HABITUATION AND DISHABITUATION OF THE PROLEG WITHDRAWAL REFLEX IN LARVAE OF THE SPHINX HAWK, MANDUCA-SEXTA

The neural circuit for the proleg withdrawal reflex (PWR) of Manduca s exta larvae exhibits activity-dependent plasticity. This study demonst rates habituation and dishabituation of PWR behavior. Repeated deflect ion of 1 or 5 mechanosensory hairs on a proleg at a 60-s interstimulus interval (ISI) for 20 trials produced a significant decrease in evoke d force of proleg withdrawal. Habituation was similar with 30-s and 60 -s ISIs and nonsignificant with a 5-min ISI or without repeated stimul ation. Habituated responses recovered after cessation of stimulation o r pinch of the body wall (dishabituation). The role of intersegmental influences was tested by severing connectives to leave different numbe rs of ganglia connected to the test segment. Habituation was robust ev en in test segments that were disconnected from the rest of the centra l nervous system. The PWR of Manduca is appropriate for further analys is of cellular mechanisms underlying learning.