Biology subjects

Seidenbecher, C. I.

Publications and source records attributed to Seidenbecher, C. I..

9 recordsLinked to original sources

bioRxiv2026

Altered theta distribution and coherence during set-shifting in older age

Cognitive flexibility is an executive function that enables adapting behaviour to a changing environment and is thus critical for daily life. The degree of its preservation upon healthy aging and the neural mechanisms underlying it are still a matter of debate. To investigate the electrophysiological correlates of cognitive flexibility in older age, we measured cognitive flexibility in 99 young (24.75 {+/-} 4.45 years) and 83 older adults (69.19 {+/-} 6.25) using electroencephalography (EEG). Compared to young adults, older adults showed a more conservative response pattern with longer reaction times, but lower error rates (speed-accuracy tradeoff). In the EEG, both age groups exhibited increased theta-power during set-shifting, with a fronto-central peak in the young, but a more fronto-lateral topography in older adults. Importantly, both groups displayed increases in theta coherence and global efficiency during set-shifting, but coherence modulations were restricted in frontocentral areas in the young but were diminished and distributed across the scalp in the older. Better set-shifting performance was most strongly associated with high coherence and global efficiency irrespective of age group. These results point to an age-related change of cortical processing underlying cognitive flexibility which involves the employment of more distributed neural resources for successful task completion.

neuroscience↗

bioRxiv2024

Activity-dependent extracellular proteolytic cascade remodels ECM to promote structural plasticity

The brains perineuronal extracellular matrix (ECM) is a crucial factor in maintaining the stability of mature brain circuitry. However, how is activity-induced synaptic plasticity achieved in the adult brain with a dense ECM? We hypothesized that neuronal activity induces cleavage of ECM components, creating space for synaptic rearrangements. To test this hypothesis, we investigated neuronal activity-dependent proteolytic cleavage of brevican, a prototypical perineuronal ECM proteoglycan, and its importance of this process for functional and structural synaptic plasticity in the rat hippocampus ex vivo. Our findings revealed that chemical long-term potentiation (cLTP) triggers a rapid brevican cleavage through the activation of an extracellular proteolytic cascade involving proprotein convertases and ADAMTS-4 and ADAMTS-5. This process is dependent on NMDA receptors and requires astrocytes. Interestingly, the extracellular full-length brevican increases upon cLTP, indicating a simultaneous secretion of ECM components. Interfering with cLTP-induced brevican cleavage did not impact the early LTP but prevented formation of new dendritic protrusions. Collectively, these results reveal a mechanism of activity-dependent ECM remodeling and suggest that ECM degradation is essential for structural synaptic plasticity.

neuroscience↗

bioRxiv2024

Frontal Theta Oscillations and Cognitive Flexibility: Age-Related Modulations in EEG Activity

Cognitive flexibility, the ability to adapt ones behaviour in changing environments, declines during aging. Electroencephalography (EEG) studies have implicated midfrontal theta oscillations in attentional set-shifting, a measure of cognitive flexibility. Little is known about the electrocortical underpinnings of set-shifting in aging. Here, we investigated aging effects on set-shifting performance by analysing theta power in 20 young (mean age: 22.5 {+/-} 2.9 years) and 19 older (mean age: 69.4 {+/-} 6.1 years) adults. Increasing shift difficulty (i.e., intra- vs. extra-dimensional shifts) elicited worse performance in both age groups, with older adults showing overall longer reaction times (RTs) and increased RT variability. Young adults exhibited amplified midfrontal theta power increases with higher shift difficulty whereas older adults showed overall lower theta power and no task-related midfrontal theta power modulation, indicating potentially distinct underlying neural mechanisms.

neuroscience↗

bioRxiv2023

Neural Extracellular Matrix Remodeling Signatures in Genetic and Acquired Mouse Models of Epilepsy

Epilepsies are multifaceted neurological disorders characterized by abnormal brain activity, e.g., caused by imbalanced synaptic excitation and inhibition. The neural extracellular matrix (ECM) is dynamically modulated by physiological and pathophysiological activity and critically involved in controlling the brains excitability. We used different epilepsy models, i.e. mice lacking the presynaptic scaffolding protein Bassoon at excitatory, inhibitory or all synapse types as genetic models for rapidly generalizing early-onset epilepsy, and intra-hippocampal kainate injection, a model for acquired temporal lobe epilepsy, to study the relationship between epileptic seizures and ECM composition. Electroencephalogram recordings revealed Bassoon deletion at excitatory or inhibitory synapses having diverse effects on epilepsy-related phenotypes. While constitutive Bsn mutants and GABAergic neuron-specific knockouts (BsnDlx5/6cKO) displayed severe epilepsy with more and stronger seizures than kainate-injected animals, mutants lacking Bassoon solely in excitatory forebrain neurons (BsnEmx1cKO) showed only mild impairments. By semiquantitative immunoblotting and immunohistochemistry we show model-specific patterns of neural ECM remodeling, and we also demonstrate significant upregulation of the ECM receptor CD44 in null and BsnDlx5/6cKO mutants. ECM-associated WFA-binding chondroitin sulfates were strongly augmented in seizure models. Strikingly, Brevican, Neurocan, Aggrecan and link protein Hapln1 levels reliably predicted seizure properties across models, suggesting a link between ECM state and epileptic phenotype.

neuroscience↗

bioRxiv2023

Depletion of neurocan in the prefrontal cortex impairs temporal order recognition, cognitive flexibility and perisomatic GABAergic innervation

The condensed form of neural extracellular matrix (ECM), perineuronal nets (PNNs), is predominantly associated with parvalbumin-expressing (PV+) interneurons in the cortex and hippocampus. PNNs are enriched in several lecticans, including neurocan (Ncan). A polymorphism in the human Ncan gene has been associated with alterations in hippocampus-dependent memory function, variation of prefrontal cortex structure, and a higher risk for schizophrenia or bipolar disorder. Ncan knockout (KO) mice show related behavioral abnormalities, such as hyperactivity. Here we focused on studying how dysregulation of Ncan specifically in the mPFC may affect cognitive and synaptic functions. Intracortical adeno-associated virus (AAV) delivery was used to express shRNA against Ncan. Analysis of PNNs in Ncan shRNA-injected mice revealed a reduction in PNNs labelling by Wisteria floribunda agglutinin (WFA) around PV+ interneurons. Reduced Ncan expression resulted in a loss of the mPFC-dependent temporal order recognition and impairment of reversal spatial learning in a labyrinth (dry maze) task. As a potential synaptic substrate of these cognitive abnormalities, we report a robust reduction in the perisomatic GABAergic innervation of PV+ cells in Ncan KO and Ncan shRNA-injected mice. We also observed an increase in the density of vGLUT1-immunopositive synaptic puncta in the neuropil of Ncan shRNA-injected mice, which was, however, compensated in Ncan KO mice. Thus, our findings highlight a functional role of Ncan in supporting perisomatic GABAergic inhibition, temporal order recognition memory and cognitive flexibility, as one of the important cognitive resources depleted in neuropsychiatric disorders. Contribution to the fieldIn this study, we asked if the extracellular matrix proteoglycan neurocan (Ncan) plays a functional role in the prefrontal cortex (PFC) of mice. Using viral delivery and expression of shRNA to knock down the expression of Ncan in the PFC, we provide evidence that neuronal Ncan is essential for the maintenance of perineuronal nets enveloping perisomatic interneurons by influencing the expression of glycoepitopes stained with Wisteria floribunda agglutinin and by modulating mRNA expression levels of other PNNs constituents. At the behavioral level, the knockdown of Ncan in mPFC impaired the temporal order recognition memory and consolidation/retrieval of spatial memories after reversal learning in the dry maze task. At the synaptic level, we found that Ncan knockdown reduced perisomatic GABAergic innervation of perisomatic interneurons and increased the density of vGLUT1+ excitatory presynaptic terminals in the neuropil of the PFC. Moreover, knockdown of Ncan changed the expression levels of several genes involved in activity-dependent synaptic remodeling. In summary, we conclude that neuronal Ncan is essential for multiple cognitive flexibility-related synaptic and cognitive functions in the PFC.

neuroscience↗

bioRxiv2022

Plasma concentrations of anti-inflammatory cytokine TGF-β are associated with hippocampal structure related to explicit memory performance in older adults

Human cognitive abilities, and particularly hippocampus-dependent memory performance typically decline with increasing age. Immunosenescence, the age-related disintegration of the immune system, is increasingly coming into the focus of research as a considerable factor contributing to cognitive decline. In the present study, we investigated potential associations between plasma levels of pro- and anti-inflammatory cytokines and learning and memory performance as well as hippocampal anatomy in young and older adults. Plasma concentrations of the inflammation marker CRP as well as the pro-inflammatory cytokines IL-6 and TNF- and the anti-inflammatory cytokine TGF-{beta}1 were measured in 142 healthy adults (57 young, 24.47 {+/-} 4.48 years; 85 older, 63.66 {+/-} 7.32 years) who performed tests of explicit memory (Verbal Learning and Memory Test, VLMT; Wechsler Memory Scale, Logical Memory, WMS) with an additional delayed recall test after 24 hours. Hippocampal volumetry and hippocampal subfield segmentation were performed using FreeSurfer, based on T1-weighted and high-resolution T2-weighted MR images. When investigating the relationship between memory performance, hippocampal structure, and plasma cytokine levels, we found that TGF- {beta}1 concentrations were positively correlated with the volumes of the hippocampal CA4-dentate gyrus region in older adults. These volumes were in turn positively associated with better performance in the WMS, particularly in the delayed memory test. Our results support the notion that endogenous anti-inflammatory mechanisms may act as protective factors in neurocognitive aging.

neuroscience↗

bioRxiv2022

Summary statistics of memory-related fMRI activity reflect dissociable neuropsychological and anatomical signatures of neurocognitive aging

Memory-related functional magnetic resonance imaging (fMRI) activations show age-related differences across multiple brain regions that can be captured in summary statistics like single-value scores. Recently, we described two single-value scores reflecting deviations from prototypical whole-brain fMRI activity of young adults during novelty processing and successful encoding. Here, we investigate the brain-behavior associations of these scores with age-related neurocognitive changes in 153 healthy older adults. All scores were associated with episodic recall performance. The memory network scores, but not the novelty network scores, additionally correlated with medial temporal gray matter and a composite measure comprising pro-active inhibition, episodic memory, tonic alertness, flexibility, and working memory. Our results thus suggest that novelty-network-based fMRI scores show high brain-behavior associations with episodic memory and that encoding-network-based fMRI scores additionally capture individual differences in global cognitive function. More generally, our results suggest that single-value scores of memory-related fMRI provide a comprehensive measure of individual differences in network dysfunction that may contribute to age-related cognitive decline.

neuroscience↗

bioRxiv2021

Motivational learning biases are differentially modulated by genetic determinants of striatal and prefrontal dopamine function

Dopaminergic neurotransmission plays a pivotal role in appetitively motivated behavior in mammals, including humans. Notably, action and valence are not independent in motivated tasks, and it is particularly difficult for humans to learn the inhibition of an action to obtain a reward. We have previously observed that the carriers of the DRD2/ANKK1 TaqIA A1 allele, that has been associated with reduced striatal dopamine D2 receptor expression, showed a diminished learning performance when required to learn response inhibition to obtain rewards, a finding that was replicated in two independent cohorts. In the present study, we first report a replication of this finding in a third independent cohort of 99 participants. Interestingly, after combining all three cohorts (total N = 281), exploratory analyses regarding the COMT Val108/158Met polymorphism suggest that homozygotes for the Met allele, which has been linked to higher prefrontal dopaminergic tone, show a lower learning bias. Our results corroborate the importance of genetic variability of the dopaminergic system in individual learning differences of action-valence interaction and, furthermore, suggest that motivational learning biases are differentially modulated by genetic determinants of striatal and prefrontal dopamine function.

neuroscience↗

bioRxiv2019

TRAF6 controls excitatory spinogenesis and excitation-inhibition balance thought binding neuroplastin

Synaptogenic mechanisms and their relevance to achieve a correct synapse density and activity in mature neurons are poorly understood. Here, we show that the tumor necrosis factor receptor-associated factor 6 (TRAF6) controls early spinogenesis by binding the cell adhesion molecule neuroplastin which is has been related to synapse formation in vivo. TRAF6-neuroplastin co-precipitations from brain samples and co-transfected HEK cells is explained by direct interaction of the proteins based on three-dimensional modelling and biochemical identification of intracellular amino acids of neuroplastin binding the TRAF-C domain of TRAF6 with micromolar affinity. TRAF6 was not only required for normal spinogenesis but also was strictly necessary to restore failed spinogenesis in neuroplastin-deficient neurons. Independently from neuroplastins extracellular adhesive properties or interaction with another known partner i.e. the plasma membrane Ca2+ ATPases, TRAF6 mediated formation of new postsynapses by neuroplastin overexpression in rat hippocampal neurons. Furthermore, TRAF6-controlled spinogenesis was required for the establishment of a correct synapse density as well as proper synaptic activity and intrinsic neuronal activity as demonstrated with intracellular and extracellular electrophysiological recordings. These findings provide a novel mechanism for early synapse formation that shapes connectivity and functioning of hippocampal neurons.

cell biology↗