Memory
It is a retention of: ·learned associations ·stored information ·skills
Basic Memory Processes
1.encoding: a)visual codes b)acoustic codes c)semantic codes d)the dual-coding theory suggests that information is remembered better when it is represented in both a visual and semantic code
2.storage: a) sense organ memory b) short term memory c) long term memory:
i)episodic (memories of specific events)
ii)procedural (the memory of how to do things)
iii)semantic (generalized knowledge about the world)
3.retrieval: a)recall b)recognition
Explicit and Implicit memory:
·explicit memory are the processes through which people try to remember something, such as details of ones last holiday - you have subjective temporal awareness of the information ·relies on the medial temporal lobes ·implicit memory is the unintentional recollection and influence of prior experiences. It operates automatically and without conscious effort – you have no awareness of the source ·relies on cerebellum, amygdala ·learning usually requires repetition ·learnt relatively slowly
The Three Levels of Memory
1. Sensory memory: ·allows comparison of stimulus with LTM to assign significance. -echoic (auditory) or iconic (visual) -fade/ loss time about 0.5 secs
2. Short-term (primary/ working) memory:
·item entering STM will be lost in about 18 seconds (Brown-Peterson procedure) unless rehearsal/ repetition which is typically verbal ·conscious of store contents ·capacity of about 7 ± 2 items ·can increase by chunking of information to allow one entry to cover several items ·chunking by imposing meaning or rule ·may be several subsystems: -recent auditory input -recent visual input -recent speech/ motor output etc. ·verbal in left hemisphere ·visual in right hemisphere ·information coded visually fades more quickly ·transfer of selected STM contents to LTM, remainder lost ·retrieval is effortless and error free
·affected by: ·primacy ·latency
·serial position – items in the middle of a list are more likely to be lost
3. Long-term (secondary memory)
·not conscious of store ·may be limitations on retrieval i.e. ‘available’ but not ‘accessible’ ·requires consolidation: once information is stored in LTM, it must be left undisturbed for a few minutes ·may be speeding by caffeine ·major disruption (ECT/ head injury) induces retrograde amnesia ·coding is mainly visual, semantic, acoustic ·information stored systematically irrespective of presentation:
1.Declarative memory (explicit): a)lexical memory: own stored vocabulary b)episodic memory: events c)semantic memory: facts
2.Procedural memory (implicit): a)motor skills b)perceptual skills c)intuitive cognitive skills
3.Perceptual Representation System (PRS): a)perceptual identification of objects and perceptual priming i.e. the enhancement of such identification through experience e.g. recognizing a style of painting
Retrieval
·recall appears to be organized according to applied strategies such as semantic clustering ·recognition alone indicates storage but incomplete retrieval i.e. bypass retrieval ·in learning word lists, mnemonic devices include forming new associations to words ·several associations to each word appear to enhance learning/ retrieval ·when a person’s internal state can aid or impede retrieval, memory is called state-dependent ·when memory can be helped or hindered by similarities in environmental context, it is termed context-dependent
Models of memory
Dual memory theory
·Atkinson and Shifferin (1971)
·information enters STM and is maintained by rehearsal, or lost by displacement
·information is transferred through the rehearsal buffer to LTM
Levels-of-Processing theory - Craik and Lockhart (1972)
·an item entering memory system is analyzed in the three stages:
1.perceptual level
2.phonetic level
3.semantic level
·each level of processing leaves a memory trace, and the deeper the level of processing the stronger the trace and the more durable the memory
·it can be aided by:
·Maintenance rehearsal – simply repeating an item over and over
·Elaborative rehearsal – involves thinking about how new material relates to information already stored in memory
·memory is enhanced more by elaborative rather than maintenance rehearsal
Transfer-Appropriate Processing
·suggests that the critical determinant of memory is how the encoding process matches up with what is ultimately retrieved. e.g. students do better at MCQ exams if they studied for an MCQ exam
Parallel Distributed Processing
·suggests that new experiences change people’s overall knowledge base, and every unit of knowledge is ultimately connected with every other unit
·the connections become stronger as they are experienced together more frequently
Information Processing
·suggested that in order for information to become firmly embedded in memory, it must pass through three stages of mental processing:
1.sensory memory 2.short-term memory 3.long-term memory
Long-term potentiation (LTP)
·the long-lasting increase in the efficiency of a single set of synapses
·postulated that it could be the substrate for associative learning
·depends on the activation of NMDA receptors in the hippocampus
Constructive memory
·is often used for complex material
·memory is not a tape recorder - we actively process information to understand it
·inferences are drawn and added to the story
·social stereotypes are used
·we tend to fit information to our existing schemata
·information which does not fit is either discarded or distorted and constructed to fit
Forgetting
·rapid loss of most acquired material initially
·two hypotheses:
1.interference theory:
·forgetting is determined by activity between learning and recall ·forgetting is item dependent - a piece of information may actually displace other information, or a piece of information makes storing or recalling other information more difficult ·new information learned in interim period impairs recall ·in the case of short-term memory, rehearsal prevents displacement by continually re-entering the same information into short-term memory
·retroactive interference: ·the learning of new material can interfere with the recall of older information
·proactive interference: ·old learning likely to impair (rather than facilitate) subsequent learning
·primacy effect: first words learned are retained better, as they have already entered LTM
·latency effect: last words learned are remembered better if tested immediately after presentation, since they are still retained in STM
It is a retention of: ·learned associations ·stored information ·skills
Basic Memory Processes
1.encoding: a)visual codes b)acoustic codes c)semantic codes d)the dual-coding theory suggests that information is remembered better when it is represented in both a visual and semantic code
2.storage: a) sense organ memory b) short term memory c) long term memory:
i)episodic (memories of specific events)
ii)procedural (the memory of how to do things)
iii)semantic (generalized knowledge about the world)
3.retrieval: a)recall b)recognition
Explicit and Implicit memory:
·explicit memory are the processes through which people try to remember something, such as details of ones last holiday - you have subjective temporal awareness of the information ·relies on the medial temporal lobes ·implicit memory is the unintentional recollection and influence of prior experiences. It operates automatically and without conscious effort – you have no awareness of the source ·relies on cerebellum, amygdala ·learning usually requires repetition ·learnt relatively slowly
The Three Levels of Memory
1. Sensory memory: ·allows comparison of stimulus with LTM to assign significance. -echoic (auditory) or iconic (visual) -fade/ loss time about 0.5 secs
2. Short-term (primary/ working) memory:
·item entering STM will be lost in about 18 seconds (Brown-Peterson procedure) unless rehearsal/ repetition which is typically verbal ·conscious of store contents ·capacity of about 7 ± 2 items ·can increase by chunking of information to allow one entry to cover several items ·chunking by imposing meaning or rule ·may be several subsystems: -recent auditory input -recent visual input -recent speech/ motor output etc. ·verbal in left hemisphere ·visual in right hemisphere ·information coded visually fades more quickly ·transfer of selected STM contents to LTM, remainder lost ·retrieval is effortless and error free
·affected by: ·primacy ·latency
·serial position – items in the middle of a list are more likely to be lost
3. Long-term (secondary memory)
·not conscious of store ·may be limitations on retrieval i.e. ‘available’ but not ‘accessible’ ·requires consolidation: once information is stored in LTM, it must be left undisturbed for a few minutes ·may be speeding by caffeine ·major disruption (ECT/ head injury) induces retrograde amnesia ·coding is mainly visual, semantic, acoustic ·information stored systematically irrespective of presentation:
1.Declarative memory (explicit): a)lexical memory: own stored vocabulary b)episodic memory: events c)semantic memory: facts
2.Procedural memory (implicit): a)motor skills b)perceptual skills c)intuitive cognitive skills
3.Perceptual Representation System (PRS): a)perceptual identification of objects and perceptual priming i.e. the enhancement of such identification through experience e.g. recognizing a style of painting
Retrieval
·recall appears to be organized according to applied strategies such as semantic clustering ·recognition alone indicates storage but incomplete retrieval i.e. bypass retrieval ·in learning word lists, mnemonic devices include forming new associations to words ·several associations to each word appear to enhance learning/ retrieval ·when a person’s internal state can aid or impede retrieval, memory is called state-dependent ·when memory can be helped or hindered by similarities in environmental context, it is termed context-dependent
Models of memory
Dual memory theory
·Atkinson and Shifferin (1971)
·information enters STM and is maintained by rehearsal, or lost by displacement
·information is transferred through the rehearsal buffer to LTM
Levels-of-Processing theory - Craik and Lockhart (1972)
·an item entering memory system is analyzed in the three stages:
1.perceptual level
2.phonetic level
3.semantic level
·each level of processing leaves a memory trace, and the deeper the level of processing the stronger the trace and the more durable the memory
·it can be aided by:
·Maintenance rehearsal – simply repeating an item over and over
·Elaborative rehearsal – involves thinking about how new material relates to information already stored in memory
·memory is enhanced more by elaborative rather than maintenance rehearsal
Transfer-Appropriate Processing
·suggests that the critical determinant of memory is how the encoding process matches up with what is ultimately retrieved. e.g. students do better at MCQ exams if they studied for an MCQ exam
Parallel Distributed Processing
·suggests that new experiences change people’s overall knowledge base, and every unit of knowledge is ultimately connected with every other unit
·the connections become stronger as they are experienced together more frequently
Information Processing
·suggested that in order for information to become firmly embedded in memory, it must pass through three stages of mental processing:
1.sensory memory 2.short-term memory 3.long-term memory
Long-term potentiation (LTP)
·the long-lasting increase in the efficiency of a single set of synapses
·postulated that it could be the substrate for associative learning
·depends on the activation of NMDA receptors in the hippocampus
Constructive memory
·is often used for complex material
·memory is not a tape recorder - we actively process information to understand it
·inferences are drawn and added to the story
·social stereotypes are used
·we tend to fit information to our existing schemata
·information which does not fit is either discarded or distorted and constructed to fit
Forgetting
·rapid loss of most acquired material initially
·two hypotheses:
1.interference theory:
·forgetting is determined by activity between learning and recall ·forgetting is item dependent - a piece of information may actually displace other information, or a piece of information makes storing or recalling other information more difficult ·new information learned in interim period impairs recall ·in the case of short-term memory, rehearsal prevents displacement by continually re-entering the same information into short-term memory
·retroactive interference: ·the learning of new material can interfere with the recall of older information
·proactive interference: ·old learning likely to impair (rather than facilitate) subsequent learning
·primacy effect: first words learned are retained better, as they have already entered LTM
·latency effect: last words learned are remembered better if tested immediately after presentation, since they are still retained in STM
2.decay theory: ·forgetting is time dependent ·BZDs taken after learning a word list improve its subsequent recall, perhaps by partly suppressing registration of new information ·repression as motivated forgetting is intuitively plausible but difficult to demonstrate
The neurophysiology of memory
Short term memory ·depends on electrical activity of neurons and functional alteration in synapses ·continuing activity hypothesis ·dynamic engram: a closed network of neurons corresponding to a single memory trace
Long term memory ·interneural hypothesis: ·results from structural changes of the neural circuit: ·increased neuroglial cells ·more branching of dendrites ·changes in synapses ·structural changes lead to formation of a structural engram ·intraneural hypothesis: ·postulates that invidividual memories are embodied in individual coded macromolecules (peptides, RNA)
·limbic system is essential for LTM: ·anterior cingulate gyrus ·hippocampus ·septal nuclei ·hypothalamus ·non-specific thalamic nuclei ·anterior thalamic nucleus ·amygdaloid nucleus ·mammillary bodies ·hippocampus: ·bilateral damage results in anterograde amnesia ·damage to posterior hypothalamus, mammillary bodies and terminal portions of fornices give rise to Korsakoff type of memory deficit ·neocortex: ·learning and memory functions are diffuse in many areas of cortex ·memory impairment depends on amount of tissue destroyed rather than its site
Neurochemistry of memory
Cholinergic system
·medial septum and diagonal band of broca project to the hippocampus ·nucleus basalis of Meynert projects to the amygdala and widely to the neocortex ·basal forebrain lesion can cause amnesia; 3 clinical syndromes:
1.Alzheimer’s disease
2.Korsakoff’s disease
3.amnesia with anterior communicating artery aneurysm
·the anticholinergic drug HYOSCINE causes amnesia
·cholinergic agonists such as ARECHOLINE, PYSOSTIGMINE, CHOLINE, and LECITHIN have been reported to improve memory
Adrenergic system
·decrease in MPHG in CSF of Korsakoff’s syndrome (McEntee and Mair, 1978) ·neuronal loss in locus coeruleus in Alzheimer’s disease ·enhancement of LTM when NA was applied to hippocampus
Serotinergic system
·ACh release is under inhibitory 5-HT tone ·5-HT inhibition or destruction of 5-HT cells increases ACh release in cortex, hippocampus and striatum ·m-chlorophenylpiperazine (mCPP), a 5-HT1C agonist impairs cognition ·ONDANSETRON, a selective 5-HT3 receptor antagonist improves cognition in animals
Opioid peptides
·high concentration in the limbic system ·enkephalins and endorphins interfere with memory formation when the experience is associated with a painful stimulus - they decrease the emotional component of the painful experience associated with learning
Ribonucleic acid (RNA)
·implicated in memory transfer ·interference with RNA synthesis impedes learning; facilitation of synthesis enhances learning
Amnesic syndrome (anterograde amnesia)
·due to two possibilities:
1.inability to transfer from STM to LTM; able to retrieve from LTM but no new memories; can show intact STM in digit span
2.retrieval deficit rather than encoding problem
Reconstructive memory
·demonstration that eye-witness accounts distorted by biased questioning ·serial reproductions of narrative show shortening and more coherent with elision of detail ·episodic memory shows effort after meaning.
The neurophysiology of memory
Short term memory ·depends on electrical activity of neurons and functional alteration in synapses ·continuing activity hypothesis ·dynamic engram: a closed network of neurons corresponding to a single memory trace
Long term memory ·interneural hypothesis: ·results from structural changes of the neural circuit: ·increased neuroglial cells ·more branching of dendrites ·changes in synapses ·structural changes lead to formation of a structural engram ·intraneural hypothesis: ·postulates that invidividual memories are embodied in individual coded macromolecules (peptides, RNA)
·limbic system is essential for LTM: ·anterior cingulate gyrus ·hippocampus ·septal nuclei ·hypothalamus ·non-specific thalamic nuclei ·anterior thalamic nucleus ·amygdaloid nucleus ·mammillary bodies ·hippocampus: ·bilateral damage results in anterograde amnesia ·damage to posterior hypothalamus, mammillary bodies and terminal portions of fornices give rise to Korsakoff type of memory deficit ·neocortex: ·learning and memory functions are diffuse in many areas of cortex ·memory impairment depends on amount of tissue destroyed rather than its site
Neurochemistry of memory
Cholinergic system
·medial septum and diagonal band of broca project to the hippocampus ·nucleus basalis of Meynert projects to the amygdala and widely to the neocortex ·basal forebrain lesion can cause amnesia; 3 clinical syndromes:
1.Alzheimer’s disease
2.Korsakoff’s disease
3.amnesia with anterior communicating artery aneurysm
·the anticholinergic drug HYOSCINE causes amnesia
·cholinergic agonists such as ARECHOLINE, PYSOSTIGMINE, CHOLINE, and LECITHIN have been reported to improve memory
Adrenergic system
·decrease in MPHG in CSF of Korsakoff’s syndrome (McEntee and Mair, 1978) ·neuronal loss in locus coeruleus in Alzheimer’s disease ·enhancement of LTM when NA was applied to hippocampus
Serotinergic system
·ACh release is under inhibitory 5-HT tone ·5-HT inhibition or destruction of 5-HT cells increases ACh release in cortex, hippocampus and striatum ·m-chlorophenylpiperazine (mCPP), a 5-HT1C agonist impairs cognition ·ONDANSETRON, a selective 5-HT3 receptor antagonist improves cognition in animals
Opioid peptides
·high concentration in the limbic system ·enkephalins and endorphins interfere with memory formation when the experience is associated with a painful stimulus - they decrease the emotional component of the painful experience associated with learning
Ribonucleic acid (RNA)
·implicated in memory transfer ·interference with RNA synthesis impedes learning; facilitation of synthesis enhances learning
Amnesic syndrome (anterograde amnesia)
·due to two possibilities:
1.inability to transfer from STM to LTM; able to retrieve from LTM but no new memories; can show intact STM in digit span
2.retrieval deficit rather than encoding problem
Reconstructive memory
·demonstration that eye-witness accounts distorted by biased questioning ·serial reproductions of narrative show shortening and more coherent with elision of detail ·episodic memory shows effort after meaning.
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