Dr Newell’s research interests have focused on the mechanisms that the brain uses to protect itself against damage from reductions of blood flow and against injury. These studies have included mechanisms of regulation of cerebral blood flow and the use of ultrasound in the diagnosis and treatment of brain disorders. He was the first neurosurgeon in the United States to perform research and publish results on the use of transcranial Doppler ultrasound in neurosurgical patients and helped introduce this technology in the United States as part of the care and treatment of patients with head injury, stroke, and cerebral aneurysms.

While at the University of Washington, Dr Newell directed a basic science laboratory and trained residents and fellows in research methods to study the mechanism of brain damage from stroke. He developed the hippocampal slice culture model for the study of ischemic brain damage and the prevention of neural death. This method utilized organotypic slice cultures, slices of the hippocampus of rat brain that were then grown for weeks in culture. After maturation, these brain slices could then be deprived of oxygen and glucose to mimic stroke conditions and used to test the effect of various compounds to protect the nerve cells from damage.