Modulation of a conditioned eyeblink response by a putative emotive stimulus conditioned with hindleg shock.

Abstract

Two experiments with rabbits showed that the differential modulation of a conditioned eyeblink response (CR) by 30-s auditory stimuli previously paired with shock was independent of the locus of shock application. In Experiment 1, the modulation occurred when the CR was trained with paraorbital shock and the 30-s stimuli were trained with either hindleg or paraorbital shock. Experiment 2 replicated the observed adequacy of hindleg shock for modulation training, under 2 different conditions of eyeblink conditioning. The data, along with the findings that the same 30-s stimuli similarly facilitate the unconditioned eyeblink and the airpuff-elicited startle response (Brandon, Bombace, Falls, & Wagner, 1991), were viewed as supporting the notion that the CRmodulation is dependent upon a conditioned fear response elicited by the 30-s cues (Wagner & Brandon, 1989). demonstrated what they referred to as the differential modulation of a conditioned eyeblink response (CR) by contextlike Pavlovian stimuli. The contextual stimuli were two 30-s auditory stimuli (designated A and B) that were trained under the arrangement that a single, 4-mA, 50-ms, paraorbital shock consistently occurred between 8 and 28 s after the onset of A, but never occurred in the presence of B. When a 1,050-ms target conditioned stimulus (CS) that had been separately pretrained to elicit an and Wagner (1991) studies that eyeblink tendencies were conditioned to the contextual stimuli and that although these were below some response threshold, so as not to be evidenced in responding to the contextual stimuli in isolation, they may nonetheless have been adequate to increase the amplitude of an eyeblink CR otherwise elicited.There are two related predictions concerning the generality of the CR modulation effect reported by Brandon and Wagner (1991) that follow from the view that the results represent the action of a conditioned emotional response. One is that contextual cues, as trained with paraorbital shock by , should modulate a range of other defensive behaviors besides the eyeblink CR. This prediction was supported by Brandon, Bombace, Falls, and Wagner (1991), who showed that the same contextual cues that modulated the eyeblink CR similarly modulated the eyeblink unconditioned response (UR) and the airpuff-elicited startle response. The second prediction, which is the focus of the present study, is that these stimuli should become effective in modulating the eyeblink CR by being paired with any of a range of aversive USs that should be equally capable of supporting the acquisition of a conditioned emotional response. That is, the eyeblink modulation otherwise observed by Brandon and Wagner and by should not be unique to contextual stimuli trained with paraorbital shock.This prediction was tested in the two experiments reported here. Both assessed the possibility that hindleg shock would be adequate to condition contextual stimuli that could subsequently modulate the amplitude of the eyeblink CR to a CS independently paired with a paraorbital US. E...

Issues in the extinction of specific stimulus-outcome associations in Pavlovian conditioning

“…When the CS is tested back in this context, then the residual excitatory strength of the CS can sum its excitatory effects with the excitatory strength conditioned to the context to result in a stronger CR than would occur when the CS is tested in a more neutral context. Investigators have, indeed, found greater levels of responding to a CS when this is tested in a more excitatory context compared to a less excitatory context (e.g., Brandon & Wagner, 1991; Grau & Rescorla, 1984). …”

Modulation of trained and extinguished stimuli by facilitators and inhibitors

“…Perhaps the simplest account of modulation is given in terms of summation of the excitatory and inhibitory strengths of the individual elements (e.g., Bombace, Brandon, & Wagner, 1991;Rescorla & Wagner, 1972). According to such a view, responding to an AB compound can be understood in terms of the summation of the strengths of the A and B elements.…”

The effects of two forms of physical activity on eyeblink classical conditioning

“…Amygdala-dependent processes can modulate delay eyeblink conditioning. For example, contextual fear conditioning prior to eyeblink conditioning can enhance the amplitude of subsequent eyeblink CRs [15-18,32] or the rate of eyeblink conditioning [57]. Amygdala lesions abolish this latter effect [57].…”