Distinguishing Memory Types

The hippocampus and the medical temporal lobes are critical for a healthy memory. They are involved in the function of the declarative memory, one of two major types of remembering. All declarative memory is conscious, meaning that a person is aware of its retrieval. It includes such tasks as the ability to briefly hold facts and then discard them or to recall episodes from earlier years.

The other main type of memory is nondeclarative, or the unconscious retrieval of information. This is the ability to walk, chew, swallow, reach for a pencil, pour a glass of water, turn on a light or put a key in the door without thinking. These skills are centered in the amygdala and other portions of the brain.

Different types of memory are often interwoven like a mental tapestry.

The ability to read is a nondeclarative memory, because once the skill of reading is mastered, it becomes an unconscious act, said Leslie Ungerleider of the National Institute of Mental Health. But remembering what has been read would be a declarative memory because it involves consciously retrieving the information.