Conditioned Taste Aversions Are Not Readily Disrupted by External Excitation

Thirsty male rats were given saccharin water followed by delayed illness. During the delay, some of the rats were exposed to events designed to stimulate their external systems (i.e., the system that processes external events such as auditory and tactile stimulation). Access to females, mild footshocks, and pain from hypertonic saline injections did not interfere with either the acquisition or extinction of a taste aversion. In fact, when administered intraperitoneally, the hypertonic saline slightly increased the strength of the aversion. Exposure to heat, which changed both skin temperature and core temperature, slightly attenuated the formation of the aversion. Overall, these results emphasize the independence of the internal system (i.e., the system that deals with internal events such as taste, illness, and core temperature) and the external system. Furthermore, the associating of events related to the internal system is not readily interfered with by events related to the external system.