Which EEG electrode lies halfway between O1 and T3?

Which EEG electrode lies halfway between O1 and T3?

• A. Oz
• B. T5
• C. C3
• D. P3

Answer: (B)

Think about how the 10-20 EEG system places electrodes along the head. O1 sits over the left occipital cortex, while T3 is over the left temporal region. The naming convention uses a region letter and a number to indicate left vs right and relative position along the anterior–posterior axis. Between the occipital area and the temporal area on the left side, the site that sits midway along that path is T5, which lies on the posterior temporal/parietal region. That’s why T5 is the best choice. Oz sits on the midline at the back of the head, C3 sits more central-left, and P3 sits over the left parietal region, none of which are the midpoint between O1 and T3.

Think about how the 10-20 EEG system places electrodes along the head. O1 sits over the left occipital cortex, while T3 is over the left temporal region. The naming convention uses a region letter and a number to indicate left vs right and relative position along the anterior–posterior axis. Between the occipital area and the temporal area on the left side, the site that sits midway along that path is T5, which lies on the posterior temporal/parietal region. That’s why T5 is the best choice. Oz sits on the midline at the back of the head, C3 sits more central-left, and P3 sits over the left parietal region, none of which are the midpoint between O1 and T3.