Fig. 5.

Axial and coronal images of group C (patients 7–10) who did not suffer from stimulation-induced speech impairments during high- or low-amplitude stimulation. The distribution of the electric field isolevels did not cover part of the fct in patients 7–9, and slightly covered part of the fct in patient 10. The boundaries of the red nucleus (RN), STN, and fct are marked in the axial and coronal images when present. The contours of the electric field isolevels are traced and color-coded where white indicates no effect on speech intelligibility and green substantially improved speech intelligibility.