In one sheep, 20 low-impedance micro-SEEG contacts shared a 1–40 Hz signal while ten other contacts in the column did not

In one sheep, one 64-contact micro-SEEG shaft, and 11.2 seconds of inter-pulse recording, we examined spatial correlation and participation ratio across contacts. The 20 contacts with listed impedance below 200 ohm had mean 1–40 Hz correlation r = 0.987 (minimum 0.93; r = 0.989 after common-average reference) and a mean MUA envelope of 4.1 µV, compared with 11.5 µV on other contacts. Ten kilo-ohm contacts in the same column had mean LFP correlation r = 0.577, similar to the other column (r = 0.554). These results indicate that the low-impedance contacts acted as one shorted node in this recording. With 43 usable contacts, monopolar LFP participation ratio was 2.30 at 120 µm pitch and 1.97 at 960 µm pitch; an eightfold reduction in contact count removed only 3–26% of participation ratio across the reported bands and references. These observations are limited to one sheep, one shaft, one run, and 11.2 seconds between 1 Hz stimulation pulses; the intervals were not true rest, and the cause of the short is unknown.

micro-SEEG · intracranial EEG · neural recording · electrode impedance · signal correlation · participation ratio · sheep · brain-computer interface