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So where are these genes expressed in the fruit fly brain?
Antibody staining indicates that the mushroom bodies contain the molecular
components that are key for learning:
•Adenylyl cyclase
•PKA
•cAMP phosphodiesterase
Proposed CS-US and behavior pathways
Characterizing different forms of memory using
modern molecular genetic techniques
•Fruit flies can learn and remember odor-shock relationships
•There are a number of mutant fly strains that have been
produced which have a variety of learning and memory related
deficits:
•Dunce
•Amnesiac
•Rutabaga
Fruit fly and sea slugs
•Radish
appear to use
•Cabbage
common mechanisms
•Turnip
Transgenic animals:
Organisms that have had genes inserted into their genome
•GFP: an array of different genetically encoded florescence
Red and green great star corals
Their GFPs can be expressed in bacteria
http://www.whitney.ufl.edu/index.htm
Transgenic animals:
GFP-like fluorescent proteins as biotechnology tools
The first application of fluorescent proteins from reef organisms for dual-color in
vivo labeling: tracing the cell progeny of left and right dorsal blastomeres in a
developing tadpole.
Transgenic animals: Its not just for GFPs
Expression of foreign or native genes can be controlled via insertion of
promoter genes
• Heat shock promoter (hsp70)
• Can be inserted next to a gene of interest (even another
inserted gene)
• Is activated by warming the animal above a threshold
temperature
Experiment:
1. Associate a hsp70 with a PKA-inhibitor gene in fruit fly
2. Heat flies
• PKA-inhibitor expression increases within 1h
• Learning is disrupted
1. Associate a hsp70 with a mutated (dysfunctional) PKA-inhibitor gene
in fruit fly
2. Heat flies
• Dysfunctional PKA-inhibitor expression increases
• Learning is NOT disrupted
This tells us SPECIFICALLY that disruption of PKA disrupts learning
Consolidation of memory and the role of gene transcription
Behavioral data: different training regimes
produce different amounts of retention
•Shock avoidance conditioning:
•Spaced= 10 trials, 15 min between trials
•Massed= 10 trials, in rapid succession
•1 trial
Results:
All produced evidence of strong initial learning but:
•1 trial group showed little retention @ 1 day
•Massed group showed little retention @ 4 days
•Spaced showed persistent retention even @ 7
days
•These results suggest that spaced training provides an
added benefit specifically relating to longer term
retention.
Consolidation of memory and the role of gene transcription
Cyclohexamide (CXM) blocks protein synthesis
•Eliminated the additive effects of spaced training trials
•Does not affect the aspect of memory related to massed trials
Consolidation of memory and the role of gene transcription
CXM does not affect short term memory (or single trial learning)
Does not affect cold-shock or anesthesiaresistant memory (ARM)
Consolidation of memory and the role of gene transcription
ASM vs ARM
•ASM:
•Earlier retention phase
•ARM:
•Follows ASM
•Insensitive (resistant) to cold-shock
•Lasts for 4 days
•Insensitive to CXM (no protein synthesis required)
•Not present in the radish mutant
Consolidation of memory and the role of gene transcription
Massed training produces ONLY ARM
Experiment: Radish vs wild-type and spaced vs massed
•Radish mutants display no apparent ARM (which is produced by massed trials)
•Thus to parse ARM from CXM consolidation we simply need to mix treatments
Predictions:
1. Wild-type spaced:
• ARM+LTM
2. Wild-type massed:
• ARM but no LTM
3. Wild-type CXM+spaced
• Only ARM
4. Radish spaced
• No ARM but LTM
5. Radish massed
• No ARM/LTM
6. Radish CXM+spaced
• No ARM/LTM
LTM is CREB-dependent:
Transgenic HS-promoted negative CREB disrupts:
•Normal CREB
•The added effects of spaced trials
•All behavioral evidence of LTM
ARM+CREB
ARM -CREB
ARM -CREB
Double mutant radish + negative CREB transgene combinations
establish ARM and LTM are functionally distinct processes.
Results of 1-day Posttest
Model describing the phases of learning and memory consolidation