Figure 3.

DCN neurons exhibit typical firing patterns following harmaline injection. (A,B) An example of a tonically firing neuron (A) that became almost completely quiescent after harmaline injection (B). (C,D) An example of a tonically firing neuron (C) that exhibited an ON/OFF firing pattern after harmaline injection (D). (E) Time expansion of the marked section in (D) showing the typical cycle of the ON/OFF pattern. Small bars above the trace mark the sorted spikes. The surgical procedure has been described in detail (Cohen and Nicolelis, 2004; Jacobson et al., 2009). In brief, adult Long Evans male rats weighing 350–500 g (Harlan, Indianapolis, IN, USA) were initially sedated by 5% isoflurane and then injected i.m. with ketamine HCl and xylazine HCl (100 and 10 mg/kg, respectively). Supplementary injections of ketamine and xylazine were given as required. The skull surface was exposed and a craniotomy, slightly larger than the electrode array, was performed above the medial and interposed nuclei. Center of implant was at −11.3 mm posterior to bregma, 1.5 mm lateral to the midline (coordinates taken from Paxinos and Watson, 1998). Arrays of 16 electrodes were lowered 4 mm from the surface of the brain and fixed using dental cement. Rats were allowed at least 2 weeks of recovery prior to recording. Electrode location was verified using histology.