Major Factors in Classical Conditioning of Planarians: Stimulus Waveform and Neural Geometry

Abstract

The classical conditioning paradigm for planarians of Thompson and McConnell (1955) has been used, with several modifications, for a number of interesting and provocative experiments on the mechanisms of memory storage (McConnell, Jacobson, and Kimble, 1959; Baxter and Kimmel, 1963; Corning and John, 1961; McConnell, 1964; Barnes and Katzung, 1963; and Hartry et al., 1964). In this paradigm the planarian is usually placed in a narrow plastic trough equipped with an electrode at each end and partially filled with water. The water forms a continuous conducting path between the two end electrodes. A trial consists of several seconds of brilliant illumination, constituting the conditioned stimulus, followed by approximately a second of electric shock, the unconditioned stimulus, administered through the water via the end electrodes. The response of the planarian during the lighted period preceding the shock is scored as a conditioned response. A response during the period of shock is scored as an unconditioned response.

A portion of the research described was supported by Public Health Service grant No. MH07603 and National Aeronautics and Space Administration grant No. NSG-625.