Figure 1.
Exaggerated beta oscillations are present in the cortex and subthalamic nucleus of 6-OHDA-lesioned anesthetized rats. A, Frontal ECoGs and time-evolving power spectrogram of ECoG activity. Exaggerated beta oscillations emerge during spontaneous activation (2) but not SWA (1). Calibration: 0.2 mV, 500 ms. a.u., Arbitrary units. B, Spectrograms of simultaneously recorded activity in cortex (ECoG) and subthalamic nucleus (STN-LFP) during spontaneous activation. Weak power at 50 Hz is line noise. C, Power spectra (Power) of ECoGs, as well as LFPs simultaneously recorded from within, immediately above and below the STN, in a representative lesioned and control animal during activation. Gray boxes indicate the classic beta band (15–30 Hz). D, E, Beta oscillations are evident in the discharges of single STN units, as shown in autocorrelograms (AC) and periodograms (Lomb). The dashed line in periodogram indicates p = 0.05. STN neurons fire either spike bursts or single spikes in time with most (but not all; arrowhead in E) beta cycles in oscillatory LFPs, as shown in spike-triggered LFP averages (STAv). Power spectra of ECoG and STN-LFP simultaneously recorded with neuron in D are also shown. Calibration: D, 0.2 mV (ECoG), 0.5 mV (unit), 0.1 mV (LFP), 100 ms; E, 0.125 mV, 100 ms. F, Beta oscillations are also reflected in rhythmic multiunit activity in STN (contacts 2–4), but not immediately above or below (contacts 1 and 5). Traces 1–5 of units and LFPs were recorded simultaneously. Calibration: 0.1 mV, 100 ms. G, Plot of STN neurons with significant oscillations in their spike trains (those recorded with silicon probes or glass electrodes are represented by diamonds and circles, respectively). H, Coherence (left) and total beta coherence at 17–23 Hz (right) between single units and LFPs in the STN as recorded with probes (n = 14 and 8 unit/LFP pairs in lesioned and control, respectively). The dashed line is the 95% confidence limit. Data are means ±1 SEM. *p = 0.005. I, Mean firing rates of STN neurons during activated brain state. Data are means ±1 SEM. *p < 0.001. Data in A–F are from different lesioned animals.