Understanding novel metaphors (e.g., Passion is a storm) requires semantic control processes to activate relevant semantic properties (i.e., intense) rather than irrelevant properties (i.e., weather). The degree to which the left inferior frontal gyrus (LIFG), which is traditionally considered a literal language semantic control region, is functionally involved in metaphor processing remains unresolved in neurocognitive theories of semantic processing. Here, high-definition transcranial direct current stimulation (HD-tDCS) was applied to the LIFG to examine its functional role in metaphor comprehension. Participants received either anodal stimulation (n = 20), which increases the excitability of neurons, or sham stimulation (n = 20), and subsequently rated metaphorical (e.g., Passion is a storm), literal (e.g., A gorilla is an ape), and nonsensical (e.g., Depression is a party) sentences on comprehensibility. Participants who received anodal stimulation rated metaphors to be less comprehensible than participants who received sham stimulation. No effects were observed for literal or nonsensical sentences. In addition, word-level semantic characteristics affected metaphor comprehensibility ratings but not literal or nonsensical sentences. These findings demonstrate that the LIFG plays a causal role in the controlled retrieval of semantic properties that is necessary for metaphor comprehension.
While known primarily for respiratory symptoms, COVID-19 has also been linked to cognitive impairments, or "brain fog", which affects attention, memory, and processing speed. Brain-fog related cognitive deficits are well-documented in hospitalized patients but less understood in non-hospitalized individuals. Brain fog may reflect dysfunction in cortical structures supporting higher-level cognition, including hippocampal, frontotemporal, and cingulate areas. These regions contribute to the P3b response, an electrophysiological measure of attention and memory used to assess cognitive deficits across neurological conditions, though sparingly in COVID-19. This study examined P3b mean amplitudes in individuals with and without COVID-19-related brain fog and pre-pandemic controls using a visual n-back paradigm. It was hypothesized that the brain fog group would show reduced amplitudes under higher cognitive loads. Results revealed reduced target-related P3b mean amplitudes in the brain fog group relative to both comparison groups, with no group differences for non-targets. This reduction was most apparent over parietal recording sites but did not significantly vary by scalp region. The brain fog group demonstrated lower accuracy and slower reaction times relative to controls. These differences persisted an average of 22.58 months following symptom resolution, suggesting brain fog may be associated with attentional resource deficits that extend beyond subjective recovery.
The term extreme environment is widely used in applied human performance research and is often assigned on the basis of environmental features alone, such as temperature, altitude, noise, isolation, or threat. Although convenient for designing controlled studies, this environment-centric convention limits generalization by overlooking individual differences, adaptation, compensation, and cases in which performance remains near typical while internal costs and vulnerability increase. We argue that extremeness should instead be treated as a dynamic, relational demand-capacity phenomenon in which external and internal demands push individuals or teams beyond normative physiological, cognitive, emotional, or behavioral operating ranges, constraining adaptive capacity and increasing instability, error risk, and delayed recovery. Building on theories of compensatory control, allostasis, workload, resilience, and adaptation, we propose a working definition centered on departures from normative operating envelopes across neurophysiology, cognition, affect, behavior, and recovery. Moving beyond mean performance change, we outline an operationalization strategy emphasizing variability, state dependence, strategy shifts, and hysteresis. We also describe experimental designs and computational approaches for quantifying extremeness before overt failure and conclude with a translational agenda for improving readiness, safety, and human-machine teaming.
While the categorical perception (CP) of musical pitch is often attributed to systematic musical training, prior work suggests that long-term experience, such as language background, can also shape pitch processing. However, it remains unclear whether musical pitch CP undergoes automatic neural processing at the pre-attentive stage. This study utilized event-related potentials (ERPs) to investigate the automatic neural representation of musical pitch CP in Mandarin-speaking non-musicians. We employed a passive auditory oddball paradigm, presenting standard, within-category, and between-category deviant tones from two pitch continua to 26 participants while recording the mismatch negativity (MMN). The results revealed that between-category deviants elicited a significantly larger MMN amplitude compared to within-category deviants. Furthermore, despite previous behavioral studies indicating varying categorization strengths across different pitch registers, the MMN-indexed categorization effect showed no significant difference between the two continua. These findings provide neurophysiological evidence for automatic categorical perception of musical pitch in non-musicians, supporting a two-stage model where early sensory processing is robust to variations that affect later, attention-dependent cognitive categorization.
Simultaneous physical and cognitive demands challenge military operational capability under prolonged stress. While the independent effects of fatigue on performance are established, no study has systematically compared the effects of isolated and combined fatigue states on performance. This study examined the effect of physical, cognitive, and combined fatigue on military marksmanship performance. Participants (N = 24; M age = 22.04 + 3.22 years, male = 20) completed three study visits, with seven days between visits, encompassing a physical, cognitive, and combined fatigue protocol and common military marksmanship tasks. Results demonstrated significant differences in marksmanship accuracy (p < .001; partial η2 = 0.57), discriminatory reaction time (p = .002; partial η2 = 0.15), and marksmanship efficiency (p < .001; partial η2 = 0.15-0.17). Posthoc decomposition confirmed that combined fatigue produced significantly greater decrements (Cohen's d = 0.78-1.12). Additionally, results revealed significant differences in self-reported mental and physical demand (p < .001), temporal demand (p = .014; partial η2 = 0.17), and effort, frustration, and perceived exertion (p's < 0.001). These findings demonstrate the negative, compounding effect of combined fatigue on military marksmanship performance and highlight the need for comprehensive training programs, interventions, and countermeasures that address the challenges of real-world combat operations.
Distractor-induced deafness (DID) refers to the impaired detection of an auditory target when it is preceded by acoustically similar, task-irrelevant distractors, despite being signaled by an auditory cue. Here, we test whether distractor processing generalizes across cue modalities using a cross-modal DID paradigm in which a visual cue signals the onset of an auditory target following varying numbers of auditory distractors. Target detection declines linearly with increasing distractor number at a cue-target stimulus-onset asynchrony (SOA) of 0 ms, but remains largely preserved at 300 ms, reproducing the behavioral DID signature. Electrophysiologically, distractors elicit a fronto-central negativity comparable to that reported in unimodal DID; under cross-modal cueing in the present experiment, however, its amplitude remains insensitive to increasing distractor load. By contrast, amplitudes in the subsequent P3 range show the expected linear decrease with increasing distractor number. Together, these findings indicate that multiple auditory distractors impair target detection irrespective of cue modality, whereas their ERP correlates appear to differ. Although the underlying neurocognitive mechanism cannot be conclusively determined from the present data alone, our findings are consistent with the possibility that cue modality influences auditory distractor processing.
Statistical learning, the ability to detect regularities between events, can be understood as an emergent property of predictive and memory-based mechanisms that continuously shape how sensory input is encoded and segmented based on prior experience. However, the extent to which statistical learning is influenced by prior context remains relatively underexplored. This work investigated whether initial exposure to a random syllable stream alters the neural and behavioral mechanisms underlying subsequent artificial language learning. In Experiment 1 (random-first group, N = 41; structure-first group; N = 40), adult participants completed a two-alternative forced-choice task after exposure to a structured stream containing trisyllabic "words," either preceded by a random stream or not. Similarly, Experiment 2 (random-first group, N = 20; structure-first group; N = 20) captured listeners' neural responses to syllable and word frequencies during exposure to the artificial language, providing a real-time index of segmentation processes. Results showed better word segmentation for the structure-first group than for the random-first group in both experiments. These findings that early exposure to randomness can interfere with the neural encoding of regularities suggest that statistical learning is not purely stimulus-driven, but dynamically shaped by learning context.
BACKGROUND:Capgras syndrome is characterized by the delusional belief that familiar individuals have been replaced by identical impostors. Current models attribute the syndrome to disrupted affective familiarity despite preserved perceptual recognition, but the underlying network mechanisms and the role of alternative sensory modalities remain unclear. METHODS:We studied a patient with Capgras syndrome following a right hemispheric hemorrhagic stroke. Neuropsychological assessment, behavioral experiments, and galvanic skin response recordings evaluated multimodal person recognition. Structural lesion mapping, disconnectome analysis, and lesion network mapping identified the neural substrates of the syndrome and the restoration of familiarity through tactile input. RESULTS:The patient recognized that his wife and son looked identical to themselves but insisted they were impostors. Object, semantic, and structural face recognition were preserved, whereas emotion recognition was impaired. Visual and auditory presentation of his son failed to evoke recognition or autonomic responses. In contrast, tactile interaction restored correct identification and robust GSR responses. Network analyses demonstrated disruption of a right-lateralized network linking face-processing regions with limbic and frontal systems involved in familiarity and belief evaluation. CONCLUSIONS:These findings support a network-disconnection model of Capgras syndrome and suggest that tactile input can transiently restore familiarity through alternative multisensory pathways.
The ventromedial prefrontal cortex (vmPFC) encodes subjective value across monetary and social outcomes, but whether it tracks individual differences in fairness preferences remains unclear. We applied computational modeling to an openly available fMRI dataset in which participants completed an Ultimatum Game with a computer, an ingroup peer, and an outgroup peer. Individual disadvantageous inequality aversion parameters (α) were estimated from behavioral data using a one-parameter Fehr-Schmidt model, and vmPFC activation was extracted trial-by-trial using a coordinate-based region of interest. Offer size predicted vmPFC activation across proposer types, consistent with a value-coding role. α moderated vmPFC responses for ingroup offers: participants with stronger inequality aversion showed a weaker vmPFC signal when receiving offers from an ingroup peer. A direct contrast of the ingroup and outgroup slopes did not reach significance, and the corresponding effect in a ventral striatum control region was null. At the subject level, α did not predict overall vmPFC engagement. These results indicate that vmPFC value signals are associated with individual fairness preferences within the ingroup context, with only weak evidence that this association differs across proposer types. The findings extend prior work on group-modulated fairness processing.
Early adolescence represents a sensitive developmental period characterized by rapid maturation of large scale brain systems and heightened vulnerability to environmental influences, such as exposure to violence. Guided by the Triple Network Model of Psychopathology and the Dimensional Model of Adversity and Psychopathology, this study examined if intrinsic functional connectivity between the default mode network, frontoparietal network, and salience network and two subcortical regions (hippocampus and amygdala) mediated associations between violence exposure and psychopathology using data from the Adolescent Brain Cognitive Development (ABCD) Social Development Study. Violence exposure domains, including conventional crime, peer victimization, witnessing violence, internet victimization and school climate, had direct associations with increased internalizing and externalizing symptoms. Internet victimization demonstrated strong associations with neurobehavioral development, influencing communication between brain networks and regions. Violence exposure was associated with decreased connectivity across cortical-subcortical pairs, except for salience network-hippocampus connectivity which increased and emerged as a consistent mediator across multiple domains of violence. These findings suggest that alterations in large scale network communication may represent intermediate neurodevelopmental vulnerabilities linking violence exposure to later psychopathology during early adolescence. Results emphasize the importance of understanding trajectories of brain development in the face of violence exposure, as they may provide insights into potential biomarkers for early intervention and inform more targeted prevention and treatment strategies.
We report a highly selective manifestation of pathological laughter in which speech initiation consistently triggers laughter, resulting in disrupted articulation. A 55-year-old male with bilateral pontine infarction exhibited laughter that was time-locked to speech, most prominent during speech production and absent during non-speech tasks. Functional MRI during speech demonstrated activation of language regions, medial prefrontal cortex, amygdala, and ventral pons, with concurrent subjective laughter. We propose that ventral pontine lesions disrupt inhibitory pathways, leading to disinhibition of brainstem laughter circuits. We use the descriptive term ‘gelastic dysarthria’ to characterize the selectively speech-triggered manifestation of pathological laughter and propose a pontine gating mechanism to account for its observed phenomenology.
BACKGROUND:Grounded in the perspective of language as a high-order cognitive organizer, language engages multiple domains, suggesting that linguistic stimulation may strengthen cognitive resources holistically. Despite its potential for promoting neuroplasticity and mitigating decline, the underlying neural mechanisms and their correlation with behavioral outcomes remain unclear. OBJECTIVE:To synthesize neuroimaging evidence on the effects of linguistic-cognitive interventions on brain structure and function across the cognitive aging continuum (healthy, SCD, MCI, and AD). METHODS:Following PRISMA 2020, we searched articles produced between 2009 and 2024 with randomized controlled trials evaluating neuroimaging outcomes following linguistic-cognitive interventions. Ten studies met inclusion criteria. Data were independently extracted by four reviewers, and risk of bias was assessed with Cochrane RoB 2.0. Neuroimaging modalities included structural measures (VBM, DTI) and functional measures (rs-fMRI, PET). RESULTS:Samples ranged from 30 to 160 participants, aged 64-82 years, with 3.4-17.1 years of education. Six studies reported significant post-intervention brain changes (five functional, one structural). Functional effects were mainly observed in the default mode network, frontoparietal regions, and hippocampal circuits. Structural findings included gray matter increases and improved white matter integrity. Neuroimaging effects were more frequent in MCI/AD and in in-person versus online/hybrid interventions. However, six studies found no significant behavioral improvement despite neural changes. Risk of bias was high in seven studies. CONCLUSIONS:Linguistic-cognitive interventions can modulate brain connectivity and, less consistently, structure in aging. Neuroimaging may be a sensitive biomarker of intervention efficacy, but larger, longitudinal, multimodal trials with ecologically valid outcomes are needed.
The present study investigated whether temporary dieting modulates neural coding of subjective preferences for edible and non-edible rewards. Forty-five dieting and 49 non-dieting healthy adults completed a gambling task while EEG was recorded. In each trial, subjects opened virtual doors to receive individually-rated high, medium, or low preference edible or non-edible rewards. Unexpectedly, dieting did not have an effect on the reward-locked event-related potential (ERP). However, the P2 was generally increased for edible rewards. In contrast, the feedback-related negativity (FRN) was not sensitive to reward type. Preference coding was found in both FRN and P3. It was most pronounced for the P3 frontally, with increased positivity for medium and high relative to low preference, only for edible rewards. Preference coding was less distinct for non-edible rewards, particularly parietally. Further analyses indicated sustained centroparietal preference coding beyond the P3, especially for edible rewards. Taken together, neural coding of subjective preferences seems to be more distinctive for primary compared to secondary rewards, possibly due to increased motivational significance and evaluative processing as well as attentional allocation for primary rewards. The absence of dieting effects indicates that subjective preferences constitute robust, possibly trait-like, phenomena not readily modulated by interventions such as short-term dieting.
Masked priming has been used to influence recognition memory familiarity by increasing or decreasing fluency. These manipulations affect Event-Related Potential (ERP) activity occurring 300-500 ms after the probe. In this article, several datasets from previously published studies were reanalyzed to investigate the effect of baseline period on ERP measurements and to determine whether two different ERP components occur during the 300-500 ms interval. In addition, a novel study was conducted to measure the effect of orthographically similar (OS) primes on ERP measures. The baseline period had little effect on ERP measures and OS word primes do not elicit disfluency effects when fluency-inducing primes are not part of the test sequence. Furthermore, three datasets provided evidence that prime effects and topography 300-400 ms was distinct from the activity occurring 400-500 ms. These effects are taken as strong evidence for models that argue fluency can affect two types of familiarity (i.e., relative and absolute familiarity, Mecklinger & Bader, 2020).
Elucidating the relationship between large-scale and small-scale spatial abilities is fundamental to advancing our understanding of spatial cognition, with training transfer effects across tasks offering a direct means of exploration. This study investigated how spatial navigation training in a large-scale environment influences both large- and small-scale spatial abilities and their underlying neural mechanisms. Participants completed 20 days of real-world campus navigation training and performed large-scale (distance judgment) and small-scale (paper folding) spatial tasks before and after training. The training group showed significant improvements in both tasks, whereas the control group did not. Brain imaging revealed increased activation in the right middle frontal gyrus (MFG) and bilateral posterior cingulate cortex (PCC) during large-scale task performance after training. In contrast, improvements in the small-scale task were associated with reduced deactivation in the right postcentral gyrus (PoCG), right precuneus, and left superior temporal gyrus (STG). Overall, these findings indicate that spatial navigation training enhances large- and small-scale spatial cognition through distinct neural mechanisms, supporting the partial dissociation model and highlighting the contribution of regions showing task-related deactivation.
Moral persuasion represents a complex form of social cognition, requiring the dynamic integration of moral reasoning, emotional regulation, attentional control, and interpersonal alignment across interacting individuals. This study investigated phase-specific neural alignment to examine how cognitive, emotional, and regulatory processes become coordinated across individuals during a dyadic moral persuasion speech interaction, using electroencephalography (EEG) hyperscanning. Fourteen same-gender dyads engaged in a structured, four-phase dialogue about a moral dilemma. Inter-brain dynamics were assessed using the Euclidean-distance of power spectral density across five EEG bands and three cortical regions (frontal, temporo-parietal, parieto-occipital).Results revealed greater inter-brain dissimilarity in frontal regions compared to posterior areas, particularly in the delta and gamma bands, suggesting differentiated regulatory and evaluative processes between participants. Furthermore, alpha-band dissimilarity varied significantly across discourse phases: divergence was higher during the persuadee’s perspective disclosure phase (PPD), while convergence increased during the final conclusion phase (FCP). This pattern may suggest an initial divergent cognitive processing followed by increased neural alignment toward resolution. By revealing region-specific patterns of inter-brain divergence and convergence, this study provides initial insights into the understanding of how neural dynamics support role- and phase-dependent cognitive and regulatory processes during moral persuasion.
Motor imagery (MI) activates motor networks without overt movement and is widely used in motor learning and rehabilitation. However, its effect on corticospinal excitability (CSE) and short-interval intracortical inhibition (SICI) have yet to be systematically evaluated. Following PRISMA guidelines, we searched PubMed, PsycINFO, MEDLINE, and SportDiscus in January 2021 and in June 2025. Studies were included if they used transcranial magnetic stimulation (TMS) to measure motor evoked potential amplitude or SICI during or after MI in healthy adults. We included 105 studies. Of 70 comparing MI with rest, 63 reported increased CSE. Post-MI facilitation was observed in 9 of 16 studies. Five of six showed greater CSE during motor execution than MI. SICI was examined in 16 studies; nine comparing MI to rest, five reported reduced inhibition, particularly with higher conditioning stimulus intensities (∼80% resting motor threshold). Type of task, imagined force, expertise and combined interventions (e.g., concurrent action observation) modulated CSE during MI. Overall, MI reliably increases CSE relative to rest and can reduce SICI under specific conditions. These results support MI as a tool for engaging motor circuits and highlight the need for standardised protocols.
Understanding environmental sound recognition provides insight into the neural and cognitive mechanisms underlying nonverbal auditory semantics. In this study, we investigated the clinical characteristics and neural correlates of environmental sound recognition impairments in primary progressive aphasia (PPA). Fifty-three patients with PPA (25 non-fluent/agrammatic, nine semantic, five logopenic, and 14 unclassified), age-matched healthy controls, and patients with other dementia syndromes were examined. Audiological measures included pure-tone thresholds, verbal sound recognition (phoneme identification), and auditory temporal acuity. Neuropsychological testing and neuroimaging with magnetic resonance imaging and N-isopropyl-p-123I-iodoamphetamine single-photon emission computed tomography were performed. Environmental sound recognition was assessed using sound-to-picture-and-word matching tasks. Across PPA subtypes, performance correlated with naming, auditory word comprehension, two-way anomia reflecting semantic memory deficits, and category fluency; however, not with basic auditory measures. Impairment was associated with reduced regional cerebral blood flow in the left posterior temporal-temporoparietal regions, and this association remained significant after accounting for regional atrophy. These findings suggest that environmental sound recognition deficits across PPA subtypes are unlikely to be explained solely by basic auditory dysfunction and may involve disruption of posterior auditory-semantic interface regions. (180)
Musical rhythm performance has previously been associated with cognitive functioning in healthy older adults. However, the extent to which performance of increasingly complicated rhythms associates with cognitive functioning is less well known. We hypothesized that older adults would perform worse than younger adults, and that executive functions and processing speed would associate with rhythm performance. Forty-nine neuropsychiatrically healthy participants were included in analyses (n = 25, ages 18-35; n = 24, ages 55-89). Neuropsychological assessment included measures of processing speed, working memory, set shifting and nonverbal reasoning. Participants learned and performed 30 musical rhythm exercises of increasing complexity. There was a significant main effect of rhythm complexity on timing error. Age also showed a significant main effect, with older adults exhibiting greater error overall. Set-shifting ability was identified as a factor in timing error in older adults. These findings suggest that older adults are less accurate than younger in performing rhythms and that performance in older adults is sensitive to baseline executive functioning. Further research on underlying differences in brain structure, metabolism and function related to rhythm performance is necessary to understand mechanisms of change in rhythm abilities and relationship with non-musical cognitive processes.
