Reassessment of area postrema's role in motion sickness and conditioned taste aversion

On the basis of classical studies on the role of the area psotrema (AP) in motion-induced emesis it was generally accepted that the AP is an essential structure for the production of vomiting in response to motion. However, in more recent studies it has been demonstrated that vomiting induced by motion can still occur in animals in which the AP has been destroyed bilaterally. It was inferred from some of these more recent studies that the AP plays no role in motion-induced emesis. From the standpoint of the current understanding of central nervous system (CNS) plasticity, redundancy, remodeling, unmasking, regeneration, and recovery of function, however, it is important to realize the limitations of using ablation procedures to determine the functional role of a given neural structure in a highly integrated, adaptable central nervous system (CNS). For example, the results of our recent investigations in cat and squirrel monkey on the role of the AP in emesis and conditioned taste aversion induced by motion indicate that while AP lesions do not prevent motion-induced emesis when animals are tested 30 days or more after surgery, the lesions do change the latency to emesis. Thus, contradictory findings from lesion studies must be evaluated not only in terms of species difference, differences in lesioning techniques and extent of lesions, and in stimulus parameters, but also in terms of duration of the recovery period, during which significant recovery of function may take place. In our judgment, inadequate consideration of the foregoing factors could lead to erroneous inferences about given structure's role in the behavior of the intact, nonablated animal.