![]() Orange lines represent north-south aligned axes blue lines represent east-west aligned axes. (I) Scatter plots of the innermost six fields in each grid cell’s autocorrelation. (H) (Left) Grid cell ellipticities, red line indicates identical ellipticity. (Right) Histograms of grid spacing ratio. (G) (Left) Grid cell spacing, red line indicates identical spacing. (Right) Histogram of grid orientation differences for experimental and control animals. (F) (Left) Grid cell orientations, red lines indicate rotations equivalent to modulo 60. Distance from the cross-correlation’s center to the nearest peak noted on top. (Right) Corresponding ENV1-ENV2 cross-correlations. Red lines indicate grid axes white text indicates ellipticity. ![]() (Middle) Corresponding autocorrelations spacing and orientation noted on top. (E) (Left) Grid cell rate maps in both environments peak firing rate and grid score noted on top. Data aligned to each animal’s first post-trained session (red line). (D) Circuity and trial time improved with training in individual animals (gray lines). Mean trial circuity and trial time noted below ENV2. (B) Trajectories (gray) from a paired session. Performance of a task induces grid rotation and rescaling. After training (mean # sessions to reach criterion = 15 range = 8–24), animals took rapid, direct paths to the reward zone upon cue onset ( Fig. Reward trials (cue onset to reward zone entry) occurred ≥ 10 times per session ( Fig. In environment two (ENV2 white walls, vanilla scent), rats navigated to a remembered, unmarked 20 cm x 20 cm zone in response to an auditory cue to receive a food reward (0.5–1 cereal units), and freely foraged for randomly scattered crushed cereal between trials ( 10) ( Fig. In environment one (ENV1 black walls, lemon scent), rats foraged for randomly scattered crushed cereal ( 2– 5, 12). We recorded neural activity in the MEC and surrounding cortical areas of seven rats as they explored two arenas (1.5 m x 1.5 m) ( Fig. While MEC plays a critical role in navigation ( 15), the degree to which remembered reward locations influence MEC neural codes remains unknown. However, these MEC spatial coding features have primarily been observed during random foraging, whereas ethologically relevant strategies often employ more complex behaviors such as goal-directed navigation ( 14). In contrast, recent work has shown that MEC spatial codes are flexible and adaptive ( 6, 11– 13). Initial experiments suggested a dissociation between representations in these regions: spatially-modulated codes sensitive to contextual features in the hippocampus and context-independent codes for position, orientation and speed in MEC ( 2, 3, 5– 10). The hippocampus and medial entorhinal cortex (MEC) contain cells that provide representations of self-location and orientation within the local spatial environment ( 1– 5). The ability to recall and navigate to a remembered reward location is essential to survival.
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