased MD in the fornix, cingulum and uncinate fasciculus in addition to reduced WM volume in the fornix was also encountered. Neuropsychological assessment was performed without significant correlations with structural data. The current results support the idea that commissural pathways play a contributory role in interhemispheric TLE seizure propagation in bilateral HS and offer new perspectives about the long-term effects on interhemispheric connectivity associated with seizure propagation patterns in TLE patients.

Summary Although everyday experiences unfold continuously over time, shifts in context, or event boundaries, can influence how those events come to be represented in memory [1–4]. Specifically, mnemonic binding across sequential representations is more challenging at context shifts, such that successful temporal associations are more likely to be formed within than across contexts [1, 2, 5–9]. However, in order to preserve a subjective sense of continuity, it is important that the memory system bridge temporally adjacent events, even if they occur in seemingly distinct contexts. Here, we used pattern similarity analysis to scalp electroencephalographic (EEG) recordings during a sequential learning task [2, 3] in humans and showed that the detection of event boundaries triggered a rapid memory reinstatement of the just-encoded sequence episode. Memory reactivation was detected rapidly (∼200–800 ms from the onset of the event boundary) and was specific to context shifts that were preceded by an event sequence with episodic content. Memory reinstatement was not observed during the sequential encoding of events within an episode, indicating that memory reactivation was induced specifically upon context shifts. Finally, the degree of neural similarity between neural responses elicited during sequence encoding and at event boundaries correlated positively with participants' ability to later link across sequences of events, suggesting a critical role in binding temporally adjacent events in long-term memory. Current results shed light onto the neural mechanisms that promote episodic encoding not only for information within the event, but also, importantly, in the ability to link across events to create a memory representation of continuous experience.

As the stream of experience unfolds, our memory system rapidly transforms current inputs into long-lasting meaningful memories. A putative neural mechanism that strongly influences how input elements are transformed into meaningful memory codes relies on the ability to integrate them with existing structures of knowledge or schemas. However, it is not yet clear whether schema-related integration neural mechanisms occur during online encoding. In the current investigation, we examined the encoding-dependent nature of this phenomenon in humans. We showed that actively integrating words with congruent semantic information provided by a category cue enhances memory for words and increases false recall. The memory effect of such active integration with congruent information was robust, even with an interference task occurring right after each encoding word list. In addition, via electroencephalography, we show in 2 separate studies that the onset of the neural signals of successful encoding appeared early (∼400 ms) during the encoding of congruent words. That the neural signals of successful encoding of congruent and incongruent information followed similarly ∼200 ms later suggests that this earlier neural response contributed to memory formation. We propose that the encoding of events that are congruent with readily available contextual semantics can trigger an accelerated onset of the neural mechanisms, supporting the integration of semantic information with the event input. This faster onset would result in a long-lasting and meaningful memory trace for the event but, at the same time, make it difficult to distinguish it from plausible but never encoded events (i.e., related false memories).SIGNIFICANCE STATEMENTConceptual or schema congruence has a strong influence on long-term memory. However, the question of whether schema-related integration neural mechanisms occur during online encoding has yet to be clarified. We investigated the neural mechanisms reflecting how the active integration of words with congruent semantic categories enhances memory for words and increases false recall of semantically related words. We analyzed event-related potentials during encoding and showed that the onset of the neural signals of successful encoding appeared early (∼400 ms) during the encoding of congruent words. Our findings indicate that congruent events can trigger an accelerated onset of neural encoding mechanisms supporting the integration of semantic information with the event input.

System memory consolidation is conceptualized as an active process whereby newly encoded memory representations are strengthened through selective memory reactivation during sleep. However, our learning experience is highly overlapping in content (i.e., shares common elements), and memories of these events are organized in an intricate network of overlapping associated events. It remains to be explored whether and how selective memory reactivation during sleep has an impact on these overlapping memories acquired during awake time. Here, we test in a group of adult women and men the prediction that selective memory reactivation during sleep entails the reactivation of associated events and that this may lead the brain to adaptively regulate whether these associated memories are strengthened or pruned from memory networks on the basis of their relative associative strength with the shared element. Our findings demonstrate the existence of efficient regulatory neural mechanisms governing how complex memory networks are shaped during sleep as a function of their associative memory strength. SIGNIFICANCE STATEMENT Numerous studies have demonstrated that system memory consolidation is an active, selective, and sleep-dependent process in which only subsets of new memories become stabilized through their reactivation. However, the learning experience is highly overlapping in content and thus events are encoded in an intricate network of related memories. It remains to be explored whether and how memory reactivation has an impact on overlapping memories acquired during awake time. Here, we show that sleep memory reactivation promotes strengthening and weakening of overlapping memories based on their associative memory strength. These results suggest the existence of an efficient regulatory neural mechanism that avoids the formation of cluttered memory representation of multiple events and promotes stabilization of complex memory networks.

Summary The hippocampus, a structure located in the temporal lobes of the brain, is critical for the ability to recollect contextual details of past episodes. It is still debated whether the hippocampus also enables recognition memory for previously encountered context-free items. Brain imaging [1, 2] and neuropsychological patient studies [3, 4] have both individually provided conflicting answers to this question. We overcame the individual limitations of imaging and behavioral patient studies by combining them and observed a novel relationship between item memory and the hippocampus. We show that interindividual variability of hippocampal volumes in a large patient population with graded levels of hippocampal volume loss and controls correlates with context, but not item-memory performance. Nevertheless, concurrent measures of brain activity using magnetoencephalography reveal an early (350 ms) but sustained hippocampus-dependent signal that evolves from an item signal into a context memory signal. This is temporally distinct from an item-memory signal that is not hippocampus dependent. Thus, we provide evidence for a hippocampus-dependent item-memory process that initiates context retrieval without making a substantial contribution to item recognition performance. Our results reconcile contradictory evidence concerning hippocampal involvement in item memory and show that hippocampus-dependent mnemonic processes are more rapid than previously believed., Highlights ► Whether the hippocampus is needed for item as well as context memory is unclear ► We tested behavior and function in a large patient group with hippocampal atrophy ► We identified a new rapid hippocampus-dependent functional signal to familiar items ► This signal is not needed for item memory but initiates context recollection

Individual experiences often overlap in their content, presenting opportunities for rapid generalization across them. In this study, we show in 2 independent experiments that integrative encoding-the ability to form individual and across memory representations during online encoding-is supported by 2 distinct neurophysiological responses. Brain potential is increased gradually during encoding and fit to a trial level memory measure for individual episodes, whereas neural oscillations in the theta range (4-6 Hz) emerge later during learning and predict participants' generalization performance in a subsequent test. These results suggest that integrative encoding requires the recruitment of 2 separate neural mechanisms that, despite their co-occurrence in time, differ in their underlying neural dynamics, reflect different brain learning rates and are supportive of the formation of opposed memory representations, individual versus across-event episodes.

Recollection of contextual information represents the core of human recognition memory. It has been associated with theta (4–8 Hz) power in electrophysiological recordings and, independently, with BOLD effects in a network including the hippocampus and frontal cortex. Although the notion of the hippocampus coordinating neocortical activity by synchronization in the theta range is common among theoretical models of recollection, direct evidence supporting this hypothesis is scarce. To address this apparent gap in our understanding of memory processes, we combined EEG and fMRI during a remember/know recognition task. We can show that recollection-specific theta-alpha (4–13 Hz) effects are correlated with increases in hippocampal connectivity with the PFC and, importantly, the striatum, areas that have been linked repeatedly to retrieval success. Together, our results provide compelling evidence that low-frequency oscillations in the theta and alpha range provide a mechanism to functionally bind the hippocampus, PFC, and striatum during successful recollection.SIGNIFICANCE STATEMENTLow-frequency oscillations are supposed to drive the binding of information across a large-scale network centered on the hippocampus, which supports mnemonic functions. The electrophysiological means to investigate this phenomenon in humans (EEG/MEG), however, are inherently limited by their spatial resolution and therefore do not allow a precise localization of the brain regions involved. By combining EEG with BOLD-derived estimates of hippocampal connectivity during recognition, we can identify the striatum and specific areas in the medial and lateral PFC as part of a circuit linked to low-frequency oscillations (4–13 Hz) that promotes hippocampus-dependent context retrieval. Therefore, the current study closes an apparent gap in our understanding of the network dynamics of memory retrieval.

Working memory (WM) can be defined as the ability to maintain and process physically absent information for a short period of time. This vital cognitive function has been related to cholinergic neuromodulation and, in independent work, to theta (4-8Hz) and alpha (9-14Hz) band oscillations. However, the relationship between both aspects remains unclear. To fill this apparent gap, we used electroencephalography (EEG) and a within-subject design in healthy humans who either received the acetylcholinesterase inhibitor galantamine (8mg) or a placebo before they performed a Sternberg WM paradigm. Here, sequences of sample images were memorized for a delay of 5s in three different load conditions (two, four or six items). On the next day, long-term memory (LTM) for the images was tested according to a remember/know paradigm. As a main finding, we can show that both theta and alpha oscillations scale during WM maintenance as a function of WM load; this resembles the typical performance decrease. Importantly, cholinergic stimulation via galantamine administration slowed down retrieval speed during WM and reduced associated alpha but not theta power, suggesting a functional relationship between alpha oscillations and WM performance. At LTM, this pattern was accompanied by impaired familiarity based recognition. These findings show that stimulating the healthy cholinergic system impairs WM and subsequent recognition, which is in line with the notion of a quadratic relationship between acetylcholine levels and cognitive functions. Moreover, our data provide empirical evidence for a specific role of alpha oscillations in acetylcholine dependent WM and associated LTM formation.

In any given common situation, when an individual controls him/herself or obeys and stops a current action when asked to do, it is because the brain executes an inhibitory process. This ability is essential for adaptive behaviour, and it is also a requirement for accurate performance in daily life. It has been suggested that there are two main inhibitory functions related to behaviour, as inhibition is observed to affect behaviour at different time intervals. Proactive inhibition permits the subject to control his behavioural response over time by creating a response tendency, while reactive inhibition is considered to be a process that usually inhibits an already initiated response. In this context, it has been established that inhibitory function is implemented by specific fronto-basal-ganglia circuits. In the present study, we investigated the role of the right inferior frontal cortex (rIFC) in response inhibition by combining into a single task the Go-NoGo task and the Stop-Signal task. Concurrently, we applied transcranial direct current stimulation (tDCS) over the IFC and recorded electroencephalography (EEG). Thus, we obtained online EEG measurements of the tDCS-induced modifications in the IFC together with the participant's performance in a response inhibition task. We found that applying bilateral tDCS on the IFC (right anodal/left cathodal) significantly increased proactive inhibition, although the behavioural parameters indicative of reactive inhibition were unaffected by the stimulation. Finally, the inhibitory-P3 component reflected a similar modulation under both inhibitory conditions induced by the stimulation. Our data indicates that an online tDCS-ERP approach is achievable, but that a tDCS bilateral montage may not be the most efficient one for modulating the rIFC.

Mismatch negativity (MMN) is an event-related brain potential that appears when an auditory regularity is violated. Two main hypotheses have been proposed to explain it: the adaptation hypothesis and the memory-based hypothesis. Critically, they differ in whether the MMN can be distinguished from the N1. In this study, we assessed the differential contribution of the N1 and the MMN using independent component analysis (ICA) combined with model-based clustering. Our results show that the neural responses associated with the standard and deviant tones are explained by three clusters of reliable ICs with frontocentral scalp distribution. Two of these clusters exhibited a common N1 for both the standard and deviant tones and one cluster showed an enhancement of the anterior N1 at the MMN time range. These results support the adaptation hypothesis, which proposes that MMN is generated by neural mechanisms similar to those associated with auditory N1.

Optimal decision-making is guided by evaluating the outcomes of previous decisions. Prediction errors are theoretical teaching signals which integrate two features of an outcome: its inherent value and prior expectation of its occurrence. To uncover the magnetic signature of prediction errors in the human brain we acquired magnetoencephalographic (MEG) data while participants performed a gambling task. Our primary objective was to use formal criteria, based upon an axiomatic model (Caplin and Dean, 2008a), to determine the presence and timing profile of MEG signals that express prediction errors. We report analyses at the sensor level, implemented in SPM8, time locked to outcome onset. We identified, for the first time, a MEG signature of prediction error, which emerged approximately 320 ms after an outcome and expressed as an interaction between outcome valence and probability. This signal followed earlier, separate signals for outcome valence and probability, which emerged approximately 200 ms after an outcome. Strikingly, the time course of the prediction error signal, as well as the early valence signal, resembled the Feedback-Related Negativity (FRN). In simultaneously acquired EEG data we obtained a robust FRN, but the win and loss signals that comprised this difference wave did not comply with the axiomatic model. Our findings motivate an explicit examination of the critical issue of timing embodied in computational models of prediction errors as seen in human electrophysiological data., Highlights ► We identified, for the first time, an MEG signature of a human prediction error. ► The waveform resembled the Feedback-Related Negativity (FRN) signal in EEG. ► MEG effects of probability and valence were emerged before the prediction error signals, 200 ms after the outcome. ► The EEG data revealed classic FRN which was modulated by probability.

In this study, we sought to dissociate event-related potentials (ERPs) and the oscillatory activity associated with signals indicating feedback about performance (outcome-based behavioral adjustment) and the signals indicating the need to change or maintain a task set (rule-based behavioral adjustment). With this purpose in mind, we noninvasively recorded electroencephalographic signals, using a modified version of the Wisconsin card sorting task, in which feedback processing and task switching could be studied separately. A similar late positive component was observed for the switch and correct feedback signals on the first trials of a series, but feedback-related negativity was observed only for incorrect feedback. Moreover, whereas theta power showed a significant increase after a switch cue and after the first positive feedback of a new series, a selective frontal beta-gamma increase was observed exclusively in the first positive feedback (i.e., after the selection of the new rule). Importantly, for the switch cue, beta-alpha activity was suppressed rather than increased. This clear dissociation between the cue and feedback stimuli in task switching emphasizes the need to accurately study brain oscillatory activity to disentangle the role of different cognitive control processes.