2017 Fiscal Year Annual Research Report
Retrosplenial/Hippocampal Circuit Control of Map Selection
Publicly Offered Research
| Project Area | Systems Science of Bio-navigation |
|---|
| Project/Area Number |
17H05986
|
|---|
| Research Institution | Institute of Physical and Chemical Research |
|---|
Principal Investigator |
McHugh Thomas 国立研究開発法人理化学研究所, 脳科学総合研究センター, チームリーダー (50553731)
|
|---|
| Project Period (FY) |
2017-04-01 – 2019-03-31
|
| Keywords | hippocampus / navigation / retrosplenial cortex / pharmacogenetics |
|---|
| Outline of Annual Research Achievements |
During the last fiscal year we established the starmaze behavioral protocol in the lab and have tested the impact of DREADD-mediated retrosplenial inhibition on navigation strategy. The behavioral task was conducted with two groups of five RSC-DREADD-mCherry (DREADD) and five RSC-mCherry (mCherry) mice each. Each mouse was subjected to a session in the star maze for fifteen days during three weeks. A central aspect of the star maze behavioral task is that probe trials are in some way representative of the mouse’s approach during training trials. Correlation analysis revealed that allocentric probe trials were positively associated with a high percentage of long training trials and egocentric probe trials followed more frequently when predominantly short paths were chosen during training trials. In contrast, allocentric probe trials were negatively correlated with short training trials and egocentric probe trials were negatively correlated with long training trials. No significant relation could be established between probe outcome and error rate in preceeding training trials, though a trend may indicate a negative correlation with egocentric probe trials. Unfortunately however, the main hypothesis we set to address in this initial experiment, RSC inhibition would alter strategy selection, was not supported by our data. The frequency of egocentric and allocentric choice of spatial strategy, as well as the amount of failed probe trials were similar between the DREADD and mCherry group
|
| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The behavioral experiments were conducted as planned. While the results do not support our initial hypothesis, this work has established this navigational task in the lab and will be used for further electrophysiological recording experiments.
|
| Strategy for Future Research Activity |
In vivo electrophysiology in freely behaving rodents has been key in understanding how neurons in the hippocampus encode spatial and contextual information (‘place cells’; McHugh et al, Cell, 1996). The experiments in the second year of the study will focus on the consequences of retrosplenial inhibition on the spatial coding in the CA1 region of the hippocampus, with a focus on how the place code changes with navigational flexibility. These experiments will employ the same behavioral training protocol (Star Maze) described above. Previous work has established this task is amenable to in vivo electrophysiology and that CA1 place cell activity can reflect the navigational strategy of the mouse (Cabral et al, 2013). RSC-Cre mice, pre-trained in the Star Maze task, will be injected with Cre-dependent AAV viruses expressing both the inhibitory Gi DREADD receptor and mCherry or in Control mice a virus expressing mCherry alone. At the time of surgery the mice will be implanted with a custom dual-site recording drive with tetrodes targeting both the retrosplenial cortex and dorsal CA1
|
