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Memory

Memory. Chapter 19 Amanda Salcido. William Scoville. Conducted an operation on HM Problem with HM Experienced epileptic seizures cense the age of ten By the age of 29 epileptic seizures become more severe and more frequent Operation removed parts of the temporal lobes Hippocampus

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Memory

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  1. Memory Chapter 19 Amanda Salcido

  2. William Scoville • Conducted an operation on HM • Problem with HM • Experienced epileptic seizures cense the age of ten • By the age of 29 epileptic seizures become more severe and more frequent • Operation removed parts of • the temporal lobes • Hippocampus • Amygdale • Adjacent areas of the cerebral cortex

  3. Results of HM surgery • Less severe and infrequent seizures • Improved intellectual ability • Anterograde amnesia • No longer recognize hospital staff • Could no longer find his way around • Partial retrograde amnesia

  4. What was derived from HM and others • There is a relationship between the amount of hippocampus and hippocampus gyrus is removed to the amount of memory less • The hippocampus is important for storing new memories • Memories are not stored in the hippocampus • Other brain structures are involved

  5. Long-term Short-term Implicit Procedural Explicit Episodic Semantic Topographic Memory

  6. Topographic memory • John O’Keefe- recorded the activity of nerve cells in the hippocampus of rats as they moved around an enclosure • Humans and monkeys- lesions in the posterior parietal cortex causes problems with orientating our selves in space

  7. Short-term memory in the brain • Short-term memory is necessary to move information into long term memory • Prefrontal cortex- part of the frontal lobe that lies in front of the area concerned with movement and speech

  8. University of California • Joaquin Fuster and colleagues • experiment on monkeys remembering the location of hidden objects • end result • prefrontal cortex contains separate processing mechanisms for remembering ‘what’ and ‘where’ an object is

  9. How memory works • Depends on specific changes in synaptic effectiveness • First experiment was in the 1970s • a marine snail Aplysia californica

  10. Experiment results • Touching the siphon causes withdrawal of the gill • Repeated touches • Habituation • Decrease in the amount of transmitters released by sensory cells at there synapses with motor cells

  11. Results continued • Noxious stimuli applied to the head or tail + a harmless stimuli applied to the siphon • Sensitization • Modification of the number of synapses in the neural circuit • Also, found that learning is not done by separate ‘memory cells’

  12. Latter findings • Tim Bliss and Terje Lomo • Short, rapid bursts of stimuli of nerve fibers that formed synapses with dendrites in the hippocampus increases the efficacy of those synapses • The nerve fibers form one of the main inputs from the cerebral cortex to the hippocampus – thus causing long-term potentiation for memory • Potentiation- increased effectiveness of synapses caused by protein synthesis

  13. When we encounter stimuli • Two things can happen • If the stimuli does not involve the synthesis of new protein • Then the results will slowly and spontaneously reverse • If the stimuli does require the synthesis of new protein • Then if will result in a more permanent change in the receptors

  14. How does the protein get the right synapses • It doesn’t • At least not all of the time • Instead it binds to any synapse in the post-synaptic cell that has been recently active

  15. Hippocampus • Depends on the synthesis of new protein for lasting change on memory • hippocampus of a mouse • Research- Knocked out the gene for a subunit of the NMDA receptor • Results: • These mice had difficulties in learning to finding a submerged platform • Research- injected with a protein synthesis inhibitor • results: • Only able to remember the correct path for 3hrs

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