Transplantation of the cockroach circadian pacemaker.

Surgical removal of the optic lobes of the cockroach Leucophaea maderae followed by transplantation of the optic lobes from another individual led to a restoration of the circadian activity rhythm in 4 to 8 weeks. The free-running period of the restored rhythm was determined by the period of the donor rhythm before surgery. The results suggest that the transplanted optic lobe contains a circadian clock that regenerates those neural connections with the host brain that are necessary to drive the circadian rhythm of activity.