Cerebral cortex最新文献

A network model of a "selection-for-action" system was proposed with the primary idea that the functions of stimulus and response selection are carried out within a visuomotor oscillatory network. To examine the network's dynamics under different sensorimotor demands, an electroencephalographic experiment was performed, contrasting visual detection and discrimination variants of a Posner cueing task. In the former, the required response can be prepared before target onset, whereas in the latter-only after target onset. Using the generalized eigenvalue decomposition method for EEG source isolation, we identified four network subcomponents: lateral motor, lateral visual, midfrontal, and midparietal sources. The local and inter-source activity relevant for spatial attention (visual and midparietal sources) were involved before target onset in both tasks but stronger for the discrimination task. The local activity and inter-source connectivity relevant for action control (motor and midfrontal sources) were involved before target onset only in the detection task. Importantly, in line with the model's predictions, we observed that proactive response preparation in the detection task entailed beta-band connectivity between the response control areas and visual areas. Moreover, we observed a response-related spatial modulation of pre-target local visual alpha activity in the detection task. These results likely reflect automatic visuomotor integration.

In visuomotor control, the right hemisphere has been associated with visuospatial, and the left hemisphere with visuotemporal processing. In right-handed individuals, asymmetric bimanual tasks result in a preferred use of the left hand for spatial processing and of the right hand for temporal processing. Here, we investigate interhemispheric interactions in the cortical visuomotor network in right-handed participants during asymmetric bimanual isometric movements using magnetoencephalography. The task involved spatially and temporally challenging visuomotor tracking with one hand and a precisely timed ballistic grip with the other creating a dual task scenario with either an optimal or a non-optimal task to hand assignment. When the right hand performed the grip without spatial demands while the left hand performed visuomotor tracking (optimal condition), preparatory broadband partial directed coherence from left premotor to right visuomotor regions were stronger than in the non-optimal condition. In contrast, the non-optimal condition showed stronger preparatory connectivity from right inferior parietal cortex to the left hemispheric visuomotor network. Reduced preparatory interhemispheric connectivity increased the chance of mirror movements during task execution. Our results indicate that the dual task problem is solved by cooperative interactions between specialized cerebral hemispheres with both a left-right and a rostro-caudal axis for temporo-spatial processing.

The neural mechanisms underlying the cognitive metacontrol states of persistence and flexibility are not yet fully understood but are thought to be modulated by frontal and striatal dopamine, respectively. In this study, we attempted to induce persistence and flexibility states by having participants engage in 2 creativity tasks (remote associates task and alternative uses task) and 2 meditation techniques (focused-attention meditation and open-monitoring meditation), to study the neural correlates of these metacontrol states and test the metacontrol model of creativity (MCC). Results show that brain areas known to be modulated by both frontal and striatal dopamine were activated in conditions that are thought to call for persistence, particularly the prefrontal cortex, anterior cingulate cortex, and basal ganglia, indicating goal-related selective attention and top-down control. In contrast, conditions that call for flexibility showed brain activation in areas of the default mode network, suggesting reduced top-down control. This pattern was much clearer for the creativity tasks than meditation. Notably, we did not find significant effects when contrasting the 2 meditation techniques and when looking at brain activation overlap between meditation and creativity at the whole-brain level. Finally, the examination of the MCC provided partial supporting evidence for the model, but its prediction for the left inferior frontal gyrus showed the exact opposite result, which calls for clarification in future research.

Adolescent depression presented higher risk of suicide than adult depression. However, the neurophysiological mechanisms underlying this phenomenon have not been elucidated. We aimed to identify structural covariance network alterations in depressed adolescents with suicidal behaviors to provide novel neuroimaging evidence for this condition. 64 first-episode, treatment-naïve depressed adolescent patients with suicidal behaviors and 48 healthy controls were enrolled. Nonnegative matrix factorization was used to identify the structural covariance networks. The Kullback-Leibler divergence method was applied to estimate the interregional relationships between the altered brain networks. Correlation analyses were conducted between altered brain networks and clinical characteristics. Patients had lower gray matter volumes in the anterior default mode network (DMN), visual network, sensorimotor network, and right executive control network than healthy controls. Morphological connections were altered in the anterior DMN, visual network, and right executive control network in patients. Correlation analyses revealed negative associations between morphological connections in anterior DMN-visual networks and illness duration in the patient group. This study revealed abnormal gray matter attributes in the anterior DMN, visual network, sensorimotor network, and executive control network in first-episode and treatment-naïve adolescent depression with suicide, which might reflect disease traits and provide essential neurobiological evidence for behavioral disturbances in depression.

Efforts in vision restoration have been focused on a condition called Retinitis Pigmentosa, where photoreceptors in the retina degenerate while the rest of the visual pathway remain mostly intact. Retinal implants that directly stimulate retinal ganglion cells have shown promising but limited results in patients so far. Apart from technical limitations, cross-modal plasticity of visual areas might contribute to this problem. We therefore investigated if the primary visual cortex (V1) of the rd10 mouse model for retinal degeneration became more sensitive to auditory or tactile sensory inputs. After reaching complete blindness confirmed by the lack of optomotor responses, activity in V1 and superior colliculus (SC) was recorded using Neuropixels probes. While we could not find any significant differences in tactile or auditory responses compared to wildtype mice, the local field potential revealed distinct oscillatory events (0.5-6 Hz) in V1 and SC resembling previously observed aberrant activity in the retina of rd10 mice. We therefore propose that aberrant retinal activity is transmitted to higher visual areas where it prevents cross-modal changes. Additionally, our results provide evidence of an intact visual cortex with promising potential for future therapeutic strategies to restore vision.

Physical exercise shows positive effects on cognitive functions such as working memory (WM) for older adults; however, large individual differences in response exist and the underlying mechanisms are not well understood. We tested the hypothesis that exercise-induced changes in cardiorespiratory fitness and leg strength would improve WM-related brain activity, which subsequently would improve WM performance. This study was based on the Umeå HIT study, a randomized controlled trial assessing the effects of watt-controlled supramaximal high-intensity interval training (HIT) versus moderate-intensity training for nonexercising older adults (N = 68). A subsample (n = 43, 66 to 79 years, 56% females) underwent task-based functional magnetic resonance imaging, testing WM. The outcomes of interest were change in WM performance, WM task activation, cardiorespiratory fitness, and leg strength. For WM performance, we found no significant between-group difference in change; however, there was a significant within-group increase for HIT in WM composites. For HIT, changes in leg strength significantly predicted increased right dorsolateral prefrontal cortex activation, which in turn predicted improved in-scanner WM task performance. Cardiorespiratory fitness did not predict WM-related functional change. These results indicate a specific physiological ingredient, namely leg strength gains, that is a potential mechanism in exercise-induced prefrontal activation and WM performance increases.

Understanding the distinct and shared neural mechanisms of generalized anxiety disorder, panic disorder, and social anxiety disorder could help address critical gaps in anxiety disorder diagnosis and treatment. This study aimed to explore common and disorder-specific brain activity and connectivity in patients with generalized anxiety disorder, panic disorder, and social anxiety disorder using resting-state functional magnetic resonance imaging. A total of 127 adults (33 with generalized anxiety disorder, 26 with panic disorder, 36 with social anxiety disorder, and 32 healthy controls) were recruited. We found that all individuals with generalized anxiety disorder, social anxiety disorder, and panic disorder showed abnormal activity in the prefrontal-limbic-cerebellar circuit and default mode network regions. Patients with panic disorder showed unique hypoconnectivity between the default mode network and sensory-motor network, whereas patients with social anxiety disorder showed unique extensive hyperconnectivity between the default mode network and other networks. In addition, increased activity in the left orbital inferior frontal gyrus was associated with depression and anxiety symptom severity, decreased activity in the left superior temporal gyrus was associated with panic symptom severity, and decreased activity in the right fusiform gyrus was correlated with social anxiety symptom severity. These findings provide valuable implications for understanding the neuropathology, diagnosing, and developing targeted therapeutic interventions for different subtypes of anxiety disorders.

Our senses receive a continuous stream of complex information, which we segment into discrete events. Previous research has related such events to neural states: temporally and regionally specific stable patterns of brain activity. The aim of this paper was to investigate whether there was evidence for top-down or bottom-up propagation of neural state boundaries. To do so, we used intracranial measurements with high temporal resolution while subjects were watching a movie. As this is the first study of neural states in intracranial data in the context of event segmentation, we also investigated whether known properties of neural states could be replicated. The neural state boundaries indeed aligned with stimulus features and between brain areas. Importantly, we found evidence for top-down propagation of neural state boundaries at the onsets and offsets of clauses. Interestingly, we did not observe a consistent top-down or bottom-up propagation in general across all timepoints, suggesting that neural state boundaries could propagate in both a top-down and bottom-up manner, with the direction depending on the stimulus input at that moment. Taken together, our findings provide new insights on how neural state boundaries are shared across brain regions and strengthen the foundation of studying neural states in electrophysiology.

The knowledge we have about how the world is structured is known to influence object recognition. One way this is demonstrated is through a congruency effect, where object recognition is faster and more accurate if items are presented in expected scene contexts. However, our understanding of the dynamic neural mechanisms that underlie congruency effects are under-explored. Using magnetoencephalography (MEG), we examine how the congruency between an object and a prior scene results in changes in the oscillatory activity in the brain, which regions underpin this effect, and whether congruency results arise from top-down or bottom-up modulations of connectivity. We observed that prior scene information impacts the processing of visual objects in behavior, neural activity, and connectivity. Processing objects that were incongruent with the prior scene resulted in slower reaction times, increased low frequency activity in the ventral visual pathway, and increased top-down connectivity from the anterior temporal lobe and frontal cortex to the posterior ventral temporal cortex. Our results reveal that the recurrent dynamics within the ventral visual pathway are modulated by the prior knowledge imbued by our surrounding environment, suggesting that the way we recognize objects is fundamentally linked to their context.