Fifty years of brain tissue mechanical testing: From in vitro to in vivo investigations

Abstract

Beginning in the 1960s many studies have been performed to investigate the mechanical properties of brain. In this paper we point out the difficulties linked with in vitro experimental protocols as well as the advantages of using recently developed non-invasive in vivo techniques, such as magnetic resonance elastography. Results of in vitro and in vivo work are compared, emphasizing the specificities and disparities of the in vitro as well as the in vivo results. In particular, a detailed discussion of the results obtained from dynamic shear experiments and magnetic resonance elastography is given before arriving at a tentative conclusion on the state of knowledge of the mechanical properties of brain.

On the characterization of the heterogeneous mechanical response of human brain tissue

“…Failing to control these testing conditions could have partially contributed to the spreading of results in the literature (Chatelin et al. 2010). Ageing does not seem to play a considerable role in the procedure.

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“…2012; Chatelin et al. 2010; Clayton et al. 2012) that showed white matter shear modulus to be 1.2–2.6 times higher than the one obtained for grey matter.…”

“…However, due to the extreme complexity of the soft tissue and the wide range of experimental methods and protocols that have been used for its characterization, the results described in the literature often differ by orders of magnitude (Chatelin et al. 2010). …”

“…Moreover, Chatelin et al. (2010) observed that the variation of results is also noticeable for a non-invasive in vivo technique such as MRE. Therefore, differences in testing protocols and conditions (when conducting in vitro testing) and/or equipment/transducers (in MRE) might be the principal cause of such a huge disparity in the results throughout the literature, also among similar species.…”

Modeling molecular mechanisms in the axon

“…In turn, the time-dependent apparent elasticity and viscosity follow the predictions outlined by the Maxwell fluid equations (Fig. 11), which may be important for developing a better understanding of the complex frequency dependence of neuronal rheological parameters in various experimental regimes [19]. …”