What is the function of the suprapharyngeal ganglia in a earthworm?

Effects of removal and regeneration of the suprapharyngeal ganglion on learning, retention, extinction and negative movements of Lumbricus terrestris were studied in a T maze with electrical punishment and a sandpaper cue at the incorrect side and a dark goal box at the correct side. Learning, retention and negative movements at the choice point were not affected by ganglionectomy or regeneration. Extinction was prolonged, and negative reactions to the sandpaper were increased, by ganglionectomy after training. Negative movements in the maze stem were decreased by ganglionectomy under both learning and extinction conditions, and increased abruptly after 30--50 days of postoperative training. Reactivity to shock decreased when ganglionectomy followed, but not when it preceded, learning. Frequency of correct turns was the only measure clearly changed by learning. Negative movements at the choice point tended to decrease, but inconsistently during learning. There was no evidence that discrimination of sandpaper contributed to learning. Ten trials per day produced fatigue but was not detrimental to health or vigor.