Cortex

Many forms of memory are thought to rely on visual imagery, but individuals who report lacking visual imagery (aphantasia) can still perform various memory tasks. There is, however, evidence that aphantasia may lead to less detailed autobiographical memories, suggesting there may be deficits in the underlying cognitive processes that support personal memories. One such process is associative memory, which requires binding of different types of information. Here, we tested whether associative visual memory is intact in aphantasia. We assessed 72 self-identified individuals with aphantasia and 77 controls who reported having visual imagery. Participants completed an associative memory task which involved memorising displays where a unique object in a specific location was associated with a particular colour fixation point. Individuals with aphantasia performed equivalently to controls for object locations and outperformed controls on the associated object-identity. In addition, whereas controls were significantly worse at remembering associated object-identity than object-location, individuals with aphantasia showed no such difference. Both groups showed good metacognitive performance evidenced by a positive correlation between confidence and accuracy; there were no significant differences in confidence between the groups. Reported strategies varied between groups: a large proportion of control participants reported using visual imagery and self-reported use of imagery positively correlated with performance. Conversely, individuals with aphantasia mostly reported using nonvisual strategies to remember the associations. Overall, the findings suggest that individuals with aphantasia can form associative memories using nonvisual strategies. Thus, difficulties with autobiographical memory in aphantasia seem unlikely to be due to fundamental issues with associative memory.

This study investigated the hemispheric contributions of the inferior frontal gyrus (IFG) to word production across constrained and unconstrained tasks. In the present study, we used focal ring transcranial direct current stimulation (tDCS) in a sham-controlled, double-blind design, combined with a Picture-Word Interference (PWI) task and a picture description task. Fifty-four healthy young adults completed both tasks within the same stimulation sessions, receiving anodal stimulation over either the left or right IFG. Following task-specific data exclusions, 52 participants were included in each of the two task analyses. In the PWI task, categorically related distractors produced semantic interference and associatively related distractors facilitated naming in response times, consistent with previous findings. Stimulation did not affect response times. In error rates, the two stimulation sites modulated the associative effect in opposite directions. Anodal stimulation of the left IFG enhanced the associative advantage in error rates, whereas anodal stimulation of the right IFG produced the opposite pattern. In the picture description task, anodal stimulation of the right IFG increased speech rate, producing significant effects on words per minute, unpruned words per minute, and syllables per minute. No equivalent effects emerged in the left IFG group. Lexical diversity and utterance length were unaffected by stimulation. Taken together, these findings provide convergent evidence for a hemispheric dissociation in word production. The right IFG appears to contribute to the regulation of speech output and the control of distractor interference, whereas the left IFG appears to support the retrieval and selection of word meanings.

Verbal fluency (VF) tasks are widely used to differentiate patients with cognitive impairment from healthy controls, but total word count produced during these tasks becomes unreliable when patients and controls exhibit comparable proficiency. This study examined, in detail, whether item-level and sequential properties of words produced during a VF task could reliably differentiate high-proficiency patients indistinguishable from controls by word count alone. Seventy-seven native Mandarin Chinese speakers (38 controls and 39 patients with mild cognitive impairment or mild dementia) completed a semantic VF task. Participants were subdivided by proficiency into four groups: high-proficiency controls (HC), low-proficiency controls (LC), high-proficiency patients (HP), and low-proficiency patients (LP). The LC and HP subgroups were matched on semantic fluency scores and thus provided a key focus for the investigation. We examined item-level properties (word frequency, contextual diversity, semantic diversity, surprisal) and sequential properties (positional frequency variation) of the words produced. Significant group differences emerged across item-level psycholinguistic properties, though these were primarily driven by the LP group, with no reliable differentiation between LC and HP. Crucially, positional frequency variation distinguished LC from HP. LC participants began their lists with high-frequency words followed by a systematic decline, whereas HP patients produced words within a consistently narrow frequency band throughout. These findings indicate that item-level psycholinguistic properties alone are insufficient to differentiate HP from LC, whereas sequential word frequency variation provides a potential index of cognitive impairment, reflecting underlying differences in semantic retrieval and memory organisation. Future work with larger samples is needed to validate generalisability.

Traditional views assume that pragmatic deficits after stroke, which compromise the interpretation of communicative intentions and non-literal meanings, follow damage to the right hemisphere (RHD), with left-hemisphere damage (LHD) primarily linked to aphasia and structural language impairment. To examine hemispheric contributions to post-stroke pragmatic profiles, we assessed 99 stroke patients (40 LHD, including 14 with aphasia of minimal-to-moderate severity; 59 RHD) and 60 healthy controls with the Assessment of Pragmatic Abilities and Cognitive Substrates (APACS). While stroke patients overall performed worse than controls, LHD and RHD profiles were largely comparable across three converging analyses: (1) permutation tests revealed no hemispheric differences except on the two tasks requiring expressive components (Interview and Figurative Language 2), which in turn lowered the composites (APACS Production and Total); (2) equivalence testing established equivalence for most measures, with only these same tasks and composites remaining inconclusive; and (3) unsupervised clustering did not group patients by lesion side. Theory of Mind was robustly associated with pragmatic performance in both groups, whereas structural language abilities related specifically to LHD performance and general cognition only to RHD. Excluding aphasic LHD patients strengthened the evidence for comparable profiles, indicating that aphasic LHD patients largely drove the residual differences. In conclusion, primary pragmatic impairment, especially in the receptive domain, emerged comparably after LHD and RHD, with the only residual LHD disadvantage limited to tasks demanding open verbal output. These findings challenge the assumption of right-hemispheric specialization for pragmatics, stressing the need for pragmatic assessment in all post-stroke patients.

The absence of voluntary visual imagery, known as aphantasia, offers a unique lens into the role of visual imagery in visual memory processes such as face recognition. While aphantasics often report difficulties, behavioral differences in standard tasks have generally been small. One possibility is that the contribution of visual imagery becomes apparent only when face recognition is especially demanding. We compared age- and gender-matched aphantasics and typical imagers on the more challenging long-form version of the Cambridge Face Memory Test (CFMT+) and on a measure of inverted face recognition. We also included tasks assessing object recognition and face perception. No group differences emerged for face perception or object recognition. By contrast, typical imagers outperformed aphantasics under high visual and mnemonic demands in face recognition in the laboratory cohort, particularly at the highest difficulty level of the CFMT+ and in inverted face recognition. This effect was attenuated or even absent in the online cohort. Drift-diffusion modelling indicated that this discrepancy was primarily driven by reduced response caution in online typical imagers. A meta-analysis of published short-form CFMT studies (total N = 432) revealed a moderate and reliable advantage for typical imagers (hedges g [≤] 0.41). Finally, across cohorts and tasks, aphantasics reported consistently lower subjective confidence, independent of accuracy. Overall, these findings suggest that visual imagery benefits face recognition, and highlight the need for caution in online testing, the predominant approach in aphantasia research.

A long-standing debate surrounding the neural bases of social concepts concerns the role of anterior temporal lobe (ATL). One perspective suggests ATL subregions are dedicated specifically to social knowledge; another suggests the ATLs constitute a domain-general hub for conceptual knowledge, but with graded functional specialisation depending on connectivity to modality specific spokes. The positions have been difficult to adjudicate due to many confounding factors in tests of social and non-social knowledge. We address these challenges via three innovations in assessment of knowledge in frontotemporal dementia (FTD). First, we introduce a new task that controls for several potential confounds. Second, we apply mixed linear models to behavioural data analysis, allowing further control over confounding factors. Third, we extend the mixed-model approach to lesion-symptom mapping, identifying cortical regions where structural pathology yields a disproportionate impairment on social versus non-social knowledge when other factors are controlled. We used these techniques to probe social and non-social knowledge in FTD subtypes: semantic dementia (SD), associated with asymmetric-bilateral ATL atrophy (n=21), and behavioural-variant (bvFTD), characterised by frontoinsular atrophy (n=24). When confounding factors were controlled, people with SD showed an equal impairment for social and non-social concepts, whereas those with bvFTD were disproportionately impaired on social concepts. The differential impairment of social concepts was associated with atrophy in the insula, orbitofrontal and ventromedial prefrontal cortex and other regions implicated in social knowledge generally. The results suggest that the bilateral ATLs constitute a domain-general semantic hub, whereas ventral prefrontal and insula cortex contribute preferentially to knowledge about people.

Research suggests that motor difficulties in Developmental Coordination Disorder (DCD) are related to altered motor sequence planning, but it is unclear which mechanisms are affected, particularly in adults. This study addresses that gap by examining how the order of upcoming movements during the planning of skilled typing sequences affects motor production in adults with DCD. Previous monkey neurophysiology and behavioural findings in humans have shown that elements of a sequence are pre-ordered prior to execution, known as competitive queuing (CQ). CQ quality is predictive of subsequent performance, with skilled performers, those with fewer errors, having a larger position-dependent difference. DCD (N=28) and control participants (N=54) performed two 4-element finger sequences from memory in a delayed sequence production task over 3 sessions. Probe trials, which involved participants performing a single press after the Go Cue, assessed motor planning at each sequence position by measuring reaction time (RT) and error rate. We found that adults with DCD had a higher error rate and were slower to initiate and perform correct sequences. In terms of planning, the DCD group showed reduced preordering of sequence elements. Whilst the DCD group had a higher error rate on a working memory task, this was not correlated with the degree of pre-ordering of presses of the upcoming sequence. These findings suggest that disrupted motor sequence planning in DCD is characterised specifically by a failure to pre-order movements during the retrieval of sequences from memory. Additionally, motor sequence pre-ordering deficits in DCD are independent of general working memory impairments. These results extend prior evidence from motor imagery paradigms, demonstrating that internal modelling deficits are evident during the execution of motor plans. HighlightsO_LIAdults with DCD show diminished pre-ordering of sequential movements during planning. C_LIO_LIThe DCD group were slower to initiate and perform correct sequences from memory. C_LIO_LIMotor sequence planning is distinct from working memory performance. C_LIO_LIThis provides evidence for the IMD hypothesis in a skilled sequential task. C_LI

Background: Transcranial direct current stimulation (tDCS) is increasingly used as an adjunct to rehabilitation for young people with cerebral palsy (CP), yet considerable variability exists in clinical response. Individualised electric field modelling provides an opportunity to estimate the distribution of electrical fields generated by the stimulation delivered to the brain and explore potential relationships with functional outcomes. Methods: Structural MRI scans from nineteen participants (10-16 years) from a previously published randomised controlled trial (ISRCTN74235136) investigating the effects of tDCS combined with motor training, underwent participant-specific finite element modelling using SimNIBS. Electric field strength was quantified within anatomically defined motor regions of interest, including the primary motor cortex (M1), dorsal premotor cortex (PMd), supplementary motor area (SMA), and a combined motor network. Global grey matter electric field metrics and stimulation focality were also extracted. Results: Estimated electric field strength differed significantly across motor regions (p<0.001), with PMd receiving significantly greater stimulation than both M1 and SMA. Electric field strength within a control region (primary visual cortex) was significantly lower than within M1 (p<0.001). Despite inter-individual variability in regional and global electric field metrics, no significant associations were observed between estimated electric field strength or focality and changes in function following intervention. Conclusion: Individualised electric field modelling demonstrated that an M1-targeted tDCS montage preferentially stimulated PMd rather than M1 in young people with CP. These findings highlight the importance of subject-specific modelling when characterising current distribution and suggest that variability in electric field strength alone does not explain variability in behavioural response.

Empirical evidence from traditional inhibitory control tasks regarding inhibitory deficits in high autistic traits has been mixed, indicating that this issue remains controversial. Although sex differences are widely documented in autistic cognitive profiles, their role in inhibitory gating mechanisms remains underexplored. Given that the expression of inhibitory gating deficits may be modulated by the social versus non-social nature of stimuli, and no prior study has investigated this topic by integrating both sex differences and stimulus domain, we addressed these two questions with the attribute amnesia paradigm. We manipulated stimulus type (non-social vs. social). In Experiment 1, participants performed a location task with animal drawings as targets and were unexpectedly asked to report animal identity on a surprise trial. High autistic trait females showed significantly higher accuracy on the surprise trial than all other groups, reflecting a failure to actively filter out task-irrelevant non-social information, that is, a reduced inhibitory gating efficiency. In Experiment 2, using face stimuli and a self-vs. other-face design, this gating deficit was no longer expressed: all groups performed at chance levels on the identity judgment, regardless of autistic trait level, sex, or face type. This dissociation aligns with a dual-mechanism framework: the inhibitory gating deficit in high autistic trait females is specific to non-social stimuli and masked by camouflaging for social ones. This study demonstrates that the inhibitory gating deficit in high autistic trait females is not a global impairment but rather a stimulus-dependent one, highlighting the need to consider sex and stimulus type.

The Visual Word Form Area (VWFA), located in ventral occipitotemporal cortex, plays a critical role in skilled reading. Researchers have theorized that the VWFA develops in its specific anatomical location due to the convergence of major white matter tracts and proximity to functionally similar regions. This suggests that precise anatomical positioning may be crucial for optimal VWFA function. Previous research has identified several functional differences in this region between typical and struggling readers (i.e. dyslexia): struggling readers show weaker text-selective responses and often exhibit a smaller or even absent VWFA. However, it remains unexplored whether the precise anatomical location of this region also differs between typical and struggling readers. We tested whether VWFA anatomy differs between children with and without dyslexia (N=87). Participants completed a functional localizer, which we used to manually define the VWFA in each individuals native anatomy. We examined whether: (1) VWFA anatomical location relates to reading ability, (2) children with dyslexia show greater variability in VWFA location compared to typical readers, and (3) VWFA location with respect to white matter tracts relates to reading ability. Results reveal that, despite being smaller in children with dyslexia, there is no relationship between VWFA location and reading ability. Specifically, individual VWFA location relative to anatomy, relative to others VWFAs, and relative to white matter tracts, is not related to reading ability. These findings suggest that while the VWFAs general anatomy may be facilitated by development, its precise location remains stable and unrelated to reading proficiency.

Previous patient and imaging studies suggest that dorsal and ventral visual stream mechanisms contribute selectively to egocentric (eye-centred) and allocentric (landmark-centred) goal-directed behaviours, respectively. However, causal evidence for this ego-allocentric dissociation in healthy brains is lacking. Based on a recent neuroimaging study, we hypothesized that perturbations to dorsal stream network hubs would disrupt both egocentric and allocentric reaches, whereas perturbations to ventral hubs would affect only allocentric reaches. Sixteen participants viewed a briefly presented target in the presence of a landmark that later shifted after a memory interval. Participants were instructed to 1) ignore the landmark and reach toward / opposite the original target location (egocentric task) or 2) reach toward the targets location fixed relative to the shifted landmark (allocentric task). Transcranial magnetic stimulation (TMS) was applied during the memory period, spanning the landmark shift, at two occipital sites, based on the network hub coordinates from our previous study and individual brain anatomy. As predicted, superior occipital TMS impaired reaction time, accuracy, and precision in both tasks, whereas inferior occipital TMS only impaired allocentric performance. Further, spatial asymmetries in the resulting error patterns were influenced by TMS site and task: superior occipital TMS influenced asymmetries more strongly in the egocentric task, whereas inferior occipital TMS only influenced spatial asymmetries in the allocentric task. Finally, a functional network analysis revealed a widespread influence of TMS on network-behavior relations and another dissociation: greater influence of superior occipital TMS on the egocentric task and of inferior occipital TMS on the allocentric task. These results establish specific causal relationships between occipital hubs, widespread cortical networks, and reach behavior, confirming a default dorsal egocentric transformation for visually aimed reaches, and a role for the ventral stream for landmark-centred actions.

Fast periodic visual stimulation (FPVS) has recently demonstrated an ability to index multiple cognitive domains such as facial expression processing, working memory, and more recently, semantic categorization in just a few minutes of recording time. The present work investigates the effects of low semantic distance and how this modulates semantic categorization responses. Twenty-seven healthy young adults completed an FPVS oddball paradigm in order to determine whether comparing fruits and vegetables of the same color would elicit semantic categorization responses. Strong oddball responses were observed up to the 10th frequency harmonic, and responses showed statistically significant right occipito-temporal lateralization that was not present in a low-level color change condition completed by participants and is opposite the pattern observed in recent word-based semantic categorization FPVS studies. The findings suggest that image-based FPVS paradigms should be investigated further as candidate tools to study conditions that affect semantic categorization such as Alzheimers disease.

Automation has been shown to weaken the sense of agency (SoA), the experience of controlling ones actions and their outcomes, by disrupting the predictive link between intention and effect. Explainable AI (XAI) has been proposed as a solution, yet the neurocognitive mechanisms through which explanations restore agency remain unclear. Across three EEG experiments using an autonomous-driving paradigm, we examined how automation and different forms of AI explanations modulate explicit agency judgments and early neural markers of agency-related predictive processing. In Experiment 1, automation reduced explicit feelings of control and was associated with reduced sensory attenuation, as reflected by increased P1-N1 amplitudes, decreased N1-P2 amplitudes, and delayed N1 latencies. In Experiment 2, distal (goal-level) explanations partially restored agency and selectively modulated early auditory responses, decreasing P1-N1 and increasing N1-P2 amplitudes. In Experiment 3, combining distal and proximal (trajectory-level) explanations produced the strongest behavioural and neural restoration of agency, yielding a graded attenuation of P1-N1 and enhanced N1-P2 responses along with accelerated N1 latencies. Across all experiments, mismatch negativity (MMN) remained unaffected, indicating that pre-attentive deviance detection is preserved regardless of agency or explainability. Together, these results identify component-specific EEG markers that track fluctuations in the sense of agency and demonstrate that multi-level intention sharing by AI systems enhances both predictive engagement and explicit control experience. This work provides a neurocognitive foundation for designing explainable autonomous systems capable of maintaining user agency.

Certain conscious contents--such as the covert name of a viewed object--arise involuntarily and resist suppression, a phenomenon captured by the Reflexive Imagery Task (RIT). Whether a subliminal prime can bias which of two simultaneously present objects captures such an involuntary naming response has not been established. We adapted a two-object RIT into a self-contained, browser-based instrument. Thirty-eight adults (M age = 21.6 years, SD = 2.3; 26 female) viewed 24 object pairs and were instructed to fixate a central cross, to refrain from thinking of the objects names, and to click an object whenever its name intruded into awareness. On each trial a masked prime (17 ms, flanked by pattern masks) was either the exact name of one object (Exact Word Prime), a semantic associate of one object (Semantic Prime), or a neutral string (No Prime), defining a primed side per trial. A post-experiment debriefing confirmed that participants noticed the masks but none consciously perceived or could identify the prime words, indicating that the primes were subliminal. Analyses excluded 91 of 912 trials (10.0%) with more than five clicks. The priming effect was robust across measures: an omnibus comparison of clicks across conditions was significant (Friedman {chi}{superscript 2}(2) = 6.59, p = .037); within both prime conditions participants clicked the primed side more than the not-primed side (Exact Word, p = .039; Semantic, p = .005); and the primed-to-not-primed ratio exceeded parity by roughly 57-59% (Laplace-smoothed ratio {approx} 1.58; one-sample Wilcoxon p < .001 for each). A Bayesian Poisson generalized linear mixed model with random participant intercepts confirmed a credible primed-side advantage (incidence rate ratio = 1.72, 95% credible interval [1.57, 1.90]) that did not differ between prime types. No general left/right response bias emerged. An exploratory ight-side x Exact Word Prime interaction was inconsistent across model classes and is reported as hypothesis-generating. The findings indicate that subliminal lexical and semantic primes can steer the spatial locus of involuntary object naming.

Attention abilities, that are critical for most real-life cognitive task, can vary greatly across individuals. A plethora of behavioral and neural metric are commonly utilized to quantify attention; however, these often yield inconsistent and non-replicable results, raising questions as to which measures reliably account for and capture individual differences. To address this tension, here we employed a within-subject cross-paradigm design and quantified both behavioral and EEG-based neural measures associated with attention functioning, to test which measures converged across a gradient of artificial and ecological tasks. We found Inter-Subject Correlation (ISC), which quantifies the similarity in the pattern of neural response across individuals, captured consistent individual differences across both an artificial (Auditory Oddball) and ecological (Attention to Speech) task, with some correlation with performance. Moreover, we found that P300 neural responses to surprising events were qualitatively similar across artificial and ecological tasks, supporting their generalization across contexts. Interestingly, traditional cognitive-behavioral measures of attention - both from speeded response-time tasks and self-report of ADHD symptoms (ASRS) were not correlated with each other nor did they explain variance in neural metrics, nor were they explained by variation in general cognitive abilities (working memory or fluid intelligence). While these results demonstrate the shortcomings of many established measures of attention to generalize across contexts, they also point to the potential of neural measures, and specifically ISC, to serve as reliable indicators of individual differences and to bridge the gap between artificial and ecological studies of attention functioning.

Introduction Language functional MRI (fMRI) is a valuable tool for presurgical planning in epilepsy. Functional MRI can be challenging in children, and head motion can compromise its utility. The candidacy of patients with ADHD for fMRI is sometimes queried regarding concerns about possible head motion. In 2020, we implemented an fMRI task training program, via telehealth and/or mock MRI. We aimed to determine whether training increased language lateralisation success and/or reduced head motion in all patients, and in those with ADHD. We also aimed to determine whether patients with ADHD exhibited more head motion during fMRI than those without ADHD. Methods We retrospectively identified 223 epilepsy (85%) and other neurosurgery patients, (241 scans including repeats) with language fMRI at Royal Children's Hospital, Melbourne, Australia, 2016-2024. There were 24 individuals with ADHD listed in the Electronic Medical Record, five of whom had diagnoses of both ADHD and autism; and nine with autism. Language lateralisation success was determined by clinician description recorded as left/right/bilateral in the medical record. 99 patients were provided the training including fMRI task practise. Head motion was quantified by maximum Framewise Displacement (FDmax; mm). Results ADHD was associated with lower language lateralisation success. Training was associated with greater language lateralisation success, across all patients, and in those with ADHD. Regarding ADHD and head motion, outliers in FDmax were seen in 5 young patients with ADHD. Data were trimmed to allow separate investigation of FDmax for the sample with and without extremes of head motion. In untrimmed data, FDmax was significantly higher in patients with ADHD than in those without. In trimmed data, FDmax was on average lower in patients with ADHD than those without, however this was not statistically supported. Regarding training and head motion, across all patients, FDmax was significantly lower for scans with training than without. In patients with ADHD, FDmax was on average lower for scans with training, however training was not associated with FDmax. Conclusions Language fMRI training was associated with higher language lateralization success, particularly in patients with ADHD. Training was associated with reduced head motion across all patients. Although some young patients with ADHD had substantial head motion, most in our sample did not move more than those without ADHD. We conclude that the training program increases success of language fMRI, and that an ADHD diagnosis should not be a contraindication to language fMRI.

Objective. Figure copy and recall tests are sensitive measures of visuoconstruction and visual episodic memory, but their clinical is constrained by labor-intensive manual scoring. We developed and validated an automated, element-level scoring pipeline using Vertex AI object detection for the tablet-based figure copy and recall tasks in the California Cognitive Assessment Battery (CCAB). The automated scoring pipeline duplicated the scoring procedures used by expert manual raters. Methods. A normative sample of 2,011 community-dwelling adults aged 18-90 completed figure copy and delayed recall trials at baseline, with subsamples retested at 1 day and at 6, 18, and 30 months. Participants completed the drawings with their index finger on a tablet computer with finger position digitized to analyze the speed and timing of individual drawing strokes A convolutional object-detection model trained on the Vertex AI AutoML Vision platform identified each of twelve canonical figure elements in rendered drawings. Separate element presence and location scores were computed after homographically warping drawings onto a canonical template to produce trial-level Element, Location, and Total scores. To compare Vertex and human scores, Vertex AI and expert human raters independently scored 1500 randomly selected drawings to evaluate inter-rater agreement, including a common subset of 100 drawings scored by Vertex AI and all raters. Results. Total scores were virtually indistinguishable (r = 0.966) from human-human agreement (mean r = 0.971) as were Element presence scores (mean r = 0.959 vs. r = 0.963). Location-score agreement (r = 0.951) was slightly below the human-human mean (r = 0.972) due to pixel-level analysis by Vertex AI that was impossible for human raters. The Vertex pipeline showed no preferential advantage for the single expert rater who categorized Elements during training. Automated scores showed strong demographic gradients, age effects on Recall (r = -0.32) were approximately twice those in Copy conditions (r = -0.16). A Memory Cost score (Recall - Copy) showed a monotonic age-related decline from +0.40 z in the youngest subjects to -0.54 z in the oldest. Kinetic analysis revealed that drawing speed and efficiency showed significant age-related changes. Overnight test-retest reliability was high (Recall r = 0.72) and the Recall trial showed a large overnight learning effect ({Delta} = +1.18) that continued with repeated tests up to 30 months ({Delta} = +0.75).

Aphasia is characterized by impaired word retrieval, yet most cognitive models of word production assume that underlying conceptual-semantic representations are largely preserved. This study investigated whether concept-level semantic structure remains decodable from BOLD signals in chronic post-stroke aphasia and which semantic models best explain neural representational geometry during covert semantic feature generation. Eight healthy adults and six individuals with chronic aphasia completed a dense-sampling fMRI protocol in which they viewed 57 pictured nouns while silently generating semantic features. Representational similarity analysis showed that an experiential model (Exp48) best matched neural geometry in both people with aphasia and controls, outperforming taxonomic (WordNet) and distributional (Word2Vec, GloVe) models. Using representational similarity decoding, concept identity was recovered well above chance in both groups. No relationship was found between decoding accuracy and language measures from individuals with aphasia. These findings suggest that experiential semantic structure remains robustly represented and decodable in chronic aphasia despite lesion-related language impairments, highlighting preserved conceptual representations alongside altered anatomy.

The vestibular system has been implicated in several aspects of self-representation, including bodily self-location, yet its role in episodic source and reality monitoring remains unclear. Moreover, symptoms of depersonalisation and derealisation (DPDR) have been associated with both vestibular dysfunction and altered source and reality monitoring. We tested whether noisy galvanic vestibular stimulation (nGVS) modulates source and reality monitoring during a word-encoding paradigm and whether this increased symptoms of DPDR. Sixty young adults (N = 30 active nGVS, N = 30 sham) encoded words that varied by context (spoken vs. imagined), agentic source (self vs. other), and valence (positive vs. threat) before completing source/reality judgments. Active nGVS reduced overall accuracy relative to sham on both reality and source monitoring. Across conditions, self-referential items were remembered with greater sensitivity compared to other-referential items, and spoken items were recalled with greater sensitivity than imagined items. We additionally show an interaction effect whereby active nGVS reduced accuracy specifically for imagined and threat-valenced items. Trait DPDR did not moderate the effects of stimulation, although higher trait DPDR was associated with a more liberal reality-monitoring response criterion. Results indicate that transient vestibular perturbation via nGVS can impair source monitoring for internalised and threatening stimuli and impairs cognitive distinctions between internally and externally generated events in general, supporting a role for vestibular input in maintaining self-other and reality boundaries in episodic memory.

The coordination of sensory processing and working memory (WM) is fundamental to cognition. Spatial organization of sensory processing and WM is known to be broadly distributed across the cortex, but finer-scale organization at the interfaces between these functions remains understudied. Although the notion of sharp parcellations of cortex into distinct functional modules dominates the field, a growing body of works support graded changes in function and anatomy in some cortical zones. Based on this and potential advantages of gradient organizational structure in frontal cortex, we hypothesized that sensory-WM interfaces in the frontal cortex are gradient-like, not boundary-like. We examined twenty bilateral cortical regions that participate in visual/auditory WM tasks. In five frontal cortical regions, group-level WM activation overlapped with sensory drive, but was spatially shifted. We compared subject-level (N=20) boundary and gradient models of change in function. Strong individual-level evidence for sensory-WM gradients was observed in pre-supplementary motor area, ventral premotor cortex, and anterior insula in both modalities and in dorsal premotor cortex for visual WM. Conversely, dorsolateral pre-frontal cortex yielded mixed results, favored distinct WM and sensory regions in the left hemisphere, and gave some evidence for gradients in the right hemisphere. These results provide evidence that sensory and WM regions in frontal cortex are largely not distinct with sharp boundaries at their interfaces but instead bleed into each other to form local rostral-caudal sensory-WM gradients. We speculate these gradients may allow efficient interfacing between sensory and WM representations, and/or fine-grained, task-dependent shifting between bottom-up sensory and top-down influences.