Journal of Neuroscience, Vol 9, 3107-3114, Copyright © 1989 by Society for Neuroscience
Operant conditioning of head-waving in Aplysia. II. Contingent modification of electromyographic activity in identified muscles
DG Cook and TJ Carew
Department of Psychology, Yale University, New Haven, Connecticut 06520.
Aplysia can readily exhibit operant conditioning of their head-waving
response when bright light is used as aversive reinforcement (Cook and
Carew, 1986). In the first paper of this series (Cook and Carew, 1989a), we
showed that the electromyographic (EMG) activity of a discrete band of neck
muscles, the lateral columellar muscles (LCMs) of Aplysia is significantly
correlated with the component of head-waving (the horizontal component)
that is modified during operant conditioning. In the present paper, we
asked whether the EMG activity of the LCMs themselves could also be
contingently modified, using the same procedures that produce operant
conditioning of the behavioral response. Differential EMG from the LCMs was
recorded in freely behaving animals with chronically implanted muscle cuff
electrodes. Animals receiving aversive reinforcement (bright light) that
was contingent upon specific patterns of LCM activity readily learned to
alter their differential EMG output. Like operant conditioning of the
head-waving response, this operant modification of LCM activity was rapidly
acquired and was specific to the contingencies of reinforcement. These
results show that a restricted group of muscles, the LCMs, exhibit the
essential features of the head-waving system observed at the behavioral
level: (1) their activity is significantly correlated with head-waving
behavior, and (2) the LCMs are capable of operant modification of their
output. Thus, this restricted response system provides a useful preparation
for examining the neural mechanisms of operant conditioning of head-waving
in Aplysia.