Fig. 2.

Raw LP signals picked up in GPi12 and STN12/01 at rest and variations in their frequency content over time.a, Off treatment, the records from both nuclei are dominated by activity with a frequency below 30 Hz. b, Same patient after the ingestion of levodopa. Low-frequency activity is reduced, and a sharply tuned band of activity appears in STN at ∼70 Hz (arrow). In both a andb, a 1 sec segment of corresponding LP is shown under the frequency sonograms. c, Another patient recorded on treatment, showing activity in STN at ∼70 and 140 Hz (arrows). d, A patient who fell drowsy during treatment with levodopa. The peak in activity at ∼70 Hz (arrow) is present when alert but not drowsy (denoted byblack bars and defined as eyes closed and low-voltage slow activity and α dropout in EEG).