Graph analysis uncovers an opposing impact of methylphenidate on connectivity patterns within default mode network sub-divisions.

BACKGROUND: The Default Mode Network (DMN) is a central neural network, with recent evidence indicating that it is composed of functionally distinct sub-networks. Methylphenidate (MPH) administration has been shown before to modulate impulsive behavior, though it is not yet clear whether these effects relate to MPH-induced changes in DMN connectivity. To address this gap, we assessed the impact of MPH administration on functional connectivity patterns within and between distinct DMN sub-networks and tested putative relations to variability in sub-scales of impulsivity. METHODS: Fifty-five right-handed healthy adults underwent two resting-state functional MRI (rs-fMRI) scans, following acute administration of either MPH (20 mg) or placebo, via a randomized double-blind placebo-controlled design. Graph modularity analysis was implemented to fractionate the DMN into distinct sub-networks based on the impact of MPH (vs. placebo) on DMN connectivity patterns with other neural networks. RESULTS: MPH administration led to an overall decreased DMN connectivity, particularly with the auditory, cinguloopercular, and somatomotor networks, and increased connectivity with the parietomedial network. Graph analysis revealed that the DMN could be fractionated into two distinct sub-networks, with one exhibiting MPH-induced increased connectivity and the other decreased connectivity. Decreased connectivity of the DMN sub-network with the cinguloopercular network following MPH administration was associated with elevated impulsivity and non-planning impulsiveness. CONCLUSION: Current findings highlight the intricate effects of MPH administration on DMN rs-fMRI connectivity, uncovering its opposing impact on distinct DMN sub-divisions. MPH-induced dynamics in DMN connectivity patterns with other neural networks may account for some of the effects of MPH administration on impulsive behavior.

Differential contribution of between and within-brain coupling to movement synchronization.

A fundamental characteristic of the human brain that supports behavior is its capacity to create connections between brain regions. A promising approach holds that during social behavior, brain regions not only create connections with other brain regions within a brain, but also coordinate their activity with other brain regions of an interaction partner. Here we ask whether between-brain and within-brain coupling contribute differentially to movement synchronization. We focused on coupling between the inferior frontal gyrus (IFG), a brain region associated with the observation-execution system, and the dorsomedial prefrontal cortex (dmPFC), a region associated with error-monitoring and prediction. Participants, randomly divided into dyads, were simultaneously scanned with functional near infra-red spectroscopy (fNIRS) while performing an open-ended 3D hand movement task consisting of three conditions: back-to-back movement, free movement, or intentional synchronization. Results show that behavioral synchrony was higher in the intentional synchrony compared with the back-to-back and free movement conditions. Between-brain coupling in the IFG and dmPFC was evident in the free movement and intentional synchrony conditions but not in the back-to-back condition. Importantly, between-brain coupling was found to positively predict intentional synchrony, while within-brain coupling was found to predict synchronization during free movement. These results indicate that during intentional synchronization, brain organization changes such that between-brain networks, but not within-brain connections, contribute to successful communication, pointing to shift from a within-brain feedback loop to a two-brains feedback loop.

Altered activation in the action observation system during synchronization in high loneliness individuals.

Lonely people tend to evaluate social exchanges negatively and to display difficulties in interactions. Interpersonal synchronization is crucial for achieving positive interactions, promoting affinity, closeness, and satisfaction. However, little is known about lonely individuals' ability to synchronize and about their brain activity while synchronizing. Following the screening of 303 participants, we recruited 32 low and 32 high loneliness participants. They were scanned while engaged in movement synchronization, using a novel dyadic interaction paradigm. Results showed that high loneliness individuals exhibited a reduced ability to adapt their movement to their partner's movement. Intriguingly, during movement adaptation periods, high loneliness individuals showed increased activation in the action observation (AO) system, specifically in the inferior frontal gyrus and the inferior parietal lobule. They did not show increased activation in the dorsomedial prefrontal cortex, which in the context of synchronization was suggested to be related to gap-monitoring. Based on these findings, we propose a model according to which lonely people may require stronger activation of their AO system for alignment, to compensate for some deficiency in their synchronization ability. Despite this hyperactivation, they still suffer from reduced synchronization capacity. Consequently, synchronization may be a relevant intervention area for the amelioration of loneliness.

Oxytocin increases the social salience of the outgroup in potential threat contexts.

A growing body of literature suggests that OT administration may affect not only prosocial outcomes, but also regulate adversarial responses in the context of intergroup relations. However, recent reports have challenged the view of a fixed role of OT in enhancing ingroup favoritism and outgroup derogation. Studying the potential effects of OT in modulating threat perception in a context characterized by racial miscegenation (Brazil) may thus afford additional clarification on the matter. In a double-blind, placebo-controlled study, White Brazilian participants completed a first-person shooter task to assess their responses towards potential threat from racial ingroup (White) or outgroup (Black) members. OT administration enhanced the social salience of the outgroup, by both increasing the rate at which participants refrained from shooting unarmed Black targets to levels similar to White targets, and by further increasing the rate of correct decisions to shoot armed Black targets (versus White armed targets). In summary, our results indicate that a single dose of OT may promote accurate behavioral responses to potential threat from members of a racial outgroup, thus offering support to the social salience hypothesis.

Language Control in Diglossic and Bilingual Contexts: An Event-Related fMRI Study Using Picture Naming Tasks.

The diglossic socio-linguistic situation in Arabic refers to the use of two language varieties in everyday life. Spoken Arabic (SA) is acquired first and used for everyday informal communication, while Literary Arabic (LA) is acquired at school and used for reading, writing and formal functions. Accordingly, the question whether LA functions as a second language had repeatedly been raised. In this study participants performed picture naming in SA in: (i) a simple naming context (SNc); (ii) a first language selection diglossic context mixing SA and LA (fLSc) and (iii) a second language selection bilingual context mixing SA and Hebrew (sLSc). Behavioral and event-related functional magnetic resonance imaging (fMRI) responses were analyzed to examine whether the comparison of picture naming in SA in different contexts will reveal differences related to control processes. Behavioral measures indicated that SA naming in SNc was easier than in fLSc and sLSc, while analysis of fMRI data revealed a significant effect of context. Region of interest analysis in six areas that were activated during the task exhibited two distinct patterns of differences in activation between fLSc and sLSc on the one hand, and SNc on the other. These results are explained in terms of the differential engagement of cognitive control modules and discussed in the light of current views suggesting that domain-general executive modules are adaptively recruited depending on the demands of the interactional context.

When first language is not first: an functional magnetic resonance imaging investigation of the neural basis of diglossia in Arabic.

In Arabic, the language used for everyday conversation ('spoken Arabic' - SA) differs markedly from literary Arabic (LA), which is used for written communication and formal functions. This fact raises questions regarding the cognitive status of the two varieties and their processing in the brain. Previous studies using auditory stimuli suggested that LA is processed by Arabic native speakers as a second language. The current study examined this issue in the visual modality. Functional magnetic resonance imaging (fMRI) responses were collected while Arabic-Hebrew bilinguals performed a semantic categorization task on visually presented words in LA, SA and Hebrew. Performance on LA was better than SA and Hebrew, which did not differ from each other. Activation in SA was stronger than in LA in left inferior frontal, precentral, parietal and occipito-temporal regions, and stronger than in Hebrew in left precentral and parietal regions. Activation in SA was also less lateralized than activation for LA and Hebrew, which did not differ from each other in terms of lateralization, though activation for Hebrew was more extensive in both hemispheres than activation for LA. Altogether, these results indicate an advantage for LA in the current study, presumably due to participants' proficiency in reading in this language. Stronger activation for SA appears to be due to the relative unfamiliarity of written word forms in SA, which could also explain differences in performance between the two languages. However, the stronger activation observed in the left parietal cortex may also reflect stronger associations among words in SA.

Inclusion motivation: Measuring the drive to be included in real time and how it is affected by loneliness.

Humans have a fundamental need to belong and affiliate with others. The term inclusion motivation, coined here, represents the drive of the individual toward an active attempt to be included, at least as equally as others, in social interactions. It is postulated to be triggered by social exclusion and further influenced by personal traits and other stable conditions. To assess inclusion motivation, we developed the active inclusion task (AIT), which is based on the cyberball paradigm. The AIT allows participants for the first time to actively influence their inclusion during conditions of fair play and exclusion, by waving a virtual hand controlled by keyboard presses. In the first step of our study, we examined how different levels of required effort affect the performance of participants (N = 154) by using two versions of the AIT that differ in the magnitude of influence generated by each keypress. Using basic measures of motivation, we found that behavioral inhibition predicted lower numbers of keypresses during exclusion compared with fair play, only when high effort was required. Conversely, higher behavioral activation predicted higher numbers of keypresses across conditions. In the second step of our study, we tested whether loneliness accounts for differences in inclusion motivation. Results show that higher loneliness score predicted higher number of keypresses during exclusion compared with fair play, only when low effort was required. Collectively, we propose that inclusion motivation should be considered as a prominent facet of motivation with the potential to explain social behavior in health and in psychopathology. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Fronto-striatal connectivity patterns account for the impact of methylphenidate on choice impulsivity among healthy adults.

Choice impulsivity depicts a preference towards smaller-sooner rewards over larger-delayed rewards, and is often assessed using a delay discounting (DD) task. Previous research uncovered the prominent role of dopaminergic signaling within fronto-striatal circuits in mediating choice impulsivity. Administration of methylphenidate (MPH), an indirect dopaminergic agonist, was shown to reduce choice impulsivity in animals and pathological populations, although significant inter-individual variability in these effects was reported. Whether MPH impacts choice impulsivity among healthy individuals, and whether variability in the impact of MPH is related to fronto-striatal activation and connectivity patterns, has yet to be assessed. Here, fifty-seven healthy young adults completed the DD task twice during fMRI scans, after acute administration of either MPH (20 mg) or placebo, in a randomized double-blind placebo-controlled design. Acute MPH administration was found to reduce choice impulsivity at the group level, yet substantial variability in this behavioral response was observed. MPH was also found to increase activation in the bilateral putamen and the right caudate, and to enhance functional connectivity between the left putamen and medial prefrontal cortex (mPFC), particularly during non-impulsive choices. Notably, the more putamen-mPFC functional connectivity increased during non-impulsive choices following MPH administration, the less an individual was likely to make impulsive choices. These findings reveal, for the first time in healthy adults, that acute MPH administration is associated with reduced choice impulsivity and increased striatal activation and fronto-striatal connectivity; and furthermore, that the magnitude of MPH-induced change in fronto-striatal connectivity may account for individual differences in the impact of MPH on impulsive behavior.

A dual-brain approach for understanding the neuralmechanisms that underlie the comforting effects of social touch.

Across different cultures, social touch is used to alleviate distress. Here we adopt a dual-brain approach with fMRI to examine whether social touch involves similar activations between the suffering 'target' and the empathizer in brain regions related to emotional sharing such as the observation-execution (mirror) network. To inspect the neural underpinnings of the effects of social touch on pain, we scanned romantic couples during a task that required one partner (the empathizer) to hold the target's hand as the latter experienced painful thermal stimulation. Empathizers and target participants were scanned sequentially, in two counterbalanced phases. Results revealed that hand-holding reduced the pain of the target participant, compared to the severity of pain in a control condition (holding a rubber ball). Importantly, during social touch we found striking shared activations between the target and empathizer in the inferior parietal lobule (IPL), a region related to the observation-execution network. The brain-to-brain analysis further revealed a positive correlation of IPL activation levels between the target and the empathizer. Finally, psychophysiological interaction (PPI) analysis in the target showed that the IPL activity during social touch was positively coupled with activity in the dorsomedial prefrontal cortex, a region that has been implicated in emotion regulation, suggesting that the interaction between the observation-execution network and emotion regulation network may contribute to pain reduction during social touch.

Different laterality patterns of the error-related negativity in corrected and uncorrected errors.

While measuring event-related brain potentials, a divided visual field paradigm was used to discern laterality patterns of the error-related negativity (ERN) in healthy human participants. Two tasks of hemispheric specialty were used (bargraph judgement, lexical decision) and a flanker task. For corrected errors in all tasks, stronger ERN amplitude was found following right visual field presentation. For corrected errors in the specialised tasks, shorter ERN latency was revealed on the side to which the stimulus was presented, while for uncorrected errors it was shorter on the other side. In the flanker task, ERN latency after corrected errors was shorter over the RH regardless of the side to which the stimulus was presented. Results are interpreted to reveal patterns of hemispheric specialisation, independence, and cooperation in error detection that depend on the type of error been committed.

Prior Knowledge Predicts Early Consolidation in Second Language Learning.

Language learning occurs in distinct phases. Whereas some improvement is evident during training, offline memory consolidation processes that take place after the end of training play an important role in learning of linguistic information. The timing of offline consolidation is thought to depend on the type of task, with generalization of implicit knowledge suggested to take more time and sleep to consolidate. The current study aims to investigate individual differences in the timing of consolidation following learning of morphological inflections in a novel language in typical adults. Participants learned to make plural inflections in an artificial language, where inflection was based on morpho-phonological regularities. Participants were trained in the evening, and consolidation was measured after two intervals: 12 h (one night) and 36 h (two nights) post training. We measured both inflection of trained items, which may rely on item-specific learning, and generalization to new untrained items, which requires extraction of morpho-phonological regularities. The results for both trained and un-trained items showed two patterns of consolidation: early versus late, that is while some participants improved during the first night, others, who deteriorated in performance during the first night, improved in the later consolidation interval. Importantly, phonological awareness in L1 predicted early consolidation for trained items. Furthermore, there was no association between participants' consolidation trajectory in trained and untrained items. Our results suggest that consolidation timing depends on the interaction between task characteristics and individual abilities. Moreover, the results show that prior meta-linguistic knowledge predicts the quality of early consolidation processes. These results are consistent with studies in rodents and humans, showing that prior knowledge accelerates consolidation of newly learnt episodic memory. Finally, the rate of consolidation across exposures to the language might explain some of the variability found in the attained level of second language proficiency.

Lexical Competition between Spoken and Literary Arabic: A New Look into the Neural Basis of Diglossia Using fMRI.

Diglossia in the Arabic language refers to the socio-linguistic situation in which Spoken Arabic (SA), which is the first to be acquired, is used for everyday communications, while Literary Arabic (LA), acquired at school for reading and writing, is also used for formal functions. Although some authors consider SA and LA as a first and second language, the question of how these are managed in the brain has not yet been understood. Using functional magnetic resonance brain imaging (fMRI) analysis, this study aimed at exploring the neural basis of diglossia during picture naming in two contexts. In the first, healthy young participants were instructed to name each image either in SA or LA on the basis of cue word appearing after the stimulus. In the second, they were instructed to name images either in SA or in Hebrew. Behavioral analysis showed that naming in SA was slightly easier than LA and considerably easier than Hebrew. fMRI analysis showed no difference between SA and LA. Hebrew compared to SA revealed activation differences explainable in terms of engagement of language control modules and second- to first-language effects. These findings, discussed in the light of previous findings in bilingual literature, support the view that dominance in diglossia is modality-dependent.

The neural bases of the learning and generalization of morphological inflection.

Affixal inflectional morphology has been intensively examined as a model of productive aspects of language. Nevertheless, little is known about the neurocognition of the learning and generalization of affixal inflection, or the influence of certain factors that may affect these processes. In an event-related fMRI study, we examined the neurocognition of the learning and generalization of plural inflections in an artificial language, as well as the influence of both affix type frequency (the proportion of words receiving a given affix) and affix predictability (based on phonological cues in the stem). Adult participants were trained in three sessions, and were scanned after the first and last sessions while inflecting trained and untrained words. Untrained words yielded more activation than trained words in medial frontal (including pre-SMA) and left inferior frontal cortices, which have previously shown activation in compositional grammatical processing. A reliance on phonological cues for untrained word inflection correlated positively with pre-SMA activation, but negatively with activation in the pars triangularis. Thus, pre-SMA may be involved in phonological cue-based composition, while the pars triangularis underlies alternative processes. Inflecting trained items yielded activation in the caudate head bilaterally, only in the first session, consistent with a role for procedural memory in learning grammatical regularities. The medial frontal and left inferior regions activated by untrained items were also activated by trained items, but more weakly than untrained items, with weakest activation for trained-items taking the high-frequency affix. This suggests less involvement of compositional processes for inflecting trained than untrained items, and least of all for trained inflected forms with high-frequency affixes, consistent with the storage of such forms (e.g., in declarative memory). Overall, the findings further elucidate the neural bases of the learning and generalization of affixal morphology, and the roles of affix type frequency and affix phonological predictability in these processes. Moreover, the results support and further specify the declarative/procedural model, in particular in adult language learning.

Enhanced reading by training with imposed time constraint in typical and dyslexic adults.

Poor reading skills of developmental dyslexics persist into adulthood with standard remediation protocols having little effect. Nevertheless, reading improves if readers are induced to read faster. Here we show that this improvement can be enhanced by training. Training follows a multi-session procedure adapted to silent sentence reading, with individually set, increasingly more demanding, time constraints (letter-by-letter masking). In both typical and dyslexic adult readers, reading times are shortened and comprehension improves. After training, the dyslexic readers' performance is similar to that of typical readers; moreover, their connected text reading times and comprehension scores significantly improve in standard reading tests and are retained at 6 months post training. Identical training without time constraints proves ineffective. Our results suggest that fluent reading depends in part on rapid information processing, which then might affect perception, cognitive processing and possibly eye movements. These processes remain malleable in adulthood, even in individuals with developmental dyslexia.

Source localization of error negativity: additional source for corrected errors.

Error processing in corrected and uncorrected errors was studied while participants responded to a target surrounded by flankers. Error-related negativity (ERN/NE) was stronger and appeared earlier in corrected errors than in uncorrected errors. ERN neural sources for each error type were analyzed using low-resolution electromagnetic tomography method of source localization. For corrected errors, the ERN source was located at the anterior cingulate (BA 24) and the medial and superior frontal regions (presupplementary motor area, BA 6), whereas it was located at the anterior cingulate (BA 24) for uncorrected errors. It is suggested that the anterior cingulate is the main source of the ERN with the presupplementary motor area contributing to ERN initiation only if the correct response tendency is sufficiently active to allow for full execution of a correction response.