Provided herein are devices and methods for reversibly controlling memory function in living non-human animals. Some variations of methods for affecting memory function comprise temporarily inhibiting neurons of the hippocampus (e.g., neurons of the dorsal CA1 field of the hippocampus) during the acquisition or retrieval of a memory. Alternatively or additionally, methods for reversibly affecting memory function comprise inhibiting neurons of the amygdala (e.g. basolateral amygdala) and/or neurons of the cingulate cortex (e.g., anterior cingulated cortex). Methods for disrupting the formation and recall of memories by inhibiting excitatory neurons expressing light-activated proteins are disclosed herein. One or more methods for reversibly affecting memory function described herein can be used to evaluate the effectiveness of pharmacological agents in treating PTSD and/or various memory disorders.