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Long-term memory

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Long-term memory

Contents

  • Taxonavigation 1
  • Name 2
  • References 3
  • Encoding of information 4
  • Dual-store memory model 5
    • Atkinson-Shiffrin memory model 5.1
    • Baddeley's model of working memory 5.2
  • Encoding of information 6
    • Sleep 6.1
  • Divisions of long term memory 7
    • Explicit memory 7.1
      • Episodic memory 7.1.1
      • Semantic memory 7.1.2
      • Autobiographical memory 7.1.3
    • Implicit memory 7.2
  • Taxonavigation 8
  • Name 9
  • References 10
  • Disorders of memory 11

Taxonavigation

Species: Hopea ponga

Name

Hopea ponga (Dennst.) Mabberley

References

  • http://www.iucnredlist.org/details/33470/0
  • http://www.biotik.org/india/species/h/hopepong/hopepong_en.html

Long-term memory (LTM) is the final stage of the dual memory model proposed by Atkinson and Shiffrin, in which data can be stored for long periods of time. While short-term and working memory persists for only about 20 to 30 seconds, information can remain in long term memory indefinitely.

According to Mazur (2006), long-term memory has also been called reference memory, because an individual must refer to the information in long-term memory when performing almost any task.

Long term memory is commonly broken down into explicit memory (declarative), which includes episodic memory,hose systems.[1][2] The slave systems include the phonological loop, the visuo-spatial sketchpad, and the episodic buffer (later added by Baddeley).[3]

Encoding of information

Long-term memory encodes information semantically for storage, as researched by Baddeley.[4] In vision, the information needs to enter working memory before it can be stored into long-term memory. This is evidenced by the fact that the speed with which information is stored into long-term memory is determined by the amount of information that can be fit, at each step, into visual working memory.[5] In other words, the larger the capacity of working memory for certain stimuli, the faster will these materials be learned.

Synaptic Consolidation is the process by which items are transferred from short term to long term memory. Within the first minutes or hours after acquisition, the engram (memory trace) is encoded within synapses, becoming resistant (though not immune) to interference from outside sources.[6][7]

As long-term memory is subject to fading in the Long-term memory (LTM) is the final stage of the dual memory model proposed by Atkinson and Shiffrin, in which data can be stored for long periods of time. While short-term and working memory persists for only about 20 to 30 seconds, information can remain in long term memory indefinitely.

According to Mazur (2006), long-term memory has also been called reference memory, because an individual must refer to the information in long-term memory when performing almost any task.

Long term memory is commonly broken down into explicit memory (declarative), which includes episodic memory, semantic memory, and autobiographical memory, and implicit memory (procedural memory).

Dual-store memory model

According to Miller, whose paper in 1956 popularized the theory of the "magic number seven", short-term memory is limited to a certain number of chunks of information, while long-term memory has a limitless store.[8]

Atkinson-Shiffrin memory model

According to the dual store memory model proposed by Richard C. Atkinson and Richard Shiffrin in 1968, memories can reside in the short-term "buffer" for a limited time while they are simultaneously strengthening their associations in long-term memory. When items are first presented, they enter short-term memory, but due to its limited space, as new items enter, older ones are pushed out. However, each time an item in short term memory is rehearsed, it is strengthened in long term memory. Similarly, the longer an item stays in short-term memory, the stronger its association becomes in long-term memory.[9]

Baddeley's model of working memory

In 1974 Baddeley and Hitch proposed an alternative theory of short term memory: Baddeley's model of working memory. According to this theory, short-term memory is divided into different slave systems for different types of input items, and there is an executive control supervising what items enter and exit those systems.[10][11] The slave systems include the phonological loop, the visuo-spatial sketchpad, and the episodic buffer (later added by Baddeley).[12]

Encoding of information

Long-term memory encodes information semantically for storage, as researched by Baddeley.[13] In vision, the information needs to enter working memory before it can be stored into long-term memory. This is evidenced by the fact that the speed with which information is stored into long-term memory is determined by the amount of information that can be fit, at each step, into visual working memory.[14] In other words, the larger the capacity of working memory for certain stimuli, the faster will these materials be learned.

Synaptic Consolidation is the process by which items are transferred from short term to long term memory. Within the first minutes or hours after acquisition, the engram (memory trace) is encoded within synapses, becoming resistant (though not immune) to interference from outside sources.[15][16]

As long-term memory is subject to fading in the natural maintenance rehearsal (several recalls/retrievals of memory) may be needed to preserve long term memories.[17] Individual retrievals can take place in increasing intervals in accordance with the principle of spaced repetition. This can happen quite naturally through reflection or deliberate recall (also known as recapitulation), often dependent on the perceived importance of the material.

Sleep

Some theories consider sleep and learning.) Sleep plays a key function in the consolidation of new memories.[18]

According to Tarnow's theory, long-term memories are stored in dream format (reminiscent of the Penfield & Rasmussen’s findings that electrical excitations of cortex give rise to experiences similar to dreams). During waking life an executive function interprets long-term memory consistent with reality checking (Tarnow 2003). It is further proposed in the theory that the information stored in memory, no matter how it was learned, can affect performance on a particular task without the subject being aware that this memory is being used. Newly acquired declarative memory traces are believed to be reactivated during NonREM sleep to promote their hippocampo-neocortical transfer for long-term storage.[19] Specifically new declarative memories are better remembered if recall follows Stage II non-rapid eye movement sleep. The reactivation of memories during sleep can lead to lasting synaptic changes within certain neural networks. It is the high spindle activity, low oscillation activity, and delta wave activity during NREM sleep that helps to contribute to declarative memory consolidation. In learning before sleep spindles are redistributed to neuronally active upstates within slow oscillations.[18] Sleep spindles are thought to induce synaptic changes and thereby contribute to memory consolidation during sleep. Here, we examined the role of sleep in the object-place recognition task, a task closely comparable to tasks typically applied for testing human declarative memory: It is a one-trial task, hippocampus-dependent, not stressful and can be repeated within the same animal.[20] Sleep deprivation reduces vigilance or arousal levels, affecting the efficiency of certain cognitive functions such as learning and memory.[21]

The theory that sleep benefits memory retention is not a new idea. It has been around since Ebbinghaus's experiment on forgetting in 1885. More recently studies have been done by Payne and colleagues and Holtz and colleagues.[22] In Payne and colleague's[23] experiment participants were randomly selected and split into two groups. Both groups were given semantically related or unrelated word pairs, but one group was given the information at 9am and the other group received theirs at 9pm. Participants were then tested on the word pairs at one of three intervals 30 minutes, 12 hours, or 24 hours later. It was found that participants who had a period of sleep between the learning and testing sessions did better on the memory tests. This information is similar to other results found by previous experiments by Jenkins and Dallenbach (1924). It has also been found that many domains of declarative memory are affected by sleep such as emotional memory, semantic memory, and direct encoding.[23]

Holtz[22] found that not only does sleep affect consolidation of declarative memories, but also procedural memories. In this experiment fifty adolescent participants were taught either word pairs (which represents declarative memory) and a finger taping task(procedural memory) at one of two different times of day. What they found was that the procedural finger taping task was best encoded and remembered directly before sleep, but the declarative word pairs task was better remembered and encoded if learned at 3 in the afternoon.[22]

Divisions of long term memory

The brain does not store memories in one unified structure, as might be seen in a computer's hard disk drive. Instead, different types of memory are stored in different regions of the brain. Long term memory is typically divided up into two major headings: explicit memory and implicit memory.[9]

Explicit memory

Explicit memory (declarative memory) refers to all memories that are consciously available. These are encoded by the hippocampus, entorhinal cortex, and perirhinal cortex, but consolidated and stored elsewhere. The precise location of storage is unknown, but the temporal cortex has been proposed as a likely candidate. Research by Meulemans and Van der Linden (2003) found that amnesiac patients with damage to the medial temporal lobe performed more poorly on explicit learning tests than did healthy controls. However, these same amnesiac patients performed at the same rate as healthy controls on implicit learning tests. This implies that the medial temporal lobe is heavily involved in explicit learning, but not in implicit learning.[24][25]

Declarative memory has three major subdivisions:

Episodic memory

Episodic memory refers to memory for specific events in time, as well as supporting their formation and retrieval. Some examples of episodic memory would be remembering someone's name and what happened at your last interaction with each other.[26][27] Experiments conducted by Spaniol and colleagues indicated that older adults have worse episodic memories than younger adults because episodic memory requires context dependent memory.[28]

Semantic memory

Semantic memory refers to knowledge about factual information, such as the meaning of words. Semantic memory is independent information such as information remembered for a test.[27] In contrast with episodic memory, older adults and younger adults do not show much of a difference in semantic memory, presumably because semantic memory does not depend on context memory.[28]

Autobiographical memory

Autobiographical memory refers to knowledge about events and personal experiences from an individual's own life. Though similar to episodic memory, it differs in that it contains only those experience which directly pertain to the individual, from across his lifespan. Conway and Pleydell-Pearce (2000) argue that this is one component of the self-memory system.[29]

Implicit memory

Implicit memory (procedural memory) refers to the use of objects or movements of the body, such as how exactly to use a pencil, drive a car, or ride a bicycle. This type of memory is encoded and it is presumed stored by the striatum and other parts of the basal ganglia. The basal ganglia is believed to mediate procedural memory and other brain structures and is largely independent of the hippocampus.[30] Research by Manelis, Hanson, and Hanson (2011) found that the reactivation of the parietal and occipital regions was associated with implicit memory.[31] Procedural memory is considered non-declarative memory or unconscious memory which includes priming and non-associative learning.[27][32]

Other categories of memory may also be relevant to the discussion of long term memory. For example:

Emotional memory, the memory for events t

Taxonavigation

Species: Hopea ponga

Name

Hopea ponga (Dennst.) Mabberley

References

  • http://www.iucnredlist.org/details/33470/0
  • http://www.biotik.org/india/species/h/hopepong/hopepong_en.html
active during emotional situations, and acts with the hippocampus and prefrontal cortex in the encoding and consolidation of emotional events.[33][34]

Minor everyday slips and lapses of memory are f

Disorders of memory

[36][35]

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