Cerebral cortex最新文献

The superficial white matter (SWM) comprises short-range fibers that connect adjacent cortical regions; however, its structural connectivity remains poorly understood. In a previous dissection study, we identified anatomical "crossings" where superficial white matter fibers converge from multiple directions. Building on this, the present study investigated superficial white matter characteristics associated with these crossings using diffusion-weighted imaging data from 10 individuals in the Human Connectome Project. A total of 605 regions of interest (ROIs) were placed at presumed crossing locations in the dominant hemisphere. Superficial white matter fibers were categorized by tract length (short, medium, and long), and streamline distribution was analyzed. Short- and medium-length fibers showed predominantly intragyral connections, while long fibers exhibited more diverse intragyral connectivity. Graph theoretical analysis identified high-efficiency regions of interest, putative hub regions, which were mapped onto cytoarchitectonic structures from the Economo-Koskinas atlas and compared with myelin concentration. High-efficiency regions for short- and middle-length fibers were mainly in primary motor and sensory areas, particularly visual regions, corresponding to high myelin concentration and cytoarchitectonic areas 1 and 5. In contrast, high-efficiency regions for long fibers were distributed in the association cortex (area 3). These findings provide new insights into the structural organization of superficial white matter and its relationship to cortical architecture.

Tinnitus is a phantom auditory perception that occurs without an external stimulus. Increasing evidence suggests that it is associated with abnormal predictive coding, in which overly strong priors may give rise to hallucinatory perception, as proposed by the "strong priors" hypothesis. Neurodynamic analysis, by characterizing the temporal evolution of brain activity, can further test the "strong priors" hypothesis in tinnitus, specifically whether tinnitus patients' brain activity is more influenced by past activity. However, the neurodynamic characteristics of tinnitus remain poorly understood. Therefore, we examined long-range and short-range temporal correlations in resting-state Electroencephalography (EEG) signals from tinnitus patients and healthy controls. We applied detrended fluctuation analysis, lifetimes, and waiting times to assess temporal correlations across multiple time scales. Our results showed that tinnitus patients exhibited stronger temporal correlations in the alpha frequency band, accompanied by heightened long-range dependencies in higher frequency bands. These findings reveal an abnormally enhanced temporal structure across multiple timescales and frequency bands in tinnitus, potentially reflecting an excessive influence of global context on intrinsic information processing and providing support for the "strong priors" hypothesis.

Humans and animals are able to rapidly, and with reasonable accuracy, estimate the number of objects in a visual scene. Visual-evoked potential studies have described a sequence of functionally distinct stages associated with numerosity perception. Recently, a specialized cognitive-perceptual system for the numerosity estimation for human stimuli (NEH), distinct from that for non-social stimuli, was revealed using virtual reality, revealing a stable NEH overestimation bias (ie perceiving more people than were shown). This bias was further increased when a social hallucination characterized by the false perception of another invisible person (presence hallucination) was induced robotically and repeatedly prior to NEH trials. However, little is known about the brain mechanisms of NEH and robot-induced presence hallucination. Here we combined virtual reality and robotically-induced presence hallucination with visual-evoked potentials to investigate the neural mechanisms and processing steps of NEH. We report that NEH induces numerosity-related components as observed for non-human numerosity stimuli and, critically that experimentally-induced presence hallucination selectively modulated the P2p component, whose amplitude correlated with NEH overestimation magnitude. This effect was localized in left extrastriate cortex, showing that robot-induced presence hallucination are integrated with NEH processing during the P2p time period and relying on social numerosity mechanisms in extrastriate cortex.

A crucial mechanism for the brain to make sense of the auditory environment is the synchronization of neural responses to external temporal regularities, such as a musical beat. It is debated whether this synchronization and the resulting beat percept reflect phase alignment of endogenous neural oscillations to the external regularity ("entrainment"), or evoked responses to the rhythmic stimulus ("tracking"). Here, we use the tempo-dependent properties of beat processing to differentiate between the two accounts. Participants listened to a repeating rhythmic pattern at different speeds. Behaviorally, they consistently tapped at the preferred beat rate (around 2 Hz) across tempi, shifting to higher metrical levels as tempo increased. We found a similar shift in EEG data, where the metrical level at which neural synchronization was strongest depended on tempo. This selective enhancement is consistent with entrainment accounts and could indeed be mimicked by an oscillator model. However, importantly, the results were also captured by a model simulating evoked responses. Together, our findings demonstrate that while neural responses to rhythm are selectively enhanced at the beat rate, this enhancement need not be taken as evidence for entrainment, but can also be explained by successive evoked responses.

Working memory is an important cognitive process that develops throughout early life. During adolescence, there is marked improvement in this process that is associated with structural and functional brain changes. These changes have been linked to age; however, endogenous testosterone is thought to regulate structural and functional changes in the brain during puberty, with differential influences across adolescence into early adulthood. Thus, testosterone may have a direct impact on brain activity that is modulated by age. The current study aimed to examine this using a working memory functional magnetic resonance imaging (fMRI) task in adolescents and young adults. Saliva samples collected prior to scanning were assayed for endogenous testosterone levels. One hundred and forty-five typically developing participants (74 female), aged 12-25 yr, completed a working memory fMRI task. Results showed that, for the most difficult versus the 0back conditions, younger female participants (≤19) only had more deactivation in the anterior cingulate cortex with higher level of testosterone. In contrast, male participants showed increased activation in the precentral gyrus with higher testosterone, regardless of age. These findings indicate sex differences in how endogenous testosterone relates to the activity of different brain regions recruited during working memory. Furthermore, these associations vary across typical adolescent development.

Noonan syndrome is the most common RASopathy and is associated with high rates of neurodevelopmental disorders. Prior neuroimaging studies in children with Noonan syndrome have identified structural effects on subcortical regions, though most focus on volumetric differences, overlooking finer morphological changes. These studies also tend to examine common genetic variants, excluding rarer forms within the Noonan syndrome spectrum. Shape analysis offers a sensitive approach to detecting subtle alterations, and when applied across variants, may reveal distinct neuroanatomical signatures. We acquired anatomical magnetic resonance imaging scans from 104 children with Noonan syndrome spectrum (ages 5 to 17, mean = 10.0) and 80 age- and sex-matched typically developing children (ages 4 to 16, mean = 9.54). Our comprehensive analysis examined local thickness and surface dilation/contraction (Jacobian), including genetic variant-specific analyses. Noonan syndrome spectrum showed widespread subcortical alterations beyond volume reduction, including thinning and surface contraction in the putamen, pallidum, thalamus, and caudate, and expansion in the accumbens. Distinct regional effects were found for PTPN11, SOS1, and other Noonan syndrome spectrum-associated variants. These findings confirm subcortical volume reductions in several regions and highlight complex, region-specific shape alterations. Importantly, neuroanatomical patterns varied across genetic variants, suggesting distinct mechanisms of brain development. Understanding these variant-specific structural profiles may provide insights into genotype-based approaches and inform future precision medicine strategies.

It is debated whether there is an abstract, format-independent representation of number in the human brain, eg whether "four" shares a neural representation with "4." Most previous studies have used magnitude to investigate this question, despite potential confounds with relative quantity processing. This study used the numerical property of parity. Electroencephalogram recordings were collected from participants performing a fixation-cross task, while viewing 20-s sequences of alternating even and odd Arabic numerals presented at 7.5 Hz: responses to parity were selectively tagged at the asymmetry frequency of 3.75 Hz. Parity asymmetry responses emerged significantly over the occipito-temporal (OT) cortex, and were larger than control asymmetry responses to isolated physical stimulus differences, replicating a previous study. Following 20-s adaptation to cross-font even numerals, larger parity responses were recorded over the right OT cortex, further supporting distinct representations of even/odd numbers; there was no corresponding control adaptation effect. Interestingly, adaptation to even canonical dot stimuli also produced significantly larger parity asymmetry responses; adaptation to even number words trended non-significantly. These results are in line with parity being processed automatically, even across formats. More generally, they suggest that parity is a useful means for probing abstract representation of number in the human brain.

Brain stimulation shows promise as an intervention to enhance executive function, particularly when paired with cognitive training. To optimize such approaches, we must understand the potential role of individual differences in intervention outcomes. We investigated the combined effects of multi-session multitasking training and prefrontal transcranial direct current stimulation (tDCS) on generalization of performance benefits, focusing on how cortical morphology predicts performance improvements. One hundred seventy-eight individuals underwent 7 Tesla MRI before completing multisession training with online stimulation. A cognitive task battery assessed improvements in trained and untrained tasks pre- and post-training. Stimulating the left or right prefrontal cortex at 1 mA during multitasking training enhanced transfer to a visual search task. Critically, cortical morphology predicted stimulation efficacy for inducing transfer. Cortical thickness in regions beneath the stimulating anode was related to reaction time changes in the most difficult visual search condition but only for the left and right 1 mA multitasking training groups. Performance was not related to cortical thickness for the groups receiving sham stimulation, 2 mA stimulation, or 1 mA stimulation with a control training task. These results highlight the importance of individual anatomical differences in modulating tDCS efficacy and identifying specific neuroanatomical features that predict generalized performance gains from combining tDCS with cognitive training.

Although episodic memory is typically impaired in older adults (OAs) compared to young adults (YAs), this deficit is attenuated when OAs can leverage their rich semantic knowledge, such as their knowledge of schemas. Memory is better for items consistent with pre-existing schemas and this effect is larger in OAs. Neuroimaging studies have associated schema use with the ventromedial prefrontal cortex (vmPFC), angular gyrus (AG), and hippocampus (HPC), but most of this research has been limited to YAs. This fMRI study investigated the neural mechanisms underlying how schemas boost episodic memory in OAs. Participants encoded scene-object pairs with varying congruency, and memory for the objects was tested the following day. Congruency with schemas enhanced object memory for YAs and, more substantially, for OAs. fMRI analyses examined cortico-hippocampal interactions at encoding. We found that a vmPFC-HPC interaction was related to enhanced subsequent memory for congruent objects in both age groups, whereas an AG-HPC interaction contributed to subsequent memory for congruent objects only in OAs. Individual difference analyses of the AG-HPC interaction suggested that OAs made use of semantic knowledge to facilitate encoding. Collectively, our findings illustrate age-related differences in how schemas influence episodic memory encoding via distinct cortico-hippocampal interactions.

To manage life's stressors, we can self-regulate our emotions or seek social regulatory support. One such strategy is reappraisal, where individuals reframe their own negative emotions (ie self-reappraisal) or help others reframe their negative emotions (ie social-reappraisal). Here, we compared the neural mechanisms underlying self- and social-reappraisal of negative autobiographical memories using standard univariate contrasts, Bayes factor, and multivariate classifier approaches. Both self- and social-reappraisal recruited regions associated with control and mentalizing, such as dorsolateral and ventrolateral prefrontal cortex and dorsomedial prefrontal cortex. However, social-reappraisal was qualitatively different from self-reappraisal in its recruitment of additional control and mentalizing regions, such as the right lateral prefrontal cortex, medial prefrontal cortex, and right temporal pole. Notably, multivariate patterns within regions associated with mentalizing-but not control-were distinguishable between self- and social-reappraisal, suggesting that different kinds of information are drawn upon when reappraising for self vs. others. Finally, both self- and social-reappraisal modulated activity in regions associated with affective responding and the perceptual representation of remembered scenes, including the mid-orbital frontal cortex, left insula, and posterior parahippocampal gyrus. Taken together, these data reveal the processes supporting self and social emotion regulation with implications for both basic and clinical research.