According to mechanistic theories of working memory (WM), information is retained as stimulus-dependent persistent spiking activity of cortical neural networks. Yet, how this activity is related to changes in the oscillatory profile observed during WM tasks remains a largely open issue. We explore joint effects of input gamma-band oscillations and noise on the dynamics of several firing rate models of WM. The considered models have a metastable active regime, i.e., they demonstrate long-lasting transient post-stimulus firing rate elevation. We start from a single excitatory-inhibitory circuit and demonstrate that either gamma-band or noise input could stabilize the active regime, thus supporting WM retention. We then consider a system of two circuits with excitatory intercoupling. We find that fast coupling allows for better stabilization by common noise compared to independent noise and stronger amplification of this effect by in-phase gamma inputs compared to anti-phase inputs. Finally, we consider a multi-circuit system comprised of two clusters, each containing a group of circuits receiving a common noise input and a group of circuits receiving independent noise. Each cluster is associated with its own local gamma generator, so all its circuits receive gamma-band input in the same phase. We find that gamma-band input differentially stabilizes the activity of the “common-noise” groups compared to the “independent-noise” groups. If the inter-cluster connections are fast, this effect is more pronounced when the gamma-band input is delivered to the clusters in the same phase rather than in the anti-phase. Assuming that the common noise comes from a large-scale distributed WM representation, our results demonstrate that local gamma oscillations can stabilize the activity of the corresponding parts of this representation, with stronger effect for fast long-range connections and synchronized gamma oscillations.
The acquisition of new orthographic representations is a rapid and highly automatic process in monolingual readers. Our study extends existing research to biliterate populations, addressing the impact of phonological inconsistencies across native (L1) and second language (L2) alphabets during orthographic learning. Behavioral and EEG signals were collected from a group of 24 Russian-English biliterates via a reading-aloud task using familiar and novel words repeated across ten consecutive blocks in three Script conditions: (1) native Cyrillic, (2) non-native Roman, and (3) ambiguous (phonologically inconsistent graphemes shared by L1 and L2 alphabets). Linear mixed-effects modelling of both behavioral and ERP data revealed reliable Block x Lexicality x Script interactions, indicating that naming latencies and brain activity changed differently across training blocks for novel and familiar words and, importantly, depending on script presentation. Particularly, novel words presented in the ambiguous script showed longer naming latencies and slower reading automatization than those presented in L1 and L2 alphabets. Nonetheless, despite this interference, their naming latencies matched those of familiar words before the end of the training, suggesting the attribution of their representations in the reader's lexicon. The enhancement of early brain responses observed for these stimuli alongside their training confirmed the improvement in their orthographic analysis and lexical access. Critically, this pattern of results was not found for familiar, already represented words, which exhibited a suppression of their brain activity across repetitions. Overall, our results indicate that phonological inconsistency interferes with novel word encoding but it does not prevent efficient attribution of orthographic representations.
The acquisition of new orthographic representations is a rapid and accurate process in proficient monolingual readers. The present study used biliterate and bialphabetic population to address the impact of phonological inconsistencies across the native (L1) and second (L2) alphabets. Naming latencies were collected from 50 Russian–English biliterates through a reading-aloud task with familiar and novel word forms repeated across 10 blocks. There were three Script conditions: (1) native Cyrillic, (2) non-native Roman, and (3) Ambiguous (with graphically identical, but phonologically inconsistent graphemes shared by both alphabets). Our analysis revealed the main effect of Script on both reading and orthographic learning: naming latencies during training were longer for the ambiguous stimuli, particularly for the novel ones. Nonetheless, novel word forms in the ambiguous condition approached the latencies for the familiar words along the exposures, although this effect was faster in the phonologically consistent trials. Post-training tests revealed similarly successful performance patterns for previously familiar and newly trained forms, indicating successful rapid acquisition of the latter. Furthermore, we found the highest free recall rates for the ambiguous stimuli. Overall, our results indicate that phonological inconsistency initially interferes with the efficiency of novel word encoding. Nevertheless, it does not prevent efficient attribution of orthographic representations; instead, the knowledge of two distinct alphabets supports a more efficient learning and a better memory for ambiguous stimuli via enhancing their encoding and retrieval.
Intracranial stereoelectroencephalography (sEEG) provides unsurpassed sensitivity and specificity for human neurophysiology. However, functional mapping of brain functions has been limited because the implantations have sparse coverage and differ greatly across individuals. Here, we developed a distributed, anatomically realistic sEEG source-modeling approach for within- and between-subject analyses. In addition to intracranial event-related potentials (iERP), we estimated the sources of high broadband gamma activity (HBBG), a putative correlate of local neural firing. Our novel approach accounted for a significant portion of the variance of the sEEG measurements in leave-one-out cross-validation. After logarithmic transformations, the sensitivity and signal-to-noise ratio were linearly inversely related to the minimal distance between the brain location and electrode contacts (slope≈−3.6). The signa-to-noise ratio and sensitivity in the thalamus and brain stem were comparable to those locations at the vicinity of electrode contact implantation. The HGGB source estimates were remarkably consistent with analyses of intracranial-contact data. In conclusion, distributed sEEG source modeling provides a powerful neuroimaging tool, which facilitates anatomically-normalized functional mapping of human brain using both iERP and HBBG data.
Effectiveness of various emotion regulation (ER) strategies have received much attention in recent research. Among the most studied ER strategies are cognitive reappraisal and expressive suppression. However, the evidence of their effectiveness is controversial and depends on the measures used. The aim of the present study was to compare the effectiveness of cognitive reappraisal and expressive suppression strategies of ER via different measures such as self-report, facial expressions (zygomaticus major and corrugator supercilii electromyography), and physiological assessment (skin conductance response and heart rate deceleration). Participants were presented with intensely unpleasant or neutral pictures and performed ER tasks. We expected that the implementation of ER strategies would reduce negative emotions, and cognitive reappraisal would produce greater reduction in negative emotions compared to expressive suppression. Self-report data showed that reappraisal had a greater effect on the reduction of negative emotions compared to suppression. There was no difference between reappraisal and suppression assessed with skin conductance response and electromyography. Curiously, heart rate deceleration increased while participants tried to suppress their emotional expressions, which could reflect efforts exerted in the attempt to suppress. The ER strategies reduced negative emotions during the presentation of unpleasant pictures partially in skin conductance response and heart rate deceleration. Overall, reappraisal is more effective in changing subjective experience, whereas the physiological reactions do not differ substantially between the two ER strategies explored. We therefore recommend that the assessment of ER strategies in the laboratory should accommodate more than one type of measures to come to more reliable conclusions.
This review aims at clarifying the concept of first language attrition by tracing its limits, identifying its phenomenological and contextual constraints, discussing controversies associated with its definition, and suggesting potential directions for future research. We start by reviewing different definitions of attrition as well as associated inconsistencies. We then discuss the underlying mechanisms of first language attrition and review available evidence supporting different background hypotheses. Finally, we attempt to provide the groundwork to build a unified theoretical framework allowing for generalizable results. To this end, we suggest the deployment of a rigorous neuroscientific approach, in search of neural markers of first language attrition in different linguistic domains, putting forward hypothetical experimental ways to identify attrition’s neural traces and formulating predictions for each of the proposed experimental paradigms.
The spatial accuracy of transcranial magnetic stimulation (TMS) may be as small as a few millimeters. Despite such great potential, navigated TMS (nTMS) mapping is still underused for the assessment of motor plasticity, particularly in clinical settings. Here, we investigate the within-limb somatotopy gradient as well as absolute and relative reliability of three hand muscle cortical representations (MCRs) using a comprehensive grid-based sulcus-informed nTMS motor mapping. We enrolled 22 young healthy male volunteers. Two nTMS mapping sessions were separated by 5–10 days. Motor evoked potentials were obtained from abductor pollicis brevis (APB), abductor digiti minimi, and extensor digitorum communis. In addition to individual MRI-based analysis, we studied normalized MNI MCRs. For the reliability assessment, we calculated intraclass correlation and the smallest detectable change. Our results revealed a somatotopy gradient reflected by APB MCR having the most lateral location. Reliability analysis showed that the commonly used metrics of MCRs, such as areas, volumes, centers of gravity (COGs), and hotspots had a high relative and low absolute reliability for all three muscles. For within-limb TMS somatotopy, the most common metrics such as the shifts between MCR COGs and hotspots had poor relative reliability. However, overlaps between different muscle MCRs were highly reliable. We, thus, provide novel evidence that inter-muscle MCR interaction can be reliably traced using MCR overlaps while shifts between the COGs and hotspots of different MCRs are not suitable for this purpose. Our results have implications for the interpretation of nTMS motor mapping results in healthy subjects and patients with neurological conditions.
People often change their beliefs by succumbing to an opinion of the majority. Such changes are often referred to as majority influence or conformity. While some previous studies have focused on the reinforcement learning mechanisms of conformity or on its internalization, others have reported evidence of changes in sensory processing evoked by majority opinion. In this study, we used magnetoencephalographic (MEG) source imaging to further investigate the remote effects of agreement and disagreement with the majority. During the first session, participants rated the trustworthiness of faces and subsequently learned how the majority of their peers had previously rated each face. To identify the neural correlates of the post-effect of agreeing or disagreeing with the group, we recorded MEG activity while participants rated faces during the next session. We found MEG traces of past disagreement or agreement with the peer group at the parietal cortices as early as approximately 230 ms after the face onset. The neural activity of the superior parietal lobule, intraparietal sulcus, and precuneus was significantly stronger if the participant’s rating had previously differed from the ratings of his or her peers. The early MEG correlates of disagreement with the majority were followed by activity in the orbitofrontal cortex starting at about 320 ms after the face onset. Altogether, the results reveal the temporal dynamics of the neural mechanism of remote effects of disagreement with the peer group: early signatures of modified face processing were followed by later markers of long-term social influence on the valuation process at the ventromedial prefrontal cortex
Magnetoencephalography (MEG) is a neuroimaging method ideally suited for non-invasive studies of brain dynamics. MEG’s spatial resolution critically depends on the approach used to solve the ill-posed inverse problem in order to transform sensor signals into cortical activation maps. Over recent years non-globally optimized solutions based on the use of adaptive beamformers (BF) gained popularity.
When operating in the environment with a small number of uncorrelated sources the BFs perform optimally and yield high spatial resolution. However, the BFs are known to fail when dealing with correlated sources acting like poorly tuned spatial filters with low signal-to-noise ratio (SNR) of the output timeseries and often meaningless cortical maps of power distribution.
This fact poses a serious limitation on the broader use of this promising technique especially since fundamental mechanisms of brain functioning, its inherent symmetry and task-based experimental paradigms result into a great deal of correlation in the activity of cortical sources. To cope with this problem, we developed a novel data covariance modification approach that allows for building beamformers that maintain high spatial resolution when operating in the environments with correlated sources.
At the core of our method is a projection operation applied to the vectorized sensor-space covariance matrix. This projection does not remove the activity of the correlated sources from the sensor-space covariance matrix but rather selectively handles their contributions to the covariance matrix and creates a sufficiently accurate approximation of an ideal data covariance that could hypothetically be observed should these sources be uncorrelated. Since the projection operation is reciprocal to the PSIICOS method developed by us earlier (Ossadtchi et al., 2018) we refer to the family of algorithms presented here as ReciPSIICOS.
We assess the performance of the novel approach using realistically simulated MEG data and show its superior performance in comparison to the classical BF approaches and well established MNE as a method immune to source synchrony by design. We have also applied our approach to the MEG datasets from the two experiments involving two different auditory tasks.
The analysis of experimental MEG datasets showed that beamformers from ReciPSIICOS family, but not the classical BF, discovered the expected bilateral focal sources in the primary auditory cortex and detected motor cortex activity associated with the audio-motor task. In most cases MNE managed well but as expected produced more spatially diffuse source distributions. Notably, ReciPSIICOS beamformers yielded cortical activity estimates with SNR several times higher than that obtained with the classical BF, which may indirectly indicate the severeness of the signal cancellation problem when applying classical beamformers to MEG signals generated by synchronous sources.
Using movies and narratives as naturalistic stimuli in human neuroimaging studies has yielded significant ad- vances in understanding of cognitive and emotional functions. The relevant literature was reviewed, with em- phasis on how the use of naturalistic stimuli has helped advance scientific understanding of human memory, attention, language, emotions, and social cognition in ways that would have been difficult otherwise. These ad- vances include discovering a cortical hierarchy of temporal receptive windows, which supports processing of dynamic information that accumulates over several time scales, such as immediate reactions vs. slowly emerging patterns in social interactions. Naturalistic stimuli have also helped elucidate how the hippocampus supports segmentation and memorization of events in day-to-day life and have afforded insights into attentional brain mechanisms underlying our ability to adopt specific perspectives during natural viewing. Further, neuroimaging studies with naturalistic stimuli have revealed the role of the default-mode network in narrative-processing and in social cognition. Finally, by robustly eliciting genuine emotions, these stimuli have helped elucidate the brain basis of both basic and social emotions apparently manifested as highly overlapping yet distinguishable patterns of brain activity.
Background and Purpose Despite the continuing efforts in multimodal assessment of the motor system after stroke, conclusive findings on the complementarity of functional and structural metrics of the corticospinal tract (CST) integrity and the role of the contralesional hemisphere are still missing. The aim of this work was to find the best combination of the motor system parameters, allowing classification of patients into three predefined groups of upper limb motor recovery.
Methods 35 chronic ischemic stroke patients (47 [26–66] y.o., 29 [6–58] months post-stroke) with only supratentorial lesion and unilateral upper extremity weakness were enrolled. Patients were divided into three groups depending on the upper limb motor recovery. Non-parametric statistical tests and regression analysis were used to investigate the relationships among structural and functional motor system parameters, probed by diffusion tensor imaging (DTI) and transcranial magnetic stimulation (TMS). In addition, stratification rules were tested, using a decision tree classifier to identify parameters explaining motor recovery.
Results Fractional anisotropy (FA) ratio in the internal capsule (IC) and absence/presence of motor evoked potentials (MEPs), were equally discriminative of the worst motor outcome group (96% accuracy). MEP presence diverged for two investigated hand muscles. Concurrently, for the three recovery groups’ classification, the best parameter combination was: IC FA ratio and Fréchet distance between the contralesional and ipsilesional CST FA profiles (91% accuracy). No other metrics had any additional value for patients’ classification.
Conclusions This study demonstrates that IC FA ratio and MEPs absence are equally important markers for poor recovery. Importantly, we found that MEPs should be controlled in more than one hand muscle. Finally, we show that better separation between different motor recovery groups may be achieved when considering the whole CST FA profile.
While univariate functional magnetic resonance imaging (fMRI) data analysis methods have been utilized successfully to map brain areas associated with cognitive and emotional functions during viewing of naturalistic stimuli such as movies, multivariate methods might provide the means to study how brain structures act in concert as networks during free viewing of movie clips. Here, to achieve this, we generalized the partial least squares (PLS) analysis, based on correlations between voxels, experimental conditions, and behavioral measures, to identify large-scale neuronal networks activated during the first time and repeated watching of three ∼5-min comedy clips. We identified networks that were similarly activated across subjects during free viewing of the movies, including the ones associated with self-rated experienced humorousness that were composed of the frontal, parietal, and temporal areas acting in concert. In conclusion, the PLS method seems to be well suited for the joint analysis of multi-subject neuroimaging and behavioral data to quantify a functionally relevant brain network activity without the need for explicit temporal models.
Females demonstrate greater risk aversion than males on a variety of tasks, but
the underlying neurobiological basis is still unclear. We studied how theta (4–7 Hz)
oscillations at rest related to three different measures of risk taking. Thirty-five
participants (15 females) completed the Bomb Risk Elicitation Task (BRET), which
allowed us to measure risk taking during an economic game. The Domain-Specific Risk-
Taking Scale (DOSPERT) was used to measure self-assessed risk attitudes as well as
reward and punishment sensitivities. In addition, the Barratt Impulsiveness Scale (BIS11)
was included to quantify impulsiveness. To obtain measures of frontal theta asymmetry
and frontal theta power, we used magnetoencephalography (MEG) acquired prior to
task completion, while participants were at rest. Frontal theta asymmetry correlated
with average risk taking during the game but only in the female sample. By contrast,
frontal theta power correlated with risk taking as well as with measures of reward and
punishment sensitivity in the joint sample. Importantly, we showed that reward sensitivity
mediated a correlation between risk taking and the power of theta oscillations localized
to the anterior cingulate cortex. In addition, we observed significant sex differences
in source- and sensor-space theta power, risk taking during the game, and reward
sensitivity. Our findings suggest that sensitivity to rewards, associated with resting-state
theta oscillations in the anterior cingulate cortex, is a trait that potentially contributes to
sex differences in risk taking.
Confidence in our retrieved memories, that is, retrospective confidence, is a metamemory process we perform daily. There is an abundance of applied research focusing on the metamemory judgments and very diverse studies including a wide range of clinical populations. However, the neural correlates that support its functioning are not well defined impeding the implementation of noninvasive neuromodulatory clinical interventions. To address the neural basis of metamemory judgments, we ran a meta‐analysis, where we used the activation likelihood estimation method on the 19 eligible functional magnetic resonance imaging studies. The main analysis of retrospective confidence revealed concordant bilateral activation in the parahippocampal gyrus, left middle frontal gyrus, and right amygdala. We also run an analysis between the two extreme levels of confidence, namely, high and low. This additional analysis was exploratory, since the minimum amount of articles reporting these two levels was not reached. Activations for the exploratory high > low confidence subtraction analysis were the same as observed in the main analysis on retrospective confidence, whereas the exploratory low > high subtraction showed distinctive activations of the right precuneus. The involvement of the right precuneus emphasizes its role in the evaluation of low confidence memories, as suggested by previous studies. Overall, our study contributes to a better understanding of the specific brain structures involved in confidence evaluations. Better understanding of the neural basis of metamemory might eventually lead to designing more precise neuromodulatory interventions, significantly improving treatment of patients suffering from metamemory problems.
The aim of this research was to study the effect of a cue signalling the upcoming of a phobic picture on the electrocortical activity provoked by the disorder-relevant stimulus in in blood-injection-injury (BII) phobia and snake phobia. A sample of 13 BII phobia participants, 12 snake phobia individuals and 14 non-phobic controls underwent an S1-S2 task, where S1 was a word that described the content of a subsequent picture (blood-related, snake and neutral) that appeared 2 seconds later (S2). We obtained the P200 and P300 ERP amplitudes provoked by the pictures. Our results reveal that P200 did not differentiate between picture contents in BII phobia while, in contrast, snake and blood-related pictures provoked the largest responses in snake phobia participants. Both blood-related and snake pictures provoked greater P300 amplitudes than neutral pictures in all the groups. Threat cues reduced the electrocortical reaction of the BII, possibly by the elicitation of anticipatory or regulatory responses. These results are indicative of a low automatic, exogenous attention towards the feared stimuli in BII phobia, as revealed by P200, probably related to a lack of attentional bias to the phobic object.
For over a decade, neuroimaging and brain stimulation studies have investigated neural mechanisms of third-party punishment, a key instrument for social norms enforcement. However, the neural dynamics underlying these mechanisms are still unclear. Previous electroencephalographic studies on third-party punishment have shown that inter-brain connectivity is linked to punishment behavior. However, no clear evidence was provided regarding whether the effect of inter-brain connectivity on third-party punishment is mediated by local neuronal states. In this study, we further investigate whether resting-state neuronal activity in the alpha frequency range can predict individual differences in third-party punishment. More specifically, we show that the global resting-state connectivity between the right dorsolateral prefrontal and right temporo-parietal regions is negatively correlated with the level of third-party punishment. Additionally, individuals with stronger local resting-state long-range temporal correlations in the right temporo-parietal cortices demonstrated a lower level of third-party punishment. Thus, our results further support the idea that global and local neuronal dynamics can contribute to individual differences in third-party punishment.
This theoretical review clarifies the concept of "language attrition " by defining the phenomenological and contextual features of its utilization, discussing the definition of contradictions, and suggesting potential directions for future research. Taking into account existing data, we regard the existing approaches to language attrition and analyze the mechanisms underlying the phenomenon. This analysis seems to be the first step in building up an integral theoretical model summarizing the available empirical data. It helps to apply a neurobiological approach, allowing to identify neural markers of language attrition at different levels of language processing and within different language categories. To this end, we propose specific experimental approaches to recording neural traces of attrition and formulate working hypotheses based on proposed experimental paradigms.
Previous studies on the acquisition of semantics in the aspectual domain have suggested that a difficult case for achieving a targetlike representation in a second language arises when learners need to preempt a first language (L1) option (Gabriele, 2009). This study investigates this issue by focusing on a learning scenario where predicate-level variability exists in the L1 input. We investigate whether Japanese learners of English can learn to invalidate event cancellation readings (Tsujimura, 2003) in English and how such knowledge develops with increasing English proficiency. We address these questions by examining how Japanese learners of English interpret accomplishment predicates that allow an event cancellation reading in Japanese but not in English. A truth-value judgment task was administered to 60 beginner, 96 intermediate, and 40 advanced Japanese learners of English as well as 20 L1 English and 20 L1 Japanese speakers. Our results showed that Japanese learners of English progressed toward a targetlike representation of aspectual entailment. We argue that such progress follows two parallel routes: a grammatical route rooted in the learners’ growing awareness of the English determiner and number morphology combined with a statistical route rooted in the learners’ inferences based on missing data.
An increased propensity for risk taking is a hallmark of adolescent behavior with significant health and social consequences. Here, we elucidated cortical and subcortical regions associated with risky and risk-averse decisions and outcome evaluation using the Balloon Analog Risk Task in a large sample of adolescents (n=256, 56% female, age 14 ± 0.6), including the level of risk as a parametric modulator. We also identified sex differences in neural activity. Risky decisions engaged regions that are parts of the salience, dorsal attention, and frontoparietal networks, but only the insula was sensitive to increasing risks in parametric analyses. During risk-averse decisions, the same networks covaried with parametric levels of risk. The dorsal striatum was engaged by both risky and risk-averse decisions, but was not sensitive to escalating risk. Negative-outcome processing showed greater activations than positive-outcome processing. Insula, lateral orbitofrontal cortex, middle, rostral, and superior frontal areas, rostral and caudal anterior cingulate cortex were activated only by negative outcomes, with a subset of regions associated with negative outcomes showing greater activation in females. Taken together, these results suggest that safe decisions are predicted by more accurate neural representation of increasing risk levels, whereas reward-related processes play a relatively minor role.
This paper presents a novel rodent avoidance test. We have developed a specialized device and procedures that expand the possibilities for exploration of the processes of learning and memory in a psychophysiological experiment. The device consists of a current stimulating electrode-platform and custom software that allows to control and record real-time experimental protocols as well as reconstructs animal movement paths. The device can be used to carry out typical footshock-avoidance tests, such as passive, active, modified active and pedal-press avoidance tasks. It can also be utilized in the studies of prosocial behavior, including cooperation, competition, emotional contagion and empathy. This novel footshock-avoidance test procedure allows flexible currentstimulating settings. In our work, we have used slow-rising current. A test animal can choose between the current rise and time-out intervals as a signal for action in footshock avoidable tasks. This represents a choice between escape and avoidance. This method can be used to explore individual differences in decisionmaking and choice of avoidance strategies. It has been shown previously that a behavioral act, for example, pedal-pressing is ensured by motivation-dependent brain activity (avoidance or approach). We have created an experimental design based on tasks of instrumental learning: pedal-pressing in an operant box results in a reward, which is either a piece of food in a feeder (food-acquisition behavior) or an escape-platform (footshock-avoidance behavior). Data recording and analysis were performed using custom software, the open source Accord.NET Framework was used for real-time object detection and tracking.