If someone is considering using essential oils to support brain performance and function one should consider a very high quality essential oil. Like high quality food it will make a big difference.
Purity and potency are the most important factors determining high quality essential oils.
Like plants they are very potent with communicating with human chemistry.
Dr. Daniel Penoel: French Aromatherapist, http://www.ecolepenoel.com/en/pedagogie/formateurs/