Table 2. Comparative quantitative analysis of various synaptic parameters in L4 and L5 of the TLN.
| Mean ± SD | Median | IQR | CV | Skewness | Variance | ||
|---|---|---|---|---|---|---|---|
| Synaptic boutons | Layers | ||||||
| Surface area (µm²) | L4 | 2.50 ± 1.78 | 2.05 | 1.67 | 0.72 | 1.97 | 3.24 |
| L5*** | 6.09 ± 0.92 | 6.05 | 0.87 | 0.15 | 4.49 | 23.04 | |
| Volume (µm³) | L4 | 0.16 ± 0.16 | 0.11 | 0.12 | 1.01 | 2.89 | 0.03 |
| L5*** | 0.63 ± 0.18 | 0.63 | 0.21 | 0.29 | 2.05 | 0.46 | |
| Active zones | |||||||
| PreAZ surface area (µm²) | L4 | 0.13 ± 0.07 | 0.11 | 0.08 | 0.54 | 1.35 | 0.005 |
| L5*** | 0.23 ± 0.05 | 0.22 | 0.07 | 0.22 | 1.86 | 0.03 | |
| PSD surface area (µm²) | L4 | 0.13 ± 0.07 | 0.11 | 0.08 | 0.53 | 1.44 | 0.005 |
| L5*** | 0.29 ± 0.15 | 0.23 | 0.16 | 0.45 | 2.77 | 0.06 | |
| Cleft width (nm) | |||||||
| Lateral | L4 | 14.11 ± 0.69 | 14.43 | 1.19 | 0.05 | 0.74 | 8.86 |
| L5*** | 17.25 ± 2.39 | 17.51 | 3.74 | 0.13 | 1.14 | 20.73 | |
| Central | L4 | 16.47 ± 1.85 | 15.72 | 3.26 | 0.11 | 0.80 | 17.09 |
| L5*** | 19.05 ± 2.94 | 18.85 | 2.95 | 0.15 | 1.82 | 30.84 | |
| Mitochondria | |||||||
| Volume (µm³) | L4 | 0.03 ± 0.04 | 0.02 | 0.02 | 1.04 | 3.71# | 0.001 |
| L5*** | 0.12 ± 0.09 | 0.07 | 0.16 | 0.87 | 8.22 | 50.30 | |
| % to the total volume | L4 n.s. | 13.11 ± 6.20 | 12.78 | 9.25 | 0.47 | 0.17 | 38.47 |
| L5 | 12.04 ± 1.20 | 11.89 | 2.18 | 0.10 | 0.57 | 23.04 | |
| Synaptic vesicles | |||||||
| Total number | L4*** | 1820.64 ± 980.34 | 1544.5 | 1119.5 | 0.54 | 0.91 | 961066.59 |
| L5 | 1518.52 ± 303.18 | 1347.21 | 541.98 | 0.19 | 2.39 | 1655452.24 | |
| Diameter (nm) | L4 | 19.80 ± 5.63 | 18.00 | 0.28 | 3.41 | 2.10 | 31.69 |
| L5*** | 36.69 ± 1.71 | 37.02 | 3.26 | 0.04 | −2.07 | 153.21 | |
| Volume (µm³) | L4 | 0.01 ± 0.01 | 0.01 | 0.01 | 1.28 | 3.95# | 0.0002 |
| L5*** | 0.05 ± 0.02 | 0.05 | 0.03 | 0.4 | 3.60# | 0.002 | |
| Pool size of SVs | |||||||
| Putative RRP at p10 nm | L4*** | 20.20 ± 18.58 | 17 | 27.25 | 0.92 | 1.11 | 345.04 |
| L5 | 5.42 ± 4.09 | 4.93 | 6.29 | 0.75 | 2.17 | 39.93 | |
| Putative RRP at p20 nm | L4*** | 48.59 ± 39.02 | 41 | 53 | 0.80 | 1.17 | 1523.14 |
| L5 | 15.21 ± 9.02 | 13.55 | 16.34 | 0.59 | 2.06 | 206.69 | |
| Putative RP 60–200 nm | L4*** | 382.1 ± 248.23 | 313 | 376.79 | 0.65 | 1.41 | 61617.55 |
| L5 | 181.86 ± 27.05 | 180.89 | 47.42 | 0.15 | 1.25 | 11469.97 | |
| Putative resting pool > 200 nm | L4 | 1251.82 ± 471.17 | 541 | 471.17 | 0.38 | 1.70 | 87678.29 |
| L5 n.s. | 1264.07 ± 301.77 | 1150.76 | 540.39 | 0.24 | 0.66 | 72853.49 | |
Summary of various structural parameter measurements provided from the detailed 3D-volume reconstructions of SBs in L4 (present study) and L5 (Yakoubi et al., 2019) of the human TLN. Mean ± SD, Median, Interquartile Range, CVs, Skewness and Variance were given for each parameter in all patients investigated. #: Values with a skew >3 indicating non-normal distributions. Abbreviations: p10 nm, p20 nm: perimeter 10 and 20 nm from AZ (see Materials and methods), n.s: not significant, ***p≤0.001.