Conditioned stimulus as a determinant of the form of the Pavlovian conditioned response.

Abstract

The role of the conditioned stimulus (CS) as a determinant of the form of the Pavlovian conditioned response (CR) was investigated in five experiments. Both stabilimeter measures of general activity and detailed observations of the behavior of the rat subjects in the presence of CSs anticipatory to a food unconditioned stimulus (US) were obtained. In Experiment 1, substantially different behaviors to light and tone CSs were observed; further, these differences were found to be dependent on specific learning experience rather than on the mere presence of different stimulation at the time of response evocation. Experiments 2 and 3 investigated the possibility that there was considerable communality of learning to light and tone CSs despite their evoking different CRs. In Experiment 2, prior conditioning of either the tone or light CS was found to block the acquisition of various behaviors to the added element when a light-tone compound stimulus was reinforced, even though the pretrained stimulus did not itself evoke those behaviors. In Experiment 3, the nature of second-order conditioned responding was found to be similar regardless of which first-order CS was used as the reinforcer. Additionally, the reinforcing powers of the light and tone CSs were found to summate. Experiments 4 and 5 examined behaviors to a variety of visual and auditory stimuli paired with food. Stimulus modality and the localizability and vertical location of visual stimuli were found to influence conditioned responding. These results suggested that in this conditioning situation, similar learning of a CS-US relation may be displayed in different overt CRs, depending on the nature of the CS.

A limited role for mediodorsal thalamus in devaluation tasks.

“…Previous data (Holland, 1977) that food cup behaviors during 10 second visual CSs are concentrated in the last 5 s of the cue. For the analysis of the test session, I report this measure as well as the percentage of time the rat spent with its head in the food cup in the 5 s after the light ended, focusing on the first half of the session, as in a previous study (Pickens, Saddoris, Gallagher, & Holland, 2005).…”

Excitation and inhibition in unblocking.

“…Furthermore, upward shifts in the reinforcer enhanced conditioning of the added tone more if US2 differed from US I, but downward shifts enhanced conditioning more if US2 was qualitatively similar to US1. The abrupt decline in startle responding in the unshifted groups probably reflects the habituation of unconditioned orienting behavior to the auditory cue (see Holland, 1977). In Phase 2, those subjects maintained the USl-goal and rear behaviors that were conditioned to the visual cues in Phase 1.…”

“…On each observation one and only one behavior was recorded. Five behavioral categories were reported: magazine-standing motionless in front of the food magazine with head or nose within the recessed food cup; cup-standing motionless in front of the extending sucrose cup while contacting that cup with face or forelimbs; head jerk-short, rapid horizontal and/or vertical movements of the head; rear-standing on rear legs, with both front legs off the floor, but not grooming; and startle-a rapid jump or change in position (see Holland, 1977, for more complete descriptions). In addition, for rear and head jerk behaviors, I recorded the direction the rat was facing (toward the foodcup, the sucrose cup, or neither).…”

Variations in Unconditioned Stimulus Processing in Unblocking.

“…Because these responses occur predominantly during the few seconds immediately before delivery of the reinforcer (Holland, 1977), we examined these behaviors during the last 5s of the 10-s CS-US intervals, as in previous studies (e.g. Holland & Gallagher, 1993b).…”