Autogenic rhythmicity in the abdominal ganglia of the crayfish: The control of swimmeret movements

Abstract

1. 1. Complete deafferentation and isolation from the rest of the central nervous system does not prevent the appearance of rhythmic, coordinated motor discharges in the first roots of the first five abdominal ganglia. These discharges appear in the same sequence as in the intact animal and are of similar duration. 2. 2. No effect, other than appearance of rhythmic discharges if previously absent, is observed on removal of the last ganglion of the abdominal chain, i.e. the one innervating the uropods and telson. 3. 3. The rhythm normally originates from the fifth abdominal ganglion, spreading to the more anterior ones at a constant speed. 4. 4. In absence of the fifth ganglion, the fourth can replace it, often without much difference in rhythmicity. 5. 5. Removal of the fourth may or may not result in the third taking over the role of pacemaker for the rhythm; the second and first ganglia were never found to acquire pacemaker function. 6. 6. Hemisection did not interfere with the appearance of discharges of both roots from all ganglia, showing that duplicate pathways are involved. 7. 7. The activity spreads always anteriorly with a delay of about 150 msec for each ganglionic interval. 8. 8. All potential pacemakers appear to have about the same preferred inherent rhythmicity of 1·5 bursts/sec. 9. 9. Each ganglion has a characteristic type of discharge, which remains unaltered whether it is driven or functions as pacemaker. The more posterior the ganglion, the longer the discharge. 10. 10. Symmetrical roots usually show very similar discharges and are never out of phase. © 1964.