FIGURE 7.

(A) Multicompartment axon models were run with diameters of 2.0, 5,7, and 10.0 μm in response to stimulation from 1 to 36 contacts on the μDBS. (B) Maximum activation distance (mm) for each fiber size based on electrode size at –1 V (top) and –3 V (bottom). Large-diameter fibers can be activated at greater distances away from the electrode. For smaller diameter fibers, larger electrode sizes reduce activation spread. (C) Firing threshold was normalized to –1 V amplitude at 9 contacts on, which is approximately the height of classic DBS contact of 1.5 mm. A multi-resolution device may be useful to target different diameter fibers; as shown in the right panel, smaller contacts activate small diameter fibers at 65.75% efficiency over 5.7 μm fibers, and require about 113.1% additional voltage to activate the same 10.0 μm fibers. Larger contact sizes preferentially activate large diameter fibers, with about 50% lower thresholds relative to 5.7 μm fibers.