Characterizing Spatial and Auditory Responses in the Gerbil Hippocampus
-
1
University of California, San Diego, United States
-
2
Ludwig-Maximilians University, Germany
The goal of our project is to identify how spatial and auditory stimulus sequences are encoded within the hippocampus of the Mongolian gerbil, a rodent with a highly developed auditory system. As a first step, we asked whether the mechanisms of spatial coding of other rodent species are also present in gerbils. We characterized the spatial firing patterns of hippocampal cells by training gerbils to search for randomly scattered food in an open arena. The walls of the arena were flexible so that they could be configured as a square (diagonal = 115 cm) or a circle (diameter = 102 cm). In addition, gerbils were trained to run on a 1- or 1.5-meter linear track. After gerbils were well-trained, we began to record the firing responses of hippocampal cells. In each box and on the linear track, we found principal cells in the CA1 and CA3 subfields of the hippocampus that showed place fields that were spatially stable and precise.
In order to measure movement-theta in the gerbil, we also recorded the local field potential (LFP) and computed its time-frequency spectrogram. As in other rodents, the LFP shows high power in the theta range (7-11 Hz). In gerbils, the peak frequency is approximately 8.5 Hz. We looked at the relationship between spiking and theta for different cell types. Putative interneurons are phase-locked to theta, firing preferentially near the trough of the theta rhythm. The power spectrum of autocorrelograms also shows that interneurons are tightly locked to the 8.5 Hz frequency. Conversely, putative principal cells show oscillation frequencies that are higher than the predominant LFP frequency. As in other rodent species, such disparity between the oscillation frequencies of cells and of the LFP is indicative of theta phase precession, which was also directly evident in cells with place fields on the linear track. Taken together, our results show that the spatial coding mechanisms in gerbils correspond to those in other rodents, in particular to those of rats.
In addition, we performed experiments to look for hippocampal responses to auditory stimuli. When the gerbil passed specific locations while running on the linear track, we played a corresponding tone. We found that the cells that showed spatial esponses during this experiment tended to have their firing fields located near the tone locations. This suggests that place field responses may be shaped by auditory stimuli. These findings indicate that gerbils can be used as a model organism to compare spatial and auditory sequence coding. Whether identical cell populations in the hippocampus can support both mechanisms remains to be determined.
Acknowledgements
This work was funded by the National Science Foundation and the German Federal Ministry of Education and Research.
Keywords:
Hippocampus,
Place fields,
Gerbil,
Theta Rhythm,
audition
Conference:
Bernstein Conference 2012, Munich, Germany, 12 Sep - 14 Sep, 2012.
Presentation Type:
Poster
Topic:
Neural encoding and decoding
Citation:
Mankin
E,
Galinato
M,
Thurley
K,
Grothe
B,
Leibold
C and
Leutgeb
S
(2012). Characterizing Spatial and Auditory Responses in the Gerbil Hippocampus.
Front. Comput. Neurosci.
Conference Abstract:
Bernstein Conference 2012.
doi: 10.3389/conf.fncom.2012.55.00047
Copyright:
The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers.
They are made available through the Frontiers publishing platform as a service to conference organizers and presenters.
The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated.
Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed.
For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions.
Received:
12 Jul 2012;
Published Online:
12 Sep 2012.
*
Correspondence:
Prof. Christian Leibold, Ludwig-Maximilians University, Munich, Germany, christian.leibold@biologie.uni-freiburg.de