FIG. 1.

Schematic of electrode placement and timeline of pontine reticular nucleus (PnO) stimulation. (A) Electrode placement overlaid on sagittal and coronal views of the rat brain from the Paxinos rat brain atlas (Paxinos and Watson, 2007). Pairs of platinum-iridium electroencephalogram (EEG) electrodes were placed over the left frontal cortex (AP=+4.0 mm and 6.1 mm, L=−2.34 mm) such that each wire “hooked” between the cranium and the dura. Carbon fiber stimulating electrode was placed in the PnO (AP=−8.00 mm, L=−1.3 mm, angle=15°, V=−8.60 mm below bregma at the midpoint of the electrode contacts). A nylon screw was used to anchor the electrode assembly in place. Electrode location was confirmed by examining sagittal and coronal anatomical images. Histology was also used to confirm electrode location in five rats; blue closed circles indicate the locations of the electrode tip. (B) Experiment timeline with three scans: baseline, electrical stimulation, and recovery from stimulation. Electrical stimulation of PnO commenced after an initial 30-sec delay, and followed a block design of 3 sec on and 57 sec off. (C) Example EEG trace during image acquisition, before and after PnO stimulation. Gradient-induced artifact was absent (extended EEG trace left). PnO-stimulus-related artifact was transient (extended EEG trace right). The PnO stimulus marker indicates the timing of the stimulation pulses delivered to the electrode.