Provided are compounds having formula I: wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 are as disclosed herein, or a pharmaceutically salt thereof. Pharmaceutical compositions comprising the compounds and methods of their use, for instance in treating senility, senile confusion, psychoses, psychoneuroses when anxiety and nervous tension were present, cerebral arteriosclerosis, nausea, depression, fatigue, debilitation, mild behavioral disorders, irritability, emotional instability, antisocial attitudes, anxiety, vertigo or incontinence, or symptom thereof, or in improving cognitive function in individuals, for instance, in individuals with Down syndrome and other conditions, are also provided.