Working reference memory following fimbra fornix lesions
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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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Working reference memory following fimbra fornix lesions

Working & Reference Memory Following Fimbra-Fornix Lesions


Purpose

Purpose

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


Predictions

Predictions

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


Subjects

Subjects

  • 6 female Long-Evans rats, housed at NIU

  • Approximately 6 months in age

  • 3 subjects receive F-F lesions

  • 3 unoperated control


Fimbria fornix lesion

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


Working memory

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


Working memory1

Working Memory

Cue 3

Cue 1

Cue 2


Working memory2

Working Memory

Cue 3

Normal

Cue 1

Cue 2


Working memory3

Working Memory

Cue 3

F-F Lesioned

Cue 1

Cue 2


Reference memory

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


Reference memory1

Reference Memory

Cue 3

Cue 1

Cue 2


Reference memory2

Reference Memory

Cue 3

Normal

Cue 1

Cue 2


Reference memory3

Reference Memory

Cue 3

F-F Lesioned

Cue 1

Cue 2


Measures

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


Working reference memory following fimbra fornix lesions

  • 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


Conclusions

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)


Things to consider

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?


References

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)


References1

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


Remember

Remember

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


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