Figure 6.

Timing of activity of B7 and evidence that the activity of B7 corresponds to the third largest unit on BN3. A, B7 is activated before and during the retraction phase of a feeding-like motor program induced by carbachol. Extracellular recordings from RN, BN2, and BN3 were made simultaneously with an intracellular recording from B7. A schematic bar above the traces indicates the protraction phase (open bars) and the retraction phase (filled bars). Note that large-unit extracellular activity in RN and BN2 occurs at essentially the same time, which is characteristic of an ingestion pattern (Morton and Chiel, 1993a,b). Neuron B7 becomes active just before the onset of the retraction phase and remains active throughout the retraction phase (as judged by activity in BN2). Action potentials in B7 correspond to the third largest extracellular unit on BN3 (line labeled 3 pointing to the BN3 trace; second largest and largest units are indicated with lines labeled 2 and 1, respectively). Between the first and second ingestive-like patterns, B7 was injected with strong hyperpolarizing current (marked with a bar labeled B). This blocked action potentials in B7 and abolished the third largest extracellular units in BN3. The hyperpolarizing artifact has been suppressed so that the voltage trace from B7 is visible; note that B7 is not generating action potentials. B, Expanded timescale excerpt of the data marked with a bar and the “B” in A. Note the one-to-one correspondence between action potentials in B7 and extracellular units in BN3. During hyperpolarization of B7, the third largest extracellular units on BN3 are completely abolished and only return when B7 is released from hyperpolarization. The hyperpolarizing artifact has again been suppressed so that the voltage trace from B7 can be shown.