Interoceptive SD of the Large Intestine Established by Mechanical Stimulation
A rhesus macaque monkey, surgically prepared with a Thiry-Vella large intestinal loop, was trained to press a lever for sugar pills on an FR 24 schedule of reinforcement. Operant discrimination was then established through differential reinforcement of the response in the presence of an interoceptive stimulus. The SD consisted of rhythmic inflation-deflation (with air at 120 mm. Hg pressure) of a small latex balloon situated in the loop. The onset of the visceral stimulus was quickly discriminated but its termination was not immediately discriminable. Extended training did not diminish the continued responding or overshoot beyond the SD termination, thus confirming our previous results, obtained by stimulating the small intestine.