A corollary discharge of total foregut motor activity is monitored by a single interneurone in the lobster Homarus gammarus.

1. In Homarus, an identified interneurone (the L cell), which possesses the largest cell body in the commissural ganglion and projects to the brain, exhibits a complex firing pattern (Fig. 2 a). 2. It is shown that the L cell discharges with each of the 4 pattern generators of the stomatogastric nervous system which organize the rhythmic motor activity of the foregut (Fig. 2 b-e). 3. Manipulation of the membrane potential of the L cell does not induce any change in the 4 rhythms (Fig. 3), and it is concluded that the L cell is driven by the 4 pattern generators. 4. The functional meaning of this complex corollary discharge of the total foregut motor activity is discussed.