Most recent results in the biomechanics of the brain.

In my opinion both papers provide important new knowledge. However, I feel that a number of statements require corrections and comments. Wu et al. (2004) discuss the effects of friction on the unconfined compression experiment results. As one of the examples Wu et al. consider the unconfined compression of brain tissues as discussed in Miller and Chinzei (1997). Fig. 7a in Wu et al. (2004) is supposed to show the experimental results obtained at the loading speed corresponding to the strain rate of 0.64 Â 10 À5 s À1 , given in Fig. 3c in Miller and Chinzei (1997), as compared to computer simulation results. Unfortunately , the scale on vertical axis in Fig. 7a in Wu et al. (2004) is in kPa (which is incorrect—it should be in Pa) giving a thousand-fold overestimation of the brain's stiffness. In Table 1, Wu et al. provide material coefficients for Ogden-type constitutive model of brain tissue, estimated based on the experimental results of Miller and Chinzei (1997). The values for shear moduli in Table 1 of Wu et al. (2004) are many orders of magnitude too high. The correct values, estimated based on the same experimental results (plus results in extension), are given in Miller and Chinzei (2002).