PEDAL LOCOMOTION IN APLYSIA-CALIFORNICA .1. SENSORY AND MOTOR FIELDS OF PEDAL NERVES

1. 1. The foot of Aplysia californica is innervated by three major pedal ganglion nerves and several minor ones. 2. 2. The pedal nerves are mixed nerves containing both sensory and motor units. 3. 3. The fields of these nerves are organized bilaterally; none cross the midline. 4. 4. Along the longitudinal axis there is overlap of the adjacent sensory-motor fields. 5. 5. The initiation and spread of pedal waves is under central control. Bilateral ablation of anterior or middle pedal nerves failed to block the initiation or spread of these contractions in the fields of the other intact nerves. 6. 6. The suction reflex also appears to be under central control as it was abolished in the fields of sectioned nerves. 7. 7. While electrical stimulation of intact nerves caused changes in activity in the other nerves, this was not seen when cut distal nerve ends were stimulated. This eliminates the possibility of communication between nerves via a peripheral nerve net. 8. 8. Bilateral ablation of the middle pedal nerves suggests that the central program for pedal locomotion is distributed to each individual pedal nerve. Since waves which stopped in the affected field resumed posterior to it, peripheral feedback which might serve to modify the program is not necessary to maintain the program once it is initiated. © 1978.