Target Audience

Brain imagers, including those with an interest in brain structure and function such as neuroscientists, psychologists, neurologists and psychiatrists, and those with interests in brain imaging methodology such as MR physicists and image analysts

Outcome/Objectives

Attendees will learn examples of how to use cutting edge brain MR methodology to study human brain organisation and plasticity

Purpose

The talk will provide examples of use of MRI to perform human brain mapping, with a focus on studies of brain plasticity. It is increasingly clear that, far from being hard wired, the adult brain shows remarkable plasticity in response to experience. Brain MRI provides exciting opportunities to monitor both structural and functional plasticity in living humans in many different contexts.

Methods

The focus will be on brain MRI, including examples using diffusion MRI and functional MRI, as well as fMRI neurofeedback. Diffusion MRI experiments discussed use diffusion tensor imaging to calculate voxelwise measures of fractional anisotropy (FA) which is used as the main marker for white matter microstructure. DTI measures are analysed on the white matter skeleton using tract based spatial statistics (TBSS). FA is compared after modulations of experience such as learning a new visuomotor skill (juggling). Related experiments in rodents assess the biological basis of these changes. Rats are trained on a new motor skill (unimanual skilled reaching) and then scanned. Immunohistochemistry is also performed to assess marker of myelin. FMRI experiments discussed use high-field, high resolution FMRI to map the somatensory cortex. A phase encoding design is used to provide reliable and reproducible maps of individual digits in single subjects. The reproducibility of these maps is tested by imaging subjects over multiple timepoints. The plasticity of these maps is tested by a scanning subjects before and after a 24 hour period when two of their digits are glued together. A similar mapping approach is also used in individuals with upper limb amputation and with vivid phantom limb sensations, to assess whether or not the maps of individual digits are preserved in the absence of the limb. Examples using real time FMRI neurofeedback will also be given. These experiment use Turbo Brain Voyager to feedback visual representations of brain activity in real-time during hand movements in healthy individuals and patients after stroke.

Results

Results will include the demonstration that experience (e.g. skill learning) evokes changes in human white matter, as assessed by diffusion MRI (Scholz et al. , 2009). Related experiments in rodents, using diffusion MRI, MTR and immunohistochemistry, suggest that these changes may in part reflect activity-dependent myelination (Sampaio-Baptista et al. , 2013). Results using high field FMRI will demonstrate that reproducible maps of individual digits in the human somatosensory cortex can be reliably found in single subjects (Kolasinski et al. , 2016). These maps show rapid remapping in response to a brief period of altered sensorimotor experience (gluing of two digits for 24 hours)(Kolasinski et al. , 2016). Results from amputees will demonstrate persistence of these maps even decades after limb amputation(Kikkert et al. , 2016). Example results from real time FMRI will demonstrate that healthy people can effectively use this feedback signal to modulate the laterality of movement-related activity in motor cortex (Neyedli et al. , 2017). A proof of principle clinical study will demonstrate that these chronic stroke patients are also able to modulate laterality of their brain activity, providing rationale for further testing to assess whether this might have clinical utility.

Discussion

These examples demonstrate how structural and functional MRI can be used to effectively map the human brain and to demonstrate how is can alter with experience.

Conclusion

These results have methodological relevance in highlighting the challenge of interpreting MR measures in biological terms. They have clinical relevance in demonstrating how methods such as real time FMRI could potentially be used for rehabilitation.

Acknowledgements

No acknowledgement found.

References

Results will include the demonstration that experience (e.g. skill learning) evokes changes in human white matter, as assessed by diffusion MRI (Scholz et al. , 2009). Related experiments in rodents, using diffusion MRI, MTR and immunohistochemistry, suggest that these changes may in part reflect activity-dependent myelination (Sampaio-Baptista et al. , 2013). Results using high field FMRI will demonstrate that reproducible maps of individual digits in the human somatosensory cortex can be reliably found in single subjects (Kolasinski et al. , 2016). These maps show rapid remapping in response to a brief period of altered sensorimotor experience (gluing of two digits for 24 hours)(Kolasinski et al. , 2016). Results from amputees will demonstrate persistence of these maps even decades after limb amputation(Kikkert et al. , 2016). Example results from real time FMRI will demonstrate that healthy people can effectively use this feedback signal to modulate the laterality of movement-related activity in motor cortex (Neyedli et al. , 2017). A proof of principle clinical study will demonstrate that these chronic stroke patients are also able to modulate laterality of their brain activity, providing rationale for further testing to assess whether this might have clinical utility.