Developmental emergence of long-term memory for sensitization in Aplysia.
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.
Wright
W G
WG
Department of Psychology, Yale University, New Haven, Connecticut, 06520, USA.
McCance
E F
EF
Carew
T J
TJ
D000818:Animals; D001048:Aplysia; D001522:Behavior, Animal / Q000502:physiology*; D008568:Memory / Q000502:physiology*; D008570:Memory, Short-Term / Q000502:physiology; D013997:Time Factors