Described herein are steroids of Formula (I): and pharmaceutically acceptable salts thereof; wherein R1, R2a, R2b, R3, R4, R5a, R5b, R6, and Z are as defined herein. Such compounds are contemplated useful for the prevention and treatment of a variety of CNS-related conditions, for example, treatment of sleep disorders, mood disorders, schizophrenia spectrum disorders, convulsive disorders, disorders of memory and/or cognition, movement disorders, personality disorders, autism spectrum disorders, pain, traumatic brain injury, vascular diseases, substance abuse disorders and/or withdrawal syndromes, and tinnitus.