Carbon dioxide - induced

Cockroaches (Periplaneta americana) learned to passively avoid electric shock in a two-compartment box after a single training trial. However, Ss exposed to CO2 gas immediately after the training trial failed to show retention of the previous experience when tested 24 h later. Results obtained are consistent with those observed in studies of retrograde amnesia in vertebrates. Article: Numerous studies of humans, rats, mice and fish have shown impaired retention of learned tasks due to the administration of various convulsant and anesthetic agents (McGaugh, 1966). These studies have generally supported the consolidation hypothesis, which states that the establishment of permanent memory of an experience depends upon the continuing activity of a labile memory trace for a period of time following that experience. Presumable, such agents as ECS, drugs, anesthetics and concussion act by disrupting the labile memory trace and thereby prevent formation of the long-term trace. Despite the considerable differences between the supraesophageal ganglia of cockroaches and the encephalized central nervous system of vertebrates (Hughes, 1965), researchers have found cockroaches to be capable of learning active avoidance (Minami & Dallenbach, 1946), passive avoidance (Ebeling, Wagner, & Reierson, 1966) and food-motivated tasks (Longo, I 964), as are most vertebrates. Given that rapid learning can occur in insects, the present experiment studied the use of CO2 gas as an amnesia-inducing agent with an invertebrate in order to examine the phyletic generality of consolidation-like processes. It was hypothesized that administration of a convulsant or anesthetic agent to cockroaches immediately following a trial of passive avoidance learning would greatly reduce retention during later testing as compared to ungassed Ss. The agent to be used was gaseous CO2, which has long been used by entomologists for immobilizing insects prior to surgery and various procedural manipulations (Williams, 1946). When the gas is applied to cockroaches, gross muscular contractions begin within 5 to 10 sec and are followed by 3 to 5 min of immobility.