Memory has stages and is continually changing.
Longterm memory can be represented by physical changes in the brain, which are localized in multiple regions. Reflexive memory or conditioned responses may be stored in the cerebellum or brain stem. Declarative memory or retention of new memories may reside in the temporal lobe or the diencephalon. Thus, these two types of memory may involve two neuronal circuits. Simple forms of learning involve changes in the effectiveness of synaptic transmission.