Glenda Halliday, PhD, is renowned internationally for her research on neurodegeneration with a major impact on understanding disease progression. Her studies on the molecular and cellular properties of the human brain have provided core neuroanatomical and biochemical information to understand the effect of neurodegenerative diseases. After developing rigorous quantitative methods for evaluating pathology in patients with defined clinical symptoms, she revealed more extensive neurodegeneration in Parkinson's disease and related syndromes than previously thought. Comparing the brains of humans and animals, she identified differences in the functional anatomy of the main regions modulating cortical activity that are involved in neurodegenerative diseases. She has defined the earliest biochemical signatures in the brains of patients with Parkinson’s disease, dementia with Lewy bodies, and frontotemporal dementias. Her research has identified previously unrecognized brain regions that degenerate selectively in these diseases and revealed the involvement of the glial cells surrounding the neurons.