Behavioral choice: neural mechanisms in Pleurobranchaea.

In the marine mollusk Pleurobranchaea, it is known that feeding occurs and withdrawal from tactile stimuli is suppressed when the sensory stimuli for feeding and withdrawal are presented simultaneously. This "dominance" of feeding behavior over withdrawal behavior occurs because the central nervous network controlling feeding inhibits the central nervous network controlling withdrawal. The inhibition is mediated by a bilaterally symmetrical pair of reidentifiable feeding neurons that are members of the "corollary discharge" population in the buccal ganglion. This study supports the hypothesis that inhibitory interactions between competing motor systems are responsible for the "singleness of action" that characterizes animal behavior.