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MEMORY (1).pptx


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MEMORY (1).pptx

  2. 2. • Higher mental function • Involvement of limbic system, higher cortex and cerebellum • Memory laid down in stages • Memory is generally stored as concepts not verbatim (word by word)
  3. 3. The Holistic Theory Of Thoughts A thought results from a “pattern” of stimulation of many parts of the nervous system at the same time, involving the cerebral cortex, thalamus, limbic system, and upper reticular formation of the brain stem. means that the whole is greater than the sum of its parts Nature of thought Pleasant or unpleasant Associated with memory
  4. 4. • Thoughts are mental cognitions—our ideas, opinions, and beliefs about ourselves and the world around us. ... • Shaped by life experiences, genetics, and education • Generally under conscious control. • In other words, if you are aware of your thoughts and attitudes, you can choose to change them. • Thoughts can be consolidated into memories
  5. 5. Learning: Acquisition of knowledge or skills. It alters the behavior of a person on the basis of past experience Memory: Acquisition, storage and retrieval of information for later recall. Memory Trace: Neural change responsible for retention or storage of knowledge
  6. 6. Consolidation The process of transferring and fixing short-term memory traces into long term memory stores Storage (encoding) Process by which information is converted into ‘usable’ form to be stored in brain Retrieval (decoding) Process of remembering the stored information Forgetting Inability to retrieve the stored information
  7. 7. When an established memory is actively recalled, it becomes labile (unstable or subject to change) and must be re-consolidated into a re-stabilized, inactive state. New information may be incorporated into the old memory trace during reconsolidation
  8. 8. BASIS OF MEMORY- SYNAPSE/ SYNAPTICE TRANSMISSION Memories are stored in the brain by changing the basic sensitivity of synaptic transmission between neurons as a result of previous neural activity. The new or facilitated pathways are called memory traces Positive and Negative Memory “Sensitization” or “Habituation” of Synaptic Transmission
  10. 10. Habituation is negative memory i.e. brain has the capability to ignore information that is of no consequence (neither rewarding or punishing). This capability results from inhibition of the synaptic pathways for this type of information Sensitization is positive memory i.e. for incoming information that causes important consequences such as pain or pleasure, the brain has a different automatic capability of enhancing and storing the memory traces, which is positive memory. It results from facilitation of the synaptic pathways
  11. 11. Based on duration • Short term memory For seconds or minutes • Intermediate long term memory For days to weeks but fades away • Long term memory For years or even life time
  12. 12. Declarative memory (what) Involves awareness or consciousness • Episodic memory memory of events & objects etc • Semantic memory memory of words, language, education etc Nondeclarative memory/ Skill (How) • Does not involve awareness • Learning to use keyboard, cycling, acrobatics etc
  13. 13. /SKILL /Recognition
  15. 15. SHORT TERM • Circuit of reverberating neurons • Presynaptic facilitation or inhibition INTERMEDIATE-LONG • Habituation • Facilitation LONG TERM • Structural changes in synapse • Long term potentiation & depression (LTP & LTD) • Rehearsal/ consolidation
  16. 16. SHORT TERM MEMORY • For a few seconds to a few minutes at a time but lasting only as long as the person continues to think about the numbers or facts • Continual neural activity resulting from nerve signals that travel around and around a temporary memory trace in a circuit of reverberating neurons • Presynaptic facilitation or inhibition Working memory “the erasable blackboard of the mind” temporarily holds and interrelates various pieces of information relevant to a current mental task
  17. 17. • A type of short term memory • Stored in prefrontal association area • New & stored information is brought into working memory for analysis/integration • Important for current mental task • Reasoning, planning, judgment, multiple tasking at one time etc • Correlates with intelligence • More the working memory more intelligent and efficient is the person • Affected by stress
  18. 18. Reverberating circuit -memory trace
  19. 19. Short term memory Can be enhanced by • Attention/concentration • Chunking • Association • Mnemonics
  20. 20. Chunking • Grouping the related information into ‘chunks’ • For example, chunking the phone numbers • Ideal size for each ‘chunk’ is 3 • Basis for making good presentations
  21. 21. INTERMEDIATE-LONG TERM MEMORY • Temporary chemical or physical changes, or both, in either the synapse presynaptic terminals or the synapse postsynaptic membrane, changes that can persist for a few minutes up to several weeks • When the sensory terminal is stimulated repeatedly but without stimulation of the facilitator terminal, signal transmission at first is great, but it becomes less and less intense with repeated stimulation until transmission almost ceases. This phenomenon is habituation
  22. 22. • If a noxious stimulus excites the facilitator terminal at the same time that the sensory terminal is stimulated, instead of the transmitted signal into the postsynaptic neuron becoming progressively weaker, the ease of transmission becomes stronger and stronger. • It will remain strong for minutes, hours, days, or, with more intense training, up to about 3 weeks • Even the noxious stimulus causes the memory pathway through the sensory terminal to become facilitated for days or weeks thereafter
  23. 23. Mechanism of facilitation (sensitization) 1.Release of serotonin from facilitator terminal 2.Activation of adenyl cyclase in sensory terminal 3.Formation of cAMP 4.Activation of protein kinase 5.Phosphorylation (blockage) of K+ Channels 6.Rise in intracellular voltage 7.Prolonged opening of Ca++channels 8.Enhanced Ca++entry in sensory terminal 9.Increased neurotransmitter release
  25. 25. Mechanisms involved • Physical and structural changes in neurons- synaptic plasticity • Increase in vesicle release sites • Increase in number of transmitter vesicles released • Increase in number of presynaptic terminals • Changes in structures of the dendritic spines that permit transmission of stronger signals • Long term potentiation (LTP) and depression (LTD) • Consolidation
  26. 26. Formation of new dendritic spines and synapses
  27. 27. Synaptic Plasticity • Ability of synapses to undergo structural and/or physical changes in response to sensory input • Leads to change in synaptic strength (post synaptic response) • Follows ‘use it or loose it’ phenomenon • A process that underlies learning & memory Enhancing your abilities is in your own hands because you can increase or decrease the effectiveness of synapses which are the locus of learning and memory
  28. 28. The following important structural changes occur: 1. An increase in vesicle release sites for secretion of transmitter substance 2. An increase in the number of transmitter vesicles released 3. An increase in the number of presynaptic terminals 4. Changes in structures of the dendritic spines tha permit transmission of stronger signals Thus, in several different ways, the structural capability of synapses to transmit signals appears to increase during establishment of true long- term memory traces
  29. 29. LONG TERM POTENTIATION (LTP) • Modifications take place as a result of increased use at a given preexisting synapse that enhance the future ability of the presynaptic neuron to excite the postsynaptic neuron. • This connection gets stronger the more often it is used • Prolonged increase in strength of existing synapse in response to high frequency stimuli • Can last for days or weeks (long enough for short term memory to be consolidated) • Especially prevalent in hippocampus • Consolidates short term memory into long term
  30. 30. AMPA NMDA
  31. 31. Glutamate from pre synaptic terminal AMDA receptor activation Na+ entry into post synaptic terminal Depolarization, EPSP generation Increased EPSP moves Mg +2 out of NMDA receptor channel Ca+2 enter post synaptic terminal
  32. 32. Activates second messenger system which has 2 effects: • Upregulates AMPA receptors on postsynaptic membrane • Releases retrograde paracrine (NO) which enhances glutamate release from presynaptic terminal
  33. 33. Long term potentiation- Mechanism • High levels of Ca+2 in post synaptic neuron • Role of NMDA and AMPA receptors in postsynaptic membrane • Activation of CaMKII (Ca+2-calmodulin dependent kinase II)
  34. 34. Long term depression (opposite to LTP) • Prolonged decrease in strength of existing synapse in response to low frequency stimuli • Can last for days or weeks • Leads to negative memory
  35. 35. Low levels of Ca+2 • Activation of phosphatase (instead of CaMKII) • Dephosphorylation & closure of AMPA receptors • Decreased number of AMPA receptors • Decreased synaptic strength
  36. 36. CONSOLIDATION of memory (declarative) • Process by which short term memory is converted into long term memory • Hippocampus consolidates short term memory into long term • Time required 5 to 10 minutes for minimum consolidation 1 hour for strong consolidation
  37. 37. Factors affecting consolidation • Rehearsal • Factors decreasing brain alertness Drowsiness Depression/low mood • Lack of interest • Disorganized knowledge acquisition • Brain concussion
  38. 38. Codification process • Comparison of new information for differences with the similar kind of stored memory • Only the differences (new files) are stored • New information is stored with similar kind of old memory
  39. 39. • Active & attentive mind consolidates in a better way • Natural tendency of brain to rehearse the new information (LPT in hippocampus) • Consolidation weakens when feeling drowsy (caution for students)
  40. 40. HIPPOCAMPUS Part of limbic system • Located on medial side of temporal lobe • Stores new memories temporarily • Consolidate new (short term memories) into long term memories • In hippocampal lesion consolidation can’t occur
  41. 41. Brain Areas Involved In Memory • No single ‘memory center’ • Many areas involved • Hippocampus, amygdala, other parts of limbic system, cerebellum, prefrontal cortex, association areas Working memory Prefrontal cortex in frontal lobe Short term memory/intermediate long term Hippocampus, para hippocampus in medial temporal lobe
  42. 42. Long term memory Association areas of cerebral cortex (act like hard disk of computer) Procedural memory Motor cortex, cerebellum, basal ganglia
  43. 43. AMNESIA -LOSS OF MEMORY (DECLARATIVE) • Anterograde amnesia Failure to establish new long term memories Lesion in hippocampus (required to convert short term memories into long term ones) • No capability for storing verbal and symbolic types of memories (declarative types of memory) in long-term memory or even in intermediate memory lasting longer than a few minutes
  44. 44. Retrograde amnesia • Failure to recall past long term memories • Lesion in hippocampus & thalamus • Thalamus works like ‘windows search’ • Some degree of retrograde amnesia occurs along with anterograde amnesia, which suggests that these two types of amnesia are at least partially related and that hippocampal lesions can cause both
  45. 45. Skill memory not affected in hippocampus lesion