The prediction of traumatic brain injury (TBI) is of great importance for the development of protective systems and treatment approaches. This is an inherently multidisciplinary problem that requires accurate modeling and simulation of the loads, geometry and material response of the various components that make up the brain. The main goal of this work is to model and simulate the high strain-rate response of brain tissue. We propose two viscohyperelastic constitutive models for brain tissue, based on the data published in the literature for strain rates up to 3000% s^-1. These new constitutive models are able to accurately capture the response of brain tissue for strains up to 40% and 60-70% respectively.