This invention provides a preparation comprising serine glycerophospholipids which comprise a mixture of serine glycerophospholipids comprising eicosapentaenoic acid (EPA) and serine glycerophospholipids comprising docosahexaenoic acid (DHA), wherein each such serine glycerophospholipid comprising EPA and each such serine glycerophospholipid comprising DHA has the formula (I): wherein R″ is serine; wherein one of R or R′ is acyl EPA or acyl DHA and the other of R or R′ is hydrogen or an acyl group; wherein the combined amount of EPA and DHA present in such mixture of serine glycerophospholipids constitutes 10-50% by weight of the total fatty acids content of the serine glycerophospholipids in said preparation; and wherein the mixture is not identical to naturally occurring human or mammalian brain PS.