| The signaled barpress (SBP) task (Steinmetz, Logue, & Miller, Beh. Neuro.,
107:1, 1993) uses a standard operant conditioning chamber. The rat at the left is
shown pressing a lever to receive food pellet reinforcement. A speaker directly above the
cage delivers a 1 sec tone on average every 25 seconds. A barpress occurring during the tone
results in food pellet delivery. Barpresses when the tone is not on are not reinforced. On
average, rats reach asymptotic learning levels in 6 days, making this an ideal task for
undergraduate behavioral neuroscience research. Professor Miller, seated, and Chris Chapleau, neuroscience and biology major, are setting up
the equipment in preparation for a conditioning session. At the
2000 annual meeting of the Society for Neuroscience, they presented data
involving a behavioral phenomenon known as learned irrelevance and the
function of the hippocampus (Miller, Doherty, Chapleau, & Allen, SFN
Abstracts, 2000). Learned irrelevance involves pre-exposure to
uncorrelated presentations of a CS and US. This pre-exposure retards
learning when the CS and US are subsequently paired during
conditioning.
While the SBP is not a classical conditioning task, uncorrelated presentation of
the tone while rats are performing on a FR8 schedule leads to a strong retardation during
SBP training. Dorsal hippocampal lesions reversed this retardation. Chapleau and Miller
are currently working on a research project that is studying dopaminergic and serotonergic
input to the hippocampus and the function of these neurotransmitter systems in encoding
the irrelevant tone stimulus.
Courtney Halleck, psychology and biology major, is the primary animal caretaker in the
Carthage Neuroscience Lab. She is shown here hand training a rat to become comfortable
with human touch and interaction.
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