Learning is defined as a relatively permanent change in behavior resulting from experience. Memory involves encoding, storing, and later retrieving knowledge about the world. There are two main types of memory: explicit (episodic and semantic) and implicit (associative, classical, and non-associative). Different forms of learning and memory involve different brain regions. Long-term potentiation in the hippocampus is important for declarative memory formation and involves strengthening of synapses through high-frequency stimulation and calcium-dependent processes.