1. Transgenic activation of the same entorhinal inputs leads to the same hippocampal network response
Jasmine Dickinson
Kentros lab
May 2012

2. Memory and the Hippocampus
Patient HM, 1953

3. Hippocampus Circuitry and the DREADD Mice
Inject CNO 
Binds to special receptors in MEC 
Increases firing in MEC
Clozapine-n-oxide (CNO) only binds to the transgenic receptors. CNO is a tool to activate the receptors.

4. Place cells and grid cells
Grid cells (Medial Entorhinal Cortex)
Place cells (hippocampus)
Grid cells code for general space
Place cells code for specific places
How do grid cells in the medial entorhinal cortex transfer their information to place cells in the hippocampus?

5. Activating Layer 2 Induces Changes in CA1 Firing
Expand field
Note: Fields return to baseline after CNO wears off
Remap to new location
Turn off
Turn on

6. Same cells, different days – normal place cells
Baseline (30 min)
CNO (2 hours)
Day 1
Day 2
Place field doesn’t change during the CNO session
Same cell fires in the same place

7. Same cells, different days – transgenic animals
Expands field
Remaps to new location
The cells remap, but they do the same thing both days
Turns on/ increases firing
Turns off

8. Correlation scores
CNO period broken down into four 30-min pieces
Both groups have well correlated fields during CNO across days, even though the +/+ group remaps

9. What does this mean?
For transgenic animals, there is an initial remapping between BL and CNO, but once the cells remaps, they stays that way.
This remapping is statistically indistinguishable from the lack of changes seen in stable recordings from control animals across multiple CNO injections suggesting stable remapping.
This argues for “hard wired” connections between MEC input and CA1. “Artificial remapping” is preserved across several synapses (DG, CA3).

10. Thanks to:
Cliff Kentros
Aldis Weible
Dave Rowland
Everyone else in the Kentros Lab
SPUR