|
Brain-Plasticity |
This collaborative research effort aims to explore the neural mechanisms underlying cortical plasticity
in healthy subjects and in patients who learn or re-learn a perceptual task. Our approach is novel
since it is strongly guided by methods from computational and cognitive neurosciences and directly
applies them to problems arising in clinical neurology and neurorehabilitation. In the experimental part
of the project, we plan to employ prototypical tasks that can be learned within a few hours or at most a
few days with repeated practice. Before and after this extensive training, our participants will take part
in functional and anatomical MR-scan sessions. We will ask the subjects to perform a task for the first
time (e.g., speed discrimination of transparent motion). After a sufficient training period, the
participants will be scanned again on the same task. We will then compare the MR-correlates of brain
structure, brain activation, brain connectivity and neural information processing before and after this
training. Voxel-based morphometry will be used to determine any small changes in grey matter
thickness and/or signal intensity before and after training. As has already been shown (Draganski et
al., 2004), intensive training can lead to significant enhancement in the MR-signals reflecting grey
matter in cortex, which underlies the processing of the sensory or sensorimotor aspects of the learned
task. Moreover, we plan to examine patients with retrochiasmatic injury and homonymous visual field
loss with respect to their global processing capacity in scene perception and in reading at the
behavioural-neuropsychological and the functional-neurobiological level. To gain more insight into the
neuronal processes underlying neuronal plasticity in adults, fMRI and neuropsychological studies will
be conducted before and after an oculomotor training program in patients recovering from posterior
infarctions and/or cerebral haemorrhaging. The results of these basic and clinical investigations will be
modelled with mean-field theory and computational models to get a better quantitative description of
the neural processes underlying perceptual skill acquisition and reacquisition after brain damage.
Powerful novel data-analysis techniques for functional MRI data will be developed and applied to
enhance our ability to extract specific correlates of neuronal plasticity during neurorehabilitation. A further aim of the research group is to gain a better understanding of how learning takes place in low-level sensory and sensorimotor circuits and compare these processes with those occurring in high-level cognitive learning. Some of the projects will focus on the low-level perceptual learning that occurs when healthy volunteers learn a new task. What changes take place in the brains of adults when they learn a new sensory or sensorimotor task? Moreover, we are interested in the brain changes that take place when patients recover from brain damage. At the macroanatomical level, the neural basis of “scaffolding” processes (Petersson, 1998), where additional brain circuits are temporally recruited to perform supplementary processing during the recovery period, will be investigated. At the microanatomical level, spike timing dependent plasticity (Masquelier and Thorpe, 2007) will be incorporated into models of higher-level motion processing required for velocity discrimination. It remains to be determined how exactly both these macro- and microanatomical changes take place. Finally, we hope to provide clinicians with new imaging approaches and diagnostic tools to map changes in grey and white matter that accompany neural learning processes. |