During this period, investigators consolidated epidemiology with neuropathology to illuminate neurodegenerative syndromes across diverse populations. Research emphasized clinico-pathological correlations, particularly in parkinsonism-dementia complex and the emergence of intraneuronal inclusions, while adopting cross-cultural comparisons to explore environmental and toxin-related etiologies. Methodological emphasis on ultrastructural analysis and tissue demonstration shaped early neurodegenerative pathology.