Table 8.

Number of electrodes used by each selected study.

Electrode N	Articles
1–16 (14)	[85, 86, 88, 91, 92, 96, 100, 102, 108, 120–122, 142, 165]
17–32 (89)	[26, 37–42, 58, 78–84, 87, 89, 90, 93–95, 97, 101, 103–107, 109, 110, 112–119, 123, 125–127, 129–141, 143–164, 166–170, 173–179]
33–64 (2)	[66, 172]
65–128 (5)	[77, 98, 99, 111, 171]
129–256 (2)	[124, 128]