Cortex

It is still a matter of scientific debate whether the line bisection bias frequently observed in patients with spatial neglect is due to attentional underawareness of the left end of the line, attentional hyperattention towards the right end, or a logarithmically compressed perception of the line. To address this question, neglect patients who showed a line bisection bias were administered additional tasks involving horizontal lines (e.g., number line estimation tasks). Their performance was compared to neglect patients not showing a line bisection bias, patients with right hemisphere damage without neglect, and healthy controls. Results indicated that patients with a line bisection bias tended to overestimate lefthand segments when they had to dissect lines into three or four equal parts. This is congruent with both the notions of an underawareness of lefthand segments as well as a logarithmic compression of the line. However, when these patients had to imagine the lines as bounded fraction number lines ranging from 0-1, the results were mixed. When the number lines ranged from 0-10, these patients showed rightward overestimation biases for the numbers 4 and 5. Additionally, all patient groups, but not healthy controls, tended to place number 1 too far to the left and number 9 too far to the right, suggesting a general bias towards endpoints. In sum, this seems more congruent with attentional accounts than a perceptual one. Spatial-numerical associations could be ruled out, as all participants showed a verbal number bisection bias towards smaller numbers (i.e., the left of the mental number line). Therefore, these findings seem to indicate that the line bisection bias is most likely due to underawareness of the left end rather than hyperattention towards the right or a logarithmic perception of the line.

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.

ObjectiveAssessing post-stroke spatial neglect in immersive Virtual Reality (iVR) may improve diagnostic accuracy due to its ability to combine experimental control with increased ecological validity. This study investigated the diagnostic accuracy of an iVR assessment relative to conventional and non-iVR digital tests. Additionally, feasibility was evaluated. MethodStroke patients performed an iVR assessment, conventional pen-and-paper tests (3 Cancellation tests and a line bisection test), and non-iVR digital tests (Digital Cancellation and Posner test). A new Bayesian statistical method was developed to address the absence of a gold standard for neglect. Instead of conventional diagnostic cut-offs, we quantified the uncertainty of classifying patients as having neglect or not and incorporated this into estimating diagnostic accuracy. Feasibility was evaluated using recruitment and drop-out rates, sample characteristics, cybersickness and user experience. Results54 stroke patients and 56 healthy controls completed the study. Both iVR and non-iVR digital tests had higher diagnostic accuracies than pen-and-paper tests, although differences were not statistically significant due to high diagnostic uncertainty (resulting from inconsistencies across tests). For 6 patients, the iVR assessment and Posner test indicated neglect, while pen-and-paper tests did not. The iVR assessment was feasible for most patients, with low cybersickness and positive evaluations. ConclusionThe iVR assessment and Posner test identified spatial biases missed by conventional tests. Inconsistencies across tests highlight the complexity of neglect assessment, suggesting that future studies should explore crucial test characteristics needed for a precise and sensitive evaluation. Furthermore, results established good feasibility of iVR neglect assessment.

Strong right-hand preference on the population level is a uniquely human feature, although the neural basis for this is still not clearly defined. Recent behavioural and neuroimaging literature suggests that hand preference may be related to the orchestrated function and size of fronto-parietal white matter tracts bilaterally. Lesions to these tracts induced during tumour resection may provide an opportunity to test this hypothesis. In the present study, a cohort of seventeen neurosurgical patients with left hemisphere brain tumours were recruited to investigate whether resection of certain white matter tracts affects the choice of hand selected for the execution of a goal-directed task (assembly of jigsaw puzzles). Patients performed the puzzles, but also tests for basic motor ability, selective attention and visuo-constructional ability, preoperatively and one month after surgery. Diffusion tractography of fronto-parietal tracts (the superior longitudinal fasciculus) and the corticospinal tract were performed, to evaluate whether resection of tracts was significantly associated with changes in hand selection. A complementary atlas-based disconnectome analysis was also conducted. Results showed a shift in hand selection despite the absence of any motor or cognitive deficits, which was significantly associated with patients with frontal and parietal resections, compared with those with resections in other lobes. In particular, this effect was significantly associated with the resection of dorsal fronto-parietal white matter connections, but not with the ventral fronto-parietal tract. Dorsal white matter pathways contribute bilaterally, with specific lateralised competencies, to control of goal-directed hand movements. We show that unilateral lesions, by unbalancing the cooperation of the two hemispheres, can alter the choice of hand selected to accomplish movements.

Language impairments caused by stroke (post-stroke aphasia) and neurodegeneration (primary progressive aphasia) have overlapping symptomatology, nomenclature and are classically divided into categorical subtypes. Surprisingly, primary progressive aphasia (PPA) and post-stroke aphasia (PSA) have rarely been directly compared in detail. Rather previous studies have compared certain subtypes (e.g., semantic variants) or have focussed on a specific cognitive/linguistic task (e.g., reading). This study assessed a large range of linguistic and cognitive tasks across the full spectra of PSA and PPA. We applied varimax-rotated principal component analysis to explore the underlying structure of the variance in the assessment scores. Similar phonological, semantic and fluency-related components were found for PSA and PPA. A combined principal component analysis across the two aetiologies revealed graded intragroup and intergroup variations on all four extracted components. Classification analysis was employed to test, formally, whether there were any categorical boundaries for any subtypes of PPA or PSA. Semantic dementia proved to form a true diagnostic category (i.e., within group homogeneity and distinct between group differences), whereas there was considerable overlap and graded variations within and between other subtypes of PPA and PSA. These results suggest that (a) a multi-dimensional rather than categorical classification system may be a better conceptualisation of aphasia from both causes, and (b) despite the very different types of pathology, these broad classes of aphasia have considerable features in common.

For years, dissociation studies on neurological single cases with brain lesions were the dominant method to infer fundamental cognitive functions in neuropsychology. In contrast, the association between deficits was considered to be of less epistemological value and even misleading. Still, principal component analysis (PCA) - an associational method for dimensionality reduction - recently became popular for the identification of fundamental functions. The current study evaluated the ability of PCA and factor analysis (FA) to overcome the association problem in behavioural data of neurological patients and to identify the fundamental variables underlying a battery of measures. Synthetic data were simulated to resemble neuropsychological data with typical dissociation patterns and, thereby, typical patterns of dependence between variables. In most experiments, PCA and FA succeeded to measure the underlying target variables with high up to almost perfect precision. However, this success was fragile and relied on the success of factor rotation, which failed its intended purpose when no test scores existed that primarily measured each underlying target variable. Further, commonly used strategies to estimate the number of meaningful factors appear to underfactor neuropsychological data, thereby consistently underestimating the dimensionality of the data. Finally, simulations suggested a high potential of PCA to denoise data, with factor rotation providing an additional filter function. This can be invaluable in neuropsychology, where measures are often inherently noisy, and PCA can be superior to common compound measures, such as the arithmetic mean, in the measurement of variables with high reliability. In summary, PCA and FA appear to be powerful tools in neuropsychology that are well capable to infer fundamental cognitive functions with high precision, but the typical structure of neuropsychological data and limited informative value of associations in neuropsychology place clear limitations and a risk of a complete failure on the methods.

IntroductionSustained attention and inhibition processes are fundamental components of attention that mature during adolescence, a transitive period between childhood and adulthood characterized by a rapid behavioral and cognitive development. The current study aimed to provide a better understanding of sustained attention and inhibition processes in typically developing adolescents (n = 26) aged 11-18. MethodsFunctional magnetic resonance images (fMRI) were acquired during two different modalities (the face and the scene) from a previously validated gradual{square}onset continuous (gradCPT) paradigm to evaluate sustained attention performances. In addition, we performed linear regression analyses to investigate how cerebral activation varied as a function of covariates of interest. ResultsWe showed a bilateral fronto-parieto-occipito brain activation during response inhibition regardless the type of task. Participants demonstrated better behavioral performances during the scene gradCPT. We observed a mainly left-lateralized pattern of activation in a fronto-cingulo-cerebellum area during the face gradCPT and an extended bilateral fronto-temporo-parieto-occipital activation during the scene gradCPT. Finally, we found associations between brain activity and behavioral attentional responses. ConclusionThis study gives a better understanding of the neural correlates of sustained attention and inhibition in a typically developing adolescent population.

Hallucinations are significant symptoms in psychiatric and neurodegenerative diseases, that may indicate advanced disease progression or worse disease forms. They are also frequent in healthy individuals, especially elderly or bereaved. Despite their relevance, studying hallucinations in controlled laboratory conditions remains challenging given the limited procedures inducing clinically relevant hallucinations. We have previously developed a robotics-based protocol capable of inducing a specific clinically relevant hallucination, presence hallucination (PH), in both healthy individuals and patients. Using this approach, we have systematically investigated the sensitivity and intensity of PH-induction, as well as its effects on various sensory, behavioral and cognitive aspects. In the present study, we pooled individual-participant data from 26 in-house experiments (totaling 580 individuals) and conducted a Bayesian analysis to estimate effects and moderators of PH-induction. PH-induction was reliably induced with a medium effect-size, and individuals with schizotypal traits were more sensitive. Furthermore, we identified that PH-induction may not strongly depend on altered agency, but found a synergistic relationship between passivity and induced PH. Collectively these results elucidate the role of somatomotor processes in aberrant own body perceptions, advance understanding of psychosis, and provide powerful statistical priors for future studies.

AO_SCPLOWBSTRACTC_SCPLOWO_ST_ABSBackgroundC_ST_ABSFragile X syndrome (FXS) is the most prevalent form of inherited intellectual disability and is the most common monogenetic cause of autism. Previous studies have linked the structural and functional alterations in FXS with impaired sensory processing and sensory hypersensitivity, which may hinder the early development of cognitive functions such as language comprehension. In this study, we compared the P1 response in event-related potential (ERP) and its habituation to repeated auditory stimuli in male children (2-7 years old) with and without FXS, and examined their association with clinical measures in these two groups. MethodsWe collected high-density electroencephalography (EEG) data in an auditory oddball paradigm from 12 children with FXS and 11 age- and sex-matched typically developing (TD) children. After standardized EEG pre-processing, we conducted a spatial principal component (PC) analysis and identified two major PCs -- a frontal PC and a temporal PC. Within each PC, we compared the P1 amplitude and inter-trial phase coherence (ITPC) between the two groups, and performed a series of linear regression analysis to study the association between these EEG measures and several clinical measures, including assessment scores for language development, non-verbal skills, and sensory hypersensitivity. ResultsAt the temporal PC, both early and late standard stimuli evoked a larger P1 response (p = 0.0037, p<0.0001, respectively) and higher ITPC (p = 0.0402, p = 0.0027) in FXS than in TD. We observed habituation of ITPC in both groups at the frontal PC (p = 0.0149 for FXS; p = 0.0244 for TD). Linear regression analysis showed that within the FXS group reduced frontal P1 response to late standard stimuli and increased habituation were associated with better languages scores. No associations were observed with non-verbal skills or sensory hypersensitivity. ConclusionWe identified P1 amplitude and ITPC in the temporal region as a contrasting EEG phenotype between the FXS and the TD groups. P1 response and habituation in the frontal region may be reflective of the language outcome in male children with FXS. These EEG measures are potential biomarkers for early diagnosis and future language development in patients with FXS.

Arithmetic fact retrieval has been suggested to recruit a left-lateralized network comprising perisylvian language areas, parietal areas such as the angular gyrus (AG), and subcortical structures such as the hippocampus. However, the underlying white matter connectivity of these areas has not been evaluated systematically so far. Using simple multiplication problems, we evaluated how disconnections in parietal brain areas affected arithmetic fact retrieval following stroke. We derived disconnectivity measures by jointly considering data from n=73 patients with acute unilateral lesions in either hemisphere and a white-matter tractography atlas (HCP-842) using the Lesion Quantification Toolbox (LQT). Whole-brain voxel-based analysis indicated a left-hemispheric cluster of white matter fibers connecting the AG and superior temporal areas to be associated with a fact retrieval deficit. Subsequent analyses of direct grey-to-grey matter disconnections revealed that disconnections of additional left-hemispheric areas (e.g., between the superior temporal gyrus and parietal areas) were significantly associated with the observed fact retrieval deficit. Results imply that disconnections of parietal areas (i.e., the AG) with language-related areas (i.e., superior and middle temporal gyri) seem specifically detrimental to arithmetic fact retrieval. This suggests that arithmetic fact retrieval recruits a widespread left-hemispheric network and emphasizes the relevance of white matter connectivity for number processing.

Multiple language assessments are necessary for diagnosing, characterising and quantifying the multifaceted deficits observed in many patients post-stroke. Current language batteries, however, tend to be an imperfect trade-off between time and sensitivity of assessment. There have hitherto been two main types of battery. Extensive batteries provide thorough information but are impractically long for application in clinical settings or large-scale research studies. Clinically-targeted batteries tend to provide superficial information about a large number of language skills in a relatively short period of time by reducing the depth of each test but, consequently, can struggle to identify mild deficits, qualify the level of each impairment or reveal the underlying component structure. In the current study, we compared these batteries across a large group of individuals with chronic stroke aphasia to determine their utility. In addition, we developed a data-driven reduced version of an extensive battery that maintained sensitivity to mild impairment, ability to grade deficits and the component structure. The underlying structure of these three language batteries (extensive, shallow and data-reduced) was analysed using cross-validation analysis and principal component analysis. This revealed a four-factor solution for the extensive and data-reduced batteries, identifying phonology, semantic skills, fluency and executive function in contrast to a two-factor solution using the shallow battery (phonological/language severity and cognitive severity). Lesion symptom mapping using participants factor scores identified convergent neural structures based on existing language models for phonology (superior temporal gyrus), semantics (inferior temporal gyrus), speech fluency (precentral gyrus) and executive function (lateral occipitotemporal cortex) based on the extensive and data-reduced batteries. The two components in the shallow battery converged with the phonology and executive function clusters. In addition, we show that multivariate prediction models could be utilised to predict the component scores using neural data, however not for every component score within every test battery. Overall, the data-reduced battery appears to be an effective way to save assessment time yet retain the underlying structure of language and cognitive deficits observed in post stroke aphasia.

Clinical research has documented a heterogeneous effect of neurodegenerative disorders on creativity. Some disorders are associated with impaired creative performance, while others may preserve, or even enhance, it. However, the underlying cognitive mechanisms that give rise to the heterogeneous behavioural manifestations remain poorly understood. From a theory-driven approach, we conducted a neuropsychological investigation to examine how frontotemporal lobar degeneration (FTLD), and Alzheimer's Disease (AD) differentially affected the cognitive mechanisms underlying creative thought (semantic cognition, episodic memory, executive control functions). In parallel, we assessed participants' verbal creative idea generation performance using the ideational fluency task (also known as the Alternate Uses Task). We analysed data from 24 individuals with FTLD [clinical consensus diagnosis corticobasal syndrome (CBS: n=20) or progressive supranuclear palsy (PSP: n=4)], 24 individuals with clinical consensus diagnosis AD, and 24 healthy individuals. We reached four major conclusions. First, while both disease groups exhibited deficits in controlled semantic retrieval and executive control functions, only participants with AD exhibited degradation in semantic representations and episodic memory. Second, both disease groups generated fewer responses in both typical and creative conditions across objects that were context-free - i.e., associated with multiple contexts (e.g., brick) and context-bound -i.e., associated with a dominant context (e.g., table knife). Third, when given a context-free object prompt, the ability to generate novel responses appeared to be preserved in participants with FTLD, which contrasted with an impaired ability when prompted to give creative uses for the context-bound object. Fourth, participants with AD produced similar levels of response novelty for both context-free and context-bound objects. From a clinical-cognitive neuroscience perspective, this study demonstrates that distinct cognitive profiles resulting from different neurodegenerative conditions yield differential effects on creative thought. As the first study to show that the contextual information of semantic stimuli can mediate the novelty of verbal responses, we suggest that future research should carefully examine how this factor influences creative task performance.

Visual imagery refers to the mental generation of visual representations of stimuli, while visual working memory involves retaining visual information for a short period without external input. Due to the conceptual overlap between these two constructs, successful performance on visual working memory tasks may rely on the use of visual imagery to rehearse items during the retention interval. Consequently, individuals with aphantasia, who lack voluntary visual imagery, may experience difficulties with such tasks. However, prior research has suggested that some individuals with aphantasia might employ non-visual strategies to compensate for this deficit. In two experiments, we examined visual working memory performance in aphantasic and control participants across a range of stimulus types. In Experiment 1, participants completed a change localization task using color squares and complex fractals; in Experiment 2, stimuli included real words, phonologically valid pseudowords, and phonologically invalid pseudowords. Across both experiments, aphantasic participants demonstrated significantly impaired visual working memory compared to controls. Notably, their performance was equally impaired for stimuli that were easily verbalizable (i.e., colors and words) and those that were not (i.e., fractals and pseudowords). Furthermore, individual differences in visual imagery ability, as measured by the Vividness of Visual Imagery Questionnaire (VVIQ), significantly predicted working memory performance across all stimulus types. These findings provide direct evidence for the critical role of visual imagery in supporting visual working memory.

BackgroundAudiovisual integration is essential for daily functions such as speech comprehension. It relies on a temporal constraint whereby events from different sensory modalities are perceptually bound within a limited temporal window, the audiovisual temporal binding window, defining the range of stimulus onset asynchronies perceived as synchronous. While correlational neuroimaging studies (fMRI, EEG) have implicated a distributed network in audiovisual integration, the causal neural underpinnings of the temporal binding window remain largely unknown. ObjectiveTo identify cortical regions causally supporting audiovisual simultaneity judgment. Methods: Direct electrical stimulation (DES) was prospectively applied to 62 cortical sites during awake brain surgery in 39 patients. Patients performed an audiovisual simultaneity judgment task with varying stimuli onset asynchronies alongside standard sensory-motor, language, and visuospatial tasks. Montreal Neurological Institute coordinates were obtained for all stimulated areas. ResultsDES selectively impaired audiovisual simultaneity judgments while sparing other standard tasks, in 7 highly focal, right-hemispheric cortical sites (<1 cm2). Three sites were situated around the intraparietal sulcus, and four near the supplementary motor area. Stimulation of left-hemisphere sites produced non-selective impairments, also affecting language-related tasks. ConclusionsThese findings provide causal evidence for a right-lateralized frontoparietal network, involving focal regions near the intraparietal sulcus and supplementary motor area, in audiovisual temporal integration. Given the established roles of these regions in attentional and decisional processes, this study refines their contribution to the temporal binding window network and underscores the clinical importance of preserving this network during awake brain surgery.

Healthy individuals tend to exhibit a subtle leftward attentional bias, a phenomenon termed pseudoneglect. While this bias is thought to reflect a right-hemisphere dominance when allocating spatial attention, the contribution of subcortical structures remains poorly understood. Although lesion and neuroimaging studies in clinical populations have implicated asymmetries in the basal ganglia and thalamus to dysfunction in spatial attention, it remains unclear whether naturally occurring subcortical asymmetries in healthy individuals predict behavioural biases in spatial attention. In this study, we investigated whether volumetric asymmetries in subcortical structures are associated with biases in spatial attention in a non-clinical population. This was achieved by using the landmark task to assess spatial biases, alongside acquiring T1-weighted MRI data from 44 healthy participants. The subcortical regions were segmented using the FIRST algorithm to estimate the volumetric asymmetry of specific regions. We found that variability in pseudoneglect was predicted by the degree of leftward lateralisation of putamen volume, indicating that the putamen contributes to the magnitude of spatial attention biases. This also suggests that the left putamen may support right-hemisphere neocortical dominance through the indirect pathway. These findings bridge anatomical and behavioural measures, highlighting the functional relevance of subcortical asymmetry in shaping attentional processes in the healthy brain. Our findings pave the way for early diagnosis of neurological disorders associated with subcortical atrophies including Parkinsons Disease and dementia. Significance StatementHemispheric dominance in cortical networks shape attentional biases, but the role of subcortical structures remains poorly understood. Here we show that natural variability in the lateralisation of the putamen predicts individual differences in pseudoneglect--a subtle leftward bias in spatial attention observed in healthy adults. Using MRI and psychophysics, we demonstrate that greater leftward putamen asymmetry is associated with stronger leftward bias, independent of eye dominance and microsaccadic behaviour, and moderated by handedness. These findings reveal a structural subcortical basis for attentional asymmetries and suggest that simple behavioural measures could serve as non-invasive markers of early subcortical changes relevant to disorders such as Parkinsons disease, Alzheimers disease, and ADHD.

The ability to understand spoken language is essential for social, vocational, and emotional health, but can be disrupted by environmental noise, injury, or hearing loss. These auditory deficits can be ameliorated by visual speech signals that convey redundant or supplemental speech information, but the brain regions critically responsible for these audiovisual (AV) interactions remain poorly understood. Previous TMS and lesion-mapping studies suggest that the left posterior superior temporal sulcus (pSTS) is causally implicated in producing the McGurk effect, an AV illusion in which auditory and visual speech are perceptually "fused." However, previous research suggests that the McGurk effect is neurally and behaviorally dissociable from other visual effects on speech perception and, therefore, may not provide a generalizable index of AV interactions in speech perception more broadly. To examine whether the left pSTS is critically responsible for AV speech integration more broadly, we measured the strength of the McGurk effect, AV facilitation effects, and AV conflict effects longitudinally over 2 years in patients undergoing surgery for intrinsic tumors in the left pSTS (n = 2) or frontal lobes (control; n = 14). Results demonstrated that left pSTS lesions impaired experience of the McGurk effect, but did not uniformly reduce visual influences on speech perception. Additionally, when multisensory behaviors were affected by a lesion, AV speech perception abilities could recover over time. Our results suggest a causal dissociation between perceptual benefits produced by congruent AV speech and perceptual modulations produced by incongruent AV speech (the McGurk effect).These data are consistent with models proposing that that the pSTS is only one of multiple critical areas necessary for AV speech interactions.

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.

While language impairment is the defining symptom of aphasia, the co-occurrence of non-language cognitive deficits and their importance in predicting rehabilitation and recovery outcomes is well documented. Despite this, people with aphasia (PWA) are rarely tested on assessments of higher order cognitive functions, making it difficult for studies to associate these functions with a consistent lesion correlate. Contrary to classic models of speech and language, cumulative evidence shows that Brocas area and surrounding regions in the left inferior frontal cortex (LIFC) are involved in, but not specific to, speech production - suggesting that these regions may be involved in higher-level cognitive functions that support language production. A better understanding of language processing in the context of other domain general cognitive functions is essential for improving aphasia treatments. This study aimed to explore the brain-behaviour relationships between tests of individual cognitive skill and language abilities in people with post-stroke aphasia, with a focus on language production deficits and their associated lesion correlates. We predicted our analysis would reveal a latent (non-language specific) cognitive component, that would be driven by damage to LIFC. We analysed the behavioural and neural correlates of an extensive battery of language and non-language cognitive tests in a sample of thirty-six adults with long-term speech production deficits from post-stroke aphasia. All participants were anomic, with relatively intact speech comprehension and no apraxia of speech. The behavioural variables were analysed using Principal Component Analysis and their neural correlates were estimated using Voxel-Based Correlational Morphology. A significant number of anomic adults showed impaired performance on tests of non-language specific cognitive function. The variance underlying behavioural performance was best captured by four orthogonal components, two higher-order cognitive components (executive functions and verbal working memory) and two linguistic processing components (phonology and semantics). Brain-behaviour relationships revealed separable neural correlates for each component in line with previous studies and an executive functions correlate in the left inferior frontal cortex (LIFC). Our findings suggest that in adults with chronic post-stroke language production deficits (anomia), higher-level cognitive functions explain more of the variance in language function than classical models of the condition imply. Additionally, lesions to the LIFC, including Brocas area, were associated with executive (dys)function, independent of language abilities, suggesting that lesions to this area are associated with non-language specific higher-level cognitive functions that support speech production. These findings support contemporary models of speech production that place language processing within the context of domain-general perception, action and conceptual knowledge.

Brain networks supporting visual memory include extrastriate and other cortical regions associated with visual perception, which manifest domain-specific processing of "where," "how," and various aspects of "what" information. However, whether and how such specialization affects memory for these types of information is still a matter of debate. Functional neuroimaging studies point to dissociable as well as common network components supporting the perception and memory of different aspects of visual information. In the current neuropsychological study, we assess the impact of stroke lesion topography on recall of identity, location, and action of event participants, as assessed by the WMS-III Family Pictures subtest. We used voxel-based lesion-behavior mapping (VLBM) to identify brain lesions specifically implicated in memory deficits for each dimension. Behavioral analysis disclosed impaired performance by both right- and left-hemisphere damage patients, with lesions on each side yielding distinct effects. VLBM analysis revealed a bi-hemispheric network supporting these various aspects of visual memory. In the right hemisphere, the network includes frontal, parietal, and temporal cortical regions and the basal ganglia. In the left hemisphere, the network is more restricted, including visual association areas and medial temporal lobe regions. We further observed that a subset of these regions - those included in the ventral ("what") stream, and in the putative core recollection network - is implicated in multiple aspects of visual memory, whereas other areas are specifically implicated in memory for specific aspects of the visual scene.

The organization of semantic knowledge within the brain has long been studied through various theoretical frameworks and is still a matter of debate. Many studies that have helped advancing our knowledge about this topic have approached it in the context of its deterioration, notably in patients with semantic dementia. In healthy subjects, the question whether and how semantic distance between concepts represented by picture or word stimuli influences brain responses remains understudied. In this study with 24 healthy subjects, we used electroencephalography (EEG) recordings coupled with a fast periodic visual stimulation (FPVS) approach, for the first time, to assess the semantic distance effect with different stimulus modalities. Picture or word stimuli from a reference category (birds) appeared every fourth item among a 4-Hz stream of either man-made objects (forming the high distance [HD] condition) or other animals (low distance [LD] condition). Within a few minutes of recording, EEG responses were observed at the pre-determined frequency of the reference category presentation (at 1 Hz), suggesting its exemplars were activated at least sufficiently to be automatically discriminated from different superordinate (HD) and basic (LD) categories, for both pictures and words. Pictures and words elicited a different pattern of response to semantic distance, with larger amplitudes for HD than LD conditions for pictures but a reversed pattern of somewhat greater amplitudes for LD than HD conditions for words. Our findings support a similarity-based structure of semantic representations and provide evidence for a differential mapping between semantic and picture/word surface representations.