Table 5.
Hemodynamic and BOLD model parameters used to compute fMRI signal. Equations and definitions are detailed in the Appendix.
| Hemodynamic Model Parameters | ||
|---|---|---|
| τs | 1.54 (seconds) | Vasodilatory signal decay constant |
| τf | 2.44 (seconds) | Flow-dependent feedback regulation constant |
| α | 0.32 | Grubb’s vessel stiffness exponent |
| E0 | 0.34 | Resting blood volume fraction |
| ε | 0.1 | Efficacy of synaptic activity to induce the signal |
| λd | 0.5 | Laminar coupling constant |
| τd | 0.5 (seconds) | Interlayer transit delay constant |
| BOLD Model Parameters | ||
|---|---|---|
| V0 | 0.02 | Resting blood volume fraction |
| ϑ0 | 188.1 (Hz) | Frequency offset at outer surface of magnetized vessels |
| TE | 0.025 (seconds) | Echo time |
| ε | 0.026 | Ratio of intra - to extravascular BOLD signal |
| r0 | 340.0 (s−1) | Slope of the intravascular relaxation rate |
| TR | 2 (seconds) | Repetition time |