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. 2019 Dec 23;117(1):689–697. doi: 10.1073/pnas.1912533117

Fig. 2.

Fig. 2.

Spatial firing. (A, Left) Schematic showing different spatial zones of the maze. (A, Right) Normalized spatial firing rates of all place cells (determined based on forced-choice and correct free-choice trials) are shown as heat maps on the linearized maze for each sequence block. Each row shows spatial firing of one place cell. Place cells were aligned according to the position of the maximal firing rate during the RR block of the first session. Vertical dashed lines divide different spatial zones on the maze. Rt, return; D, delay; T, track; Rw, reward. Triangles indicate sample place cells shown in B–E. (B–E) Sample place cells that showed trajectory- and/or session-dependent firing outside the track zone. Shown is neural activity during correct free-choice trials. Spatial spike raster (Top) and spatial firing-rate plots (Bottom; smoothed by a Gaussian kernel with σ = 4 cm; shading, SEM) are shown along the linearized maze separately for sessions 1 (Left) and 2 (Right). Colors denote different sequence blocks. P values for the main effects of trajectory and session as well as trajectory × session interaction (ANCOVA) are indicated for each sample place cell. (F) Percentages of place cells in each zone that were significantly responsive to trajectory, session, and/or the trajectory × session interaction (ANCOVA, P < 0.05). The horizontal dashed line indicates the level of chance (binomial test, alpha = 0.05). (G) Pie charts showing percentages of place cells with peak firing inside (Top) or outside (Bottom) the track zone that had place fields in 1, 2, 3, or 4 blocks in each session (Left, session 1; Right, session 2). (H and I) Each block was divided in half (∼7 trials each), and the difference in place-field peak-firing locations (H; Left, cumulative plot; Right, mean ± SEM) and spatial correlation of place-cell population vectors (I; Left, cumulative plot; Right, mean ± SEM) were computed between the halves of each block (within block), between the adjacent halves of adjacent blocks (between blocks), and between the corresponding halves of identical blocks of the 2 sessions (between sessions) for the track zone and the rest of the maze (outside track). ***P < 0.0005 (Kruskal–Wallis tests followed by Bonferroni’s post hoc tests).