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Abstract
In the real world, task-relevant, conditioned stimuli are often embedded in a varying
background, from which they have to be segregated. Besides sensory mechanisms, associative
learning assumingly plays an important role for the segregation of the conditioned
from the background stimuli, especially if conditioned and background stimuli are
spectro-temporally structured, and psychophysically similar. We therefore investigated
the influence of spectro-temporally structured background tones on associative learning
of conditioned tones depending on the complexity of the behavioral task and the psychophysical
similarity between conditioned and background tones. Frequency-modulated tone sweeps
were used as conditioned stimuli, and persisting frequency-modulated tones as background.
In a shuttle-box, Mongolian gerbils were subjected to a simple detection task, or
to a more complex discrimination task. In contrast to detection learning, introduction
or change of background tones affected discrimination performance both during learning
and at the stage of retrieval, especially when conditioned and background tones were
spectro-temporally similar. The change from a familiar to a new background tone at
the stage of retrieval caused a prefrontal dopamine increase and lead to relearning
of task-relevant associations. We conclude that conditioned stimuli and background
stimuli are processed concomitantly, which might provide contextual information, but
requires additional cognitive processing.