Spontaneous Recovery from Extinction Depends on the Reconsolidation of the Acquisition Memory in an Appetitive Learning Paradigm in the Honeybee (Apis mellifera)

In an appetitive olfactory learning paradigm, two CS-only trials presented after memory is consolidated lead to extinction. On day 1, all animals were subjected to three CS-US pairings (A1-A3) with an ITI of 10 min (acquisition). After 24 h, on day 2, two CS-only (C1, C2) trials were presented with an ITI of 10 min. At each time point after the last CS-only trial, a subgroup of animals was tested with one CS-only trial (retention test). Data of the acquisition phase and the CS-only presentations after 24 h were pooled for all subgroups (retrieved, nonretrieved). For detailed information on performance during acquisition and CS-only trials of the different subgroups, see supplemental Figure 2-1 A-E (available at www.jneurosci.org as supplemental material). Asterisks indicate significant differences (p < 0.05) in the CRs between retrieved and nonretrieved animals of one subgroup. % CR, Percentage of animals that show a proboscis extension response during CS presentation; black circles and bars, retrieved group; gray circles and bars, nonretrieved group. The number in parentheses represents the number of animals in the different subgroups.

In an appetitive olfactory learning paradigm, five CS-only trials presented after memory is consolidated lead to extinction and spontaneous recovery. On day 1, all animals were subjected to three CS-US pairings (A1-A3) with an ITI of 10 min (acquisition). After 24 h, on day 2, five CS-only trials (C1-C5) were presented with an ITI of 10 min. At each time point after the last CS-only trial, a subgroup of animals was tested with one CS-only trial (retention test). Data from the acquisition phase and the CS-only presentations after 24 h were pooled for all subgroups (retrieved, nonretrieved). For detailed information on performance during acquisition and CS-only trial of the different subgroups, see supplemental Figure 3-1 A-E (available at www.jneurosci.org as supplemental material). Asterisks indicate significant differences (p < 0.05) in the CRs between retrieved and nonretrieved animals of one subgroup. For the retrieved groups, only bars with different letters differ significantly from one another (p < 0.05); nonretrieved groups do not differ from each other. % CR, Percentage of animals that show a proboscis extension response during CS presentation; black circles and bars, retrieved group; gray circles and bars, nonretrieved group. The number in parentheses represents the number of animals in the different subgroups.

Emetine (Eme; 10 mm) applied systemically 30 min before acquisition blocks long-term memory at 24 h after acquisition. Emetine was injected into the flight muscle 30 min before three CS-US pairings with an ITI of 10 min (acquisition). Memory was tested 24 h after acquisition (retention test), (emetine, n = 57; PBS, n = 61). The asterisk indicates a significant difference between the CRs (p < 0.05). Arrow, Time of injection; gray, PBS-injected control group; black, emetine-injected group; % CR, percentage of animals that show a proboscis extension response during CS presentation.

Emetine (Eme; 10 mm) applied systemically 30 min before presentation of five CS-only trials blocks spontaneous recovery at a 24 h retention test. On day 1, animals were subjected to three CS-US (A1-A3) pairings with an ITI of 10 min (acquisition). After 24 h, on day 2, emetine was injected into the flight muscle 30 min before five CS-only trials (C1-C5). CS-only trials were presented with an ITI of 10 min. On day 3, memory was tested (retention test). The asterisk indicates a significant difference between the CRs (p < 0.05). A, Retrieved groups (emetine, n = 66; PBS, n = 43). B, Nonretrieved groups (emetine, n = 53; PBS, n = 49). Arrow, Time of injection; gray, PBS-injected control group; black, emetine-injected group; % CR, percentage of animals that showed a proboscis extension response during CS presentation.

Emetine (Eme; 10 mm) applied systemically 30 min before presentation of two CS-only trials blocks extinction at a 24 h retention test. On day 1, animals were subjected to three CS-US pairings (A1-A3) with an ITI of 10 min (acquisition). After 24 h, on day 2, emetine was injected into the flight muscle 30 min before two CS-only trials (C1,C2) with an ITI of 10 min. On day 3, memory was tested (retention test). The asterisk indicates a significant difference between the CRs (p < 0.05). A, Retrieved groups (emetine, n = 54; PBS, n = 41). B, Nonretrieved groups (emetine, n = 51; PBS, n = 57). Arrow, Time of injection; gray, PBS-injected control group; black, emetine-injected group; % CR, percentage of animals that showed a proboscis extension response during CS presentation.