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Abstract
Hibernators display severe changes in brain structure during deep torpor, including
alterations in synaptic constitution. To address a possible effect on long-term memory,
we examined learning behavior and memory of the hibernator Marmota marmota. In two
operant conditioning tasks, the marmots learned to jump on two boxes or to walk through
a tube. The animals were trained during their active season. Performance improved
during the training phase and remained stable in a last test, four weeks before entrance
into hibernation. When retested after six months of hibernation, skills were found
to be unimpaired (box: before hibernation: 258.2+/-17.7 s, after hibernation: 275.0+/-19.8
s; tube: before hibernation: 158.4+/-9.0 s, after hibernation: 137.7+/-6.3 s). Contrary
to these findings, memory seemed to be less fixed during the active season, since
changes in test procedure resulted in impaired test performance. Besides the operant
conditioning, we investigated the animals' habituation to a novel environment by repeated
open field exposure. In the first run, animals showed exploratory behavior and thus
a high locomotor activity was observed (63.6+/-10.7 crossed squares). Upon a second
exposure, all animals immediately moved into one corner and locomotion ceased (7.2+/-1.9
crossed squares). This habituation was not altered even after hibernation (6.1+/-1.1
crossed squares). We thus conclude that long-term memory is unaffected by hibernation
in Alpine marmots.