Electrode Site Span
Electrode site span is the distance along a shank from the first electrode site to the last — the length of tissue one placement samples at once, as distinct from the shank length, which is how deep the probe can reach.
Electrode site span is the distance along a shank from the first electrode site to the last, which is the length of tissue one placement samples at once, as distinct from the shank length, which determines how deep the probe can reach. Both are quoted in millimetres and the two are often confused: a 10 mm shank with 32 sites at 100 µm has a 3.1 mm span near its tip and 7 mm of bare shank behind it.
Span follows from site count and pitch: 16 sites at 50 µm cover 0.75 mm, 32 at 100 µm cover 3.1 mm, and the 3D Matrix arrays reach 10 mm. It is chosen against the structure: about a millimetre spans the mouse cortex, two the rat's, and a hippocampal profile that crosses CA1 and the dentate wants three or more. A span longer than the target spends channels in tissue that is not the question; one shorter than the target has to be positioned on it, which is the Vector design's approach to deep targets — a short array on a long body.
Shank length, the other number, is set by the depth of the target plus the tissue above it: 1.5 to 60 mm across the catalog, with 5 and 10 mm the common lengths. A longer shank is stiffer for the same thickness and is the reason the deepest designs use a 50 µm substrate or a support body. Layouts and their model-number fields are under Probe Geometry; targets under Anatomy and Targeting.
Typical values
| Span, 16 sites at 50 µm | 0.75 mm |
|---|---|
| Span, 32 sites at 100 µm | 3.1 mm |
| Longest catalog span (Matrix 3D array) | about 10.5 mm |
| Shank length, catalog | 1.5 to 60 mm (5 and 10 mm most common) |