A.

Lag (ms)-50 50

Lag (ms)-50 50

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Isolation Distance10 100 10000

0.1

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1st half vs. 2nd half

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Supplementary Figure 1

Spike sorting and isolation quality of clusters.

A: (Top); Example of auto-correlograms and cross-correlograms of 20 CA1 units recorded simultane-ously. (Bottom); Average (± s.d.) of unit waveforms. B: Comparison between the average spike ampli-tudes of the first and second halves of all the recording sessions. (Top); Percent change on the chan-nel with the highest amplitude. (Bottom); Change in the Euclidean distance between the amplitudes on all the channel. C: Distribution of L-ratio measures and Isolation Distance index.

100 μmR

ippl

e po

wer

Cel

l pos

ition

0

max

Hippocampal contours and probe marks are traced onto coronal sections

4: Hippocampus and silicon probepositions are reconstructed foreach coronal section

1 2 3

A.

B.

C.

D.

Supplementary Figure 2

3D anatomy, electrode track reconstruction and cell location

A: Scheme of the mouse brain showing the hippocampus and position of the shanks of silicon probes. B: Example of coronal sections with the position of the silicon probes’ shanks in red. Image reconstruct-ed by overlaying DAPI and DiI fluorescence images. C: CA contour on each slice were drawn using customized Matlab routine (1-2-3). Traces were scaled, aligned and visualized in 3D (4). D: Example of CA1 ripple activity (top), ripple power (middle) and putative position of recorded cells (bottom) (See Methods). E: Example of coronal sections with silicon probes shanks oriented along the proximodistal axis, targeting CA1 (top) and CA3 (bottom). F: Summary diagram of shanks’ locations for all experi-ments. Dots connected by lines correspond to the shanks from the same silicon probe. G: Number of LV cells and CM cells recorded in CA1 and CA3 for different mice.The color code correponds to the ones in F.

CA1

CA1

Fasciola

cinereum

Subiculum

CA2

1mmv

F.

E.

G. Animal ID LV cells CM cells

TG08 7 TG10 9 TG11 11 TG15 22 TG16 9 TG18 6 TG23 34 TG24 31 TG25 26 TG26 1 TG39 7 TG40 17 TG41 4 TG42 10 TG43 3 TG44 12

20 23 33 35 22 19 31 35 29 3 9 13 4 7 4 12

TG08 0 TG10 0 TG11 1 TG16 1 TG18 1 TG22 0

9 6 4 19 27 5

CA

1C

A3

0 50 100 150 2000

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a ph

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C. D.

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Supplementary Figure 3

Theta phase precession in Landmark-vector cells and Context-modulated cells

A: Example of theta phase precession in LV cell. Position on the belt is plotted on the x axis, and the theta phase at which each spike occured is plotted on the y axis. B: Overlay of normalized position within each field. C,D: Same as A, B, for CM cells. E: Theta phase precession depicted for all the spikes of LV cells. F: Same as E for CM cells. G: Circular mean and confidence interval for all the fields.

C.G.

Relative distance0 1

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confidence

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D.

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4Place fields ‘switching’

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istri

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00

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. of c

ells

(%)

Supplementary Figure 4

Cell activity and dynamics in CA3

A,B,C: Example of LV cell (A), switching (B) and drifting (C) cells in CA3. D: Field emergence of switching cells as a function of trials. E: Cumulative distribution of (D) for CA1 and CA3 (P=0.81, unpaired Kolmogorov-Smirnov test). F: Trajectories of drifting place fields along the trials. Field drift starting positions are aligned on 0. G: Distribution of drift rates. H: Number of drifting and switchingcells, in CA1 and CA3, for different mice.

max

0 Hz

0 1Position (a.u)

220

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6

190

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Place fields drifting

24

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0 1

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l num

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190

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19

0 1Position (a.u)

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Tria

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Object addition

H.Animal ID TG08 4 TG10 13 TG11 7 TG15 14 TG16 4 TG18 5

13 0 23 21 15 8

TG08 3 TG16 7 TG18 10 TG22 1

4 7 12 2

CA

1C

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# cellsdrifting

#cellsswitching

A.DriftingSwitchingRecorded unit

Dee

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m

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coun

t

B.-24.8

Supplementary Figure 5

Relative repartion of switching and drifting cells along CA1 radial axis

A: Examples of shanks from four different silicon probes with cell positions. B: Distribution of depth-differ-ences between pairs of neurons from the same shank. Red arrow indicates the mean. (Mean of the differ-ence versus 0, P<0.001, one-tailed t-test)