Adult Aplysia exhibit both short-term and long-term memory for sensitization in the gill and siphon withdrawal reflex. Previous developmental studies showed that short-term memory for sensitization emerges late in juvenile development (stage 12; Rankin and Carew, 1988; Wright et al., 1991). In the present study, we examined the development of long-term memory for sensitization. Long-term sensitization of the siphon withdrawal reflex was quantified as an increase in mean response duration observed 20- 24 h after receiving a training regime of one or more 90-min sessions of electrical shock to the tail. In the first three experiments we assessed the capacity for long-term sensitization in adults and in juveniles of stages late 12 and early 12. Animals in all three age classes showed long-term sensitization. In a fourth experiment we simultaneously trained and tested both early stage 12 animals and stage 11 animals with identical stimulus parameters that were scaled down to a level appropriate to the smaller stage 11 animals. Under these conditions, the early stage 12 animals demonstrated long-term sensitization, while the stage 11 animals still showed no evidence of long-term sensitization. These results indicate that long-term sensitization first emerges at early stage 12, which is the same developmental stage in which short-term sensitization first emerges. Although these behavioral data do not elucidate underlying mechanisms, the fact that short-term and long-term memory emerge according to the same developmental timetable is consistent with the possibility that these two forms of memory may share at least some common mechanistic features.
ASJC Scopus subject areas
- Experimental and Cognitive Psychology
- Cognitive Neuroscience
- Behavioral Neuroscience