Artificial control of swimming in goldfish by brain stimulation: confirmation of the midbrain nuclei as the swimming center.

The midbrain locomotor region including the nucleus of the medial longitudinal fasciculus (Nflm) was electrically stimulated in free-moving goldfish. Stimulation of sites on the midline induced forward movement, whereas that of sites off midline induced turning toward the stimulated side. The closer the site of stimulation to Nflm, the lower the threshold stimulus intensity required to evoke locomotor movement. Using a wirelessly controlled two-channel microstimulator, the locomotion of goldfish in the horizontal plane could be controlled directly by stimulating Nflm for movements involving the trunk and tail. Forward and turning movements could be arbitrarily induced in goldfish equipped with the stimulation device and electrodes implanted in or near the right and left Nflm. Together with previous observations, these findings confirm the role of Nflm in driving spinal segmental rhythm generators initiating swimming, which involves rhythmic contractions of the trunk musculature.