Biology subjects

Gramann, K.

Publications and source records attributed to Gramann, K..

At least 19 recordsLinked to original sources

bioRxiv2026

Hexadirectional modulation of EEG gamma band activity

The medial temporal lobe (MTL) houses specialised cell types supporting spatial representation in the human brain. Among these are grid cells that encode the location of the navigator, displaying a geometrically structured anchoring to the environment. While macroscopic grid-cell-like coding in humans is typically investigated using functional magnetic resonance imaging or invasive electrophysiological methods in clinical populations, we demonstrate the feasibility of using non-invasive scalp electroencephalography (EEG) to capture the characteristic six-fold modulation of high-frequency activity source-localised to the MTL. We found hexadirectional modulations of the low- and high-gamma band activity by movement direction in virtual reality. Furthermore, individual preference to use an allocentric reference frame was linked to higher hexadirectional modulation in the low gamma band and encoding a location along the putative grid axes of high gamma band predicted faster retrieval of the remembered location. The use of scalp EEG to capture grid-cell-like activity and its functional relevance sets the foundation for investigating the MTL activity in richer experimental contexts.

neuroscience↗

bioRxiv2026

The role of cognitivo-motor interaction in landmark reliance and navigational deficits in older adults

Declining spatial navigation abilities are a critical hallmark of aging, where the loss of spatial abilities precedes global cognitive impairment. While navigational decline is traditionally attributed to deficits in higher-order cognitive functions, emerging cognitive-motor frameworks suggest that age-related sensorimotor alterations play a significant, yet previously overlooked, role. Here, we investigate the coupling between locomotor integrity and navigation by combining an immersive virtual-reality path-integration paradigm with systematic manipulations of landmark availability and reliability, while recording gait kinematics alongside neural dynamics using high-density mobile-EEG from 30 young and 32 older adults. We demonstrate that older adults accumulate angular homing error more rapidly than younger adults, a deficit linked to altered gait dynamics. These age-dependent differences are reflected in increased mid-frontal theta activity, highlighting a robust coupling between gait-related sensorimotor alterations and decline in navigation. Older adults also exhibited increased reliance on visual landmarks, and particularly those with degraded gait, yet this compensatory reweighting of navigational cues remained less efficient and less precise than in younger adults. These findings highlight sensorimotor gait alterations as a central determinant of age-related navigation deficits, challenging the traditional separation of motor and cognitive domains and identifying locomotor integrity as a critical target for preserving spatial navigation abilities.

neuroscience↗

bioRxiv2025

From Perception to Appraisal: Hierarchical Brain Responses to Natural and Built Features in Urban Environments

Exposure to urban rather than natural environments has been linked to elevated stress and diminished well-being, prompting interest in the underlying mechanisms and influences of specific urban elements. This study investigated how semantic and lower-level visual characteristics of urban scenes influence subjective experience and underlying neural processes. A total of 63 adults viewed street-level photographs depicting urban environments with varying proportions of vegetation, buildings, vehicles, and sky visibility while electroencephalography (EEG) was recorded. Subjective ratings indicated that urban scenes with more greenery compared to built elements were consistently perceived as more positive. In terms of lower-level image features, images with higher non-straight edge density also led to scenes being perceived as more positive. In contrast, a more visible sky area and a higher mean metric depth led to more negative scene appraisal. On a neural level, urban scenes with higher greenery/built ratios enhanced visual evoked P1 amplitudes, while higher straight-edge density led to more pronounced N1 amplitudes. Further analysis showed that later P3 and LPP components were associated with subjective ratings on higher-level evaluative but not basic affective dimensions. These results partially replicate previous studies, suggesting that urban greenery exerts an effect on subjective well-being and influences early visual processing. Moving forward, Neuro-Urbanism research should employ more diversified stimuli and leverage immersive or in situ paradigms to refine our understanding of the relationship between greenery in urban environments and well-being to inform evidence-based urban design strategies. HighlightsO_LIHigher proportions of greenery in urban environments lead to more positive responses across a variety of subjective rating scales. C_LIO_LIMore urban greenery elicited more pronounced P1 amplitudes, replicating previous findings. C_LIO_LIEarliest visual processing (P1) responds to natural elements of the environment, before processing of visual features characteristic of artificial elements (N1). C_LIO_LILater ERP components (P3, LPP) are associated with subjective scene appraisal of higher level and aesthetic evaluation, pointing to a separation between perceptual and evaluative processes. C_LI

neuroscience↗

bioRxiv2025

Theta activity supports landmark-based correction of naturalistic human path integration

How do humans integrate landmarks to update their spatial position during active navigation task? Using immersive virtual reality and high-density mobile EEG, we investigated the neural underpinnings of landmark-based recalibration during path integration. Our findings reveal that a briefly presented intramaze landmark effectively corrected accumulated homing errors. However, this effect was transient and less optimal when participants were highly confident in their self-motion-based spatial representation suggesting that internal priors hinder the assimilation of novel spatial cues. At the neural level, RSC theta-band activity supported these recalibration processes. When fine adjustments of the spatial representation were sufficient, landmark presentation elicited stronger theta-band activity and greater phase resetting compared to when substantial spatial updating was necessary. Our results also revealed motor-related theta activity that scaled with acceleration during rotational corrections, highlighting the dual role of theta in the flexible integration of multimodal signals, involved in both landmark-based spatial updating and self-motion encoding.

neuroscience↗

bioRxiv2025

Attentional cueing effects are reversed during locomotion

Everyday human cognition and behaviour evolved in dynamic and ever-changing environments, but static paradigms still dominate experimental research despite concerns about generalisability of the results. In the case of attention, traditional stationary studies show that pre-orienting attention with spatial cues leads to faster, more accurate responses. However, how movement and environmental features shape such attentional processes in everyday behaviour remains unknown. Here we show that active movement through curved corridors reverses the typical spatial attention effect, with faster response times and higher accuracy for stimuli incongruent to implicit spatial cues provided by the movement direction, contradicting previous findings from static settings. We found that early (N1) and late (P3) attention-related electrophysiological responses were modulated by environmental features and motor demands. The posterior N1-component, reflecting visuo-spatial attention, showed decreasing amplitudes as turning angles and motor-control demands increased for congruent stimuli appearing on the side of the turning direction. Similarly, the P3-complex varied with motor and visual processing demands for congruent stimuli, showing decreased amplitudes as motor-control demands increased. We propose that congruent stimuli, displayed against a dynamically changing visual context, increase pulvino-cortical processing load and slowing early visual processing that affect behavioural responses. Incongruent stimuli, however, are displayed against a predictable context allowing faster target processing. These findings challenge attentional mechanisms assumed consistency across static and dynamic settings, revealing instead their dependence on behavioural and environmental context. We advocate for naturalistic paradigms, arguing that moving beyond static experiments could reshape core views on cognition and behaviour.

neuroscience↗

bioRxiv2024

Congruency effects on object recognition persist when objects are placed in the wild: An AR and mobile EEG study

Objects in expected locations are recognised faster and more accurately than objects in incongruent environments. This congruency effect has a neural component, with increased activity for objects in incongruent environments. Studies have increasingly shown differences between neural processes in realistic environments and tasks, and neural processes in the laboratory. Here, we aimed to push the boundaries of traditional cognitive neuroscience by tracking the congruency effect for objects in real world environments, outside of the lab. We investigated how neural activity is modulated when objects are placed in real environments using augmented reality while recording mobile EEG. Participants approached, viewed, and rated how congruent they found the objects with the environment. We found significant differences in ERPs and higher theta-band power for objects in incongruent contexts than objects in congruent contexts. This demonstrates that real-world contexts impacts how objects are processed, and that mobile brain imaging and augmented reality are effective tools to study cognition in the wild.

neuroscience↗

bioRxiv2024

Mobile EEG for Neurourbanism Research - What Could Possibly Go Wrong?A Critical Review with Guidelines

Based on increasing incidents of mental ill-health associated with living in dense urban environments, the field of Neurourbanism developed rapidly, aiming at identifying and improving urban factors that impact the health of city dwellers. Neurourbanism and the closely related field of Neuro-Architecture have seen a surge in studies using mobile electroencephalography (EEG) to investigate the impact of the built and natural environment on human brain activity moving from the laboratory into the real world. This trend predominantly arises from the ready availability of affordable and portable consumer hardware, which not only guarantees operational simplicity but also frequently incorporates automated data analysis functions. This significantly streamlines the process of EEG data acquisition, analysis, and interpretation, seemingly challenging the necessity of specialized expertise in the method of EEG or neurosciences in general. As a consequence, numerous studies in the field of Neurourbanism have used such off-the-shelf systems in laboratory and real-world experimental protocols including active movement of participants through the environment. However, the recording and analysis of EEG data entails numerous requisites, the disregard of which may culminate in errors during data acquisition, processing, and subsequent interpretation, potentially compromising the scientific validity of the outcomes. The often relatively low number of electrodes offered by affordable and portable consumer EEG systems further restricts specific analyses approaches to the low-dimensional EEG data. Crucially, a large part of Neurourbanism studies used black-box analyses provided by such consumer systems or incorrectly applied complex data-driven analyses methods that are incompatible with the recorded low-dimensional data. The current manuscript delineates the prerequisites concerning EEG hardware and analytical methodologies applicable to stationary and mobile EEG protocols, whether conducted within a controlled laboratory environment or in real-world settings. It conducts a comprehensive review of EEG studies within the domain of Neurourbanism and Neuro-Architecture, assessing their adherence to these prerequisites. The findings reveal severe deficiencies in the utilization of hardware and data processing methods, thereby rendering these studies unsuitable for scientific scrutiny. Consequently, the present paper provides guidelines for the selection of EEG hardware and analytical strategies for researchers engaged in mobile EEG recordings, be it within a laboratory or real-world context, aimed at steering future investigations in the field of Neurourbanism and Neuro-Architecture.

neuroscience↗

bioRxiv2023

Human Brain Dynamics Dissociate Early Perceptual and Late Motor-Related Stages of Affordance Processing

Affordances, the opportunity for action offered by the environment to an agent, are vital for meaningful behavior and exist in every interaction with the environment. There is an ongoing debate in the field about whether the perception of affordances is an automated process. Some studies suggest that affordance perception is an automated process that is independent from the visual context and bodily interaction with the environment, while others argue that it is modulated by the visual and motor context in which affordances are perceived. The present paper aims to resolve this debate by examining affordance automaticity from the perspective of sensorimotor time windows. We replicated a previous study on affordance perception in which participants actively moved through doors of different width in immersive 3D virtual environments. To investigate the impact of different forms of bodily interactions with an environment, i.e., the movement context (physical vs. joystick movement), we used the identical virtual environment from Djebbara and colleagues (2019) but displayed it on a 2D screen with participants moving through different wide doors using the keys on a standard keyboard. We compared components of the event-related potential (ERP) from the continuously recorded electroencephalogram (EEG) that were previously reported to be related to affordance perception of architectural transitions (passable and impassable doors). Comparing early sensory and later motor-related ERPs, our study replicated ERPs reflecting early affordance perception but found differences in later motor-related components. These results indicate a shift from automated perception of affordances during early sensorimotor time windows to movement context dependence of affordance perception at later stages suggesting that affordance perception is a dynamic and flexible process that changes over sensorimotor stages.

neuroscience↗

bioRxiv2022

The BeMoBIL Pipeline for automated analyses of multimodal mobile brain and body imaging data

Advancements in hardware technology and analysis methods allow more and more mobility in electroencephalography (EEG) experiments. Mobile Brain/Body Imaging (MoBI) studies may record various types of data such as motion or eye tracking in addition to neural activity. Although there are options available to analyze EEG data in a standardized way, they do not fully cover complex multimodal data from mobile experiments. We thus propose the BeMoBIL Pipeline, an easy-to-use pipeline in MATLAB that supports the time-synchronized handling of multimodal data. It is based on EEGLAB and fieldtrip and consists of automated functions for EEG preprocessing and subsequent source separation. It also provides functions for motion data processing and extraction of event markers from different data modalities, including the extraction of eye-movement and gait-related events from EEG using independent component analysis. The pipeline introduces a new robust method for region-of-interest-based group-level clustering of independent EEG components. Finally, the BeMoBIL Pipeline provides analytical visualizations at various processing steps, keeping the analysis transparent and allowing for quality checks of the resulting outcomes. All parameters and steps are documented within the data structure and can be fully replicated using the same scripts. This pipeline makes the processing and analysis of (mobile) EEG and body data more reliable and independent of the prior experience of the individual researchers, thus facilitating the use of EEG in general and MoBI in particular. It is an open-source project available for download at https://github.com/BeMoBIL/bemobil-pipeline which allows for community-driven adaptations in the future.

neuroscience↗

bioRxiv2022

No need for extensive artifact rejection for ICA - A multi-study evaluation on stationary and mobile EEG datasets

ObjectiveElectroencephalography (EEG) studies increasingly make use of more ecologically valid experimental protocols involving mobile participants who actively engage with their environment (MoBI; Gramann et al., 2011). These mobile paradigms lead to increased artifacts in the recorded data that are often treated using Independent Component Analysis (ICA). When analyzing EEG data, especially in a mobile context, removing samples regarded as artifactual is a common approach before computing ICA. Automatic tools for this exist, such as the automatic sample rejection of the AMICA algorithm (Palmer et al., 2011), but the impact of the two factors movement intensity and the automatic sample rejection has not been systematically evaluated yet. ApproachWe computed AMICA decompositions on eight datasets from six open-access studies with varying degrees of movement intensities using increasingly conservative sample rejection criteria. We evaluated the subsequent decomposition quality in terms of the component mutual information, the amount of brain, muscle, and "other" components, the residual variance of the brain components, and an exemplary signal-to-noise ratio. Main resultsWe found that increasing movements of participants led to decreasing decomposition quality for individual datasets but not as a general trend across all movement intensities. The cleaning strength had less impact on decomposition results than anticipated, and moderate cleaning of the data resulted in the best decompositions. SignificanceOur results indicate that the AMICA algorithm is very robust even with limited data cleaning. Moderate amounts of cleaning such as 5 to 10 iterations of the AMICA sample rejection with 3 standard deviations as the threshold will likely improve the decomposition of most datasets, irrespective of the movement intensity.

neuroscience↗

bioRxiv2022

HArtMuT - Modeling eye and muscle contributors in neuroelectric imaging

Magneto- and electroencephalography (M/EEG) measurements record a mix of signals from the brain, eyes, and muscles. These signals can be disentangled for artifact cleaning e.g. using spatial filtering techniques. However, correctly localizing and identifying these components relies on head models that so far only take brain sources into account. We thus developed the Head Artefact Model using Tripoles (HArtMuT). This volume conduction head model extends to the neck and includes brain sources as well as sources representing eyes and muscles that can be modeled as single dipoles, symmetrical dipoles, and tripoles. We compared a HArtMuT 4-layer Boundary Element Model (BEM) with the EEGLAB standard head model on their localization accuracy and residual variance (RV) using a HArtMuT Finite Element Model as ground truth. We also evaluated the RV on real-world data of mobile participants, comparing different HArtMuT BEM types with the EEGLAB standard head model. We found that HArtMuT improves localization for all sources, especially non-brain, and localization error and RV of non-brain sources were in the same range as those of brain sources. The best results were achieved by using cortical dipoles, muscular tripoles, and ocular symmetric dipoles, but dipolar sources alone can already lead to convincing results. We conclude that HArtMuT is well suited for modeling eye and muscle contributions to the M/EEG signal. It can be used to localize sources and to identify brain, eye, and muscle components. HArtMuT is freely available and can be integrated into standard software.

neuroscience↗

bioRxiv2021

Mobile brain/body imaging of landmark-based navigation with high-density EEG

Coupling behavioral measures and brain imaging in naturalistic, ecological conditions is key to comprehend the neural bases of spatial navigation. This highly-integrative function encompasses sensorimotor, cognitive, and executive processes that jointly mediate active exploration and spatial learning. However, most neuroimaging approaches in humans are based on static, motion constrained paradigms and they do not account for all these processes, in particular multisensory integration. Following the Mobile Brain/Body Imaging approach, we aimed to explore the cortical correlates of landmark-based navigation in actively behaving young adults, solving a Y-maze task in immersive virtual reality. EEG analysis identified a set of brain areas matching state-of-the-art brain imaging literature of landmark-based navigation. Spatial behavior in mobile conditions additionally involved sensorimotor areas related to motor execution and proprioception usually overlooked in static fMRI paradigms. Expectedly, we located a cortical source in or near the posterior cingulate, in line with the engagement of the retrosplenial complex in spatial reorientation. Consistent with its role in visuo-spatial processing and coding, we observed an alpha power desynchronization while participants gathered visual information. We also hypothesized behavior-dependent modulations of the cortical signal during navigation. Despite finding few differences between the encoding and retrieval phases of the task, we identified transient time-frequency patterns attributed, for instance, to attentional demand, as reflected in the alpha/gamma range, or memory workload in the delta/theta range. We confirmed that combining mobile high-density EEG and biometric measures can help unravel the brain structures and the neural modulations subtending ecological landmark-based navigation.

neuroscience↗

bioRxiv2020

Human retrosplenial theta and alpha modulation in active spatial navigation

Spatial navigation is a complex cognitive process based on multiple senses that are integrated and processed by a wide network of brain areas. Previous studies have revealed the retrosplenial complex (RSC) to be modulated in a task-related manner during navigation. However, these studies restricted participants movement to stationary setups, which might have impacted heading computations due to the absence of vestibular and proprioceptive inputs. Here, we investigated neural dynamics of RSC in an active spatial navigation task where participants actively ambulated from one location to several other points while the position of a landmark and the starting location were updated. The results revealed theta power in the RSC to be pronounced during heading changes but not during translational movements, indicating that physical rotations induce human RSC theta activity. This finding provides a potential evidence of head-direction computation in RSC in healthy humans during active spatial navigation.

bioengineering↗

bioRxiv2020

Landmark-Based Turn-by-Turn Instructions Enhance Incidental Spatial Knowledge Acquisition

The augmentation of landmarks in auditory navigation instructions had been shown to improve incidental spatial knowledge acquisition during assisted navigation. Here, two driving simulator experiments are reported that replicated this effect even when adding a three-week delay between navigation and spatial tasks and varying the degree of detail in the provided landmark information. Performance in free- and cued-recall of landmarks and driving the route again without assistance demonstrated increased landmark and route knowledge when navigating with landmark-based compared to standard instructions. The results emphasize that small changes to existing navigation systems can foster spatial knowledge acquisition during every-day navigation.

neuroscience↗

bioRxiv2020

Architectural Affordance Impacts Human Sensorimotor Brain Dynamics

Action is a medium of collecting sensory information about the environment, which in turn is shaped by architectural affordances. Affordances characterize the fit between the physical structure of the body and capacities for movement and interaction with the environment, thus relying on sensorimotor processes associated with exploring the surroundings. Central to sensorimotor brain dynamics, the attentional mechanisms directing the gating function of sensory signals share neuronal resources with motor-related processes necessary to inferring the external causes of sensory signals. Such a predictive coding approach suggests that sensorimotor dynamics are sensitive to architectural affordances that support or suppress specific kinds of actions for an individual. However, how architectural affordances relate to the attentional mechanisms underlying the gating function for sensory signals remains unknown. Here we demonstrate that event-related desynchronization of alpha-band oscillations in parieto-occipital and medio-temporal regions covary with the architectural affordances. Source-level time-frequency analysis of data recorded in a motor-priming Mobile Brain/Body Imaging experiment revealed strong event-related desynchronization of the alpha band to originate from the posterior cingulate complex and bilateral parahippocampal areas. Our results firstly contribute to the understanding of how the brain resolves architectural affordances relevant to behaviour. Second, our results indicate that the alpha-band originating from the posterior cingulate complex covaries with the architectural affordances before participants interact with the environment. During the interaction, the bilateral parahippocampal areas dynamically reflect the affordable behaviour as perceived through the visual system. We conclude that the sensorimotor dynamics are developed for processing behaviour-relevant features in the designed environment.

neuroscience↗

bioRxiv2020

Brain dynamics of assisted pedestrian navigation in the real-world

Conducting neuroscience research in the real world remains challenging because of movement- and environment-related artifacts as well as missing control over stimulus presentation. The present study demonstrated that it is possible to investigate the neuronal correlates underlying visuo-spatial information processing during real-world navigation. Using mobile EEG allowed for extraction of saccade- and blink-related potentials as well as gait-related EEG activity. In combination with source-based cleaning of non-brain activity and unfolding of overlapping event-related activity, brain activity of naturally behaving humans was revealed even in a complex and dynamic city environment.

neuroscience↗

bioRxiv2020

Identifying key factors for improving ICA-based decomposition of EEG data in mobile and stationary experiments

Recent developments in EEG hardware and analyses approaches allow for recordings in both stationary and mobile settings. Irrespective of the experimental setting, EEG recordings are contaminated with noise that has to be removed before the data can be functionally interpreted. Independent component analysis (ICA) is a commonly used tool to remove artifacts such as eye movement, muscle activity, and external noise from the data and to analyze activity on the level of EEG effective brain sources. While the effectiveness of filtering the data as one key preprocessing step to improve the decomposition has been investigated previously, no study thus far compared the different requirements of mobile and stationary experiments regarding the preprocessing for ICA decomposition. We thus evaluated how movement in EEG experiments, the number of channels, and the high-pass filter cutoff during preprocessing influence the ICA decomposition. We found that for commonly used settings (stationary experiment, 64 channels, 0.5 Hz filter), the ICA results are acceptable. However, high-pass filters of up to 2 Hz cutoff frequency should be used in mobile experiments, and more channels require a higher filter to reach an optimal decomposition. Fewer brain ICs were found in mobile experiments, but cleaning the data with ICA proved to be important and functional even with 16 channels. Based on the results, we provide guidelines for different experimental settings that improve the ICA decomposition.

neuroscience↗

bioRxiv2020

The Impact of Hand Movement Velocity on Cognitive Conflict Processing in a 3D Object Selection Task

Detecting and correcting incorrect body movements is an essential part of everyday interaction with ones environment. The human brain provides a monitoring system that constantly controls and adjusts our actions according to our surroundings. However, when our brains predictions about a planned action do not match the sensory inputs resulting from that action, cognitive conflict occurs. Much is known about cognitive conflict in 1D/2D environments; however, less is known about the role of movement characteristics associated with cognitive conflict in 3D environment. Hence, we devised an object selection task in a virtual reality (VR) environment to test how the velocity of hand movements impacts human brain responses. From a series of analyses of EEG recordings synchronized with motion capture, we found that the velocity of the participants hand movements modulated the brains response to proprioceptive feedback during the task and induced a prediction error negativity (PEN). Additionally, the PEN originates in the anterior cingulate cortex and is itself modulated by the ballistic phase of the hands movement. These findings suggest that velocity is an essential component of integrating hand movements with visual and proprioceptive information during interactions with real and virtual objects.

neuroscience↗