Biology subjects

Higgen, F. L.

Publications and source records attributed to Higgen, F. L..

7 recordsLinked to original sources

bioRxiv2023

Cortical high gamma power relates to movement speed and is disproportionately reduced after stroke

Motor cortical high-gamma oscillations (60 to 90 Hz) occur at the onset of movement and are spatially focused over the contralateral primary motor cortex. Although high-gamma oscillations are widely recognized for their significance in human motor control, their precise function on a cortical level remains elusive. Importantly, their relevance in human stroke pathophysiology is unknown. Understanding the neurophysiological processes of motor coding could be an important step in improving motor recovery after stroke. We recorded magnetoencephalography data during a thumb movement speed task in 14 chronic stroke survivors, 15 age-matched control participants and 29 healthy young participants. Motor cortical high-gamma oscillations showed a strong relation with movement speed as trials with higher movement speed were associated with greater high-gamma power. Stroke survivors showed reduced cortical high-gamma power, surpassing the effect attributable to decreased movement speed in these participants. Even though motor skill acquisition was evident in all groups, it was not linked to high-gamma power. Our study is, to our knowledge, the first to quantify high-gamma oscillations after stroke, revealing a reduction in movement-related high-gamma power. Moreover, we provide strong evidence for a pivotal role of motor cortical high-gamma oscillations in encoding movement speed.

neuroscience↗

bioRxiv2023

Early functional connectivity alterations in contralesional motor networks influence outcome after severe stroke

Connectivity studies have significantly extended the knowledge on motor network alterations after stroke. Compared to interhemispheric or ipsilesional networks, changes in the contralesional hemisphere are poorly understood. Data obtained in the acute stage after stroke and in severely impaired patients are remarkably limited. This study aimed to investigate early functional connectivity changes of the contralesional parieto-frontal motor network and their relevance for the functional outcome after severe motor stroke. Resting-state functional imaging data were acquired in 19 patients within the first two weeks after severe stroke. Nineteen healthy participants served as a control group. Functional connectivity was calculated from five key motor areas of the parieto-frontal network on the contralesional hemisphere as seed regions and compared between the groups. Connections exhibiting stroke-related alterations were correlated with clinical follow-up data obtained after 3 to 6 months. The main finding was an increase in coupling strength between the contralesional supplementary motor area and the sensorimotor cortex. This increase was linked to persistent clinical deficits at follow-up. Thus, an upregulation in contralesional motor network connectivity might be an early pattern in severely impaired stroke patients. It might carry relevant information regarding the outcome which adds to the current concepts of brain network alterations and recovery processes after severe stroke.

neuroscience↗

bioRxiv2022

Normalization of aperiodic ECoG components indicates fine motor recovery after sensory cortical stroke in mice

Electrophysiological signatures of ischemic stroke might help to develop a deeper understanding of the mechanisms of recovery. Here, analyses of multichannel electrocorticography (ECoG) in awake mice demonstrated that the shape of power spectral density (PSD) is modulated in the vicinity of sensory cortical stroke. PSD consists of both rhythmic oscillatory and non-rhythmic, aperiodic components. The alteration of spectrum shape was reflected in a transient increase of aperiodic exponents, while the relative power and frequency of slow oscillations remained unchanged in the peri-infarct cortex. Exponents derived from motor areas significantly correlated with recovery of fine motor deficits of the contralateral forepaw thus indicating functional modifications of neuronal activity. In conclusion, aperiodic spectral exponents exhibited a unique spatiotemporal profile in the mouse cortex after stroke and might complement future studies providing a dynamic link from pathophysiology to behavior.

neuroscience↗

bioRxiv2020

Sensory capability and information integration independently predict cognitive status in healthy older adults

Ageing is characterized by changes in sensory and cognitive abilities. While there is evidence that decline in sensory acuity and enhanced multisensory integration predict cognitive status in healthy older adults, potential mechanistic links between these age-related alterations remain unclear. In the current study, we assessed performance of younger and older healthy adults in a visuotactile delayed match-to-sample task and related indices of multisensory integration to unisensory perceptual thresholds and cognitive assessment data. Additionally, we applied transcranial alternating current stimulation (tACS) to modulate cortical networks found to underlie visuotactile interactions and working-memory matching in our previous work. Analysing response times and signal detection measures, we found older adults to show enhanced multisensory integration and benefit more from successful working memory matching. Both measures predicted cognitive status and correlated positively with each other, suggesting that they likely reflect a common underlying tendency to integrate information. Sensory capability, however, independently predicted cognitive status. tACS with beta frequency (20 Hz) accelerated task performance and this effect was more pronounced in the older group. We conclude that sensory capability and information integration represent independent predictors of cognitive status. Finally, we discuss a potential role of the parietal cortex in mediating augmented integration in older adults.

neuroscience↗

bioRxiv2019

Crossmodal Pattern Discrimination in Humans and Robots: A Visuo-Tactile Case Study

The quality of crossmodal perception hinges on two factors: The accuracy of the independent unimodal perception and the ability to integrate information from different sensory systems. In humans, the ability for cognitively demanding crossmodal perception diminishes from young to old age.\n\nTo research to which degree impediments of these two abilities contribute to the age-related decline and to evaluate how this might apply to artificial systems, we replicate a medical study on visuo-tactile crossmodal pattern discrimination utilizing state-of-the-art tactile sensing technology and artificial neural networks. We explore the perception of each modality in isolation as well as the crossmodal integration.\n\nWe show that in an artificial system the integration of complex high-level unimodal features outperforms the comparison of independent unimodal classifications at low stimulus intensities where errors frequently occur. In comparison to humans, the artificial system outperforms older participants in the unimodal as well as the crossmodal condition. However, compared to younger participants, the artificial system performs worse at low stimulus intensities. Younger participants seem to employ more efficient crossmodal integration mechanisms than modelled in the proposed artificial neural networks.\n\nOur work creates a bridge between neurological research and embodied artificial neurocognitive systems and demonstrates how collaborative research might help to derive hypotheses from the allied field. Our results indicate that empirically-derived neurocognitive models can inform the design of future neurocomputational architectures. For crossmodal processing, sensory integration on lower hierarchical levels, as suggested for efficient processing in the human brain, seems to improve the performance of artificial neural networks.

neuroscience↗

bioRxiv2019

Reduced frontal white matter microstructure in healthy older adults with low tactile recognition performance

Aging leads to a reduction of connectivity in large-scale structural brain networks. Sensory processing and other cognitive processes rely on information flow between distant brain areas. However, data linking age-related structural brain alterations to cognitive functioning, especially sensory processing, is sparse.\n\nAiming to determine group differences in sensory processing between older and younger participants, we implemented a complex tactile recognition task and investigated to what extent changes in microstructural white matter integrity of large-scale brain networks might reflect success in task performance. Structural brain integrity was accessed by means of diffusion-weighted imaging and fractional anisotrophy.\n\nThe data revealed that poor performance in complex tactile recognition in older, neurologically healthy individuals is related to decreased structural integrity pronounced in the anterior corpus callosum. This region was strongly connected to the prefrontal cortex. Our data suggests decreased fractional anisotrophy in the anterior corpus callosum as a surrogate marker for progressed brain aging, leading to disturbances in networks relevant for higher-order cognitive processing. Complex tactile recognition might be a sensitive marker for identifying these starting cognitive impairments in older adults.

neuroscience↗

bioRxiv2019

Congruency effects can compensate for deficits of healthy older adults in crossmodal integration

One of the pivotal challenges of aging is to maintain independence in the activities of daily life. In order to adapt to changes in the environment, it is crucial to continuously process and accurately combine simultaneous input from different sensory systems, i.e., crossmodal integration.\n\nWith aging, performance decreases in multiple cognitive domains. The processing of sensory stimuli constitutes one of the key features of this deterioration. Age-related sensory impairments affect all modalities, substantiated by decreased acuity in visual, auditory or tactile detection tasks.\n\nHowever, whether this decline of sensory processing leads to impairments in crossmodal integration remains an unresolved question. While some researchers propose that crossmodal integration degrades with age, others suggest that it is conserved or even gains compensatory importance.\n\nTo address this question, we compared behavioral performance of older and young participants in a well-established crossmodal matching task, requiring the evaluation of congruency in simultaneously presented visual and tactile patterns. Older participants performed significantly worse than young controls in the crossmodal task when being stimulated at their individual unimodal visual and tactile perception thresholds. Performance increased with adjustment of stimulus intensities. This improvement was driven by better detection of congruent stimulus pairs (p<0.01), while detection of incongruent pairs was not significantly enhanced (p=0.12).\n\nThese results indicate that age-related impairments lead to poor performance in complex crossmodal scenarios and demanding cognitive tasks. Performance is enhanced when inputs to the visual and tactile systems are congruent. Congruency effects might therefore be used to develop strategies for cognitive training and neurological rehabilitation.

neuroscience↗