Omega-6 fatty acids are also needed in feline cognition diets. The important omega-6 fatty acid that plays a role in brain support and cognition is arachidonic acid. Arachidonic acid, or AA, is found in animal sources such as meat and eggs. AA is required in cat diets, as felines convert insignificant amounts of it from linoleic acid due to the limited enzyme delta-6 desaturase. Like DHA, arachidonic acid is often found in the brain tissues of cats and seems to have a supporting role in brain function. In a 2000 study completed by Contreras "et al.", it was found that DHA and AA made up 20% of the fatty acids in the mammalian brain. Arachidonic acid makes up high amounts in the membrane of most cells and has many pro-inflammatory actions.