Article Figures & Data
Figures
- Figure 1.
Effects of PI-LOC on functional connectivity strength. A, Average regional connectivity strength S during wakefulness and after loss of consciousness (PI-LOC); yellow to red colors indicate increasing connectivity strength. B, Lower figure shows significant p values of between-condition decreases in connectivity strength S of left and right hemisphere (LH and RH); light to dark blue colors indicate increasing significance. The dotted line depicts the FDR threshold (q = 0.05; see Materials and Methods).
- Figure 2.
Effects of PI-LOC on brain topological properties. Figure shows topological changes of brain functional networks across wakefulness (black) and PI-LOC (gray). A–C, Summary statistics for clustering (C, Crandom, γ = C/Crandom) (A), path length (L, Lrandom, λ = L/Lrandom) (B), and small-worldness (σ = γ/λ) (C) were performed on MODWT scale 3 (0.03–0.07 Hz) throughout a range of 36–50% connection probability (Table 2). Error bars indicate 95% CI.
- Figure 3.
Changes in mean degree and short/long-range connections. A, Group average networks for wakefulness and loss of consciousness. During PI-LOC, brain functional networks decreased in mean degree; depicted at correlation threshold r = 0.3. B, Ratio of long- to short-range connections at PI-LOC compared with wakefulness (mean and SEM values of all long/short-range correlations). Both long- and short-range correlations decreased significantly during PI-LOC; * indicates significance of wakefulness versus PI-LOC for one-sample t test (p < 0.05, one-sided). The reduction in long-range connections was significantly stronger; * indicates significance of wakefulness versus PI-LOC for paired t test (p < 0.05).
Tables
Parameter Wakefulness PI-LOC Pulse (beats/min) 77.5 ± 18.6 71.6 ± 19.0 BPSystolic (mmHg)† 132.9 ± 14.0 117.4 ± 13.1* BPDiastolic (mmHg)† 70.5 ± 10.8 61.1 ± 12.8 SpO2 (%) 98.3 ± 1.4 95.3 ± 1.6* CO2 (%)† 29.5 ± 11.7 35.3 ± 9.4 RF (breaths/min)† 11.3 ± 3.6 12.6 ± 4.1 Results are expressed as mean ± SD of the whole group (n = 15).
↵*Significance of wakefulness versus PI-LOC (paired t test, p < 0.05).
↵†BP data of one subject; CO2 and RF data of three subjects had to be excluded from analysis due to recording problems. BP (blood pressure), SpO2 (oxyhemoglobin saturation), CO2 (endexpiratory carbon dioxide), RF (respiratory rate).
Metric Wakefulness PI-LOC t values p values Clustering coefficient, C* 0.69 ± 0.03 0.65 ± 0.04 −2.19 0.026 Clustering ratio, γ* 1.11 ± 0.03 1.19 ± 0.13 1.86 0.046 Path length, L* 1.42 ± 0.02 1.43 ± 0.05 0.27 0.393 Path length ratio, λ* 1.01 ± 0.01 1.00 ± 0.00 −0.80 0.220 Small-worldness, σ* 1.10 ± 0.04 1.19 ± 0.13 1.90 0.043 Connectivity strength, S† 0.32 ± 0.09 0.22 ± 0.13 −2.58 0.013 Regional diversity, D† 0.19 ± 0.02 0.20 ± 0.03 1.70 0.059 Global integration, I† 36.3 ± 8.9% 27.4 ± 12.9% −2.35 0.039 ↵*Means (±SD), t and p values (one-sided) are provided. Metrics C, L, γ, λ, and σ were calculated on pooled graphs in the applied range of thresholds.
↵†Metrics S, D, and I were tested on the unthresholded connectivity matrices. Both analyses were performed on correlation coefficients of MODWT scale 3 (0.03–0.07 Hz).
Subsystems Wakefulness PI-LOC t values Neocortical connections Association–association 0.35 ± 0.09 0.23 ± 0.12 −2.89* Association–primary 0.40 ± 0.12 0.24 ± 0.17 −2.62* Primary–primary 0.50 ± 0.12 0.41 ± 0.15 −1.21 Neocortical/(para)limbic connections Limbic–primary 0.24 ± 0.12 0.13 ± 0.17 −2.33* Paralimbic–primary 0.32 ± 0.10 0.24 ± 0.19 −1.47 Association–limbic 0.20 ± 0.10 0.13 ± 0.13 −1.82 Association–paralimbic 0.29 ± 0.10 0.23 ± 0.15 −1.48 Limbic/paralimbic connections Limbic–limbic 0.20 ± 0.10 0.21 ± 0.14 0.31 Limbic–paralimbic 0.24 ± 0.11 0.23 ± 0.14 −0.29 Paralimbic–paralimbic 0.31 ± 0.11 0.31 ± 0.14 −0.04 Connections including the subcortical subsystem Association–subcortical 0.24 ± 0.12 0.12 ± 0.14 −4.19** Limbic–subcortical 0.24 ± 0.12 0.21 ± 0.16 −0.38 Paralimbic–subcortical 0.25 ± 0.11 0.16 ± 0.15 −2.46* Primary–subcortical 0.32 ± 0.14 0.17 ± 0.18 −2.87* Subcortical–subcortical 0.36 ± 0.11 0.26 ± 0.14 −1.84 Whole-brain connectivity 0.31 ± 0.10 0.22 ± 0.14 −2.57*
