Memory

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