Navigation Links

For computer memory, see computer storage.

Memory is a property of the human mind: the ability to retain information. Memory is much studied by cognitive psychology and neuroscience. There are multiple types of classifications for memory based on duration, nature and retrieval of perceived items.

The main stages in the formation and retrieval of memory, from an information processing perspective, are:

  • Encoding (processing and combining of received information)
  • Storage (creation of a permanent record of the encoded information)
  • Retrieval/Recall (calling back the stored information in response to some cue for use in some process or activity)

Classification by duration

A basic and generally accepted classification of memory is based on the duration of memory retention, and identifies three distinct types of memory: sensory memory, short-term memory, and long-term memory.

The sensory memory corresponds approximately to the initial moment that an item is perceived. Some of this information in the sensory area proceeds to the sensory store, which is referred to as short-term memory. Sensory memory is characterized by the duration of memory retention from milliseconds to seconds and short-term memory from seconds to minutes. These stores are generally characterised as of strictly limited capacity and duration, whereas in general stored information can be retrieved in a period of time which ranges from days to years; this type of memory is called long-term memory.

It may be that short-term memory is supported by transient changes in neuronal communication, whereas long-term memories are maintained by more stable and permanent changes in neural structure that are dependent on protein synthesis. Some psychologists, however, argue that the distinction between long- and short-term memories is arbitrary, and is merely a reflection of differing levels of activation within a single store.

If we are given a random seven-digit number, we may remember it only for a few seconds and then forget (short-term memory). On the other hand, we can remember telephone numbers for many years (assuming we use them often enough). Those long-lasting memories are said to be stored in long-term memory.

Additionally, the term working memory is used to refer to the short-term store needed for certain mental tasks - it is not a synonym for short-term memory, since it is defined not in terms of duration, but rather in terms of purpose. Some theories consider working memory to be the combination of short-term memory and some attentional control. For instance, when we are asked to mentally multiply 45 by 4, we have to perform a series of simple calculations (additions and multiplications) to arrive at the final answer. The ability to store the information regarding the instructions and intermediate results is what is referred to as working memory.

Classification by information type

Long-term memory, the largest part of any model, can be divided into declarative (explicit) and procedural (implicit) memories.

Declarative memory requires conscious recall, in that some conscious process must call back the information. It is sometimes called explicit memory, since it consists of information that is explicitly stored and retrieved.

Declarative memory can be further sub-divided into semantic memory, which concerns facts taken independent of context; and episodic memory, which concerns information specific to a particular context, such as a time and place. Semantic memory allows the encoding of abstract knowledge about the world, such as "Paris is the capital of France". Episodic memory, on the other hand, is used for more personal memories, such as the sensations, emotions, and personal associations of a particular place or time. Autobiographical memory - memory for particular events within one's own life - is generally viewed as either equivalent to, or a subset of, episodic memory. Visual memory is part of memory preserving some characteristics of our senses pertaining to visual experience. We are able to place in memory information that resembles objects, places, animals or people in sort of a mental image.[1]

In contrast, procedural memory (or implicit memory) is not based on the conscious recall of information, but on an implicit learning. Procedural memory is primarily employed in learning motor skills and should be considered a subset of implicit memory. It is revealed when we do better in a given task due only to repetition - no new explicit memories have been formed, but we are unconsciously accessing aspects of those previous experiences. Procedural memory involved in motor learning depends on the cerebellum and basal ganglia.

Classification by temporal direction

A further major way to distinguish different memory functions is whether the content to be remembered is in the past, retrospective memory , or whether the content is to be remembered in the future, prospective memory . Thus, retrospective memory as a category includes semantic memory and episodic/autobiographical memory. In contrast, prospective memory is memory for future intentions, or remembering to remember (Winograd, 1988). Prospective memory can be further broken down into event- and time-based prospective remembering. Time-based prospective memories are triggered by a time-cue, such as going to the doctor (action) at 4pm (cue). Event-based prospective memories are intentions triggered by cues, such as remembering to post a letter (action) after seeing a mailbox (cue). Cues do not need to be related to the action (as the mailbox example is), and lists, sticky-notes, knotted hankerchiefs, or string around the finger (see box) are all examples of cues that are produced by people as a strategy to enhance prospective memory.

Memory disorders

Much of the current knowledge of memory has come from studying memory disorders. Loss of memory is known as amnesia. There are many sorts of amnesia, and by studying their different forms, it has become possible to observe apparent defects in individual sub-systems of the brain's memory systems, and thus hypothesize their function in the normally working brain.

The physiology of memory

Brain areas such as the hippocampus, the amygdala or the mammillary bodies and are thought to be involved in certain kinds of memory. For example, the hippocampus is believed to be involved in spatial learning and declarative learning. It has been demonstrated that damage to these structures can result in impaired performance on certain memory tasks. However, it is not sufficient to describe memory, and its counterpart learning, as soley dependant on specific brain regions. Learning and memory are attributed to changes in neuronal synapses.

Related topics

External links


(Date:4/24/2014)... Carbon offsetting initiatives could be improved with new insights ... , Scientists studying the Amazon Basin have revealed ... trees across the region by comparing satellite maps with ... enable researchers to assess more accurately the amount of ... factor in carbon offset schemes, in which trees are ...
(Date:4/24/2014)... turtle in North America, weighing in at up to ... from Florida and the University of Vermont have discovered ... , Examining museum specimens and wild turtles, the scientists ... Once heavily hunted for turtle meat alligator snapper ... the 1960s the riverine populations have been deeply ...
(Date:4/24/2014)... out a welcome mat to bacteria seeking to invade, and ... published this week in the Proceedings of the National ... between microbe and host that researchers can exploit to protect ... plant Arabidopsis puts out a molecular signal that ... hostile army were unknowingly passing by a castle, and the ...
Breaking Biology News(10 mins):Amazon rainforest survey could improve carbon offset schemes 2Two new US turtle species described 2Two new US turtle species described 3How a plant beckons the bacteria that will do it harm 2How a plant beckons the bacteria that will do it harm 3
... Current arthritis medications can ease the pain, but ... aggressive treatments: use of very limited available drugs ... to find new therapeutic targets for arthritis by ... interrupted, may prevent arthritis pain caused by joint ...
... More than 300 people and 30 companies are expected ... career fair on March 13, 2009 at NJIT. The ... 3:30 p.m. in NJIT,s Campus Center, unites industry professionals ... "Explore the Leading Edge of the ...
... by the Wildlife Conservation Society, have helped the government ... protect more than 600 gorillas, along with other threatened ... Called Deng Deng National Park, the new ... kilometers) in sizeapproximately the size of the City of ...
Cached Biology News:Inhibiting proteins may prevent cartilage breakdown in arthritis patients 2NJIT to host major biomedical engineering showcase and career fair 2Wildlife Conservation Society helps Cameroon create new national park 2Wildlife Conservation Society helps Cameroon create new national park 3
Other biology definitionOther Tags