BIOLOGY AND PSYCHOLOGY OF MEMORY


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Khushbu    on Jul 25, 2012 Says :

very informative regarding memory system of human body
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1 : PSYCHOLOGY AND BIOLOGY OF MEMORY Presenter: Dr.Damodar Chairperson: Ms. S.Malarmathi
2 : Memory Memory is the process that allows individual to store information for recall at a later time A process by which information is registered, retained in the brain, retrieved and recalled.
3 : INTRODUCTION Greek -merimna(care, thought) Anglo-Fr. Memorie , mind, memory, remembrance or record Latin memoria – faculty of remembering, memory, remembrance Ribot's Law of retrograde amnesia was hypothesized in 1881 by Théodule Ribot. It states that there is a time gradient in retrograde amnesia, so that recent memories are more likely to be lost than the more remote memories.
4 : Ivan Pavlov believed that conditioning strengthened connections between the CS center and UCS center in the brain Karl Lashley’s studies attempted to see if disrupting certain connections between cortical brain areas would disrupt abilities to learn associations.
5 : Found that learning and memory did not depend on connections across the cortex. Also found that learning did not depend on a single area of the cortex. Hermann Ebbinghuas was a German psychologist who pioneered the experimental study of memory, and is known for his discovery of the forgetting curve and the spacing effect. He was also the first person to describe the learning curve
6 : Memory Encoding the processing of information into the memory system Storage the retention of encoded information over time Retrieval process of getting information out of memory
7 : THEORIES ABOUT MEMORY Theories of General Memory Function Information Processing Theories Theory of Working Memory Levels of Processing Theory
8 : THEORY OF GENERAL MEMORY FUNCTIONS ENCODING Process of receiving sensory input & transforming it into a form, or code, which can be stored Active process Requires selective attention Other aspects of encoding: Elaboration: associating with other information visual imagery :adding richness to the material being remembered self-referent:To make personally relevant
9 : Encoding Aids Mnemonics Chunking organizing items into familiar, manageable units use of acronyms HOMES-Huron, Ontario, Michigan, Erie, Superior
10 : Encoding Aids Hierarchies Organization of knowledge under narrower concepts/headings Rehearsal conscious repetition of information
11 : STORAGE Process of actually putting coded information into memory Three stages of memory storage: sensory store: retains the sensory image for only a small part of a second short term memory (STM): lasts for about 20 to 30 seconds without rehearsal of the information long term memory: suggested to be permanent
12 : RETRIEVAL Process of gaining access to stored, coded information not a random process cues can help with retrieval context cues:Information that appers near a word or phrase and provide clue to its retrieval Mood:Memory is aided by providing same emotional state as was present at the acquisition phase memories are reconstructions (Bartlett, 1932)
13 : INFORMATION PROCESSING THEORIES The basic concept is that storage of memory is a multi step process Proposed by Richard Atkinson and Richard Shiffin in 1968 Commonly known as Multi store model / modal model / dual process model
14 : The Modal Memory System
15 : SENSORY REGISTER Earliest stage of memory sense organs have a limited ability to store information visual or iconic memory– 1 second, 11 to 16 items (George Sperling) auditory or echoic memory - 4 to 5 seconds (Dorwin et al) Haptic (touch) memory Most of the information is lost; simply decays from the register. Sensory memories act as a buffer for the stimuli received through senses. Information is passed from sensory memory into short-term memory by attention.
16 : SHORT TERM MEMORY Paying attention to sensory memories generates the information in STM In Freudian term it is called conscious memory and is created by our paying attention to external stimuli or internal thoughts or both. Peterson and Peterson (1959) - 15 to 30 seconds, unless people rehearse the material Miller (1956) - 7+ or -2 items can increase capacity by "chunking“ ie clumping several items into a chunk.
17 : mostly encodes memory acoustically, can also retain visuospatial images, can be at a semantic level. 2 major concepts for retaining information in STM: -organization -repetition
18 : Short term memory to Long term memory Serial positioning has a role: Primacy effect: first word gets rehearsed more and gets transferred to LTM Reccency effect: words at end are available in STM Rehearsal: Two types Mainatenance rehearsal Elaborative rehearsal
19 : LONG TERM MEMORY Freud: called it preconscious and unconscious memory Preconscious meaning information is easily available Unconscious because data is not available during normal consciousness. Varies from minutes to years And has virtually limitless capacity
20 : Long Term Memory
21 : THEORY OF WORKING MEMORY In 1974, Alan Baddeley and Graham Hitch proposed their triportite Working memory model as an alternative to the short term store in ‘Multi store’ memory model. The model is composed of 4 main component Central Executive: which acts as an supervisory system,& control flow of information to n from its slave systems. Slave Systems: The Phonological Loop Visuo-spatial sketchpad The Episodic Buffer
22 :
23 : Central Executive: Drives the whole system and allocates the data to multi system. It also deals with cognitive tasks such as mental arithmetic and problem solving. The Visuo-spatial sketchpad( aka the inner eye): Stores the information in visual or spatial form. The Phonological loop: deals with written and spoken material. Two types 1.Acoustic stores: deals with speech perception 2.Articulatory control process(acoustic loop): it is used to rehearse and store information from Phonological store.
24 : The Episodic Buffer: it is dedicated to linking information across domains to form intergrated units of verbal, spatial and visual information with time sequensing( chronological oredring). It is also believed to have links to LTM and sematic memory.
25 : LEVELS OF PROCESSING THEORY Proposed by Fergus I.M. Craik and Robert S. Lockhart in 1972. Reported that memory is just a byproduct of depth of information processing and there is no clear cut distinction between STM and LTM. Concentrates on processes involved in memory Non structured approach: memory is just what happens as a result of processing information
26 : Three ways of processing: Shallow processing- 2 forms 1.Structured processing(ie appearance): encodes on physical form of something 2.Phonemic processing: encodes the sounds Shallow processing involves only maintenance rehearsal and hence leads to very short term retention
27 : Deep Processing: This involves Semantic Processing- This happens when we encode the meaning of a word and relate it to similar word with similar meaning. Deep processing leads involves elaborative rehearsal of information and hence leads better recall.
28 : Biology of Memory Karl Lashley (1950) trained rats to solve maze, then cut out pieces of their cortex and retested their memory of maze partial memory retained
29 : Where Are Memories Stored?
30 : NEUROANATOMIC CORRELATES OF MEMORY In mammals, the first neurons observed to demonstrate LTP were found in the structures of the medial temporal lobe of the brain, including the hippocampus and surrounding regions. Other brain regions identified as important to declarative memory include the medial diencephalon, basal forebrain, prefrontal cortex, subcortical nuclei, and cerebral white matter pathways.
31 : Medial temporal lobes The temporal lobe is a large brain region with several anatomically distinct areas. The structures in the medial aspect of the temporal lobes, including the hippocampus, its surrounding cortex, and the amygdala, are most important for memory.
32 : Hippocampus and related structures The human hippocampus and associated cortices are located bilaterally in the cerebral hemispheres, Recent studies indicate that projections from area CA1 of the hippocampus to the subiculum and prefrontal cortex can express several forms of neuronal plasticity and probably play an important role in consolidating information into LTM
33 :
34 : THE HIPPOCAMPUS AND CONSOLIDATION- Scoville & Milner 1957, stated that Hippocampus and related structures have a role in memory consolidation and that memories are temporarily stored in Hippocampus until they can be transferred to more stable cortical system. Acc to another study by Nadel & Moscovitch, retained memories become more resistant to disruption by hippocampal damage because each time a similar experience occurs or the original memory is recalled, a new Engram( a change in the brain that stores memory) is established and linked to the original engram, making the memory easier to recall and original engram more difficult to disrupt.
35 : THEORIES OF HIPPOCAMPAL FUNCTION O’ keefe and Nadel- Hippocampus constructs and stores allocentric maps of the external world from the sensory input it receives. Allocentric refers to the representation of space based on relation among external objects and landmarks The Configural association theory- ( Rudy & Sunderland, 1992)- hippocampus plays role in the retention of behavioural significance of combination of stimuli but not to individual stimulus.
36 : Brown & Aggleton ,2001- concurred that rhinal cortex not hippocampus plays role in object recognition however hippocampus plays role in recognising spatial arrangement of object
37 : Amygdala It plays an important role in emotional and autonomic behaviors and has substantial interconnections with brain regions involved in memory consolidation (eg, hippocampal formation, thalamus, hypothalamus, prefrontal cortex, basal forebrain). Studies of nonhuman primates suggest that damage to the amygdala itself does not impair the ability to learn new information, provided the information is neutral in emotional valence
38 : Medial diencephalon The diencephalon is a region of several important nuclei located at the top of the brainstem. The regions important to memory functioning include portions of the thalamus and hypothalamus In particular, patients who have injuries involving the midline structures of these regions demonstrate severe anterograde amnesia and often demonstrate a temporally graded retrograde amnesia
39 :
40 : The structures most often implicated in diencephalic amnesia include the dorsomedial nucleus of the thalamus, the mamillary bodies of the hypothalamus, and the white matter (mamillothalamic) tract connecting these structures. Some animal studies have shown that the internal medullary lamina of the thalamus is also important to memory
41 : Basal forebrain The basal forebrain is located superior to the optic chiasm and includes the medial septal nuclei, nucleus accumbens, anterior hypothalamus, diagonal band of Broca, nucleus basalis of Meynert, and part of the prefrontal cortex.
42 : The septal nuclei and nucleus basalis of Meynert in particular, have extensive connections to and from the hippocampal formation, amygdala, and neocortex and are believed to be important to memory functioning . Basal forebrain neurons are rich in the neurotransmitter acetylcholine, which is important to memory functioning
43 : The prefrontal cortex Memory for temporal order of events. -working memory: ability to maintain relevant memories while a task is being completed. Therefore patient with PFC damage have difficulty in tasks that involve series of responses. while some areas of PFC perform fundamental cognitive processes during all working memory tasks some areas seem to mediate specific kind of working memory.
44 : Subcortical nuclei and white matter The ability to search and retrieve information from LTM. These observations come primarily from studies of patients who have basal ganglia diseases, such as Parkinson’s disease and Huntington’s disease, or white matter disorders, such as diffuse ischemic cerebrovascular disease and multiple sclerosis. Damage to subcortical nuclei or white matter is associated with slowed information processing, inefficient learning, and poor free recall
45 : Cerebellum & Striatum Explicit memories of experiences are presumed to be stored in the circuits of brain that mediated their original perception, while implicit memories of sensorimotor learning are presumed to be stored in sensorimotor circuits (Ohyama et al, 2003) Cerebellum is thought to store memories of learned sensorimotor skills
46 : Striatum- thought to store memories for consistent relationship between stimuli & responses- the type of memory that develop incrementally over many trials. This form of learning is known as habit formation.
47 : WORKING MEMORY DLPFC is considered important structure involved in working memory. Both simple maintenance of information over a delay and the manipulation of that information requires DLPFC function. DLPFC activation is usually observed in conjunction with the posterior cortical areas that receives input from variety of specialized sensory cortices. Most important among them is inferior parietal lobule – storing working memory
48 : SYNAPTIC MECHANISM OF MEMORY Hebbian synapse occurs when the successful stimulation of a cell by an axon leads to the enhanced ability to stimulate that cell in the future. Increases in effectiveness occur because of simultaneous activity in the presynaptic and postsynaptic neurons. Such synapses may be critical for many kinds of associative learning
49 : MEMORY AS CHANGE OF SYNAPTIC STRUCTURE AND EFFICACY A synapse is a functional juxtaposition of two or more neurons When a neuron is stimulated to a sufficient degree, neurotransmitters are released from the axon terminal into the microscopic space that separates it from neighboring neurons
50 : The presence of neurotransmitters within this region produces characteristic changes in the membranes of adjacent neurons. Memories are believed to be the result of structural and functional changes of neuronal activity and synaptic transmission in response to experience.
51 :
52 : Neuronal processes underlying short-term memory A neuron’s function can be modified by intense activity, such as high frequency stimulation by a presynaptic neuron. Such activity increases the responsiveness and efficiency of postsynaptic membranes, with some neurons being capable of increased responsiveness lasting from several minutes to more than an hour after active stimulation has ceased.
53 : This temporary increase in synaptic effectiveness is known as posttetanic potentiation (PTP) and reflects one possible way that newly presented information may be remembered PTP may cause neurons activated during learning to remain active for a brief time after learning has ceased, thus allowing a trace of that information to remain available for recall.
54 : Another proposed mechanism by which neuronal activity may be maintained for a brief period is by means of a feedback loop. Excitatory input entering a closed loop could be maintained after active input ceases if neurons within that loop are excitatory . Such neuronal feedback systems are known as reverberatory circuits . The time that elapses before information in STM degrades is believed to be a function of PTP strength or the level of neuronal excitement in reverberatory circuits. More intense changes in these neuronal dynamics typically are associated with more persistent memory, whereas weaker changes are associated with more rapid forgetting.
55 : Neuronal processes underlying long-term memory The ability to encode information into a more permanent long-term storage system is believed to be a function of long-term potentiation (LTP). LTP is similar to PTP, in that high-intensity stimulation increases the effectiveness of the neuronal synapse. LTP is more powerful and enduring than PTP, however, and cannot be produced by activation of only a single presynaptic neuron in a single pathway.
56 : Instead, a minimum number of inputs must be present to produce an effect. When neurons in the brain’s memory consolidation centers are activated by LTP, enzymes in the neuronal membrane are released and form a chemical messenger known as cyclic adenosine monophosphate (cAMP). This messenger activates specific proteins, including cAMP-response element binding protein, which promotes a synaptic growth process that strengthens the functional relationships among active neurons. These neuronal changes are believed to provide the biologic substrate for consolidation of information into LTM [21–23].
57 : MECHANISMS Three mechanisms: Induction of LTP( learning)- studies on NMDA receptor, 2 requirments- Glutamate must bind presynaptic neuron and postsynaptic neuron must be partially depolarized ?ca influx & AP? induction of LTP. This co-occurance is necessary to learn associations
58 : Maintenance & expression of LTP ( storage & Recall)- Mechanisms Only those synapses that are depolarised before the high frequency stimulation are involved in LTP The long term maintenance involves structural changes, which depends on protein synthesis Prysynaptic changes are involved in the maintenance & expression of LTP at synapses having NMDA receptors
59 : NO synthesised in the post synapticaly in response to ca influx diffuses back into terminal buttons of presynaptic neurons which is necessary for maintenance of LTP Structural changes occur at NMDA synapses in association with long lasting LTP Increase in no of synapses Increase in no & size of dendritic spines Increase in no of postsynaptic receptors
60 :
61 :
62 : NEURAL SYSTEMS IN DECLARATIVE MEMORY HF and linked regions in MTL in interaction with parts of Pre-frontal Cortex-episodic memory Engrams are stored in Neocortex HF with amygdala-emotional memories The HF consist of hippocampus proper, the entorhinal cortex-connection with the cortex
63 : NEURAL SYSTEMS IN IMPLICIT MEMORY Procedural memory Basal ganglia and cerebellum- procedural memory The time variant activation of primary & secondary motor cortex-skill learning Cerebellum- important in close loop tasks that require continuous visuomotor feedback as well as fast error control. also play role in new stimulus response mappings
64 : Basal ganglia receives excitatory glutaminergic projections from cortex and thalamus, integrate them with monoaminergic inputs and send them via globus pallidus and substantia nigra pars reticulate to thalamus, which projects it back to prefrontal cortex. These parallel processing loops are critical for integration of sensorimotor, cognitive and emotional information.
65 : NEUROPLASTICITY Refers to changes in neural pathways and synapses which are due to changes in behaviour, environment and neural processes, as well as changes resulting from bodily injury Neuroplasticity has replaced the formerly-held position that the brain is a physiologically static organ, and explores how - and in which ways - the brain changes throughout life
66 : Studies of how physiology relates to learning often focus on invertebrates and try to generalize to vertebrates. The aplysia is a slug-like invertebrate that is often studied due to its large neurons. This allows researchers to study basic processes such as: Habituation. Sensitization
67 : Habituation is a decrease in response to a stimulus that is presented repeatedly and accompanied by no change in other stimuli. Results in a change in the synapse between the sensory neurons and the motor neurons. Sensory neurons fail to excite motor neurons as they did previously
68 : Sensitization Is an increase in response to a mild stimulus as a result to previous exposure to a more intense stimulus. Changes at identified synapses include: Serotonin released from a facilitating neuron blocks potassium channels in a presynaptic neuron. Prolonged release of transmitter from that neuron results in prolonged
69 : Memory disorders in clinical populations Normal aging Studies confirm a strong negative relationship between age and performance on tests of learning and memory Alzheimer’s disease and mild cognitive Impairment Specifically, patients who have MCI and Alzheimer’s disease typically demonstrate poor retention and rapid forgetting of newly learned information which differs from the inefficient retrieval difficulties associated with normal aging
70 : Subcortical and white matter diseases Patients who have subcortical degenerative diseases or white matter disorders often display similar memory profiles. Early disease stages are characterized by poor delayed free recall, often at the same level of impairment as seen in patients who have Alzheimer’s disease of similar disease staging/severity.
71 : Frontal lobe dementia They typically occur within the context of poor planning, organization, attention, and mental flexibility. Ability to sustain attention is disturbed, and learning strategies are inefficient
72 : Amnesic Korsakoff syndrome Their ability to encode new information into LTM is severely impaired . Patients demonstrate equally poor free recall and recognition and at times ‘‘recall’’ information that was never presented, a phenomenon known as confabulation Depression Patients who have clinical depression frequently have impaired attention and STM, often secondary to vegetative signs
73 : Benzodiazepine Patients taking high dosages of benzodiazepine for long periods perform poorly on tasks requiring sustained attention and report improved concentration after discontinuation of the medication
74 : IMPLICATIONS Memory distortions One factor contributing to memory distortion is that similar brain regions are important for both visual imagery and long term storage. Eg dreaming about an event or imagining an event. Because of reconstructive nature of memory- eyewitness testimony is not reliable Screen memory-recollection that is partially true and partially false. We tend to remember only a part of true memory as the whole event is too painful
75 : Infantile amnesia The apparent absence of conscious memory for experiences from approx. 3 years of life. Traditional view Repression( psychoanalytical theory) Retrieval failure ( developmental psychology) Declarative memory doesn’t develop fully till the third year of life, whereas non declarative memory emerges early in life
76 : Although rudimentary capacity for declarative memory is present early in life , it is only memories represented become more complex, language abilities allow for more elaborate description of events, declarative memory becomes more organized and better interconnected with other information.
77 : SUMMARY Animal studies and observations of patients who have brain diseases show that memory is not a unitary factor but instead can be parsed into overlapping but dissociable constructs; that encoding, retention, and retrieval processes depend on the integrity of several distinct brain regions; and that the creation of new memories depends on structural and functional changes within the neuronal systems of those brain regions.
78 : Much remains to be learned, however, regarding the specific biologic, genetic, and information-processing mechanisms underlying many features of this complex cognitive construct. As this knowledge base grows, new and improved pharmacologic and behavioral treatments for patients who have memory disorders may be realized.
79 : FUTURE DIRECTIONS Genetic variation in BDNF has been shown to impact hippocampal function and episodic memory- risk for schizophrenia Risk genes for depression and anxiety may affect amygdala-cingulate and amygdala-hippocampal interactions that are important for fear extinction Memory impairment is important predictor for treatment especially in schizophrenia & neurorehabilitation programs to improve memory are being explored
80 : THANK YOU

 

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