24, p < 0.05). Whether or not individual PPC cells passed the criterion for showing tuning to acceleration or self-motion could not be predicted by the cluster isolation of the cells (Z-scores for large-sample binomial comparisons of PPC cells with isolation scores above and below the median isolation distance ranged from 0.66 to 1.76, p values ranged from 0.08 to 0.51). To determine whether PPC cells exhibit anticipatory firing, as described in primates prior to eye or hand movements

(see Andersen and Buneo, 2002 for review), we analyzed whether the time window within which PPC cells showed self-motion tuning extended to include movements from path segments that preceded Selleckchem Perifosine or succeeded the animal’s actual position (Figure 4). The cells showed tuning to upcoming actions that occurred up

to 500 ms after the spikes. The tuning of the cells fell off almost immediately BAY 73-4506 research buy after a movement was executed, suggesting that the tuning was genuinely anticipatory and not related to the temporal structure of the animal’s movements (Figures 4B and 4C). Thus, PPC cells in rats express information about ongoing and impending movements during unrestrained foraging, whereas grid-cell maps are independent of the state of motion. Since PPC cells showed tuning to self-motion and acceleration in the open field, we reasoned that spatial correlates may emerge when particular behaviors are executed reliably at particular not locations (see also McNaughton et al., 1989 and McNaughton et al., 1994). To determine this we recorded from the same rats as in the open field in a hairpin maze comprised of a stack of 10 interconnected, equally

sized alleys running north-to-south (Figure 5A) (Derdikman et al., 2009). The maze was constructed by inserting opaque Perspex walls in to floor grooves in the open field arena, allowing us to maintain the same recording location and spatial cues outside the arena. The rats were trained to make repeated east-to-west and west-to-east traversals during 20 min recording sessions, receiving a food reward at the end of each lap. The maze limited the rats’ modes of movement to sequences of straight running, left turns, and right turns, causing the emergence of apparently-spatial firing fields. Cells that preferred straight running fired in maze alleys, while other cells fired just before or after turns, and other cells fired during the turns themselves (Figure 5B). The firing fields were stable within and between recording sessions and the discharge correlates were the same for east- and westbound trajectories (Figure 5B). Simultaneously recorded grid cells also expressed discrete firing fields in the hairpin maze (Figure 5C).