SCIENTIFIC ACTIVITIES - Fields Institute - University of Toronto
SCIENTIFIC ACTIVITIES - Fields Institute - University of Toronto
SCIENTIFIC ACTIVITIES - Fields Institute - University of Toronto
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Brain<br />
Neuromechan<br />
BRAIN TISSUE IS AN INHOMOGENEOUS, MULTIscaled,<br />
multi-layered, and inter-connected set <strong>of</strong> neurons, glial<br />
cells, and vascular networks. So far, the biophysics and dynamics<br />
<strong>of</strong> the cell types within these networks have been studied<br />
individually, as well as their network interactions.<br />
On the other hand, the macroscopic mechanical response<br />
<strong>of</strong> the brain to traumatic injuries has also been the object <strong>of</strong><br />
intense experimental and computational studies. However, a<br />
full understanding <strong>of</strong> brain physics and dynamics can only be<br />
achieved by linking biomechanical and biochemical processes<br />
taking place in the brain at different length and time scales, and<br />
by accounting for the interactions <strong>of</strong> and feedback among the<br />
brain’s networks.<br />
The aim <strong>of</strong> this first interdisciplinary workshop on<br />
Brain Neuromechanics was to bring together experts from<br />
different areas <strong>of</strong> brain research, such as applied mathematics,<br />
neuroscience, engineering, neurosurgery, to present the latest<br />
developments in their fields and discuss opportunities for longterm<br />
research collaborations.<br />
The first speaker, James Drake, Chief Neurosurgeon<br />
at the Hospital for Sick Children in <strong>Toronto</strong>, set the tone<br />
for the workshop by delivering a talk on the inseparability<br />
<strong>of</strong> neurosurgery and neuromechanics. Improved medical<br />
diagnoses, treatment strategies and clinical protocols can be<br />
achieved only through discoveries in fundamental brain science.<br />
In particular, hydrocephalus, a brain condition known from<br />
the time <strong>of</strong> Hippocrates and characterized by an abnormal<br />
accumulation <strong>of</strong> spinal fluid within the fluid-containing<br />
spaces <strong>of</strong> the brain, remains a puzzle for neurosurgeons even<br />
today; the two surgical treatments currently used display no<br />
statistical difference with regard to the efficacy <strong>of</strong> treating<br />
hydrocephalus. Some <strong>of</strong> the subsequent talks showed<br />
promising new advances in the understanding <strong>of</strong> the underlying<br />
mechanisms that give rise to hydrocephalus. Miles Johnston<br />
(Sunnybrook) showed that, in the rat brain, interstitial fluid<br />
pressures increased after antibody administration into a lateral<br />
16 FIELDSNOTES | FIELDS INSTITUTE Research in Mathematical Sciences<br />
ventricle, suggesting that capillary absorption might play a<br />
pivotal role in the onset <strong>of</strong> hydrocephalus. This finding provides<br />
the exciting possibility that some forms <strong>of</strong> hydrocephalus<br />
may be treatable with pharmacological agents rather than<br />
through surgical interventions. Richard Penn (Chicago)<br />
presented a novel macroscopic biomechanical model <strong>of</strong><br />
fluid-structure interactions in the brain which could explain<br />
the onset <strong>of</strong> hydrocephalus. So far, the model appears to be<br />
in agreement with preliminary experiments on dog brains.<br />
Kathleen Wilkie (Waterloo) introduced a new age-dependent<br />
fractional viscoelastic model for the brain and showed that the<br />
natural pulsations <strong>of</strong> the brain cannot be the primary cause<br />
<strong>of</strong> either infant or adult hydrocephalus. Almut Eisentrager<br />
(Oxford) presented a novel multi-fluid poro-elastic model<br />
<strong>of</strong> hydrocephalus which incorporates blood pulsations on<br />
the cardiac cycle time scale and thus can be used to simulate<br />
spinal fluid pressure fluctuations in clinical infusion tests.<br />
Finally, Corina Drapaca (Penn State) presented the first<br />
neuro-mechanical models that couple the biomechanics and<br />
biochemistry <strong>of</strong> the brain. One model, based on the triphasic<br />
theory, shows that normal pressure hydrocephalus (NPH) can<br />
be caused by an ionic imbalance in the absence <strong>of</strong> increased<br />
intracranial pressure. This represents a significant finding in<br />
NPH research, opening the door to the possibility <strong>of</strong> treating<br />
hydrocephalus using pharmaceutical agents. The other model<br />
can incorporate non-invasive neuro-imaging measurements<br />
and can then be used to investigate the brain’s mechanics<br />
under different clinical scenarios. Although Martin Ostoja-<br />
Starzewski’s (Urbana-Champaign) talk did not focus on<br />
hydrocephalus, his MRI-based finite element approach to<br />
study traumatic brain injuries could also be used in computer<br />
simulations <strong>of</strong> hydrocephalus. In addition, a novel extension <strong>of</strong><br />
continuum mechanics to fractal porous media was introduced to<br />
address the random fractal geometry <strong>of</strong> the brain.<br />
The talks given by Alan Wineman (UMichigan) and<br />
Katerina Papoulia (Waterloo) served to remind the audience