Compounds are provided according to Formula ( I ): and pharmaceutically acceptable salts thereof, and pharmaceutical compositions thereof； wherein R 1 , R 2 , R 3a , R 3b , R 4 , R 5a , R 5b , R 6a , and R 6b are as defined herein. Compounds of the present invention are contemplated useful for the prevention and treatment of a variety of CNS-related conditions.
