Biology subjects

Braass, H.

Publications and source records attributed to Braass, H..

3 recordsLinked to original sources

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↗

bioRxiv2023

Ventral premotor cortex influences spinal cord activation during force generation

Force generation is a crucial element of dexterity and a highly relevant skill of the human motor system. How cerebral and spinal components interact and how spinal activation is influenced by cerebral primary motor and premotor areas is poorly understood. Here we conducted combined cortico-spinal functional MRI during a simple visually guided isometric force generation task in a group of 20 healthy young subjects. Activation was localized in the ipsilateral cervical spinal cord and contralateral primary motor and premotor areas. The main finding is that spinal activation was influenced by ventral premotor cortex activation. Spinal activation was furthermore significantly correlated with primary motor cortex activation while increasing target forces led to an increase in the amount of activation. These data indicate that human premotor areas such as the ventral premotor cortex might be functionally connected to the lower cervical spinal cord contributing to distal upper limb functions, a finding which extends our understanding about human motor function beyond the animal literature.

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↗