Importance of the environment in conditioned behavior

The purpose of this study was to determine whether an entire experimental situation, and not an individual single stimulus, could be employed to generate a conditioned response. Experiments were conducted on four adult cats. Each cat was conditioned in two different experimental environments (Situation I and Situation II), which consisted of two compartments that differed with respect to color, shape and illumination. Experiments were carried out separately on each cat; experimental sessions, which lasted 30 min, were conducted two or three times a week. Two cats (Nos. 1 and 2) were first trained during 15 sessions in Situation I, and then during 15 subsequent sessions in Situation II. During each session in Situation I, electrical stimulation, which was applied to the basal forebrain area (BFA), evoked a slow-wave EEG pattern; in addition, the animals would close their eyes and lie down (i.e., they exhibited typical presleep behavior). After three to five sessions, this behavior began to appear as soon as the cats were introduced into the experimental compartment, even before stimulation was applied. In a further series of sessions, the cats were placed for 15 sessions in Situation II, wherein stimulation was applied to the lateral hypothalamus (LH). Stimulation of the LH evoked a desynchronized EEG pattern that was accompanied by excitatory behavior. In the other two cats (Nos. 3 and 4), the animals were first trained for 15 sessions in Situation II; subsequently, they were trained for 15 sessions in Situation I. Finally, a test of cross-stimulation was performed. Stimulation of the BFA (which was previously used in Situation I) was applied, one time only, to cats 1 and 2 in Situation II; stimulation of the LH (which was previously used in Situation II) was applied, once only, to cats 3 and 4 in Situation I. In both cases, the animals did not exhibit any of the previously observed behavioral reactions or EEG patterns of activity. The preceding results confirm our hypothesis that, in each situation, a conditioned reaction was established in response to the totality of the experimental environment.