Journal of Neuroscience, Vol 8, 4434-4439, Copyright © 1988 by Society for Neuroscience
Context-US learning in Aplysia californica
RM Colwill, RA Absher and ML Roberts
Howard Hughes Medical Institute, Columbia University, College of Physicians and Surgeons, New York, New York 10032.
Two experiments explored learning about the relation between an
unconditioned stimulus (US) and the context in which that US was delivered
in Aplysia californica. Subjects were exposed to 2 different contexts. They
received a series of moderate electric shock USs in one context but not in
the other. Experiment 1 revealed that the context- shock pairings were
sufficient to establish an association between that context and the shock.
That association was demonstrated by the ability of the reinforced context
to enhance a defensive reflex and to reduce learning about a conditioned
stimulus (CS) that was subsequently paired with the shock US. Experiment 2
provided evidence that the context-US association could be extinguished by
simple nonreinforced exposure to the reinforced context. These results show
that context conditioning is not unique to vertebrate learning. We argue
that this learning is difficult to accommodate within current
contiguity-based neuronal models of learning.