Distinct Neural Substrates Research Articles

Updates in Motor Learning: Implications for Physical Therapist Practice and Education.

Over the past 3 decades, the volume of human motor learning research has grown enormously. As such, the understanding of motor learning (ie, sustained change in motor behavior) has evolved. It has been learned that there are multiple mechanisms through which motor learning occurs, each with distinctive features. These mechanisms include use-dependent, instructive, reinforcement, and sensorimotor adaptation-based motor learning. It is now understood that these different motor learning mechanisms contribute in parallel or in isolation to drive desired changes in movement, and each mechanism is thought to be governed by distinct neural substrates. This expanded understanding of motor learning mechanisms has important implications for physical therapy. It has the potential to facilitate the development of new, more precise treatment approaches that physical therapists can leverage to improve human movement. This Perspective describes scientific advancements related to human motor learning mechanisms and discusses the practical implications of this work for physical therapist practice and education.

Hippocampal-Cortical Encoding Activity Predicts the Precision of Episodic Memory.

Our recollections of past experiences can vary in both the number of specific event details accessible from memory and the precision with which such details are reconstructed. Prior neuroimaging evidence suggests the success and precision of episodic recollection to rely on distinct neural substrates during memory retrieval. In contrast, the specific encoding mechanisms supporting later memory precision, and whether they differ from those underlying successful memory formation in general, are currently unknown. Here, we combined continuous measures of memory retrieval with model-based analyses of behavioral and neuroimaging data to tease apart the encoding correlates of successful memory formation and mnemonic precision. In the MRI scanner, participants encoded object-scene displays and later reconstructed features of studied objects using a continuous scale. We observed overlapping encoding activity in inferior prefrontal and posterior perceptual regions to predict both which object features were later remembered versus forgotten and the precision with which they were reconstructed from memory. In contrast, hippocampal encoding activity significantly predicted the precision, but not overall success, of subsequent memory retrieval. The current results align with theoretical accounts proposing the hippocampus to be critical for representation of high-fidelity associative information and suggest a contribution of shared cortical encoding mechanisms to the formation of both accessible and precise memory representations.

False memories activate distinct brain regions in females and males

The constructive process of memory is generally successful; however, it can also lead to memory failures such as false memories. Although true memories and false memories rely on some of the same brain regions, these memory types are also mediated by distinct neural substrates. Of relevance, there is a growing body of evidence that there are sex differences in the brain during true memories. However, no studies have investigated whether there are neural sex differences during false memories. In the current fMRI study, across all subjects, false memories produced activity in the precentral sulcus and superior parietal lobule, replicating previous findings. Males produced greater activity than females in the precuneus, posterior cingulate cortex, parietooccipital sulcus, and fusiform gyrus. Females produced greater activity than males in the medial prefrontal cortex, anterior cingulate cortex, paracentral lobule, supramarginal gyrus, lateral sulcus, cingulate sulcus, the putamen, and V1. An interaction analysis revealed a significant interaction between sex and region with a higher magnitude of activity in the hippocampus for males than females and a higher magnitude of activity in V1 for females than males. The current results suggest that false memories are supported by distinct brain regions and cognitive processes in females and males.

Distinct Neural Substrates Support Phonological and Orthographic Working Memory: Implications for Theories of Working Memory.

Prior behavioral and neuroimaging evidence supports a separation between working memory capacities in the phonological and orthographic domains. Although these data indicate distinct buffers for orthographic and phonological information, prior neural evidence does indicate that nearby left inferior parietal regions support both of these working memory capacities. Given that no study has directly compared their neural substrates based on data from the same individuals, it is possible that there is a common left inferior parietal region shared by both working memory capacities. In fact, those endorsing an embedded processes account of working memory might suggest that parietal involvement reflects a domain-general attentional system that directs attention to long-term memory representations in the two domains, implying that the same neural region supports the two capacities. Thus, in this work, a multivariate lesion-symptom mapping approach was used to assess the neural basis of phonological and orthographic working memory using behavioral and lesion data from the same set of 37 individuals. The results showed a separation of the neural substrates, with regions in the angular gyrus supporting orthographic working memory and with regions primarily in the supramarginal gyrus supporting phonological working memory. The results thus argue against the parietal involvement as supporting a domain-general attentional mechanism and support a domain-specific buffer account of working memory.

Functional connectivity evidence for state-independent executive function deficits in patients with major depressive disorder

BackgroundPersistent neurocognitive deficits are often associated with poor outcomes of major depressive disorder (MDD). Executive dysfunction is the most common cognitive deficit in MDD. However, it remains unclear which subcomponent of executive dysfunction is state-independent with distinct neural substrates. MethodsA comprehensive neurocognitive test battery was used to assess four subcomponents of executive function (working memory, inhibition, shifting, and verbal fluency) in 95 MDD patients and 111 matched healthy controls (HCs). After 6 months of paroxetine treatment, 56 patients achieved clinical remission (rMDD) and completed the second-time neurocognitive test. Network-based statistics analysis was utilized to explore the changes in functional connectivity (FC). ResultsCompared with the HCs, all the four subcomponents of MDD patients were significantly impaired. After treatment, there was a significant improvement in working memory, inhibition, and verbal fluency in the rMDD group. And shifting and verbal fluency of the rMDD group remained impaired compared with the HCs. Fifteen functional connections were interrupted in the MDD group, and 11 connections remained in a disrupted state after treatment. Importantly, verbal fluency was negatively correlated with the disrupted FC between the right dorsal prefrontal cortex and the left inferior parietal lobule in patients with MDD and remitted MDD. LimitationsThe correlation analysis of the association between cognitive impairment and connectivity alterations precluded us from making causal inferences. ConclusionsVerbal fluency is the potential state-independent cognitive deficit with distinct neural basis in patients with MDD.

Better the devil you know than the devil you don't: Neural processing of risk and ambiguity

Risk and ambiguity are inherent in virtually all human decision-making. Risk refers to a situation in which we know the precise probability of potential outcomes of each option, whereas ambiguity refers to a situation in which outcome probabilities are not known. A large body of research has shown that individuals prefer known risks to ambiguity, a phenomenon known as ambiguity aversion. One heated debate concerns whether risky and ambiguous decisions rely on the same or distinct neural circuits. In the current meta-analyses, we integrated the results of neuroimaging research on decision-making under risk (n = 69) and ambiguity (n = 31). Our results showed that both processing of risk and ambiguity showed convergence in anterior insula, indicating a key role of anterior insula in encoding uncertainty. Risk additionally engaged dorsomedial prefrontal cortex (dmPFC) and ventral striatum, whereas ambiguity specifically recruited the dorsolateral prefrontal cortex (dlPFC), inferior parietal lobe (IPL) and right anterior insula. Our findings demonstrate overlapping and distinct neural substrates underlying different types of uncertainty, guiding future neuroimaging research on risk-taking and ambiguity aversion.

Diffusion property and functional connectivity of superior longitudinal fasciculus underpin human metacognition

Metacognition as the capacity of monitoring one's own cognition operates across domains. Here, we addressed whether metacognition in different cognitive domains rely on common or distinct neural substrates with combined diffusion tensor imaging (DTI) and functional magnetic resonance imaging (fMRI) techniques. After acquiring DTI and resting-state fMRI data, we asked participants to perform a temporal-order memory task and a perceptual discrimination task, followed by trial-specific confidence judgments. DTI analysis revealed that the structural integrity (indexed by fractional anisotropy) in the anterior portion of right superior longitudinal fasciculus (SLF) was associated with both perceptual and mnemonic metacognitive abilities. Using perturbed mnemonic metacognitive scores produced by inhibiting the precuneus using TMS, the mnemonic metacognition scores did not correlate with individuals' SLF structural integrity anymore, revealing the relevance of this tract in memory metacognition. To further verify the involvement of several cortical regions connected by SLF, we took the TMS-targeted precuneus region as a seed in a functional connectivity analysis and found the functional connectivity between precuneus and two SLF-connected regions (inferior parietal cortex and precentral gyrus) mediated mnemonic metacognition performance. These results illustrate the importance of SLF and a putative white-matter grey-matter circuitry that supports human metacognition.

Distinct neural substrates of receptive and responsive aspects of empathy in patients with neurodegenerative disease

AbstractBackgroundThe way we interact with each other is influenced by how we perceive and evaluate socioemotional signals and adapt our interpersonal behavior to them (Lieberman, 2007). In this study, we investigated the neurostructural substrates of two key aspects of interpersonal behavior: socioemotional sensitivity and behavioral self‐management, using a neurodegenerative disease lesion model.MethodSocioemotional sensitivity and behavioral self‐management were measured by obtaining informant reports from two subscales of the Revised Self‐Monitoring Scale (RSMS)(Lennox & Wolfe, 1984). Scores were correlated with structural volume using voxel‐based morphometry. The study enrolled 360 participants, including 251 patients diagnosed with one of five neurodegenerative disease syndromes causing diverse structural brain changes (77 behavioral variant frontotemporal dementia, 30 semantic variant primary progressive aphasia, 33 non‐fluent variant primary progressive aphasia, 57 progressive supranuclear palsy, and 54 Alzheimer’s disease) and 109 neurologically healthy older controls.ResultSensitivity to others’ social cues was significantly predicted by volume in predominantly right‐hemispheric paralimbic ventro‐anterior‐ and mesio‐temporal regions, some of which are known to support auditory and visual social signal reading, while the remaining regions were part of the frontotemporal semantic appraisal network (Yeo, et al., 2011), involved in making social evaluations. In contrast, capacity to make behavioral adjustments in response to social cues was uniquely predicted by volume in predominantly right‐hemispheric neocortical frontal regions that comprise the cingulo‐opercular stable task control network (Dosenbach, et al., 2007), involved in maintaining attention during socioemotional tasks.ConclusionOur results clarify how receptive and responsive aspects of empathy rely on distinct, predominantly right‐hemispheric anterior fronto‐temporal brain regions, largely comprising two intrinsically connected networks including the semantic appraisal and cingulo‐opercular task control networks, along with right temporal structures mediating person perception. The fidelity with which this questionnaire method revealed these specific brain networks shows that standardized informant reports are valuable tools in assessing the complex socioemotional constructs involved in empathy. Lastly, the specificity of these brain‐behavior correlations provides further evidence that observable, measurable patterns of decreased empathy in patients with brain disorders can be a direct result of differently localized brain lesions.

Distinct neural substrates of individual differences in components of reading comprehension in adults with or without dyslexia

Reading comprehension is a complex task that depends on multiple cognitive and linguistic processes. According to the updated Simple View of Reading framework, in adults, individual variation in reading comprehension can be largely explained by combined variance in three component abilities: (1) decoding accuracy, (2) fluency, and (3) language comprehension. Here we asked whether the neural correlates of the three components are different in adults with dyslexia as compared to typically-reading adults and whether the relative contribution of these correlates to reading comprehension is similar in the two groups. We employed a novel naturalistic fMRI reading task to identify the neural correlates of individual differences in the three components using whole-brain and literature-driven regions-of-interest approaches. Across all participants, as predicted by the Simple View framework, we found distinct patterns of associations with linguistic and domain-general regions for the three components, and that the left-hemispheric neural correlates of language comprehension in the angular and posterior temporal gyri made the largest contributions to explaining out-of-scanner reading comprehension performance. These patterns differed between the two groups. In typical adult readers, better fluency was associated with greater activation of left occipitotemporal regions, better comprehension with lesser activation in prefrontal and posterior parietal regions, and there were no significant associations with decoding. In adults with dyslexia, better fluency was associated with greater activation of bilateral inferior parietal regions, better comprehension was associated with greater activation in some prefrontal clusters and lower in others, and better decoding skills were associated with lesser activation of bilateral prefrontal and posterior parietal regions. Extending the behavioral findings of skill-level differences in the relative contribution of the three components to reading comprehension, the relative contributions of the neural correlates to reading comprehension differed based on dyslexia status. These findings reveal some of the neural correlates of individual differences in the three components and the underlying mechanisms of reading comprehension deficits in adults with dyslexia.

Distinct neural substrates for the perception and imagery of scenes

Distinct neural substrates for the perception and imagery of scenes

Common and distinct neural substrates of sentence production and comprehension

Functional neuroimaging and lesion-symptom mapping investigations implicate a left frontal–temporal–parietal network for sentence processing. The majority of studies have focused on sentence comprehension, with fewer in the domain of sentence production, which have not fully elucidated overlapping and/or unique brain structures associated with the two domains, particularly for sentences with noncanonical word order. Using voxel-based lesion symptom mapping (VLSM) we examined the relationship between lesions within the left hemisphere language network and both sentence comprehension and production of simple and complex syntactic structures in 76 participants with chronic stroke-induced aphasia. Results revealed shared regions across domains in the anterior and posterior superior temporal gyri (aSTG, pSTG), and the temporal pole (adjusted for verb production/comprehension). Additionally, comprehension was associated with lesions in the anterior and posterior middle temporal gyri (aMTG, pMTG), the MTG temporooccipital regions, SMG/AG, central and parietal operculum, and the insula. Subsequent VLSM analyses (production versus comprehension) revealed critical regions associated with each domain: anterior temporal lesions were associated with production; posterior temporo-parietal lesions were associated with comprehension, implicating important roles for regions within the ventral and dorsal stream processing routes, respectively. Processing of syntactically complex, noncanonical (adjusted for canonical), sentences was associated with damage to the pSTG across domains, with additional damage to the pMTG and IPL associated with impaired sentence comprehension, suggesting that the pSTG is crucial for computing noncanonical sentences across domains and that the pMTG, and IPL are necessary for re-analysis of thematic roles as required for resolution of long-distance dependencies. These findings converge with previous studies and extend our knowledge of the neural mechanisms of sentence comprehension to production, highlighting critical regions associated with both domains, and further address the mechanism engaged for syntactic computation, controlled for the contribution of verb processing.

Taking the sublexical route: brain dynamics of reading in the semantic variant of primary progressive aphasia.

Reading aloud requires mapping an orthographic form to a phonological one. The mapping process relies on sublexical statistical regularities (e.g. 'oo' to |uː|) or on learned lexical associations between a specific visual form and a series of sounds (e.g. yacht to/jɑt/). Computational, neuroimaging, and neuropsychological evidence suggest that sublexical, phonological and lexico-semantic processes rely on partially distinct neural substrates: a dorsal (occipito-parietal) and a ventral (occipito-temporal) route, respectively. Here, we investigated the spatiotemporal features of orthography-to-phonology mapping, capitalizing on the time resolution of magnetoencephalography and the unique clinical model offered by patients with semantic variant of primary progressive aphasia (svPPA). Behaviourally, patients with svPPA manifest marked lexico-semantic impairments including difficulties in reading words with exceptional orthographic to phonological correspondence (irregular words). Moreover, they present with focal neurodegeneration in the anterior temporal lobe, affecting primarily the ventral, occipito-temporal, lexical route. Therefore, this clinical population allows for testing of specific hypotheses on the neural implementation of the dual-route model for reading, such as whether damage to one route can be compensated by over-reliance on the other. To this end, we reconstructed and analysed time-resolved whole-brain activity in 12 svPPA patients and 12 healthy age-matched control subjects while reading irregular words (e.g. yacht) and pseudowords (e.g. pook). Consistent with previous findings that the dorsal route is involved in sublexical, phonological processes, in control participants we observed enhanced neural activity over dorsal occipito-parietal cortices for pseudowords, when compared to irregular words. This activation was manifested in the beta-band (12-30 Hz), ramping up slowly over 500 ms after stimulus onset and peaking at ∼800 ms, around response selection and production. Consistent with our prediction, svPPA patients did not exhibit this temporal pattern of neural activity observed in controls this contrast. Furthermore, a direct comparison of neural activity between patients and controls revealed a dorsal spatiotemporal cluster during irregular word reading. These findings suggest that the sublexical/phonological route is involved in processing both irregular and pseudowords in svPPA. Together these results provide further evidence supporting a dual-route model for reading aloud mediated by the interplay between lexico-semantic and sublexical/phonological neurocognitive systems. When the ventral route is damaged, as in the case of neurodegeneration affecting the anterior temporal lobe, partial compensation appears to be possible by over-recruitment of the slower, serial attention-dependent, dorsal one.

Distinct neural substrates underlying target facilitation and distractor suppression: A combined voxel-based morphometry and resting-state functional connectivity study

Selective attention, the ability to filter relevant from a sea of sensory information, relies on the prioritization of goal-relevant information (target facilitation) and the suppression of goal-irrelevant information (distractor suppression). Although several lines of evidence have shown that target facilitation and distractor suppression were mediated by distinct mechanisms, the underlying neural substrates remain unclear. To address this question, we acquired structural and resting-state magnetic resonance imaging scans, as well as behavioral data from a modified Posner cueing task. Specifically, the location of a target (Target Cue, TC) and a distractor (Distractor Cue, DC) was either cued in advance to separately trigger target facilitation and distractor suppression, or no predictive information was provided, serving as a baseline. We combined voxel-based morphometry (VBM) and resting-state functional connectivity (rsFC) analyses to explore the neural correlates of behavioral benefits, yielding the following results. First, behavioral data showed faster responses to TC and DC conditions compared to baseline, the benefits of which were named TC-benefit and DC-benefit. Second, the VBM analysis revealed that the gray matter volume (GMV) in the superior frontal (SFG) and postcentral gyrus inversely correlated with individual TC-benefit, while the GMV in the superior parietal lobe, middle frontal gyrus, and angular gyrus inversely correlated with individual DC-benefit, indicating that target facilitation and distractor suppression was associated with the GMV of distinct and distributed regions in the frontoparietal cortex. Third, the rsFC analysis with the SFG as a seed region further found distinct patterns of rsFC for target facilitation and distractor suppression. Specifically, individual TC-benefit were positively correlated with distributed connections between the SFG and brain regions, mainly within the ventral attention and somato-motor network; but individual DC-benefit were positively correlated with centralized connections between the SFG and brain regions, mainly within the frontoparietal, dorsal attention and ventral attention network. Finally, a multiple linear regression analysis showed that the GMV and rsFC could jointly explain individual differences in TC- and DC-benefit. Taken together, these results provided neural evidence for different structural and functional substrates underlying target facilitation and distractor suppression.

Hippocampal and prefrontal contributions to memory retrieval: Examination of immediate early gene, NMDA receptor and environmental interactions.

Animals can use a range of strategies to recall important locations. These include simple stimulus-response strategies and more complex spatial (place) strategies, which are thought to have distinct neural substrates. The hippocampus-and NMDA receptor activation therein-is considered to be crucial for spatial, but not response strategies. The medial prefrontal cortex has also been implicated in memory retrieval; however, evidence concerning its specific role is equivocal. Both hippocampal and prefrontal regions have been associated with flexible behavioural responding (e.g. when task demands change). Here, we investigated the use of spatial and non-spatial strategies in the Morris water maze and their associated brain areas in rats using immediate early gene (IEG) imaging of Zif268 and c-Fos. Specifically, we charted the involvement of hippocampal and prefrontal subregions during retrieval of spatial and non-spatial memories. Behavioural flexibility was also examined using intact and partial cue configurations during recall. Results indicated that regions of both the hippocampus (area CA3) and prefrontal cortex (anterior cingulate cortex) were preferentially engaged in spatial memory recall compared to response learning. In addition, both spatial and non-spatial memories were dependent on NMDA receptor activation. MK801 impaired recall performance across all groups and reduced IEG activation across hippocampal and prefrontal regions. Finally, IEG results revealed divergent patterns of Zif268 and c-Fos activity and support the suggestion that Zif268 plays a functional role in the recall of long-term memories.

Aberrant Gray Matter Volume and Cortical Surface in Paranoid-Type Delusional Disorder

Introduction: Delusions are core symptoms of schizophrenia-spectrum and related disorders. Despite their clinical relevance, the neural correlates underlying such phenomena are unclear. Recent research suggests that specific delusional content may be associated with distinct neural substrates. Objective: Here, we used structural magnetic resonance imaging to investigate multiple parameters of brain morphology in patients presenting with paranoid type delusional disorder (pt-DD, n = 14) compared to those of healthy controls (HC, n = 25). Methods: Voxel- and surface-based morphometry for structural data was used to investigate gray matter volume (GMV), cortical thickness (CT) and gyrification. Results: Compared to HC, patients with pt-DD showed reduced GMV in bilateral amygdala and right inferior frontal gyrus. Higher GMV in patients was found in bilateral orbitofrontal and in left superior frontal cortices. Patients also had lower CT in frontal and temporal regions. Abnormal gyrification in patients was evident in frontal and temporal areas, as well as in bilateral insula. Conclusions: The data suggest the presence of aberrant GMV in a right prefrontal region associated with belief evaluation, as well as distinct structural abnormalities in areas that essentially subserve processing of fear, anxiety and threat in patients with pt-DD. It is possible that cortical features of distinct evolutionary and genetic origin, i.e. CT and gyrification, contribute differently to the pathogenesis of pt-DD.

Contribution of Intellectual Disability-Related Genes to ADHD Risk and to Locomotor Activity in Drosophila.

Attention deficit hyperactivity disorder (ADHD) is a common, highly heritable neuropsychiatric disorder. ADHD often co-occurs with intellectual disability, and shared overlapping genetics have been suggested. The aim of this study was to identify novel ADHD genes by investigating whether genes carrying rare mutations linked to intellectual disability contribute to ADHD risk through common genetic variants. Validation and characterization of candidates were performed using Drosophila melanogaster. Common genetic variants in a diagnostic gene panel of 396 autosomal intellectual disability genes were tested for association with ADHD risk through gene set and gene-wide analyses, using ADHD meta-analytic data from the Psychiatric Genomics Consortium for discovery (N=19,210) and ADHD data from the Lundbeck Foundation Initiative for Integrative Psychiatric Research for replication (N=37,076). The significant genes were functionally validated and characterized in Drosophila by assessing locomotor activity and sleep upon knockdown of those genes in brain circuits. The intellectual disability gene set was significantly associated with ADHD risk in the discovery and replication data sets. The three genes most consistently associated were MEF2C, ST3GAL3, and TRAPPC9. Performing functional characterization of the two evolutionarily conserved genes in Drosophila melanogaster, the authors found that their knockdown in dopaminergic (dMEF2) and circadian neurons (dTRAPPC9) resulted in increased locomotor activity and reduced sleep, concordant with the human phenotype. This study reveals that a large set of intellectual disability-related genes contribute to ADHD risk through effects of common alleles. Utilizing this continuity, the authors identified TRAPPC9, MEF2C, and ST3GAL3 as novel ADHD candidate genes. Characterization in Drosophila suggests that TRAPPC9 and MEF2C contribute to ADHD-related behavior through distinct neural substrates.

Grant Report on the Effects of Childhood Maltreatment on Neurocircuitry in Adolescent Depression.

This report describes the protocol for an ongoing project funded by the National Institutes of Health (R01MH108155) that is focused on effects of childhood maltreatment (MALTX) on neurocircuitry changes associated with adolescent major depressive disorder (MDD). Extant clinical and neuroimaging literature on MDD is reviewed, which has relied on heterogeneous samples that do not parse out the unique contribution of MALTX on neurobiological changes in MDD. Employing a 2 × 2 study design (controls with no MALTX or MDD, MALTX only, MDD only, and MDD + MALTX), and based on a cohesive theoretical model that incorporates behavioral, cognitive and neurobiological domains, we describe the multi-modal neuroimaging techniques used to test whether structural and functional alterations in the fronto-limbic and fronto-striatal circuits associated with adolescent MDD are moderated by MALTX. We hypothesize that MDD + MALTX youth will show alterations in the fronto-limbic circuit, with reduced connectivity between the amygdala (AMG) and the prefrontal cortex (PFC), as the AMG is sensitive to stress/threat during development. Participants with MDD will exhibit increased functional connectivity between the AMG and PFC due to self-referential negative emotions. Lastly, MDD + MALTX will only show changes in motivational/anticipatory aspects of the fronto-striatal circuit, and MDD will exhibit changes in motivational and consummatory/outcome aspects of reward-processing. Our goal is to identify distinct neural substrates associated with MDD due to MALTX compared to other causes, as these markers could be used to more effectively predict treatment outcome, index treatment response, and facilitate alternative treatments for adolescents who do not respond well to traditional approaches.

Neural correlates of semantic and syntactic processing in German Sign Language

The study of deaf and hearing native users of signed languages can offer unique insights into how biological constraints and environmental input interact to shape the neural bases of language processing. Here, we use functional magnetic resonance imaging (fMRI) to address two questions: (1) Do semantic and syntactic processing in a signed language rely on anatomically and functionally distinct neural substrates as it has been shown for spoken languages? and (2) Does hearing status affect the neural correlates of these two types of linguistic processing? Deaf and hearing native signers performed a sentence judgement task on German Sign Language (Deutsche Gebärdensprache: DGS) sentences which were correct or contained either syntactic or semantic violations. We hypothesized that processing of semantic and syntactic violations in DGS relies on distinct neural substrates as it has been shown for spoken languages. Moreover, we hypothesized that effects of hearing status are observed within auditory regions, as deaf native signers have been shown to activate auditory areas to a greater extent than hearing native signers when processing a signed language. Semantic processing activated low-level visual areas and the left inferior frontal gyrus (IFG), suggesting both modality-dependent and independent processing mechanisms. Syntactic processing elicited increased activation in the right supramarginal gyrus (SMG). Moreover, psychophysiological interaction (PPI) analyses revealed a cluster in left middle occipital regions showing increased functional coupling with the right SMG during syntactic relative to semantic processing, possibly indicating spatial processing mechanisms that are specific to signed syntax. Effects of hearing status were observed in the right superior temporal cortex (STC): deaf but not hearing native signers showed greater activation for semantic violations than for syntactic violations in this region. Taken together, the present findings suggest that the neural correlates of language processing are partly determined by biological constraints, but that they may additionally be influenced by the unique processing demands of the language modality and different sensory experiences.

Differential parietal activations for spatial remapping and saccadic control in a visual memory task

Remapping is a process that updates visual information in internal spatial representations across eye movements, allowing for stable perception of the environment. Previous work has demonstrated visual remapping activity in parietal cortex during saccades, but it remains unclear whether remapping is triggered by overt saccades only (or by attentional shifts also), and whether it engages parietal areas only (or other cortical areas). Here, we used fMRI to investigate spatial remapping during two visuospatial memory tasks requiring either overt (accompanied by a saccade) or covert (with central fixation) attention shifts to peripheral distracters. Participants had to remember the position and color of a lateralized dot during a saccade or attention shift, requiring them to update the dot position in memory, and then indicate if a second dot matched the first. Differential activation patterns were observed within parietal cortex as a function of the different visual, motor, and interhemispheric remapping demands in the saccade task, presumably mediating the maintenance of spatial position in perceptual and motor maps. Remapping engaged parietal areas adjacent to, but not overlapping with, those activated by saccade execution, while it did not engage the frontal eye fields, pointing to distinct neural substrates for ocular motor and spatial updating processes. No differential activation related to remapping was found during the covert attention shift task, suggesting that this condition did not necessitate the same remapping as the saccade condition. Overall these results further elucidate the mechanisms of spatial remapping in human parietal cortex and their relationship with attention processing and ocular motor behavior, with implications for understanding visuospatial attention deficits in hemispatial neglect.

Neural substrates of self- and external-preoccupation: A voxel-based morphometry study.

IntroductionSelf‐ and external‐preoccupation have been linked to psychopathological states. The neural substrates underlying self‐ and external‐preoccupation remain unclear. In the present study, we aim to provide insight into the information‐processing mechanisms associated with self‐ and external‐preoccupation at the structural level.MethodsTo investigate the neural substrates of self‐ and external‐preoccupation, we acquired high‐resolution T1‐weighted structural images and Preoccupation Scale scores from 1,122 young subjects. Associations between regional gray matter volume (rGMV) and Preoccupation Scale subscores for self‐ and external‐preoccupation were estimated using voxel‐based morphometry.ResultsSignificant positive associations between self‐preoccupation and rGMV were observed in widespread brain areas such as the bilateral precuneus and posterior cingulate gyri, structures known to be associated with self‐triggered self‐reference during rest. Significant negative associations between external‐preoccupation and rGMV were observed only in the bilateral cerebellum, regions known to be associated with behavioral addiction, sustained attention, and reward system.ConclusionOur results reveal distinct neural substrates for self‐ and external‐preoccupation at the structural level.