A search for the mammalian brain site(s) mediating occasion setting learning

grantor: University of TorontoUsing a conditional contextual discrimination paradigm, I have been able to simultaneously assess two types of learning: A complex occasion setting learning and a simple Pavlovian learning. An occasion setter is a discriminative cue (feature) that predicts whether or not a target stimulus is followed by a reinforced event (US). Behavioural evidence has demonstrated that discriminative control of the occasion setter does not rest with simple excitatory associations between the feature and the US or between the feature and the target stimulus. In all of the experiments presented here, one context (feature) predicted that access to a saccharin solution (target) would be followed by a LiCl injection (US), while a second context predicted that the identical saccharin solution would be followed by a saline injection. All control animals learn to suppress fluid consumption in the first relative to the second context (occasion setting) and all acquire an aversion to the LiCl paired context on a subsequent place test (Pavlovian learning). Pavlovian aversions to the "danger" context can be abolished and the occasion setting properties remain intact. Having demonstrated a behavioural double dissociation between the types of learning, the focus of this thesis is to identify the neuroanatomical loci mediating the two separate learning systems. (Abstract shortened by UMI.)M.Sc