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König, P.

Publications and source records attributed to König, P..

28 records · Page 2Linked to original sources
bioRxiv2020

Spike-timing-dependent plasticity can account for aftereffects of dual-site transcranial alternating current stimulation

Transcranial alternating current stimulation (tACS), applied to two brain sites with different phase lags, has been shown to modulate stimulation-outlasting functional EEG connectivity between the targeted regions. Given the lack of knowledge on mechanisms of tACS aftereffects, it is difficult to further enhance effect sizes and reduce variability in experiments. In this computational study, we tested if spike-timing-dependent plasticity (STDP) can explain stimulation-outlasting connectivity modulation by dual-site tACS and explored the effects of tACS parameter choices. Two populations of spiking neurons were coupled with synapses subject to STDP, and results were validated via a re-analysis of EEG data. Our simulations showed stimulation-outlasting connectivity changes between in- and anti-phase tACS, dependent on both tACS frequency and synaptic conduction delays. Importantly, both a simple network entraining to a wide range of tACS frequencies as well as a more realistic network that spontaneously oscillated at alpha frequency predicted that the largest effects would occur for short conduction delays between the stimulated regions. This finding agreed with experimental EEG connectivity modulation by 10 Hz tACS, showing a clear negative correlation of tACS effects with estimated conduction delays between regions. In conclusion, STDP can explain connectivity aftereffects of dual-site tACS. However, not all combinations of tACS frequency and application sites are expected to effectively modulate connectivity via STDP. We therefore suggest using appropriate computational models and/or EEG analysis for planning and interpretation of dual-site tACS studies relying on aftereffects. HighlightsO_LINetwork model with STDP explains EEG connectivity change after dual-site tACS C_LIO_LIEffects are predicted to depend on tACS frequency and conduction delays C_LIO_LIEEG data confirm dependence on conduction delays between regions C_LIO_LIModel can be used to estimate and maximize experimental effects C_LI

neuroscience↗
bioRxiv2020

Let Me Make You Happy, And I'll Tell You How you look around: Using an Approach-Avoidance Task as an Embodied Mood Prime in a Free-Viewing Task

The embodied approach of human cognition suggests that concepts are deeply dependent upon and constrained by an agents physical bodys characteristics, such as performed body movements. In this study, we attempted to broaden previous research on emotional priming, investigating the interaction of emotions and visual exploration. We used the joystick-based approach-avoidance task to influence the emotional states of participants, and subsequently, we presented pictures of news web pages on a computer screen and measured participants eye movements. As a result, the number of fixations on images increased, the total dwell time increased, and the average saccade length from outside of the images towards the images decreased after the bodily congruent priming phase. The combination of these effects suggests increased attention to web pages image content after the participants performed bodily congruent actions in the priming phase. Thus, congruent bodily interaction with images in the priming phase fosters visual interaction in the subsequent exploration phase.

neuroscience↗
bioRxiv2020

Embodied Spatial Knowledge Acquisition in Immersive Virtual Reality: Comparison of Direct Experience and Map Exploration

Investigating spatial learning in virtual environments allows studying different sources of information under controlled conditions. We built a virtual environment in the style of a European village and investigated spatial knowledge acquisition by experience in the virtual environment and by the use of an interactive map. We tested knowledge of cardinal directions, building-to-building orientation, and judgment of direction between buildings. We find that judgment of directions was more accurate after virtual reality exploration than after map exploration, and the opposite results were observed for knowledge of cardinal directions and relative orientation between buildings. Further, the alignment effect was confined to the map exploration condition. Taken together, our results suggest that the source of spatial exploration differentially influenced spatial knowledge acquisition.

neuroscience↗
bioRxiv2019

Neurophysiological correlates of collective perceptual decision-making

Humans frequently coordinate with others in daily life. A recent study on perceptual decision-making showed that dyad members with similar individual performances attain a higher joint performance than the better dyad member (i.e., a collective benefit). However, little is known about the physiological basis of these results. Here, we replicate this earlier work and also investigate the neurophysiological correlates of decision-making using EEG.\n\nIn a two interval forced choice task, co-actors individually indicated presence of a target stimulus with a higher contrast and then indicated their confidence on a rating scale. Viewing the individual ratings, dyads made a joint decision. Replicating earlier work, we found a positive correlation between the similarity of individual performances and collective benefit.\n\nWe analyzed event related potentials (ERPs) in three phases (i.e., stimulus onset, response, and feedback) using explorative cluster mass permutation tests. At stimulus onset, ERPs were significantly linearly related to our manipulation of contrast differences, validating our manipulation of task difficulty. For individual and joint responses, we found a significant centro-parietal error-related positivity for correct versus incorrect responses, which suggests that accuracy is already evaluated at the response level. At feedback presentation, we found a significant late positive fronto-central potential elicited by incorrect joint responses, suggesting a stronger emotional response to negative as compared to positive feedback. In sum, these results demonstrate that response- and feedback-related components elicited by an error-monitoring system differentially integrate conflicting information exchanged during the joint decision-making process.

neuroscience↗
bioRxiv2019

Spatially modulated alpha-band activity does not mediate tactile remapping and fast overt orienting behavior

Posterior oscillatory alpha-band activity is commonly associated with spatial-attentional orienting and prioritization across sensory modalities. It has also been suggested to mediate the automatic transformation of tactile stimuli from a skin-based, somatotopic reference frame into an external one. Previous research has not convincingly separated these two possible roles of alpha-band activity. In particular, the use of delay paradigms, implemented to allow temporal evolution of segregable oscillatory brain responses to stimulus, motor planning, and response, have prohibited strong conclusions about a causal role of oscillatory activity in tactile-spatial transformations. Here, we assessed alpha-band modulation with massive univariate deconvolution, an analysis approach that disentangles brain signals overlapping in time and space. Thirty-one participants performed a delay-free, visual serial-search task in which saccade behavior was unrestricted. A tactile cue to uncrossed or crossed hands was either informative or uninformative about visual target location. Alpha-band suppression following tactile stimulation was lateralized relative to the stimulated hand over centro-parietal sensors, but relative to its external location over parieto-occipital sensors. Alpha-band suppression reflected external touch location only after informative cues, challenging the proposition that posterior alpha-band lateralization indexes automatic tactile transformation. Moreover, alpha-band suppression occurred ~200 ms later than externally directed saccade responses after tactile stimulation. These findings suggest that alpha-band activity does not play a causal role in tactile-spatial transformation but, instead, reflects delayed, supramodal processes of attentional re-orienting.

neuroscience↗
bioRxiv2019

Learning of Spatial Properties of a Large-scale Virtual City with an Interactive Map

On the basis of embodied/-enacted theories of the mind, investigations of spatial cognition related to real world environments have become current research interests. How this perspective relates to acquiring spatial knowledge not by active exploration, but through map learning, however, remains unresolved. Therefore, we designed a large virtual city comprised of over 200 houses, suitable for active exploration or spatial learning based on a map. Here, we report our results after single and repeated 30-minute training sessions using an interactive city map. We tested subjects knowledge of the orientation of houses towards cardinal north and of two houses relative to each other and the locations of two houses towards each other in a pointing task. Our results revealed that a single training session was sufficient to repeatedly view the majority of houses covering a large area of the city. However, repeated training sessions were necessary to improve the performance level and reveal significant differences between tasks. In contrast to a previous study in a real world city, performance in the two orientation tasks was better than in the pointing task. The lack of distance and the lack of angular difference effects onto task performance suggest the use of a global reference frame. Performance was positively correlated with a self-report on spatial abilities (FRS) in the absolute orientation and pointing task but not the relative orientation task. Overall, our results suggest that training with an interactive city map enhances abstract knowledge, not directly available from an embodied perspective.

neuroscience↗
bioRxiv2019

Probing Neural Networks for Dynamic Switches of Communication Pathways

Dynamic communication and routing play important roles in the human brain to facilitate 2exibility in task solving and thought processes. Here, we present a network perturbation methodology that allows to investigate dynamic switching between different network pathways based on phase offsets between two external oscillatory drivers. We apply this method in a computational model of the human connectome with delay-coupled neural masses. To analyze dynamic switching of pathways, we define four new metrics that measure dynamic network response properties for pairs of stimulated nodes. Evaluating these metrics for all network pathways, we found a broad spectrum of pathways with distinct dynamic properties and switching behaviors. Specifically, we found that 60.1% of node pairs can switch their communication from one pathway to another depending on their phase offsets. This indicates that phase offsets and coupling delays play an important computational role for the dynamic switching between communication pathways in the brain.

neuroscience↗
bioRxiv2018

The social situation affects how we process feedback about our actions

Humans achieve their goals in joint action tasks either by cooperation or competition. In the present study, we investigated the neural processes underpinning error and monetary rewards processing in such cooperative and competitive situations. We used electroencephalography (EEG) and analyzed event-related potentials (ERPs) triggered by feedback in both social situations. 26 dyads performed a joint four-alternative forced choice (4AFC) visual task either cooperatively or competitively. At the end of each trial, participants received performance feedback about their individual and joint errors and accompanying monetary rewards. Furthermore, the outcome, i.e. resulting positive, negative or neutral rewards, was dependent on the pay-off matrix, defining the social situation either as cooperative or competitive. We used linear mixed effects models to analyze the feedback-related-negativity (FRN) and used the Thresholdfree cluster enhancement (TFCE) method to explore activations of all electrodes and times. We found main effects of the outcome and social situation at mid-line frontal electrodes. The FRN was more negative for losses than wins in both social situations. However, the FRN amplitudes differed between social situations. Moreover, we compared monetary with neutral outcomes in both social situations. Our exploratory TFCE analysis revealed that processing of feedback differs between cooperative and competitive situations at right temporo-parietal electrodes where the cooperative situation elicited more positive amplitudes. Further, the differences induced by the social situations were stronger in participants with higher scores on a perspective taking test. In sum, our results replicate previous studies about the FRN and extend them by comparing neurophysiological responses to positive and negative outcomes in a task that simultaneously engages two participants in competitive and cooperative situations.

neuroscience↗
bioRxiv2017

Deep Sequencing Reveals Transient Segregation of T Cell Repertoires in Splenic T Cell Zones During an Immune Response

Immunological differences between hosts, such as diverse T-cell receptor (TCR) repertoires, are widely credited for reducing the risk of pathogen spread and adaptation in a population. Within-host immunological diversity might likewise be important for robust pathogen control, but to what extent naive TCR repertoires differ across different locations in the same host is unclear. T-cell zones (TCZs) in secondary lymphoid organs provide secluded micro-environmental niches. By harboring distinct TCRs, such niches could enhance within-host immunological diversity. On the other hand, rapid T cell migration is expected to dilute such diversity. Here, we combined tissue micro-dissection and deep sequencing of the TCR {beta} chain to examine the extent to which TCR repertoires differ between TCZs in murine spleens. In the absence of antigen, we found little evidence for differences between different TCZs of the same spleen. Yet, three days after immunization with sheep red blood cells, we observed a >10-fold rise in the number of clones that appeared to localize to individual zones. Remarkably, these differences largely disappeared at 4 days after immunization, when hallmarks of an ongoing immune response were still observed. These data suggest that in the absence of antigen, any repertoire differences observed between TCZs of the same host can largely be attributed to random clone distribution. Upon antigen challenge, segregated TCR compartments appear and disappear within days. Such \"transient mosaic\" dynamics could be an important barrier for pathogen adaptation and spread during an immune response.

immunology↗
bioRxiv2017

Entorhinal cortex receptive fields are modulated by spatial attention, even without movement.

Grid cells have been identified in the entorhinal cortex in a variety of species and allow for the precise decoding of position in space (1-7). Along with potentially playing an important role in navigation, grid cells have recently been hypothesized to make a general contribution to mental operations, including remembering the past and thinking about the future (8,9). A prerequisite for this hypothesis is that grid cell activity does not critically depend on physical movement. Directed attention, which contributes to virtually all mental operations and can be separated from physical movement provides a good test case to investigate this hypothesis. Overt attention in the form of fixational eye movements leads to grid-like firing fields in the monkey entorhinal cortex (3). Here we show that movement of covert attention, without any physical movement, also elicits spatial receptive fields with a triangular tiling of the space. In monkeys trained to maintain central fixation while covertly attending to a stimulus moving in the periphery we identified a significant population (20/141, 14% neurons at a FDR<5%) of entorhinal cells with spatially structured receptive fields. Further, we were able to identify a population of neurons that were labeled as grid cells on an individual basis. This contrast with our recordings obtained in the hippocampus, where grid-like representations were not observed. Our results provide compelling evidence that neurons in macaque entorhinal cortex do not rely on physical movement. Notably, these results support the notion that grid cells may be capable of serving a variety of different cognitive functions and suggest that grid cells are a versatile component of many neural algorithms.

neuroscience↗