Recent study finds eating fish—baked or broiled, never fried—is associated with larger gray matter volumes in brain areas responsible for memory and cognition in healthy elderly people.
Type of fish is not important but the frequency, once a week, is key for ‘brain thickening’ effects possibly reducing risk for alshimers’s.
https://www.theatlantic.com/health/archive/2014/08/this-is-your-brain-on-fish/375638/