Figure 5.

Simultaneous paired recordings of a DLM soma and an Area X pallidal terminal with a single electrode during Area X inactivation. A, The raster plots show the responses of DLM (red) and pallidal (blue) units, and GABA was infused into Area X over the period indicated by the vertical bar on the left (for 90 s). Raw traces from the last 5 s of the numbered trials (1–4) are shown in B. The plots on the right side of the raster plots show mean firing rates of the DLM (red) and the pallidal (blue) units in each trial. Note that the time course of increased DLM activity after GABA infusion is completely matched with the decreased pallidal activity. This DLM unit had very low spontaneous activity before GABA infusion. C, Strong correlation between the duration of the ISI of pallidal firing and the number of DLM spikes occurring during the individual ISIs, calculated from the paired recording in the transition period during which the DLM unit started to fire tonically (trial #2 in A and B). The line indicates the linear least-squares fit through the data and has an r value of 0.95 and a slope of 1 DLM spike/27.4 ms pallidal ISI. D, Examples of spontaneous sustained firing of DLM spikes from two different single DLM recordings (D₁) and one paired DLM soma–pallidal terminal recording (D₂). In the paired recording, DLM spikes are truncated to enhance the visibility of the pallidal spikes (arrows). Note that the trains of high-frequency DLM firing were accompanied by pauses in pallidal firing.