Biology subjects

Quandt, F.

Publications and source records attributed to Quandt, F..

4 recordsLinked to original sources

bioRxiv2025

Short-term microglia depletion via CSF-1R inhibition promotes functional network reorganization and motor recovery after cortical ischemia

BACKGROUNDPharmacological options to promote long-term rehabilitation after stroke remain limited. Microglia play a complex role in post-stroke pathology, contributing both to repair and secondary injury. How short-term depletion during the subacute phase affects functional recovery remains unknown. METHODSWild-type mice were trained in a skilled reaching task and underwent permanent distal medial cerebral artery occlusion or sham intervention. Mice received either a colony-stimulating factor 1 receptor inhibitor or vehicle treatment between days 3 and 7 post-stroke to deplete microglia. Fine motor performance was assessed behaviorally while bilateral cortical activity was recorded longitudinally through epidural electrocorticography. RESULTSMicroglia depletion did not affect infarct size but resulted in near-complete restoration of fine motor function by day 7, coinciding with maximal microglial depletion. Recovery of fine motor function was accompanied by significant functional connectivity changes in bilateral sensorimotor networks, including increased beta-band connectivity in the ipsilesional motor cortex, which correlated with contralateral fine motor improvement. After microglial repopulation, cells showed altered morphology and gene expression profiles. CONCLUSIONSTransient microglial modulation during the subacute phase after stroke promotes cortical network reorganization and motor recovery, highlighting a potential time window for future translational studies.

neuroscience↗

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↗

bioRxiv2019

Sensory and auditory evoked responses mimic synchronization of cortical oscillations induced by Transcranial Magnetic Stimulation

BackgroundEntrainment of cortical oscillations by repetitive Transcranial Magnetic Stimulation (rTMS) is an attractive approach to modulate brain function non-invasively in humans. Here, we applied rTMS in order to modulate oscillatory activity in ventral premotor cortex (PMv), primary motor cortex (M1), and anterior intraparietal sulcus (aIPS). These areas are thought to contribute to recovery after motor stroke and our overarching goal is to enhance their impact by rTMS. To this end, we established a setup with bifocal, neuronavigated rTMS combined with EEG and tested its technical feasibility. MethodsBifocal zero-phase lag synchronized rTMS at 11Hz was applied in seven young healthy volunteers to the target pairs (i) PMv and M1 and (ii) aIPS and M1. Adapting to the close vicinity between target areas, we used two small, commercially available coils and applied subthreshold stimuli in order to avoid motor evoked potentials (MEPs). Besides a parieto-occipital sham stimulation, we also included auditory and sensory stimulation in a further control experiment. ResultsFirst, subthreshold TMS led to a phase synchronization and evoked time-averaged potentials in the EEG. However, the same findings could be elicited by peripheral, somatosensory stimulation combined with auditory stimulation. Second, despite the small coils neuronavigation analysis showed that in most participants aIPS and M1 or PMv and M1 could not precisely be targeted due to their vicinity and restriction in coil positioning. Third, bifocal subthreshold rTMS tended to sum up where the induced fields showed the greatest overlap resulting in overt MEPs and thus raising potential safety issues. ConclusionsThe presented data show refinements for bifocal rTMS studies regarding (i) spurious entrainment or resetting effects on brain oscillations, (ii) precise anatomical targeting of areas in close vicinity, and (iii) summing up of overlapping induced electrical fields.

neuroscience↗