Hippocampal CA1 neurons recording from mice foraging in three different environments over 10 days.

The recordings were performed in 12 C57BL/6J male mice. In 4 mice, 1 microdrive with a bundle of 4 tetrodes was implanted in the right hippocampal area CA1, and the other 8 mice were implanted with two microdrives each, with 4 tetrodes in each hemispheres (area CA1: 1.8mmDL, 1.8mmRC, ~1.1mm deep). Mice were 4-6 month old (30-34g.) at the time of the implantation surgery. Custom-made, reusable microdrives (Axona) with 4 tetrodes each were utilized. Two screws were soldered to the grounding wires and screwed until they pierced the Dura, which served as a ground/reference for EEG recordings (one in olfactory-bulb and one in the cerebellum). Data was recorded utilizing Neuralynx amplifiers and the total number of neurons provided by data-set is 1326.
Animals were food deprived for four hours before each recording session over the experimental period of 7-10 days. Animal’s were reconnected to 16 or 32 channels for every single session of ten minutes and introduced in the same region of the arena relative to the recording room in each of the three environments. The animals were introduced in the arena 4 times a day adding a total time of 40 min per environment which is concateneted in a single experiment for each environment for the data provided. Each environment is approximately 50 cm wide with walls that are 40 cm in height. All three environments present a cue card on the internal side of the enclosure with the same orientation relative to the room for all three environments (north on our plots in Fig. 1) to act as a reference point for navigation. Environment A was a square enclosure with black walls and white floor that had ground food (vanilla cookie) spread over the surface of the floor and also a small pellet ~10cm away from the S-E corner of the environment. Environment B was a circular enclosure with black walls and brown textured floor with ground food (cocoa flavored puffed rice) spread over the surface. Environment C was a circular enclosure with white walls and floor and no food. We used these differences in shape and reward distribution to enhance the animal’s ability to differentiate between the environments. Animals were release to freely explore the environments and eat the food.
Results from the experiments are described in:
Jercog PE, Ahmadian Y, Woodruff C, Deb-Sen R, Abbott LF, Kandel ER. Heading direction with respect to a reference point modulates place-cell activity. bioRxiv. 2018 Jan 1:433516. doi: https://www.biorxiv.org/content/10.1101/433516v1