The present invention relates to compounds of formula (I): or a pharmaceutically acceptable salt, hydrate, solvate, or prodrug thereof, wherein U, J, V, X, R2a, R2b, R2c, R5 and t are as described herein. The present invention relates generally to inhibitors of histone deacetylase and to methods of making and using them. These compounds are useful for promoting cognitive function and enhancing learning and memory formation. In addition, these compounds are useful for treating, alleviating, and/or preventing various conditions, including for example, neurological disorders, memory and cognitive function disorders/impairments, extinction learning disorders, fungal diseases and infections, inflammatory diseases, hematological diseases, and neoplastic diseases in humans and animals.