White matter degeneration revealed by fiber-specific analysis relates to recovery of hand function after stroke.

Recent developments of higher-order diffusion-weighted imaging models have enabled the estimation of specific white matter fiber populations within a voxel, addressing limitations of traditional imaging markers of white matter integrity. We applied fixel based analysis (FBA) to investigate the evolution of fiber-specific white matter changes in a prospective study of stroke patients and upper limb motor deficit over 1 year after stroke. We studied differences in fiber density and macrostructural changes in fiber cross-section.

Altered topology of large-scale structural brain networks in chronic stroke.

Beyond disruption of neuronal pathways, focal stroke lesions induce structural disintegration of distant, yet connected brain regions via retrograde neuronal degeneration. Stroke lesions alter functional brain connectivity and topology in large-scale brain networks. These changes are associated with the degree of clinical impairment and recovery.

Cortical atrophy and transcallosal diaschisis following isolated subcortical stroke.

Following acute ischemic stroke, isolated subcortical lesions induce gray matter atrophy in anatomically connected, yet distant cortical brain regions. We expand on previous studies by analyzing cortical thinning in contralesional, homologous regions indirectly linked to primary stroke lesions via ipsilesional cortical areas. For this purpose, stroke patients were serially studied by magnetic resonance imaging (diffusion tensor imaging and high-resolution anatomical imaging) in the acute (days 3-5) and late chronic stage one year after stroke.

The control of complex finger movements by directional information flow between mesial frontocentral areas and the primary motor cortex.

Complex movements require the interplay of local activation and interareal communication of sensorimotor brain regions. This is reflected in a decrease of task-related spectral power over the sensorimotor cortices and an increase in functional connectivity predominantly in the upper alpha band in the electroencephalogram (EEG). In the present study, directionality of information flow was investigated using EEG recordings to gain better understanding about the network architecture underlying the performance of complex sequential finger movements.