Motor rehabilitation: From neuroscience insight towards individualized treatment
C. Weiller, Freiburg - Deutschland

Brain functions are organized in distributed, segregated networks with input and output.
Reorganization due to lesions or intervention mainly takes place within the framework of these nets
The effects of lesions, dysfunction and stimulation or intervention depend on the pre-existing individual network architecture and the site and type of intervention.
Modern brain imaging allows the identification of network architecture as well as the effects of rehabilitation on the brain.
A new combination of fMRI to detect activation hot spots as network nodes with diffusion tensor based fibre tracking to delineate the connections between the nodes allows the anatomical description of networks in the human brain. A general anatomical framework for interaction between the postrolandic brain regions with the frontal lobe seems to emerge:
a dorsal pathway along the superior longitudinal fascicle maps preprocessed sensory, auditory or visuo-spatial information from the temporal or parietal lobe with motor programs in the premotor cortex.
This dorsal system is embraced by a ventral network, running through the extreme capsule, which connects to the lateral prefrontal cortex. It is used for top- down control of postrolandic brain regions by the frontal lobe and for the generation of internal, conscious behaviour as in imagery. Applied to the domains of motor, language and attentional control, these networks relate to symptoms as hemiparesis, aphasia and neglect in patients.
Understanding of such networks provides a basis for a knowingly intervention:
The motor cortex in stroke patients can be stimulated through intense training (e.g.; constraint induced movement therapy) or DC or TMS stimulation with in part long-lasting effects. Network access to the motor system beyond M1 is feasible in patients and has been demonstrated with fMRI:
- The postcentral cortex can be activated through sensory stimulation and passive movement
- The dorsal premotor cortex (Pmd) through imagery of movement
- The ventral premotor cortex (Pmv) through watching and imitation in videotherapy
Transhemispheric access to M1 of the infarcted hemisphere poses a special challenge. Network analysis determines a connection of Pmd of one hemisphere to M1 of the other hemisphere via callosal fibres and PmD of the other hemisphere. Accordingly, mirror- training in healthy subjects of the right hand (visualised in a mirror as a “left” hand) leads to improvement of  function in the (untrained) left hand, which is correlated to BOLD changes in right PmD. Thus, transhemispheric influence of one M1 is feasible through mirror training of the ipsilateral hand and this change is mediated by premotor cortices.