Long-term memory is an archive of information about past events in our lives and knowledge we have learned. For example, long-term memory can contain details of our last summer holiday, the fact that Paris is the capital of France, information about how to ride a bicycle and so on.
Much of this information is stored in the form of schemas or organized packets of knowledge and is used extensively during language comprehension.
Long-term memory (LTM) is a relatively permanent memory store with an unlimited capacity and duration, containing different components such as episodic Opens in new window (personal events), semantic Opens in new window (facts and information), and procedural Opens in new window (actions and skills) memory.
As is the case for memory Opens in new window in general, long-term memory has several distinct types.
We’ll spend the remainder of this study surveying the various forms of long-term memory.
Long-term Memory Systems
Although most assessment instruments have simply divided long-term memory into visual and auditory components, research and applied psychologists have developed a more elaborate organization of long-term memory structures that is now widely accepted and seems consistent with actual brain structures and functions.
The primary division of long-term memory is into declarative (explicit) Opens in new window and nondeclarative (implicit) memory Opens in new window.
Declarative memory defines the capacity to learn, store, and recall information explicitly; it is memory for facts and events. This form of long-term memory is demonstrated by speaking, and arises with conscious recall.
- Episodic memory stores information about events together with their spatio-temporal context. It contains episodes, or personally experienced events—for example, what you did on your birthday last year.
- Semantic memory is devoted to storing general knowledge about words, objects, and concepts, of the sort learned in school (Tulving 1972). Knowing that Thomas Jefferson wrote the Declaration of Independence is an example of semantic memory Opens in new window.
We are usually consciously aware of declarative information, which is sometimes referred to as explicit memory Opens in new window. This memory form is impaired in amnesia Opens in new window, in particular, the capacity to encode and retrieve new episodic information.
Brain lesions can cause anterograde amnesia Opens in new window, which denotes the difficulty to form new memories. They can also induce retrograde amnesia Opens in new window, i.e. an incapacity to retrieve memories that were formed before the injury injury.
Semantic memory is comparatively less vulnerable, but may be impaired through lesions to distinct anatomical structures.
Nondeclarative memory refers to the capacity to learn information implicitly, mainly through repeated exposure to a stimulus or task.
- Procedural memory holds procedural knowledge. It is memory for skill, demonstrated by doing, and arises without conscious recall.
Knowing how to ride a bicycle, is a good example of this memory type. A person who knows how to ride a bike can demonstrate that s/he has this ability only by actually doing it.
The subconscious nature of procedural memory becomes evident when we learn how to perform some skill—such as playing the piano—forget how, but then show improvement when we attempt to perform the action at a later date.
- Priming relates to the fact that seeing a word or image seems to prime (promt) the individual’s ability to come up with the correct response.
During priming, cues prompt accurate recall or performance without the individual’s recollection of the acquired information or that it was previously learned. Priming occurs even when people say that they do not remember any exposure to the stimulus.
- Classical conditioning is a phenomenon in which the individual learns the predictive relationship of one environmental stimulus with another. Automatic stimulus-response associations can be formed through conditioning.
The conditioning begins when an initially neutral stimulus is paired with an unconditioned stimulus that elicits a reflex response. The conditioning is complete when the neutral stimulus elicits the response in the absence of the unconditioned stimulus. The classic example is Pavlov’s dog learning that a sound reliably predicted the delivery of food.
Nondeclarative memories depend on brain areas that are involved in the sensory and perceptual processing of information, and are relatively preserved in amnesia.