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Neuroscience of Learning & memory


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learning and memory

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Neuroscience of Learning & memory

  1. 1. Learning & Memory
  2. 2. Learning • According to Eric Kandel “Learning is a process by which we acquire knowledge about the world” • Kimble “Learning refers to more or less permanent change in behaviour which occurs as a result of practice”
  3. 3. • Further definition says, “Learning is either a case of differential strengthening of one from a number of responses evoked by a situation of need or formation of receptor evoked connections”
  4. 4. What is Memory ? • According to Kandel “Memory is a process by which that knowledge of the world is encoded, stored and later retrieved”
  5. 5. Types of Memory Explicit Episodic Semantic Implicit Associative Classical eg: pavlov’s experiment Operant Eg: Pigeon pecks a key Non- associative Habituation Eg: Dog aroused by tone played Sensitization Eg: dog reacts to less tone
  6. 6. • Different forms of learning are affected differentially by lesions in different locations Defects in memory storage for object recognition
  7. 7. • Hippocampal system does initial steps in long term memory storage • Memories of single event can be stored in multiple locations • Each new explicit memory is formed by 4 sequential processes a) Encoding b) Consolidation c) Storage d) Retrieval
  8. 8. Implicit Memory • They are stored differently on how they are acquired • Operant conditioning involves the straitum and cerebellum • Classical, sensitization and habituation involves sensory and motor systems
  9. 9. Processes of Learning • Donald Hebb stated, “when a axon of cell A excites cell B and repeatedly or persistently takes part in firing it, some growth process of metabolic changes take place in one or both cells so that A’s efficiency as one of the cells firing B is increased”
  10. 10. Habituation •What happens in nervous system to produce habituation? •Experiments performed in Aplysia californica, the sea slug, were designed to address this problem
  11. 11. Sensitization
  12. 12. 1 • Axonic syanpse occurs • Serotonin (5 hydroxytryptamine) is released by pre and post synaptic axon • Activates G protein • Adenyl cyclase 2 • cAMP Produced • Activates cAMP dependent kinase • Close k channels • Opens ca channels 3 • Activation of 5HT pathway by tail stimulation , therefore causes more substance to be released by siphon stimulation • Leads to response by gills
  13. 13. • Short term tail stimulation • Long term tail stimulation • Structural changes occur in pre synaptic terminals
  14. 14. Long term potentiation • Hippocampus is important storage for declarative memory • High frequency train of stimuli applied to fibers afferent to hippocampus increase amplitude of EPSPs in target neuron • Pre and post synaptic cells both be active at same time
  15. 15. Experimental set up for demonstrating LTP Made Stimuli applied Amplitudes Of post synaptic Potentials For single stimulus Hebbs rule at work
  16. 16. Glutamate binds to metabotropic receptor, activating PLC and to NMDA receptors NMDA can bind glutamate but no current will flow through the channels unless Mg++ Is displaced
  17. 17. High frequency stimulation opens glutamate Non NMDA channels leading to hypopolarization. This dislodges Mg++ , Ca++ enters the cell. Calcium triggers activity of Ca dependent kinases. Calcium calmodulin kinase phosphorylates non NMDA channels increasing their sensitivity To glutamate and a messenger is sent to presyanptic terminal to increase the release of transmitter substance
  18. 18. References • Learning and Memory • Neurobiology linster • Learning and Memory by John H. Byrne, Ph.D., Department of Neurobiology and Anatomy, The UT Medical School at Houston