Biology subjects

Kohn, N.

Publications and source records attributed to Kohn, N..

12 recordsLinked to original sources

bioRxiv2026

Exploring the role of multivariate associations between brain networks and gut microbiota in (food) value-based decision-making

Food reward valuation and decision making are key psychological processes regulating eating behaviour. Stress and negative affect can shape these processes, increasing vulnerability to overeating high caloric, ultra-processed foods and thereby elevating obesity risk. Yet not all individuals under stress exhibit such behavioural shifts, highlighting the need to understand which modulating factors explain this inter individual variability. Emerging evidence suggests that anxiety-/stress-induced changes in gut microbiota might alter reward sensitivity via the gut-brain axis. An integrative framework linking microbiota, neural, and affective processes is thus essential for explaining individual differences in emotional eating, yet such a framework is still lacking. To this end, supervised linked independent component analysis (Super- BigFLICA) was used to explore multivariate gut-brain latent components guided by affective and body composition indexes in healthy participants (N = 592) from the Healthy Brain Study. Next, general linear models were used to identify if any of the observed components were predictive of elevated unhealthy food valuation and choice in a food auction task. A multimodal component was predictive of both food valuation and choice. This component was characterized by co-occurring changes in several gut bacterial taxa at the genus level (e.g., UCG-010 and DTU089), specific connectivity between reward-related brain regions (e.g., nucleus accumbens, caudate), and was clearly linked to elevated anxiety sensitivity, life-event impact, and body mass index. These findings demonstrate the feasibility of supervised gut-brain integration for predicting behaviour and reveal a potential phenotype linking microbiota composition, brain function, and emotional state that should be further investigated

neuroscience↗

bioRxiv2026

Associative emotional memory encoding: Insights from network stability analysis of an fMRI-driven bilinear dynamics

The interplay between emotion and memory is a central topic in cognitive neuroscience, with open questions about the underlying neuronal mechanisms. This article studies dynamic interactions among the hippocampus, amygdala, and orbitofrontal cortex during an fMRI associative memory encoding task. Participants were clustered into three condition groups: Neutral-Neutral, Neutral-Emotional, or Emotional-Emotional, and viewed image pairs associated with their assigned condition. Using the dynamic causal modeling framework, we explore several dynamic models and show that a stochastic bilinear state-space model best describes the neuronal dynamics in all conditions. Furthermore, we use graph and control theory techniques to both validate and analyze the model. In particular, we analyze the network dynamics of each condition using tools from graph theory and stability theory and discuss the differences in the strength and direction of connectivity as well as the stability of each of these networks. We confirm the prior finding that memory is enhanced in emotional conditions, in particular in the Neutral-Emotional condition. In our work, this enhanced memory is associated with increased hippocampus-amygdala coupling and overall network connectivity. In addition, we show that in the Emotional-Emotional condition, the coupling of the hippocampus and amygdala, as well as the whole network connectivity increases when the first images valence is substantially less negative rated than the second image. This pattern mirrors the Neutral-Emotional condition, where the first image is neutral compared with the second one. Moreover, our model-based analyses suggest that the amygdala predominantly influences the other two regions in the Neutral-Emotional condition, whereas the OFC plays a dominant role in the other two conditions. Combined data-driven modeling, stability analyses, and graph-theory tools led to new insights and enhanced the mechanistic understanding of cortical dynamics of emotional associative memory. We discuss these insights, utilize these analytical tools to generalize our findings to some unmeasured conditions, and highlight the potential of these techniques to inform the design of future regulatory mechanisms.

neuroscience↗

bioRxiv2025

The elusive neural signature of emotion regulation capabilities: evidence from a large-scale consortium

Cognitive reappraisal is a fundamental emotion regulation strategy for mental and physical well-being, but how its neural mechanisms relate to individual differences remains poorly understood. In a consortium effort analyzing 40 fMRI datasets (N=2,175), we examined the relationship between neural activation during reappraisal tasks and three core individual difference indices of reappraisal capabilities: (1) trait questionnaires, (2) task-based affective ratings, and (3) amygdala down-regulation. Strikingly, there was no shared overlap across these three common indices. Only a very weak correlation emerged between amygdala down-regulation and task-based affective ratings. Whole-brain analyses revealed no reliable neural associations with trait questionnaires, and associations with task-based affective ratings fell outside canonical emotion regulation networks (e.g., prefrontal circuitry). Moreover, amygdala down-regulation, often interpreted as a stable individual marker, was confounded by person-specific whole-brain responses -- a limitation extending to fMRI research beyond the emotion regulation domain. These findings challenge the assumption that an individuals prefrontal activity is a valid indicator of their reappraisal capabilities and suggest that common trait, behavioral, and neural measures might capture distinct facets of emotion regulation. More broadly, our results highlight concrete methodological challenges for fMRI research on individual differences, with implications extending beyond emotion regulation to the neuroscience of personality, psychopathology, and general well-being.

neuroscience↗

bioRxiv2023

Emotional information facilitates or disrupts memory integration through distinct hippocampal processes of reactivation and connectivity

Emotion has a significant impact on how related experiences are organized into integrated memories. However, the neurobiological mechanisms of how emotion modulates memory integration for related information with different valences remain unclear. In this between-subject functional magnetic resonance imaging (fMRI) study, we investigated different emotional modulations of memory integration by manipulating the valence of stimuli used in an associative memory paradigm. Three groups of participants were tested: one group integrated emotional (i.e., negative) information with neutral information, one group integrated two emotional pieces of information, and one control group integrated two neutral pieces of information. Behaviorally, emotional information facilitated its integration with neutral information but interfered with the other emotional information. Neurally, the emotion-induced facilitation effect, occurring on memory integration of neutral and emotional information, was associated with increased trial-specific reactivation in the hippocampus during both encoding and retrieval. This facilitated integration was also supported by strengthened hippocampal connectivity with the amygdala, as well as a set of neocortical areas related to emotion regulation and the default mode network (DMN). In contrast, the emotion-induced interference effect, occurring on memory integration of two emotional pieces of information, was associated with impaired hippocampal trial-specific reactivation during retrieval that appeared to offset the facilitating effect of increased reactivation during encoding. Similar but relatively weak hippocampal connectivity was found underlying this interfered integration. Taken together, emotional information facilitates memory integration with neutral information, while disrupting the integration with other emotional information, through distinct dynamical processes of hippocampal trial-specific reactivation and connectivity.

neuroscience↗

bioRxiv2020

Multivariate associative patterns between the gut microbiota and large-scale brain network connectivity

Research on the gut-brain axis has accelerated substantially over the course of the last years. Many reviews have outlined the important implications of understanding the relation of the gut microbiota with human brain function and behavior. One substantial drawback in integrating gut microbiome and brain data is the lack of integrative multivariate approaches that enable capturing variance in both modalities simultaneously. To address this issue, we applied a linked independent component analysis (LICA) to microbiota and brain connectivity data. We analyzed data from 58 healthy females (mean age = 21.5 years). Magnetic Resonance Imaging data were acquired using resting state functional imaging data. The assessment of gut microbial composition from feces was based on sequencing of the V4 16S rRNA gene region. We used the LICA model to simultaneously factorize the subjects large-scale brain networks and microbiome relative abundance data into 10 independent components of spatial and abundance variation. LICA decomposition resulted in four components with non-marginal contribution of the microbiota data. The default mode network featured strongly in three components, whereas the two-lateralized fronto-parietal attention networks contributed to one component. The executive-control (with the default mode) network was associated to another component. We found the abundance of Prevotella genus was associated to the strength of expression of all networks, whereas Bifidobacterium was associated with the default mode and frontoparietal-attention networks. We provide the first exploratory evidence for multivariate associative patterns between the gut microbiota and brain network connectivity in healthy humans, taking into account the complexity of both systems.

neuroscience↗

bioRxiv2020

The dynamic transition between neural states is associated with the flexible use of memory

Flexible behavior requires switching between different task conditions. It is known that such task- switching is associated with costs in terms of slowed reaction time, reduced accuracy, or both. The neural correlates of task-switching have usually been studied by requiring participants to switch between distinct task demands that recruit different brain networks. Here, we investigated the transition of neural states underlying switching between two opposite memory-related processes (i.e., memory retrieval and memory suppression) in a memory task. We investigated 26 healthy participants who performed a Think/No-Think task while being in the fMRI scanner. Behaviorally, we show that it was more difficult for participants to suppress unwanted memories when a No-Think was preceded by a Think trial instead of another No- Think trial. Neurally, we demonstrate that Think-to-No-Think switches were associated with an increase in control-related and a decrease in memory-related brain activity. Neural representations of task demand, assessed by decoding accuracy, were lower immediately after task switching compared to the non-switch transitions, suggesting a switch-induced delay in the neural transition towards the required task condition. This suggestion is corroborated by an association between condition-specific representational strength and condition-specific performance in switch trials. Taken together, we provided neural evidence from the time-resolved decoding approach to support the notion that carry-over of the previous task-set activation is associated with the switching cost leading to less successful memory suppression. Significance statementOur brain can switch between multiple tasks but at the cost of less optimal performance during transition. One possible neuroscientific explanation is that the representation of the task condition is not easy to be updated immediately after switching. Thus, weak representations for the task at hand explain performance costs. To test this, we applied brain decoding approaches to human fMRI data when participants switched between successive trials of memory retrieval and suppression. We found that switching leads to a weaker representation of the current task. The remaining representation of the previous, opposite task is associated with inferior performance in the current task. Therefore, timely updating of task representations is critical for task switching in the service of flexible behaviors.

neuroscience↗

bioRxiv2020

Hippocampal-medial prefrontal event segmentation and integration contribute to episodic memory formation

How do we encode our continuous life experiences for later retrieval? Theories of event segmentation and integration suggest that the hippocampus binds separately represented events into an ordered narrative. Using a functional Magnetic Resonance Imaging (fMRI) movie watching-recall dataset, we quantified two types of neural similarities (i.e., activation pattern similarity and within-region voxel-based connectivity pattern similarity) between separate events during movie watching and related them to subsequent retrieval of events as well as retrieval of sequential order. We demonstrated that compared to forgotten events, successfully remembered events were associated with distinct activation patterns in the hippocampus and medial prefrontal cortex. By contrast, similar connectivity patterns between events were associated with memory formation and were also relevant for retaining events in the correct order. We applied the same approaches to an independent movie watching fMRI dataset as validation and highlighted again the role of hippocampal activation pattern and connectivity pattern in memory formation. We propose that distinct activation patterns represent neural segmentation of events while similar connectivity patterns encode context information, and therefore integrate events into a narrative. Our results provide novel evidence for the role of hippocampal-medial prefrontal event segmentation and integration in episodic memory formation of real-life experience.

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bioRxiv2019

Probing the neural dynamics of mnemonic representations in humans

Memories are not stored as static engrams, but as dynamic representations affected by processes occurring after initial encoding. Previous studies revealed changes in activity and mnemonic representations in visual processing areas, parietal lobe, and hippocampus underlying repeated retrieval and suppression. However, these neural changes are usually induced by memory modulation immediately after memory formation. Here, we investigated 27 healthy participants with a two-day functional Magnetic Resonance Imaging design to probe how established memories are dynamically modulated by retrieval and suppression 24 hours after learning. Behaviorally, we demonstrated that established memories can still be strengthened by repeated retrieval. By contrast, repeated suppression had a modest negative effect, and suppression-induced forgetting was associated with individual suppression efficacy. Neurally, we demonstrated item-specific pattern reinstatements in visual processing areas, parietal lobe, and hippocampus. Then, we showed that repeated retrieval reduced activity amplitude in the ventral visual cortex and hippocampus, but enhanced the distinctiveness of activity patterns in the ventral visual cortex and parietal lobe. Critically, reduced activity was associated with enhanced representation of idiosyncratic memory traces in ventral visual cortex and precuneus. In contrast, repeated memory suppression was associated with the reduced lateral prefrontal activity, but relative intact mnemonic representations. Our results replicated most of the neural changes induced by memory retrieval and suppression immediately after learning and extended those findings to established memories after initial consolidation. Active retrieval seems to promote episode-unique mnemonic representations in the neocortex after initial encoding but also consolidation. HighlightsO_LIRepeated retrieval strengthened consolidated memories, while repeated suppression had a modest negative effect. C_LIO_LIPattern reinstatements of individual memories were detected in the visual area, parietal lobe, and hippocampus after 24 hours. C_LIO_LIAfter repeated retrieval, reduced activity amplitude was associated with increased distinctiveness of activity patterns in the ventral visual cortex and right precuneus. C_LIO_LIRepeated suppression was associated with the reduced lateral prefrontal activity, but unchanged mnemonic representations. C_LI

neuroscience↗

bioRxiv2019

Common neural and transcriptional correlates of inhibitory control across emotion, memory, and response inhibition

Inhibitory control is crucial for regulating emotions, and it may also enable memory control. However, evidence for their shared neurobiological correlates is limited. Here, we report meta-analyses of neuroimaging studies on emotion regulation, or memory control, and link neural commonalities to transcriptional commonalities using the Allen Human Brain Atlas (AHBA). Based on 95 fMRI studies, we reveal a role of the right inferior parietal lobule embedded in a frontal-parietal-insular network during emotion and memory control, which is similarly recruited during response inhibition. These co-activation patterns also overlap with the networks associated with "inhibition", "cognitive control", and "working memory" when consulting the Neurosynth. Using the AHBA, we demonstrate that emotion and memory control-related brain activity patterns are associated with transcriptional profiles of a specific set of "inhibition-related" genes. Gene ontology enrichment analysis of these "inhibition-related" genes reveal associations with the neuronal transmission and risk for major psychiatric disorders as well as seizures and alcoholic dependence. In summary, this study identified a neural network and a set of genes associated with inhibitory control across emotion regulation, memory control. These findings facilitate our understanding of the neurobiological correlates of inhibitory control and may contribute to the development of novel brain stimulation and pharmacological interventions.

neuroscience↗

bioRxiv2019

Medial prefrontal decoupling from the default mode network benefits memory

In the last few years the involvement of the medial prefrontal cortex (mPFC) in memory processing has received increased attention. It is centrally involved when we use prior knowledge (schemas) to improve learning of new material. With the mPFC also being one of the core hubs of the default mode network (DMN) and the DMNs role in memory retrieval, we decided to investigate whether the mPFC in a schema paradigm acts independently of the DMN. We tested this with data from a cross-sectional developmental study. During retrieval of schema items, the mPFC decoupled from the DMN with the degree of decoupling predicting memory performance. This finding suggests that a demand specific reconfiguration of the DMN supports schema memory. Additionally, we found that in the control condition, which relied on episodic memory, activity in the parahippocampal gyrus was positively related to memory performance. We interpret these results as a demand specific network reconfiguration of the DMN: a decoupling of the mPFC to support schema memory and a decoupling of the parahippocampal gyrus facilitating episodic memory. This supports the notion of dynamic reconfiguration of brain networks in response to task demands in the sense of process specific alliances.

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bioRxiv2019

Differences in strategic abilities but not associative processes explain memory development

Childrens learning capabilities change while growing up. One framework that describes the cognitive and neural development of childrens growing learning abilities is the two-component model. It distinguishes processes that integrate separate features into a coherent memory representation (associative component) and executive abilities, such as elaboration, evaluation and monitoring, that support memory processing (strategic component). In an fMRI study using an object-location association paradigm, we investigated how the two components influence memory performance across development. We tested children (10-12 yrs., n=31), late adolescents (18 yrs., n=29) and adults (25+ yrs., n=30) of either sex. For studying the associative component, we also probed how the utilisation of prior knowledge (schemas) facilitates memory across age groups. Children had overall lower retrieval performance, while adolescents and adults did not differ from each other. All groups benefitted from schemas, but this effect did not differ between groups. Performance differences between groups were associated with deactivation of the dorsal medial prefrontal cortex (dmPFC), which in turn was linked to executive functioning. These patterns were stronger in adolescents and adults and seemed absent in children. This pattern of results suggests the childrens executive system, the strategic component, is not as mature and thus cannot facilitate memory performance in the same way as in adolescents/adults. In contrast, we did not find age-related differences in the associative component; with activity in the angular gyrus predicting memory performance systematically across groups. Overall our results suggest that differences of executive rather than associative abilities explain memory differences between children, adolescents and adults.

neuroscience↗

bioRxiv2018

Stress matters: a double-blind, randomized controlled trial on the effects of a multispecies probiotic on neurocognition

Probiotics are microorganisms that can provide health benefits when consumed. Recent animal studies have demonstrated that probiotics can reverse gut microbiome-related alterations in anxiety and depression-like symptoms, in hormonal responses to stress, and in cognition. However, in humans, the effects of probiotics on neurocognition remain poorly understood and a causal understanding of the gut-brain link in emotion and cognition is lacking. We aimed to fill this gap by studying the effects of a probiotics intervention versus placebo on neurocognition in healthy human volunteers.\n\nWe set out to investigate the effects of a multispecies probiotic (Ecologic(R)Barrier) on specific neurocognitive measures of emotion reactivity, emotion regulation, and cognitive control using fMRI. Critically, we also tested whether the use of probiotics can buffer against the detrimental effects of acute stress on working memory. In a double blind, randomized, placebo-controlled, between-subjects intervention study, 58 healthy participants were tested twice, once before and once after 28 days of intervention with probiotics or placebo.\n\nProbiotics versus placebo did not affect emotion reactivity, emotion regulation, and cognitive control processes at brain or behavioral level, neither related self-report measures. However, relative to the placebo group, the probiotics group did show a significant stress-related increase in working memory performance after versus before supplementation (digit span backward, p=0.039, {eta}p2=.07). Interestingly, this change was associated with intervention-related neural changes in frontal cortex during cognitive control in the probiotics group, but not in the placebo group. Overall, our results show that neurocognitive effects of supplementation with a multispecies probiotic in healthy women become visible under challenging (stress) situations. Probiotics buffered against the detrimental effects of stress in terms of cognition, especially in those individuals with probiotics-induced changes in frontal brain regions during cognitive control.\n\nHighlightsO_LIWe ran a randomized placebo-controlled fMRI study with a multispecies probiotic\nC_LIO_LIProbiotics did not affect neurocognitive measures of emotion and cognitive control\nC_LIO_LIProbiotics did affect stress-related working memory and neural correlates\nC_LIO_LIProbiotics in healthy individuals can support cognition under stress\nC_LI

neuroscience↗