The project is concerned with the dynamic behavior of the brain and spinal cord under impact loading. The main focus will be the construction of structural finite-element computer models of the human and rhesus head and neck. To support the above goal, we propose to: 1) Exercise the first-generation, linear finite-element (FE) computer model of the human head and neck to crown impact with and without padding protection. 2) Improve the capability of the present FE model by including nonlinear material and geometric properties in its formulation. By so doing, we should extend the ability of the FE model to simulate contact and noncontact impact situations where large displacement and finite strains are expected in the head and neck. 3) Construct a similar dynamic model for the rhesus head and neck. 4) Perform dynamic tests on fresh human and rhesus autopsy cervical spines to determine its mechanical and failure characteristics in tension, compression, flexion, extension, lateral bending and torsion. These data are prerequisites to a realistic large displacement FE model. 5) Use the technique of computerized tomography (CT) to determine the geometry and inertial tensor of the rhesus head and neck prior to trauma. The post-trauma CT scans will be used to detect the primary traumatic lesion sites. 6) Validation studies, using 4 rhesus monkeys per year, will be undertaken to verify the effects of the impact vectors on the field quantities; e.g., linear and angular head head accelerations, dynamic intracranial pressure and CT lesions. Four each will be used in superior-inferior, occipital and temporal head head impacts. 7) Inasmuch as these are very expensive and highly monkeys, we are obliged to do the neuropathology even though they only they only indirectly support the FE effort. The brains and spinal cords monkeys will be examined with standard neurohistologic procedures with procedures with particular emphasis on axon degeneration using silver techniques.