The human brain's memory involves three basic processes: encoding, storage and retrieval. Memories are stored in the hippocampus, where neurons in the brain connect to various cortexes responsible for different processes. For instance, neurons go from the hippocampus to the visual cortex for memories seen by the eyes and to the auditory cortex for memories associated with sound.
The human brain contains more than 100 billion neurons, the brain structures that transmit messages. Neurons create more than 1 trillion connections in the brain, and combine to help increase the brain's storage capacity and storage retrieval. Scientists believe the human brain has a memory capacity equivalent to 2.5 petabytes.
Encoding occurs when neurons make connections from the hippocampus to other parts of the brain. The memory is stored for long-term retrieval when humans make similar connections to other experiences. For example, a person who tastes a new kind of apple may relate the experience to tasting an apple in the past. Retrieval occurs when a concept, such as "red" or "apple," triggers the memory of an apple from the past. Each time a memory is recalled, it becomes increasingly strengthened. When the same neurons fire over and over, they become part of long-term memories that are more easily remembered.