Towards a reliable characterization of the mechanical behaviour of brain tissue: the effects of post-mortem time and sample preparation

Since the early seventies, the material properties of brain tissue have been studied using avariety of testing techniques. However, data reported in literature show large discrepancieseven in the linear viscoelastic region. In the current study, the effect of the sample preparationprocedure and of post-mortem time on the mechanical response of porcine brain tissue isexamined. Samples from the thalamus region were prepared with different techniques and weretested for different loading histories. Each sample was tested in oscillatory shear tests (1%strain amplitude, 1-10 Hz frequencies) followed by sequences of 5% strain loading-unloadingcycles. The stress response to the loading-unloading cycles showed a clear dependency onpost-mortem time, becoming more stiff with increasing time. This dependency was affectedby the mechanical history induced by the preparation procedure.