Figure 1.
Corticosubthalamic recordings during beta frequency stimulation in parkinsonian patients. A, Surgical setup, sagittal view of the subthalamic area, 11 mm lateral to the midline; (modified from Schaltenbrand and Bailey, 1959). Z.i., Zona incerta; IC, internal capsule; H2, field H2 of Forel; Ra. Prl., prelemniscal radiation; SNr, substantia nigra pars reticulata. Three microelectrodes were implanted using the central, anterior, and either lateral or medial trajectory in the BenGun arrangement. Stimulation was delivered through macro-tips located dorsal to the STN while LFPs and units were recorded from microtips within the STN. EEG was recorded from midline locations. B, Example signals: EEG, LFP, unit activity, and BUA (generated using the unit channel). C, Oscillations were detected from the spectral power of the LFP (example patient, 23 Hz peak, corrected for 1/f falloff). D, A Kalman filter was used to generate an artifact free signal (red) using the raw signal (black) and a model of the average artifact (blue). E, When the stimulus frequency was well matched to the peak beta frequency, consecutive cycles of stimulation at the same phase (blue, green, orange, or red) occurred coincidentally.