PMC

Individual navigation templates assisted screw placement of lumbar pedicle

Individual navigation templates bonded tightly to the anatomical structure of corresponding rear of vertebrae

(a) distance between the cortical bone and the screw in the axial plane; (b) distance in the sagittal plane

(a) axial projection; (b) frontal projection; (c) sagittal projection; 1 — insertion point, 2 — center of pedicle, 3 — position of the screw tip

(A) A 1000 cm (10 meter) long virtual linear track for imaging experiments. ‘L’ and ‘R’ indicate cues on the left and right sides of the track, respectively. (B) Left and right cue templates with cues on the left and right sides of the track. (C) Examples of individual cue cells responding to the left- (top) or right-side cues (bottom) in layer 2 of the MEC. For each cell: top: ΔF/F versus linear track position for a set of sequential traversals. Middle: mean ΔF/F versus linear track position. Bottom: overlay of the cue template and aligned mean ΔF/F (black) according to the spatial shift, which gave the highest correlation between them (Materials and Methods). (D) Left and right cue cell sequences aligned to left- (top) and right-side cues (bottom), respectively. In each row the mean ΔF/F of a single cell along the track, normalized by its maximum, is plotted. The cells are sorted by the spatial shifts identified from the correlationof their mean ΔF/F to the cue template. (E) Bilateral scores of all left and right cells in D. Left: bilateral scores of individual cells (dots). Right: kernel density distribution of bilateral scores. Note that the bilateral scores show a strong bimodal distribution. (F) Percentages of cue cells among all cells activeduring virtual navigation (active cells were determined as cells identified using independent component analysis, Materials and Methods) . Left bar: all left and right cue cells. Middle bar: left cue cells. Right bar: right cue cells. Individual data points that were pooled for this are the percentages of cue cells in 12 FOVs in layer 2, p=6.90 × 10⁻⁴. (G) Comparison of cue scores of left and right cue cells in layer 2. Individual data points are cue scores of cells in D,p=1.67 × 10⁻⁵. All data were generated using layer 2 cue cells in 12 FOVs in four mice. ***p≤0.001. Student’s t-test.
Figure 5—source data 1.Cue scores, bilateral scores and percentages of left and right cue cells.

(A) An 1800 cm (18 meter) long virtual track for imaging experiments. ‘L’, ‘R’ and ‘L/R’ indicate cues on the left, right and both sides of the track, respectively. (B) Left, right, and both-side cue templates of the track in A. (C–G) Results for layer 2 cells, which were generated from 40 FOVs in six mice. (C) Comparison of cue scores. From left to right: scores of cells that passed the threshold of left, right, and both-side templates. Among the both-side cells, from left to right: all both-side cells; both-side cells that also passed thresholds of left and right templates; both-side cells that were not classified as left and right cells ( cells). Statistics: column 1 to 3: p=6.33 × 10⁻³⁹, Column 2 to 3: p=6.90 × 10⁻⁵². (D) Pie chart showing the percentage of both-side cells that were also classified as left and right cells (white) and non-left and non-right cells (gray). (E) Cue cell sequences aligned to left- and right-side cues. Each row shows the mean ΔF/F along the track of a single cell, normalized by its maximum. The cells are sorted by the spatial shifts calculated from the correlation of the mean ΔF/F to the cue template. (F) Bilateral scores of left and right cells shown in C. Left: bilateral scores of individual cells (dots). Right: kernel density distribution of bilateral scores. Note that the distribution of bilateral scores is bimodal . (G) Percentages of cue cells. Left bar: all left and right cue cells. Middle bar: left cue cells. Right bar: right cue cells. Individual data points that were pooled for summary plots are cue cells from 40 FOVs in layer 2, p=7.12 × 10⁻⁶. (H–L) Similar to C-G but for layer 3 cells, from 37 FOVs in two mice. (H) Statistics: column 1 to 3: p=4.54 × 10⁻²⁸. Column 2 to 3: p=5.30 × 10⁻³². (L) Percentages of cue cells. Individual data points that were pooled for summary plots are cue cells from 37 FOVs in layer 3, p=0.041. *p≤0.05. ***p≤0.001. Student’s t-test.
Figure 5—figure supplement 4—source data 1.Cue scores, bilateral scores and percentages of cue cells in layers 2 and 3 on a 18-meter virtual linear track.

Method: The goal of this analysis is to investigate whether cells with cue-correlated activity patterns show consistently shifted responses to individual cues. Since cue cells were largely chosen based on the correlation of their activity patterns to a specific cue template (), this procedure could artificially select cells with activity patterns consistently shifted from individual cues and thus having high correlations to the template (comparability, high cue scores). Consequently, when these selected cue cells were ordered based on their spatial shifts, their responses were very likely to form consistent sequences at individual cues (as in and ). To avoid this artifact, here we classified cells with cue-correlated activity using a different approach in order to investigate whether having responses with consistent spatial shifts to individual cues is a true feature of cue cells. This analysis was performed on data collected in layers 2 and 3 of the MEC when mice navigated along an 18-meter track (). The track contained a large number of cues (10 cues), which allowed a more precise classification of cells with cue-correlated activity even when choosing only half the number of cues (method described below). Each cue template was split into two half-templates (templates 1 and 2), each containing half of the cues of the original template. The cues on the two templates were non-overlapping. Cue wells were first classified using one of the half-templates (i.e., template 1). The spatial shifts found from the correlation to template 1 was compared to that found for the other half-template (template 2), which was not used to classify the cells. The hypothesis was that if the response of a cue cell was shifted by the same distance from each cue, then the spatial shifts would be similar between these two half-templates. An example with two half-templates is shown in A. R1 and R2 are two half-templates with cues on the right side of the track. We calculated the percentage of cells that maintained similar spatial shifts across the two half-templates (the difference of the spatial shifts on R1 and R2 is less than 25 cm). We found that a large fraction of cue cells (76.9% and 80.3% for cells identified on R1 and R2, respectively) had very similar shifts on the two half-templates. A similar example for left-side cues is shown in (B). To further confirm that this high percentage of cells with consistent spatial shifts to cues was not found only by using a particular set of half-templates, we repeated this analysis for cells in both layers 2 and 3 using multiple sets of half-templates comprised of various combinations of cues from the original templates. This more strict analysis of spatial shifts of cue cells data together indicate that cue cells respond to individual cues with consistent spatial shifts.
Figure details: (A) Spatial shifts of cue cells classified using two half-templates of the right cue template (R template). The R template was split into two half-templates: R1 and R2. Spatial shifts of cue cells classified using R1 and R2 are shown in a1 and a2, respectively. a1: From top to bottom: (1) Classification of cue cells (R1 cue cells) using R1 template. (2) Ordered R1 cell responses based on their spatial shifts to R1 (R1 shifts). (3) Ordered R1 cell responses based on their spatial shifts to R2 (R2 shifts). Note that the activity patterns in both (2) and (3) consistently shift from individual cues, indicating that R1 cue cells generally had similar spatial shifts on R1 and R2. (4) Difference in spatial shifts of R1 cells on R1 and R2. Each dot is one cell. The fraction of cue cells (76.9%) with very similar spatial shifts on R1 and R1 (less than 25 cm absolute shift differences, marked by red parenthesis) a2: similar to a1 but for cue cells (R2 cue cells) classified using R2 template. (B) Similar to A but for left cue template (L template). (C) Summary of the percentages of cells in layers 2 and 3 with very similar spatial shifts (less than 25 cm absolute shift differences) on multiple pairs of half-templates (5 and 2 pairs for layers 2 and 3, respectively) comprised of different combinations of cues on the left and right cue templates (L1, L2, R1, R2). All analyses showed similar results. Red lines indicate the mean of each group.

(A) Left and right cue scores in layer 2 of the MEC. The locations of each circle/dot on the x and y axes represent the right and left cue scores for a cell, respectively. The solid line indicates the threshold for each type of score that was used to determine the corresponding cue cell type. Cells are color-coded according to whether they were right cue cells (magenta circles), left cue cells (green dots), or cells with cue scores that exceeded both right and left cue score thresholds (green dots with magenta outline). The scores of cells below all thresholds are shown as gray circles. The distributions of right and left scores are shown on the top and left of the plots with corresponding colors indicating cue scores above thresholds. (B) Spatial shifts on left and right templates for the 14 layer 2 cue cells (from 12 FOVs in four mice) that passed the thresholds of both templates. Each dot represents one cell. The bigger dot contains two data points with identical x and y coordinates. The gray dotted line indicates x = y. (C–G) Cue cells classified using the both-side cue template, which included cues on both left and right sides of the track. We classified cells using a threshold specific to the both-side template (B). However, we concluded that the cues on both sides were not well represented by the classified cells based on the following three reasons: 1.) The cue scores of both-side cue cells were significantly lower than those of left and right cue cells (D). Since the cue score is defined to be the mean correlation of a cell's response to individual cues, independent of the number of cues on a template, the low cue scores indicate that the responses of both-side cue cells did not correlate well to cues on both sides of the track. 2.) 64% of both-side cue cells were also classified as left or right cue cells, which only strongly responded to cues on one side (E, cell examples in F and G, the first and second panels). 3.) The rest of both-side cue cells (36%) only weakly correlated to the both-side template (E, cell examples in F and G, the third panels), as reflected by their lower cue scores (D). Cue cell sequences aligned to both-side cue template (top). Each row is mean ΔF/F of a single cell along the track, normalized by its maximum. The cells are sorted by the spatial shifts of their mean ΔF/F to the both-side cue template. (D) Comparison of cue scores. From left to right: scores of cells that passed the threshold of left, right, and both-side templates. Among the both-side cue cells, from left to right: all both-side cue cells; both-side cue cells that also independently had left and right cue scores that exceeded the thresholds for those scores; both-side cue cells that were not classified as left and right cue cells (non-left/non-right cells). p value: column 1 to 3: 4.35 × 10⁻³⁷. Column 2 to 3: 4.08 × 10⁻⁶³. Column 4 to 5: 7.16 × 10⁻⁴. (E) Pie chart showing the percentage of both-side cue cells that were also classified as left and right cue cells (white) and non-left and non-right cue cells (gray). (F) Three examples of both-side cue cells. Left: a both-side cue cell that is also identified as a left cue cell; middle: same but for a right cue cell; Right: a cell uniquely identified as a both-side cue cell (non-left/non-right cue cells). For each cell: top: ΔF/F versus linear track position for a set of sequential traversals. Middle: mean ΔF/F versus linear track position. Bottom: overlay of the cue template and aligned mean ΔF/F (black) according to the spatial shift. The left (green) and right cues (magenta) in the both-side cue templates are also shown in corresponding colors. (G) Cue cell sequences of both-side cue cells. From left to right: both-side cue cells also identified as left cue cells, right cue cells, and cells only identified as both-side cue cells (non-left/non-right cue cells). In each row the mean ΔF/F of a single cell along the track, normalized by its maximum, is plotted. The cells are sorted by the spatial shifts calculated from the correlation of each cell's mean ΔF/F to the cue template. (H) Calculation of the bilateral score. In the two cases shown, cartoon illustrations of activity patterns show examples of cells with responses to cues only on oneside (case 1) or to cues on both sides (case 2).
Figure 5—figure supplement 2—source data 1.Cue scores, spatial shifts and both-side cue template.