The Development of Patterned Activity by implanted Ganglia and their Peripheral Connexions in Periplaneta Americana
1. The isolation of a thoracic ganglion from the rest of the central nervous system results in a loss of differentiation of the motor output, although repetitive rhythms may appear during the later stages of isolation. Total isolation of the ganglion in vitro results in a further reduction of motor activity to low-frequency, steady-level discharges in a few fibres of some nerves only. 2. Two or three months after implantation a steady low-frequency discharge can be recorded from many of the branches of the implant ganglion, and these may have functional contacts with adjacent muscles. There is little evidence of afferent connexions. 3. Four to seven months after implantation the efferent connexions of the implanted ganglion often show a highly differentiated pattern of spontaneous electrical activity, and the ganglion will respond in a remarkably delayed and progressive manner to the stimulation of adjacent sense organs. 4. The spontaneous rhythms of the long-term implant ganglion may be determined by a balance between central and peripheral input levels similar to those occurring during progressive isolation of the ganglion. 5. The functional relationship between the host and the donor ganglion appears to consist largely of an inhibitory effect exerted by the host ganglion on the donor or implant ganglion. A justification for this in adaptive terms can be found.