Biology subjects

Nierhaus, T.

Publications and source records attributed to Nierhaus, T..

14 recordsLinked to original sources

bioRxiv2026

Remembering touch: Somatosensory cortex supports long-term memory for dynamic vibrotactile patterns.

The neural substrates of tactile long-term memory (LTM) in humans remain poorly understood, as relatively few neuroimaging studies have addressed this question. Here, we asked whether retrieval of tactile stimulation engages modality-specific representations in the primary and secondary somatosensory cortices (S1 and S2), alongside domain-general retrieval networks. Participants learned 16 tactile trajectories, each presented for 1.2 s on the left thumb through sequential activation of 10 vibrating dots on a Braille-like display. Three learning sessions within one week were followed by a recognition test during functional magnetic resonance imaging (fMRI). In the final sample (n = 26), we contrasted BOLD responses during successful recognition of learned stimuli with those during correct rejection of novel stimuli. Successful recognition was associated with increased activity in contralateral S1 and S2, alongside activation in the hippocampus as well as frontal and parietal regions implicated in memory retrieval. A psychophysiological interaction analysis (PPI) further revealed increased task-dependent connectivity between the hippocampus and contralateral S1 and S2 during successful recognition. Together, these findings suggest that tactile long-term memory retrieval relies on coordinated hippocampal-somatosensory interactions and may engage long-term memory representations in somatosensory cortex.

neuroscience↗

bioRxiv2026

Time- and performance-dependent enhancement of tactospatial working memory caused by online anodal tDCS of the posterior parietal cortex

BackgroundSpatial working memory (WM) relies on posterior parietal cortex (PPC) within a distributed fronto-parietal network, yet whether online anodal transcranial direct current stimulation (tDCS) of PPC modulates tactile WM, and how behavioral effects unfold over time, remains unclear. ObjectiveWe tested whether online anodal tDCS over left PPC modulates performance in a tactospatial WM task and whether stimulation effects vary over time and as a function of baseline performance. MethodsIn a double-blind, sham-controlled, within-subject crossover design, 32 healthy adults completed two counterbalanced sessions (Active, Sham). Each session comprised baseline, stimulation, and post-stimulation phases while participants performed a retro-cued delayed match-to-sample task with vibrotactile patterns delivered to the left index finger. During the stimulation phase, participants received either 2 mA anodal or sham tDCS over left PPC for 15 min, depending on session. Behavioral accuracy was analyzed using a sliding-window approach combined with cluster-based permutation testing. ResultsActive stimulation induced a significant, gradual improvement in WM accuracy relative to sham, emerging approximately eight minutes after stimulation onset and corresponding to a [~]5% performance increase (Hedges g = 0.43). Stimulation effects were baseline-dependent, with individuals showing lower initial WM performance exhibiting larger behavioral gains, whereas high performers showed minimal benefits. ConclusionsThese findings show that online anodal stimulation of left PPC can modulate tactile WM performance in a time- and baseline-dependent manner. More broadly, the results suggest that behavioral effects of parietal tDCS emerge gradually during ongoing stimulation and depend on initial cognitive state. HighlightsO_LIOnline anodal PPC-tDCS enhances tactile working memory C_LIO_LIBehavioral gains emerge after [~]8 min of stimulation C_LIO_LIActive stimulation improves accuracy by [~]5% versus sham C_LIO_LILower baseline performers show larger stimulation benefits C_LIO_LISliding-window analyses capture dynamic online tDCS effects C_LI

neuroscience↗

bioRxiv2025

Molecular structure of the ESCRT III-based archaeal CdvAB cell division machinery

Most prokaryotes divide using filaments of the tubulin-like FtsZ protein, while some archaea employ instead ESCRT-III-like proteins and their filaments for cell division and cytokinesis. The alternative archaeal system comprises Cdv proteins and is thought to bear some resemblance to ESCRT-III-based membrane remodelling in other domains of life, including eukaryotes, especially during abscission. Here we present biochemical, crystallographic and cryo-EM studies of the Sulfolobus Cdv machinery. CdvA, an early non-ESCRT component, adopts a PRC-domain/coiled-coil fold and polymerises into long double-stranded helical filaments, mainly via hydrophobic interfaces. Monomeric CdvB adopts the canonical ESCRT-III fold in both a closed and a distinct "semi-open" conformation. Soluble CdvB2 filaments are composed of subunits in the closed state, appearing to transition to the open, active state only when polymerised on membranes. Short N-terminal amphipathic helices in all CdvB paralogues, B, B1 and B2, mediate membrane binding and are required for liposome recruitment in vitro. We provide a molecular overview of archaeal ESCRT-III-based cytokinesis machinery, the definitive demonstration that CdvB proteins are bona fide ESCRT-III homologues and we reveal the molecular basis for membrane engagement. Thus, we illuminate conserved principles of ESCRT-mediated membrane remodelling and extend them to an anciently diverged archaeal lineage. Significance statementMembrane remodelling by ESCRT-III proteins is a fundamental and conserved process across the tree of life. The archaeal ESCRT-III-based cell division system (Cdv) drives cytokinesis in many archaeal groups, yet the molecular architecture of its components remained unknown, making it difficult to decipher the molecular mechanisms employed for cell division and cytokinesis in these organisms. We present structures of the Cdv machinery in Sulfolobus organisms that have been used previously to study the cell division process. We show that CdvA forms unexpected antiparallel helical filaments, while the ESCRT-III homologues retain the canonical fold we show they share with eukaryotic proteins. We demonstrate that N-terminal helices mediate membrane binding and that membrane contact, rather than polymerisation alone, likely triggers activation of Cdv ESCRT-IIIs.

molecular biology↗

bioRxiv2025

The P50 predicts conscious perception under tactile but not electrical somatosensory stimulation in human EEG

Past research has not reached consensus about the neural correlates of conscious somatosensory perception. Different studies have identified ERP components at various latencies as predictors of somatosensory detection, but it is still largely unclear which factors are responsible for this variation. Here, for the first time we directly compare the event-related potential correlates of stimulus detection under tactile versus electrical peri-threshold stimulation in a between-groups design, while controlling for task-relevance and post-perceptual processes with a visual-somatosensory matching task. We show that the P50 component predicts conscious perception under tactile, but not electrical stimulation: while electrical stimulation evokes a P50 already for subliminal stimuli, there is no subliminal P50 for tactile stimulation. In contrast, the P100 and N140 components robustly predict conscious detection in both stimulation groups. Tactile stimulation produced a clearly separable N80 component for detected stimuli, that appeared as part of the N140 under electrical stimulation. The P300 predicted conscious detection even though we controlled for post-perceptual processes, suggesting that it partly reflects aspects of subjective experience. Our results demonstrate that the neural correlates of somatosensory detection depend on the type of stimulation used, limiting the scope of previous results achieved using electrical stimulation.

neuroscience↗

bioRxiv2024

Decoding Parametric Grip-Force Anticipation from fMRI-Data

Previous functional magnetic resonance imaging (fMRI) studies have shown that activity in premotor and parietal brain-regions covaries with the intensity of upcoming grip-force. However, it remains unclear how information about the intended grip-force intensity is initially represented and subsequently transformed into a motor code before motor-execution. In this fMRI study, we used multivoxel pattern analysis (MVPA) to decode where and when information about grip-force intensities is parametrically coded in the brain. Human participants performed a delayed grip-force task in which one of four cued levels of grip-force intensity had to be maintained in working memory (WM) during a 9-second delay-period preceding motor execution. Using time-resolved MVPA, with a searchlight approach and support vector regression (SVR), we tested which brain regions exhibit multivariate WM codes of anticipated grip-force intensities. During an early delay-period, we observed above-chance decoding in the ventromedial prefrontal cortex (vmPFC). During a late delay-period, we found a network of action-specific brain regions, including the bilateral intraparietal sulcus (IPS), left dorsal premotor cortex (l-PMd) and supplementary motor areas (SMA). Additionally, cross-regression decoding was employed to test for temporal generalization of activation patterns between early and late delay-periods with those during cue presentation and motor execution. Cross-regression decoding indicated temporal generalization to the cue-period in the vmPFC, and to motor-execution in the l-IPS and l-PMd. Together, these findings suggest that the WM representation of grip-force intensities undergoes a transformation where the vmPFC encodes information about the intended grip-force, which is subsequently converted into a motor code in the l-IPS and l-PMd before execution.

neuroscience↗

bioRxiv2024

Thalamocortical interactions reflecting the intensity of flicker light-induced visual hallucinatory phenomena

The thalamus has a critical role in the orchestration of cortical activity. Aberrant thalamocortical connectivity occurs together with visual hallucinations in various pathologies and drug-induced states, highlighting the need to better understand how thalamocortical interactions may contribute to hallucinatory phenomena. However, concurring symptoms and physiological changes that occur during psychopathologies and pharmacological interventions make it difficult to distil the specific neural correlates of hallucinatory experiences. Flicker light stimulation (FLS) at 10 Hz reliably and selectively induces transient visual hallucinations in healthy participants. Arrhythmic flicker elicits fewer hallucinatory effects while delivering equal amounts of visual stimulation, together facilitating a well-controlled experimental setup to investigate the neural correlates of visual hallucinations driven by flicker rhythmicity. In this study, we implemented rhythmic and arrhythmic FLS during fMRI scanning to test the elicited changes in cortical activation and thalamocortical functional connectivity. We found that rhythmic FLS elicited stronger activation in higher-order visual cortices compared to arrhythmic control. Consistently, we found that rhythmic flicker selectively increased connectivity between ventroanterior thalamic nuclei and higher-order visual cortices compared to arrhythmic control, which was also found be positively associated with the subjective intensity of visual hallucinatory effects. As these thalamic and cortical areas do not receive primary visual inputs, it suggests that the thalamocortical connectivity changes relate to a higher-order function of the thalamus, such as in the coordination of cortical activity. In sum, we present novel evidence for the role of specific thalamocortical interactions with ventroanterior nuclei within visual hallucinatory experiences. Importantly, this can inform future clinical research into the mechanistic underpinnings of pathologic hallucinations.

neuroscience↗

bioRxiv2023

Flicker light stimulation induces thalamocortical hyperconnectivity with LGN and higher-order thalamic nuclei

The thalamus is primarily known as a relay for sensory information; however, it also critically contributes to higher-order cortical processing and coordination. Thalamocortical hyperconnectivity is associated with hallucinatory phenomena that occur in various psychopathologies (e.g., psychosis, migraine aura) and altered states of consciousness (ASC, e.g., induced by psychedelic drugs). However, the exact functional contribution of thalamocortical hyperconnectivity in forming hallucinatory experiences is unclear. Flicker light stimulation (FLS) can be used as an experimental tool to induce transient visual hallucinatory phenomena in healthy participants. Here, we use FLS in combination with fMRI to test how FLS modulates thalamocortical connectivity between specific thalamic nuclei and visual areas. We show that FLS induces thalamocortical hyperconnectivity between LGN, early visual areas and proximal upstream areas of ventral and dorsal visual streams (e.g., hV4, VO1, V3a). Further, an exploratory analysis indicates specific higher-order thalamic nuclei, such as anterior and mediodorsal nuclei, to be strongly affected by FLS. Here, the connectivity changes to upstream cortical visual areas directly reflect a frequency-dependent increase in experienced visual phenomena. Together these findings contribute to the identification of specific thalamocortical interactions in the emergence of visual hallucinations. HighlightsO_LIFlicker light stimulation (FLS) induces thalamocortical hyperconnectivity between the first-order thalamic LGN and early visual cortices, likely due to entrainment. C_LIO_LIThalamocortical connectivity between LGN and upstream visual areas, but not V1, is associated with the intensity of visual hallucinations. C_LIO_LIThalamocortical connectivity changes with higher-order thalamic nuclei, such as anterior and mediodorsal nuclei, show strongest modulation by flicker frequency, which corresponds to the intensity of visual hallucinations. C_LI

neuroscience↗

bioRxiv2021

The bacterial actin-like cell division protein FtsA forms curved antiparallel double filaments upon binding of FtsN

Cell growth and division of walled bacteria depend on the synthesis and remodelling of peptidoglycan (PG). These activities are carried out by two multiprotein complexes, the elongasome and the divisome during cell elongation and division, respectively. Filaments of tubulin-like FtsZ form the cytoplasmic scaffold for divisome assembly, the Z-ring. In E. coli, the actin homologue FtsA anchors the Z-ring to the membrane and recruits downstream divisome components, including bitopic FtsN. FtsN is recruited late and activates the periplasmic PG synthase FtsWI. To start unravelling the activation mechanism involving FtsA and FtsN, we showed that E. coli FtsA forms antiparallel double filaments on lipid monolayers when also binding FtsNs cytoplasmic tail, and that Vibrio maritimus FtsA crystallised as an equivalent double filament. We structurally located the FtsA-FtsN interaction site in FtsAs IA-IC interdomain cleft and confirmed FtsA double filament formation in vivo using site-specific cysteine cross-linking. FtsA-FtsN double filaments reconstituted on and in liposomes preferred negative Gaussian curvature, as was previously shown for the elongasomes actin, MreB. MreB filaments serve as curvature-sensing "rudders", orienting insertion of PG around the cells circumference. We propose that curved antiparallel FtsA double filaments function similarly in the divisome: FtsA filaments, together with dynamic FtsZ filaments orient and concentrate cell-constricting septal PG synthesis in the division plane.

microbiology↗

bioRxiv2021

Enhanced processing of aversive stimuli on embodied artificial limbs by the human amygdala

Body perception has been extensively investigated, with one particular focus being the integration of vision and touch within a neuronal body representation. Previous studies have implicated a distributed network comprising the extrastriate body area (EBA), posterior parietal cortex (PPC) and ventral premotor cortex (PMv) during illusory self-attribution of a rubber hand. Here, we set up an fMRI paradigm in virtual reality (VR) to study whether and how threatening (artificial) body parts affects their self-attribution. Participants (N=30) saw a spider (aversive stimulus) or a toy-car (neutral stimulus) moving along a 3D-rendered virtual forearm positioned like their real forearm, while tactile stimulation was applied on the real arm in the same (congruent) or opposite (incongruent) direction. We found that the PPC was more activated during congruent stimulation; higher visual areas and the anterior insula (aIns) showed increased activation during aversive stimulus presentation; and the amygdala was more strongly activated for aversive stimuli when there was stronger multisensory integration of body-related information (interaction of aversiveness and congruency). Together, these findings suggest an enhanced processing of aversive stimuli within the amygdala when they represent a bodily threat.

neuroscience↗

bioRxiv2021

Respiration, heartbeat, and conscious tactile perception

Previous studies have shown that timing of sensory stimulation during the cardiac cycle interacts with perception. Given the natural coupling of respiration and cardiac activity, we investigated here their joint effects on tactile perception. Forty-one healthy female and male human participants reported conscious perception of finger near-threshold electrical pulses (33% null trials) and decision confidence while electrocardiography, respiratory activity, and finger photoplethysmography were recorded. Participants adapted their respiratory cycle to expected stimulus onsets to preferentially occur during late inspiration / early expiration. This closely matched heart rate variation (sinus arrhythmia) across the respiratory cycle such that most frequent stimulation onsets occurred during the period of highest heart rate probably indicating highest alertness and cortical excitability. Tactile detection rate was highest during the first quadrant after expiration onset. Inter-individually, stronger respiratory phase-locking to the task was associated with higher detection rates. Regarding the cardiac cycle, we confirmed previous findings that tactile detection rate was higher during diastole than systole and newly specified its minimum at 250 - 300 ms after the R-peak corresponding to the pulse wave arrival in the finger. Expectation of stimulation induced a transient heart deceleration which was more pronounced for unconfident decision ratings. Inter-individually, stronger post-stimulus modulations of heart rate were linked to higher detection rates. In summary, we demonstrate how tuning to the respiratory cycle and integration of respiratory-cardiac signals are used to optimize performance of a tactile detection task. Significance statementMechanistic studies on perception and cognition tend to focus on the brain neglecting contributions of the body. Here, we investigated how respiration and heartbeat influence tactile perception: Respiration phase-locking to expected stimulus onsets corresponds to highest heart rate (and presumably alertness/cortical excitability) and correlates with detection performance. Tactile detection varies across the heart cycle with a minimum when the pulse reaches the finger and a maximum in diastole. Taken together with our previous finding of unchanged early ERPs across the cardiac cycle we conclude that these effects are not a peripheral physiological artifact but a result of cognitive processes that model our bodys internal state, make predictions to guide behavior, and might also tune respiration to serve the task.

neuroscience↗

bioRxiv2020

Late cortical potentials are not a reliable marker of somatosensory awareness

Two types of scalp-recorded event-related potentials have been proposed as neural correlates of perceptual awareness in humans: an early, modality-specific negativity and a late, modality-independent positivity. However, whether these potentials genuinely reflect perception or result from task demands remains controversial. To address this question, we compared results from a classical somatosensory detection task (direct report task) to a somatosensory-visual matching task, in which overt reports were decorrelated from target detection, equated the behavioural relevance of detected and undetected stimuli, and mitigated the influence of attentional processes. By means of Bayesian model selection, we show that the early N140 component was the first to reflect target detection in both tasks, whereas the late P300 component was task dependent, with strong detection effects in the direct report task that were absent in the matching task. We conclude that the P300 is not a genuine correlate of somatosensory awareness but reflects postperceptual processing.

neuroscience↗

bioRxiv2020

A novel approach for assessing hypoperfusion in stroke using spatial independent component analysis of resting-state fMRI data

Individualized treatment of acute stroke depends on the timely detection of ischemia and potentially salvageable tissue in the brain. Using functional MRI (fMRI), it is possible to characterize cerebral blood flow from blood-oxygen-level-dependent (BOLD) signals without the administration of exogenous contrast agents. In this study, we applied spatial independent component analysis to resting-state fMRI data of 37 stroke patients scanned within 24 hours of symptom onset, 17 of whom received follow-up scans the next day. Our analysis revealed "Hypoperfusion spatially-Independent Components" (HICs) whose spatial patterns of BOLD signal resembled regions of delayed perfusion depicted by dynamic susceptibility contrast MRI. These HICs were detected even in the presence of excessive patient motion, and disappeared following successful tissue reperfusion. The unique spatial and temporal features of HICs allowed them to be distinguished with high accuracy from other components in a user-independent manner (AUC = 0.95, accuracy = 0.96, sensitivity = 1.00, specificity = 0.96). Our study therefore presents a new, non-invasive method for assessing blood flow in acute stroke that minimizes interpretative subjectivity and is robust to severe patient motion.

neuroscience↗

bioRxiv2019

BOLD activation patterns and graph metrics associated with conscious tactile perception

Theories of human consciousness substantially vary in the proposed spatial extent of brain activity associated with conscious perception as well as in the assumed functional alterations within the involved brain regions. Here, we investigate which local and global changes in brain activity accompany conscious somatosensory perception following electrical finger nerve stimulation, and whether there are whole-brain functional network alterations by means of graph metrics. Thirty-eight healthy participants performed a somatosensory detection task and reported their decision confidence during fMRI. For conscious tactile perception in contrast to undetected near-threshold trials (misses), we observed increased BOLD activity in the precuneus, the intraparietal sulcus, the insula, the nucleus accumbens, the inferior frontal gyrus and the contralateral secondary somatosensory cortex. For misses compared to correct rejections, bilateral secondary somatosensory cortices, supplementary motor cortex and insula showed greater activations. The analysis of whole-brain functional network topology for hits, misses and correct rejections, did not result in any significant differences in modularity, participation, clustering or path length, which was supported by Bayes factor statistics. In conclusion, for conscious somatosensory perception, our results are consistent with an involvement of (probably) domain-general brain areas (precuneus, insula, inferior frontal gyrus) in addition to somatosensory regions; our data do not support the notion of specific changes in graph metrics associated with conscious experience. For the employed somatosensory submodality of fine electrical current stimulation, this speaks for a global broadcasting of sensory content across the brain without substantial reconfiguration of the whole-brain functional network resulting in an integrative conscious experience.

neuroscience↗

bioRxiv2019

Heart-Brain Interactions Shape Somatosensory Perception and Evoked Potentials

Human perception either refers to the external world, exteroception, or internal body parts such as the heart, interoception. How these two types of perception interact is poorly understood. Using electroencephalography, we identify two heartbeat-related modulations of conscious somatosensory perception: (i) When stimulus timing coincided with systole of the cardiac cycle, participants were less likely to detect and localize somatosensory stimuli, and late components (P300) of the somatosensory-evoked potential (SEP) were attenuated. (ii) The amplitude of the heartbeat-evoked potential (HEP) negatively correlated with detection bias (criterion) and localization accuracy. Furthermore, higher HEP amplitudes were followed by decreases in both early and late SEP amplitudes. Both heartbeat-related effects were independent of the alpha oscillations influence on somatosensory processing. We conclude that internal signals are integrated into our conscious perception of the world, and connect our results to predictive processing (heartbeat-coupled stimulus timing) and attentional shifts between exteroception and interoception (HEP amplitude).

neuroscience↗