This is an informative excerpt from Dr Mercola:-
Animal-based omega-3 fat, such as krill oil, is essential for optimal health, and particularly critical for brain health. It even offers hope for healing and restoring brain function after a traumatic brain injury
Low concentrations of EPA and DHA have been shown to result in an increased risk of death from all causes and accelerate cognitive decline
Recent research suggests that fish oil can help slow down age-related brain atrophy
Older women with the highest levels of omega-3 fatty acids had better preservation of their brain as they aged than those with the lowest levels, which might mean they would maintain better brain function for an extra year or two
Previous research has also confirmed the beneficial effect of omega-3 fat on brain function in youngsters, concluding that DHA intake is a robust modulator of functional cortical activity