Table 1.
Lowest stimulation thresholds for model PTNs (P2, P3, P4), cortical interneurons (t1, n2 and n3) and association fibers (a1, a2) as a function of waveform type. The table also shows the sites and mechanisms of activation and the phase of the waveform at which stimulation occurred.
| Model Neuron (diameter) | Pulse type | Lowest threshold | Stimulation | Phase of waveformb | |||
|---|---|---|---|---|---|---|---|
| A/μs | % of MSOa | Site | Mechanism | ||||
| P2 (20 μm) | Mono | PA | 97.7 | 57% | Axonal bend in white matter | Charge accumulation at the bend | 1st 2nd 2nd 3rd |
| AP | 263.1 | 154% | |||||
| Bi | AP-PA | 73.4 | 72% | ||||
| PA-AP | 107.3 | 106% | |||||
| P3 (20 μm) | Mono | PA | 90.9 | 53% | |||
| AP | 252.9 | 148% | |||||
| Bi | AP-PA | 70.7 | 70% | ||||
| PA-AP | 98.4 | 97% | |||||
| P4 (20 μm) | Mono | PA | 105.9 | 62% | |||
| AP | 291.4 | 170% | |||||
| Bi | AP-PA | 81.5 | 80% | ||||
| PA-AP | 114.4 | 113% | |||||
| Collateral of P1 (6 μm collateral, 20 μm main axon) | Mono | PA | 64.8 | 38% | Collateral termination | Charge accumulation at axonal termination | |
| AP | 165.5 | 97% | |||||
| Bi | AP-PA | 48.2 | 47% | ||||
| PA-AP | 72.2 | 71% | |||||
| t1 (6μm) | Mono | PA | 65.7 | 38% | Axonal termination (gray matter) | Charge accumulation at axonal termination | |
| AP | 162.6 | 95% | |||||
| Bi | AP-PA | 48.0 | 47% | ||||
| PA-AP | 72.7 | 72% | |||||
| n2 (6μm) | Mono | PA | 116.7 | 68% | |||
| AP | 289.8 | 170% | |||||
| Bi | AP-PA | 85.1 | 84% | ||||
| PA-AP | 127.5 | 125% | |||||
| n3 (6 μm) | Mono | PA | 127.9 | 75% | |||
| AP | 318.1 | 186% | |||||
| Bi | AP-PA | 93.4 | 92% | ||||
| PA-AP | 139.7 | 137% | |||||
| a1 (10 μm) | Mono | PA | 171.7 | 101% | Axonal terminationc (gray matter, M1) | Charge accumulation at axonal | 2nd 1st 3rd 2nd |
| AP | 104.8 | 61% | |||||
| Bi | AP-PA | 106.7 | 105% | ||||
| PA-AP | 79.1 | 78% | |||||
| a2 (20 μm) | Mono | PA | 70.2 | 41% | |||
| AP | 40.6 | 24% | |||||
| Bi | AP-PA | 41.6 | 41% | ||||
| PA-AP | 31.1 | 31% | |||||
a
All values above 100 % for the Magstim 200 stimulator, and 120 % for the Magstim Rapid stimulator are outside the range of values that the stimulator can provide.
b
Phase of pulse waveform for which stimulation occurred. Each row corresponds to the pulse types displayed in the second column.
c
For all pulse types, except monophasic PA, the threshold for activation at the bend after the fiber leaves the somato-sensory cortex was very similar to this one.