"Polyunsaturated lipids are an acceptable substitute when monounsaturated lipids are not readily available"
Gee, it's nice that pure olive oil tastes so good :-) (There are super Italian and Greek communities in Ottawa.)
"Especially DHA seems to be important."
True. But always keep in mind that the deterioration rate of our various brain components may vary, perhaps greatly. The required replacement rate, times the efficiency of transfer of dietary component to our brain, is what will determine the correct dietary response.
