SRCD Poster 2001

CS-reminder induced recovery from overshadowing in an appetitive Pavlovian preparation.

Kosuke Sawa (JSPS (Nagoya University), UCLA) & Aaron P. Blaisdell (UCLA)

Discussion

Introduction

References

Method

Results

•Pavlov (1927) noted that a CS shows reduced behavioral control (i.e., overshadowing) if it was paired with the US in the presence of a more salient CS than if the more salient CS was absent.

•Acquisition-based theories (e.g., Rescorla & Wagner, 1972) attribute overshadowing to a reduced CS-US association. By contrast, performance-based theories (e.g., Miller & Matzel, 1988) treat overshadowing as a performance (e.g., retrieval) deficit.

•Several demonstrations that the response to the overshadowed CS can be augmented, such as by posttraining extinction of the overshadowing CS (e.g., Kaufman & Bolles, 1981) or reexposure to the overshadowed CS (i.e., a reminder treatment, e.g., Kasprow, Cacheiro, Balaz & Miller, 1982), support the performance account of overshadowing.

•A performance account of overshadowing (and other cue-competition effects, such as blocking) has recently been challenged as being limited to conditioned suppression procedures. Using an appetitive conditioning preparation, Holland (1999) failed to find recovery from overshadowing or blocking when the competing stimulus, the overshadowing or blocking CS respectively, was extinguished.

•In the present research, we explored the effect of pre-test exposure to the overshadowed CS (i.e., a reminder treatment) in an appetitive conditioning paradigm to establish whether overshadowing of appetitive conditioning is due to an acquisition or performance deficit.

•In an appetitive conditioning procedure, we obtained overshadowing of a soft tone by a loud noise, and recovery from overshadowing when the tone was presented prior to testing.

•This establishes the generality of a performance account of overshadowing.

•Contemporary acquisition theories cannot explain the present result (but see Dickinson & Burke, 1996; Van Hamme & Wasserman, 1994 for recent modifications of acquisition theories that allow them to explain some retrospective revaluation effects).

•Two possibilities for our success in obtaining recovery from overshadowing while Holland (1999) failed.

–A) we used a reminder treatment while Holland used extinction of the competing CS.

–B) We gave 8 overshadowing trials while Holland gave 32 (but see his Exp. 5). It has been shown that overshadowing is attenuated with more trials (Bellingham & Gillette, 1981; Stout, Arcediano, Escobar & Miller, 2003). Perhaps configural learning (e.g., within-compound associations) predominate with extended training, thereby mitigating the effects of extinction of competing CS A on responding to target CS X.

•

Bellingham, W. P. & Gillette, K. (1981). Attenuation of overshadowing as a function of nondifferential compound conditioning trials. Bulletin of the Psychonomic Society, 18, 218-220.

Dickinson, A. & Burke, J. (1996). Within-compound associations mediate the retrospective revaluation of causality judgments. Quarterly Journal of Experimental Psychology, 49(B), 60-80.

Holland, P.C. (1999). Overshadowing and blocking as acquisition deficits: No recovery after extinction of overshadowing or blocking cues. Quarterly Journal of Experimental Psychology, 52(B), 307-333.

Kasprow, W. J., Cacheiro, H., Balaz, M. A. & Miller, R. R. (1982). Reminder-induced recovery of associations to an overshadowed stimulus. Learning and Motivation, 13, 155-166.

Kaufman, M.A. & Bolles, R. C. (1981). A nonassociative aspect of overshadowing. Bulletin of the Psychonomic Society, 18, 318-320.

Miller, R. R. & Matzel, L. D. (1988). The comparator hypothesis: A response rule for the expression of associations. In G. H. Bower (Ed.), The psychology of learning and motivation (Vol. 22, pp. 51-92). San Diego: Academic Press.

Pavlov, I. P. (1927). Conditioned reflexes. Oxford: Oxford University Press.

Rescorla, R. A. & Wagner, A. R. (1972). A theory of Pavlovian conditioning: Variations in the effectiveness of reinforcement and nonreinforcement. In A. H. Black & W. F. Prokasy (Eds.), Classical conditioning II: Current research and theory (pp. 64-99). New York: Appleton-Century-Crofts.

Stout, S., Arcediano, F., Escobar, M. & Miller, R. R. (2003). Overshadowing as a function of trial number: Dynamics of first- and second-order comparator effects. Learning & Behavior, 31, 85-97.

Van Hamme, L. J. & Wasserman, E. A. (1994). Cue competition in causality judgments: The role of nonpresentation of compound stimulus elements. Learning & Motivation, 25, 127-151.

Figure 1. Mean discrimination ratio across two-trial blocks.

Figure 2. Mean discrimination ratio across two-trial blocks

pooled across reminder and test days.

Figure 3. Mean discrimination ratio across two-trial block

pooled across OV and Acq groups.

•Subjects.

Forty water-restricted female (M = 251.5g) Long-Evans rats with a prior experimental history with cues unrelated to those used here.

•Apparatus.

Each of eight experimental chambers measuring 30 x 25 x 20 cm was housed in separate sound- and light-attenuating environmental isolation chests with a background noise of 62 dB(A).

•Stimuli.

Overshadowing CS A = a noise (15 dB(A) above background)

Overshadowed CS X = a low-frequency tone (4 dB(A) above background).

All CSs were 10 s in duration.

Acclimation. Day 1: Rats were first trained to drink from the dipper during one 60-min session in which water was delivered every 20 ± 15s. During acclimation, CSs A and X were presented twice.

Phase 1 (Overshadowing Training). Days 2-5: In Groups OV.Rem and OV.Con, rats received two AX-water US pairings (AX+) during each 20-min session for a total of 8 trials. In Groups Acq.Rem, Acq.Con, and Gen.Dec, rats received 2 X+ trials per daily session. Each trial occurred 8 and 15 min into the session.

Phase 2 (Reminder Treatment). On Day 6, subjects in Groups OV.Rem and Acq.Rem received two presentations of CS X during a 6 min session. Subjects in the other three groups remained in their home cages during this session but received equivalent handling.

Testing. Day 7: rats received four nonreinforced presentations of CS X (Groups OV.Rem, OV.Con, Acq.Rem, & Acq.Con) or AX (Group Gen.Dec). A discrimination ratio (nosepoking during the CS and during a 30-s prestimulus period) assessed conditioning. Trials occurred at 4, 10, 17, and 25 min into a 30-min session.

AX?

handling

X+

Gen.Dec

handling

X+

Acq.Con

X-

X+

Acq.Rem

handling

AX+

OV.Con

X-

AX+

OV.Rem

Prediction

Test

Phase 2

Phase 1

Group

Note: A = Noise, X = Tone, + = Water US. CR and ‘cr’ indicate a strong and weak response, respectively. “handling” indicates that subjects received equivalent handling.