TABLE 3.

Some Types of Memory

Memory System	Major Anatomical Structures Involved	Length of Storage of Memory	Type of Awareness	Examples	Disorder that can Impair Memory
Semantic memory	Extrasylvian temporal lobes	Minutes to years	Explicit (associated with conscious awareness) or implicit	Knowing who was the first president of the United States, the color of a lion, and how a fork differs from a comb	Semantic dementia
Episodic memory	Medial temporal lobes, hippocampus, anterior thalamic nucleus, mammillary body, fornix, prefrontal cortex	Minutes to years	Usually explicit	Remembering what you had for dinner last night and what you did for your last birthday	Alzheimer’s disease
Procedural memory	Basal ganglia, cerebellum, parietal lobe, supplementary motor area, premotor cortex	Minutes to years	Usually implicit	Riding a bicycle, learning the sequence of numbers on a touchtone phone “by touch”	Ideational and ideomotor apraxia
SECs	Social: ventral prefrontal cortex Non-social: dorsal prefrontal cortex	Minutes to years	Usually implicit	Social: how to go on a date Non-social: how to set the clock on your VCR	Behavioral-variant frontotemporal dementia

Adapted with permission from Budson AE, Price BH: Memory dysfunction. N Engl J Med 2005; 352:692–699

SEC = structured event complex.