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Working & Reference Memory Following Fimbra-Fornix Lesions

Working & Reference Memory Following Fimbra-Fornix Lesions. Purpose. To determine the role of the septo-hippocampal system in working and reference memory. Predictions. Lesions of the fimbria-fornix will produce deficits in spatial working and reference memories. Subjects.

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Working & Reference Memory Following Fimbra-Fornix Lesions

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  1. Working & Reference Memory Following Fimbra-Fornix Lesions

  2. Purpose • To determine the role of the septo-hippocampal system in working and reference memory

  3. Predictions • Lesions of the fimbria-fornix will produce deficits in spatial working and reference memories

  4. Subjects • 6 female Long-Evans rats, housed at NIU • Approximately 6 months in age • 3 subjects receive F-F lesions • 3 unoperated control

  5. Fimbria-fornix lesion • Rats will be anesthetized with a mixture of isofluorane and oxygen during the surgery. • Lesions will be made using standard stereotaxic techniques with the aid of a surgical microscope. • Prior to making the incision, the hair will be shaved and the surrounding area will be scrubbed with Betadine. • There will be two lesion sites per hemisphere, using coordinates with respect to bregma and the surface of the dura: -1.3mm posterior, 1.5mm lateral, and –3.6 mm ventral; -1.5mm posterior, 0.5mm lateral, and 3.3 mm ventral. • Fimbria-fornix lesions will be produced by passing 1.5mAmp current for 40 seconds. • Following lesion incision will be sutured • General appearance and weight will be monitored every day for the duration of behavioral testing

  6. Working Memory • Prior to training with baited arms, rats will be given two habituation sessions (15 min) in which the rats will be free to explore the radial eight-arm maze • Rats will receive five training sessions in which each arm of the radial eight-arm maze will be baited with one half of a fruit loop • placed into the center of the maze and the arms visited will be recorded • After all of the arms have been visited or 15 minutes has elapsed the rats will be removed from the apparatus • maze will be cleaned with Windex prior to running the next rat

  7. Working Memory Cue 3 Cue 1 Cue 2

  8. Working Memory Cue 3 Normal Cue 1 Cue 2

  9. Working Memory Cue 3 F-F Lesioned Cue 1 Cue 2

  10. Reference Memory • Subsequent to completion of working memory training sessions • Rats will receive five training sessions in which only four of the eight arms will be baited • After all of the arms with bait have been visited or 15 minutes has elapsed, the rats will be removed from the apparatus

  11. Reference Memory Cue 3 Cue 1 Cue 2

  12. Reference Memory Cue 3 Normal Cue 1 Cue 2

  13. Reference Memory Cue 3 F-F Lesioned Cue 1 Cue 2

  14. Measures • Several measures will be used to characterize the rat’s performance: • number of repeat visits to an arm (errors) • time to visit all arms

  15. Main effect of day F(4,16)=30, p<.05 • Main effect of group F(1,4)=697.69, p<.05 • Significant dayXgroup interaction F(4,16)=18, p<.05

  16. Conclusions • F-F lesions distrupt working and reference memory • Discuss literature that supports this and contradicts this • Packard M Hirsh R White N (1989) Differential effects of fornix and caudate nucleus lesions on two radial maze tasks: evidence for multiple memory systems. • Future work (recovery, model for memory impairments, Alzheimer's disease)

  17. Things to consider • How are the rats solving these two tasks? • Is reference memory the same as place learning? • What do these studies imply in terms of the role of the hippocampus in memory?

  18. References • Chapter 11 • Working memory & Reference memory (pg. 319-20) • Spatial memory in Radial Maze (pg. 326-29) • Memory mechanisms (pg.332-43) • Chapter 12 • Memory in food storing birds (pg. 354-58)

  19. References • pubmed.org • psycinfo • Terms • Working memory & reference memory • Hippocampus & fimbria-fornix • Place learning • Spatial memory • Morris water maze • Important People • David Olton • Larry Squire • Eric Kandel • Ian Whishaw

  20. Remember • Think conceptually when reading the literature, don’t just describe methods of study.

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