A-Series Polytrode & Tetrode Probes
A-Series probes whose recording sites are clustered rather than spaced evenly along the shank, so that several sites see the same neuron at once and a sorter can separate it from its neighbours by the amplitude pattern across them.
Why cluster sites at all
A single electrode site records a neuron as one waveform, and two neurons of similar size and distance produce waveforms a sorter cannot reliably tell apart. Clustering sites solves that geometrically: a neuron near the shank is seen by several sites at different offsets, and the ratio of amplitudes across those sites is close to unique to its position. That ratio is what a spike sorter separates on.
Two layouts, one principle
Polytrode designs run a dense column of sites down the shank, so clusters overlap and a unit is seen by a rolling group of neighbours. 82 of the 144 catalog designs are polytrodes, carrying a median of 32 sites per shank — twice the A-Series median — most often at 177 µm².
Tetrode designs place discrete groups of four, separated along the shank. 62 designs take this form, most often at 121 µm², for a median of 8 sites per shank. Each group resolves units at its own depth, with gaps between groups.
The choice between them is whether you want a continuous span you can follow a unit through, or discrete well-isolated depths with known separation.
What clustering costs
Reach. A fixed site budget spent on cluster density is not spent on covering a trajectory: a 64-channel polytrode samples less of a track than a 64-channel linear array. Choose a clustered layout when the question is which neurons; choose a linear layout when the question is how activity varies with depth.
Specifications
Silicon, 15 µm as standard with a 50 µm option on some designs. 4 to 256 sites on 1 to 9 shanks. Sites are iridium as standard.
Related product line
The Q-Trode Series is the dedicated single-tetrode line — one four-site cluster on one shank. The tetrode designs here are A-Series probes carrying several such groups.