Max Planck Institute for Human Cognitive and Brain Sciences

The effects of mindfulness on body awareness and interoception have been proposed as potential mechanisms for its salutary effects. However, research investigating the relationship between mindfulness and body awareness using psychophysical measures is limited. In this study, we compared 31 expert meditators with 33 matched controls on somatosensory accuracy using a somatosensory signal detection task (SSDT) alongside interoception self-report instruments. Our main hypothesis was that meditators would show increased accuracy within the SSDT, indicating higher somatosensory accuracy (body awareness) and that this would be accompanied by neural correlates of increased alpha modulation over the somatosensory cortex as measured through EEG. Participants were asked to detect a near-threshold tactile sensation, which was combined with a non-informative light in 50% of the cases. Associations between prestimulus alpha activity and responses were analysed on a trial-by-trial basis. Contrary to our expectation, instead of an increase in accuracy, we observed a decrease in the decision threshold in meditators, while we found a decrease in prestimulus alpha power in meditators. A trial-by-trial analysis revealed a negative relationship between prestimulus alpha activity and the report of touch. Meditators self-reported higher interoceptive abilities compared to readers. These findings suggest that lower prestimulus alpha activity may have increased the probability of reporting touch within the SSDT, providing a potential mechanism for the increase in response rate in meditators. Our study indicates that meditation practice alters body awareness as shown by modulated prestimulus alpha activity, potentially decreasing the filter function over the somatosensory cortex.

The process of brain folding is thought to play an important role in the development and organisation of the cerebrum and the cerebellum. The study of cerebellar folding is challenging due to the small size and abundance of its folia. In consequence, little is known about its anatomical diversity and evolution. We constituted an open collection of histological data from 56 mammalian species and manually segmented the cerebrum and the cerebellum. We developed methods to measure the geometry of cerebellar folia and to estimate the thickness of the molecular layer. We used phylogenetic comparative methods to study the diversity and evolution of cerebellar folding and its relationship with the anatomy of the cerebrum. Our results show that the evolution of cerebellar and cerebral anatomy follows a stabilising selection process. We observed 2 groups of phenotypes changing concertedly through evolution: a group of 'diverse' phenotypes - varying over several orders of magnitude together with body size, and a group of 'stable' phenotypes varying over less than 1 order of magnitude across species. Our analyses confirmed the strong correlation between cerebral and cerebellar volumes across species, and showed in addition that large cerebella are disproportionately more folded than smaller ones. Compared with the extreme variations in cerebellar surface area, folial anatomy and molecular layer thickness varied only slightly, showing a much smaller increase in the larger cerebella. We discuss how these findings could provide new insights into the diversity and evolution of cerebellar folding, the mechanisms of cerebellar and cerebral folding, and their potential influence on the organisation of the brain across species.

The effects of mindfulness on body awareness and interoception have been proposed as potential mechanisms for its salutary effects. However, research investigating the relationship between mindfulness and body awareness using psychophysical measures is limited. In this study, we compared 31 expert meditators with 33 matched controls on somatosensory accuracy using a somatosensory signal detection task (SSDT) alongside interoception self-report instruments. Our main hypothesis was that meditators would show increased accuracy within the SSDT, indicating higher somatosensory accuracy (body awareness) and that this would be accompanied by neural correlates of increased alpha modulation over the somatosensory cortex as measured through EEG. Participants were asked to detect a near-threshold tactile sensation, which was combined with a non-informative light in 50% of the cases. Associations between prestimulus alpha activity and responses were analysed on a trial-by-trial basis. Contrary to our expectation, instead of an increase in accuracy, we observed a decrease in the decision threshold in meditators, while we found a decrease in prestimulus alpha power in meditators. A trial-by-trial analysis revealed a negative relationship between prestimulus alpha activity and the report of touch. Meditators self-reported higher interoceptive abilities compared to readers. These findings suggest that lower prestimulus alpha activity may have increased the probability of reporting touch within the SSDT, providing a potential mechanism for the increase in response rate in meditators. Our study indicates that meditation practice alters body awareness as shown by modulated prestimulus alpha activity, potentially decreasing the filter function over the somatosensory cortex.

Reward improves memory through both encoding and consolidation processes. In this preregistered study, we tested whether reward effects on memory generalize from high-rewarded items to low-rewarded but episodically related items. Fifty-nine human volunteers incidentally encoded associations between unique objects and repeated scenes. Some scenes typically yielded high reward, whereas others typically yielded low reward. Memory was tested immediately after encoding ( n = 29) or the next day ( n = 30). Overall, reward had only a limited influence on memory. It did not enhance consolidation and its effect did not generalize to episodically related stimuli. We thus contribute to understanding the boundary conditions of reward effects on memory.

Background So far, previous research suggests positive effects of mental demands at the workplace. However, it may depend on how stressfull these demands are perceived on an individual level. Objective The aim was to build on previous research by investigating how mental demands are related to stress, overload, and work discontent and whether this relationship is mediated by individuals resources, such as resilience. Method A sub-sample of the LIFE Adult Cohort (n = 480) was asked to answer questions on sociodemographic characteristics, objective stress (using the Trier Inventory of Chronic Stress (TICS)), and perceptions of stress with regard to verbal and executive mental demands at work. Results According to generalized linear regression models, higher verbal as well as executive mental demands were associated with higher levels of chronic stress, work overload and discontent. Higher levels of resilience were associated with lower levels of these outcomes. Analyses regarding interaction effects revealed that the interaction between resilience and perceived stress of verbal mental demands was significant only in terms of work overload. Conclusion Higher perceived stressfulness of mental demands was associated with higher chronic stress, work overload and work discontent. Therefore, mental demands should be targeted by occupational interventions that aim to improve job conditions and employees‘ overall well-being. Besides resilience, other potential influencers or personal resources should be focused on in future studies to develop interventions.

Human language is supported by a cortical network involving Broca's area, which comprises Brodmann Areas 44 and 45 (BA44 and BA45). While cytoarchitectonic homolog areas have been identified in nonhuman primates, it remains unknown how these regions evolved to support human language. Here, we use histological data and advanced cortical registration methods to precisely compare the morphology of BA44 and BA45 in humans and chimpanzees. We found a general expansion of Broca's areas in humans, with the left BA44 enlarging the most, growing anteriorly into a region known to process syntax. Together with recent functional and receptorarchitectural studies, our findings support the conclusion that BA44 evolved from an action-related region to a bipartite system, with a posterior portion supporting action and an anterior portion supporting syntactic processes. Our findings add novel insights to the longstanding debate on the relationship between language and action, and the evolution of Broca's area.

Evoked neural responses to sensory stimuli have been extensively investigated in humans and animal models both to enhance our understanding of brain function and to aid in clinical diagnosis of neurological and neuropsychiatric conditions. Recording and imaging techniques such as electroencephalography (EEG), magnetoencephalography (MEG), local field potentials (LFPs), and calcium imaging provide complementary information about different aspects of brain activity at different spatial and temporal scales. Modeling and simulations provide a way to integrate these different types of information to clarify underlying neural mechanisms. In this study, we aimed to shed light on the neural dynamics underlying auditory evoked responses by fitting a rate-based model to LFPs recorded via multi-contact electrodes which simultaneously sampled neural activity across cortical laminae. Recordings included neural population responses to best-frequency (BF) and non-BF tones at four representative sites in primary auditory cortex (A1) of awake monkeys. The model considered major neural populations of excitatory, parvalbumin-expressing (PV), and somatostatin-expressing (SOM) neurons across layers 2/3, 4, and 5/6. Unknown parameters, including the connection strength between the populations, were fitted to the data. Our results revealed similar population dynamics, fitted model parameters, predicted equivalent current dipoles (ECD), tuning curves, and lateral inhibition profiles across recording sites and animals, in spite of quite different extracellular current distributions. We found that PV firing rates were higher in BF than in non-BF responses, mainly due to different strengths of tonotopic thalamic input, whereas SOM firing rates were higher in non-BF than in BF responses due to lateral inhibition. In conclusion, we demonstrate the feasibility of the model-fitting approach in identifying the contributions of cell-type specific population activity to stimulus-evoked LFPs across cortical laminae, providing a foundation for further investigations into the dynamics of neural circuits underlying cortical sensory processing.

The left temporo-parietal cortex (TPC) is crucial for phonological decoding, i.e., for learning and retaining sound-letter mappings, and appears hypoactive in dyslexia. Here, we tested the causal contribution of this area for reading in typical readers with transcranial magnetic stimulation (TMS) and explored the reading network's response with fMRI. By investigating the underlying neural correlates of stimulation-induced modulations of the reading network, we can help improve targeted interventions for individuals with dyslexia. 28 typical adult readers overtly read simple and complex words and pseudowords during fMRI after effective and sham TMS over the left TPC. To explore differences in functional activation and effective connectivity within the reading network, we performed univariate and multivariate analyses, as well as dynamic causal modeling. While TMS-induced effects on reading performance and brain activation showed large individual variability, multivariate analyses revealed a shift in activation in the left inferior frontal cortex for pseudoword reading after effective TMS. Furthermore, TMS increased effective connectivity from the left ventral occipito-temporal cortex to the left TPC. In the absence of effects on reading performance, the observed changes in task-related activity and the increase in functional coupling between the two core reading nodes suggest successful short-term compensatory reorganization in the reading network following TMS-induced disruption. This study is the first to explore neurophysiological changes induced by TMS to a core reading node in typical readers while performing an overt reading task. We provide evidence for remote stimulation effects and emphasize the relevance of functional interactions in the reading network.

A current proposal for a computational notion of self is a representation of one’s body in a specific time and place, which includes the recognition of that representation as the agent. This turns self-representation into a process of self-orientation, a challenging computational problem for any human-like agent. Here, to examine this process, we created several ‘self-finding’ tasks based on simple video games, in which players (N = 124) had to identify themselves out of a set of candidates in order to play effectively. Quantitative and qualitative testing showed that human players are nearly optimal at self-orienting. In contrast, well-known deep reinforcement learning algorithms, which excel at learning much more complex video games, are far from optimal. We suggest that self-orienting allows humans to flexibly navigate new settings.

The effective transverse relaxation rate (R 2 *) is sensitive to the microstructure of the human brain like the g-ratio which characterises the relative myelination of axons. However, the fibre-orientation dependence of R 2 * degrades its reproducibility and any microstructural derivative measure. To estimate its orientation-independent part (R 2,iso *) from single multi-echo gradient-recalled-echo (meGRE) measurements at arbitrary orientations, a second-order polynomial in time model (hereafter M2) can be used. Its linear time-dependent parameter, β 1 , can be biophysically related to R 2,iso * when neglecting the myelin water (MW) signal in the hollow cylinder fibre model (HCFM). Here, we examined the performance of M2 using experimental and simulated data with variable g-ratio and fibre dispersion. We found that the fitted β 1 can estimate R 2,iso * using meGRE with long maximum-echo time (TE max ≈ 54 ms), but not accurately captures its microscopic dependence on the g-ratio (error 84%). We proposed a new heuristic expression for β 1 that reduced the error to 12% for ex vivo compartmental R 2 values. Using the new expression, we could estimate an MW fraction of 0.14 for fibres with negligible dispersion in a fixed human optic chiasm for the ex vivo compartmental R 2 values but not for the in vivo values. M2 and the HCFM-based simulations failed to explain the measured R 2 *-orientation-dependence around the magic angle for a typical in vivo meGRE protocol (with TE max ≈ 18 ms). In conclusion, further validation and the development of movement-robust in vivo meGRE protocols with TE max ≈ 54 ms are required before M2 can be used to estimate R 2,iso * in subjects.

Background Stress-related disorders such as anxiety and depression are highly prevalent and cause a tremendous burden for affected individuals and society. In order to improve prevention strategies, knowledge regarding resilience mechanisms and ways to boost them is highly needed. In the Dynamic Modelling of Resilience – interventional multicenter study (DynaM-INT), we will conduct a large-scale feasibility and preliminary efficacy test for two mobile- and wearable-based just-in-time adaptive interventions (JITAIs), designed to target putative resilience mechanisms. Deep participant phenotyping at baseline serves to identify individual predictors for intervention success in terms of target engagement and stress resilience. Methods DynaM-INT aims to recruit N = 250 healthy but vulnerable young adults in the transition phase between adolescence and adulthood (18–27 years) across five research sites (Berlin, Mainz, Nijmegen, Tel Aviv, and Warsaw). Participants are included if they report at least three negative burdensome past life events and show increased levels of internalizing symptoms while not being affected by any major mental disorder. Participants are characterized in a multimodal baseline phase, which includes neuropsychological tests, neuroimaging, bio-samples, sociodemographic and psychological questionnaires, a video-recorded interview, as well as ecological momentary assessments (EMA) and ecological physiological assessments (EPA). Subsequently, participants are randomly assigned to one of two ecological momentary interventions (EMIs), targeting either positive cognitive reappraisal or reward sensitivity. During the following intervention phase, participants' stress responses are tracked using EMA and EPA, and JITAIs are triggered if an individually calibrated stress threshold is crossed. In a three-month-long follow-up phase, parts of the baseline characterization phase are repeated. Throughout the entire study, stressor exposure and mental health are regularly monitored to calculate stressor reactivity as a proxy for outcome resilience. The online monitoring questionnaires and the repetition of the baseline questionnaires also serve to assess target engagement. Discussion The DynaM-INT study intends to advance the field of resilience research by feasibility-testing two new mechanistically targeted JITAIs that aim at increasing individual stress resilience and identifying predictors for successful intervention response. Determining these predictors is an important step toward future randomized controlled trials to establish the efficacy of these interventions.

Auditory perception is fundamental to human development and communication. Yet, no long-term studies have been performed on the plasticity of the auditory system as a function of musical training from childhood to adulthood. The long-term interplay between developmental and training-induced neuroplasticity of auditory processing is still unknown. We present results from AMseL (‘Audio and Neuroplasticity of Musical Learning’), the first longitudinal study on the development of the human auditory system from primary school age until late adolescence. This 12-year project combined neurological and behavioral methods including structural magnetic resonance imaging, magnetoencephalography, and auditory tests. A cohort of 112 typically developing participants (51 male, 61 female), classified as ‘musicians’ (n=66) and ‘non-musicians’ (n=46), was tested at five measurement time points. We found substantial, stable differences in the morphology of auditory cortex between musicians and non-musicians even at the earliest ages, suggesting that musical aptitude is manifested in macroscopic neuroanatomical characteristics. Maturational plasticity led to a continuous increase in white matter myelination and systematic changes of the auditory evoked P1-N1-P2 complex (decreasing latencies, synchronization effects between hemispheres, and amplitude changes) regardless of musical expertise. Musicians showed substantial training-related changes at the neurofunctional level, in particular more synchronized P1 responses and bilaterally larger P2 amplitudes. Musical training had a positive influence on elementary auditory perception (frequency, tone duration, onset ramp) and pattern recognition (rhythm, subjective pitch). The observed interplay between ‘nature’ (stable biological dispositions and natural maturation) and ‘nurture’ (learning-induced plasticity) is integrated into a novel neurodevelopmental model of the human auditory system. Significance statement We present results from AMseL (‘Audio and Neuroplasticity of Musical Learning’), a 12-year longitudinal study on the development of the human auditory system from childhood to adulthood that combined structural magnetic resonance imaging, magnetoencephalography, and auditory discrimination and pattern recognition tests. 66 musicians and 46 non-musicians were tested at five time points. Substantial, stable differences in the morphology of auditory cortex were found between the two groups even at the earliest ages, suggesting that musical aptitude is manifested in macroscopic neuroanatomical characteristics. We also observed neuroplastic and perceptual changes with age and musical practice. This interplay between ‘nature’ (stable biological dispositions and natural maturation) and ‘nurture’ (learning-induced plasticity) is integrated into a novel neurodevelopmental model of the human auditory system.

The effect of transcranial direct current stimulation (tDCS) on neurobiological mechanisms underlying executive function in the human brain remains elusive. This study aims at examining the effect of anodal and cathodal tDCS over the left dorsolateral prefrontal cortex (DLPFC) in comparison with sham stimulation on resting-state connectivity as well as functional activation and working memory performance. We hypothesized perturbed fronto-parietal resting-state connectivity during stimulation and altered working memory performance combined with modified functional working memory-related activation. We applied tDCS with 1 mA for 21 min over the DLPFC inside an fMRI scanner. During stimulation, resting-state fMRI was acquired and task-dependent fMRI during working memory task performance was acquired directly after stimulation. N = 36 healthy subjects were studied in a within-subject design with three different experimental conditions (anodal, cathodal and sham) in a double-blind design. Seed-based functional connectivity analyses and dynamic causal modeling were conducted for the resting-state fMRI data. We found a significant stimulation by region interaction in the seed-based ROI-to-ROI resting-state connectivity, but no effect on effective connectivity. We also did not find an effect of stimulation on task-dependent signal alterations in working memory activation in our regions of interest and no effect on working memory performance parameters. We found effects on measures of seed-based resting-state connectivity, while measures of effective connectivity and task-based connectivity did not show any stimulation effect. We could not replicate previous findings of tDCS stimulation effects on behavioral outcomes. We critically discuss possible methodological limitations and implications for future studies.

Groups coordinate more effectively when individuals are able to learn from others’ successes. But acquiring such knowledge is not always easy, especially in real-world environments where success is hidden from public view. We suggest that social inference capacities may help bridge this gap, allowing individuals to update their beliefs about others’ underlying knowledge and success from observable trajectories of behaviour. We compared our social inference model against simpler heuristics in three studies of human behaviour in a collective-sensing task. Experiment 1 demonstrated that average performance improved as a function of group size at a rate greater than predicted by heuristic models. Experiment 2 introduced artificial agents to evaluate how individuals selectively rely on social information. Experiment 3 generalized these findings to a more complex reward landscape. Taken together, our findings provide insight into the relationship between individual social cognition and the flexibility of collective behaviour.

Our understanding of the genetics of the human cerebral cortex is limited both in terms of the diversity and the anatomical granularity of brain structural phenotypes. Here we conducted a genome-wide association meta-analysis of 13 structural and diffusion magnetic resonance imaging-derived cortical phenotypes, measured globally and at 180 bilaterally averaged regions in 36,663 individuals and identified 4,349 experiment-wide significant loci. These phenotypes include cortical thickness, surface area, gray matter volume, measures of folding, neurite density and water diffusion. We identified four genetic latent structures and causal relationships between surface area and some measures of cortical folding. These latent structures partly relate to different underlying gene expression trajectories during development and are enriched for different cell types. We also identified differential enrichment for neurodevelopmental and constrained genes and demonstrate that common genetic variants associated with cortical expansion are associated with cephalic disorders. Finally, we identified complex interphenotype and inter-regional genetic relationships among the 13 phenotypes, reflecting the developmental differences among them. Together, these analyses identify distinct genetic organizational principles of the cortex and their correlates with neurodevelopment.

Autism is a neurodevelopmental condition involving atypical sensory-perceptual functions together with language and socio-cognitive deficits. Previous work has reported subtle alterations in the asymmetry of brain structure and reduced laterality of functional activation in individuals with autism relative to non-autistic individuals (NAI). However, whether functional asymmetries show altered intrinsic systematic organization in autism remains unclear. Here, we examined inter- and intra-hemispheric asymmetry of intrinsic functional gradients capturing connectome organization along three axes, stretching between sensory-default, somatomotor-visual, and default-multiple demand networks, to study system-level hemispheric imbalances in autism. We observed decreased leftward functional asymmetry of language network organization in individuals with autism, relative to NAI. Whereas language network asymmetry varied across age groups in NAI, this was not the case in autism, suggesting atypical functional laterality in autism may result from altered developmental trajectories. Finally, we observed that intra- but not inter-hemispheric features were predictive of the severity of autistic traits. Our findings illustrate how regional and patterned functional lateralization is altered in autism at the system level. Such differences may be rooted in atypical developmental trajectories of functional organization asymmetry in autism.

Although artificial neural networks (ANNs) were inspired by the brain, ANNs exhibit a brittleness not generally observed in human perception. One shortcoming of ANNs is their susceptibility to adversarial perturbations—subtle modulations of natural images that result in changes to classification decisions, such as confidently mislabelling an image of an elephant, initially classified correctly, as a clock. In contrast, a human observer might well dismiss the perturbations as an innocuous imaging artifact. This phenomenon may point to a fundamental difference between human and machine perception, but it drives one to ask whether human sensitivity to adversarial perturbations might be revealed with appropriate behavioral measures. Here, we find that adversarial perturbations that fool ANNs similarly bias human choice. We further show that the effect is more likely driven by higher-order statistics of natural images to which both humans and ANNs are sensitive, rather than by the detailed architecture of the ANN.