Simultaneous and backward fear conditioning as a function of number of CS-UCS pairings.

Abstract

Four experiments examined the possibility that the outcome of simultaneous and backward fear conditioning procedures might depend upon the number of CS-UCS pairings. A punishment procedure will rats as subjects and shock as the UCS was used; the amount of suppression produced by response-contingent CS presentations indexed the strength of acquired fear. Experiments 1, 3, and 4 examined the suppressive tendencies of simultaneous-and backward-trained CSs after 0, 10, 20, 40, 80, and 160 pairings. The pattern of data suggested that initial pairings have the effect of increasing suppressive tendencies of the CS, while subsequent pairings decrease them. In addition, evidence of fear inhibition was found after 160 pairings in the case of the backward paradigm. Experiment 2 examined several nonassociative accounts based upon differential shock exposure. Groups given 10 pairings or 80 pairings were compared to ggroups given 10 pairings plus 70 shock-alone presentations. The results indicated that number of pairings, rather than number of UCS occurrences, is the important factor in decreasing the initial suppression. The evidence for eventual inhibition in the backward paradigm suggests that this occurs through the acquisition of inhibitory tendencies which are antagonistic to the previously conditioned excitation.

One-trial backward fear conditioning in rats as a function of US intensity

“…The present evidence that a backward conditioning procedure can produce reliable excitatory conditioning is in agreement with a number of empirical and theoretical articles (Cautela, 1965 ;Champion & Jones, 1961;Heth, 1976 ;Hcth & Rescorla, 1973;Mahoney & Ayres, 1976;Matsumiya, 1960;Mowrer & Aiken, 1954;Terry & Wagner, 1975). Moreover, this investigation has demonstrated that the US intensity parameter is a critical determinant of such conditioning.…”

“…Recently, a number of studies (Heth , 1976 ;Heth & Rescorla, 1973;Mahoney & Ayres, 1976) have demonstrated reliable excitatory effects in a backward fear conditioning paradigm. Although the differences between backward and control groups in each of these studies were significant, the levels of conditioning obtained in the one-trial backward conditioning procedure by Mahoney and Ayres (1976) were extremely small, and no replication of their results has since been reported.…”

Excitatory and inhibitory learning with absent stimuli.

“…One potential objection to this interpretation is that it demands that simultaneous pairings of two associatively-activated event representations resulted in inhibition. Although this possibility may seem unlikely, there is evidence that simultaneous first-order conditioning can yield inhibition after extensive training (e.g., Heth, 1976;Moscovitch & LoLordo, 1972). The results of Experiments 1a and 1b might stand as an analogous situation in which simultaneous activation of two representations led to a net inhibitory relationship.…”

“…In contrast, if the tone preceded the noise, one might expect inhibitory learning similar to that observed in Experiments 1a and 1b. These expectations are based on the knowledge that consistent forward CS→US pairings result in excitatory learning (e.g., Pavlov, 1927), whereas backward US→CS conditioning typically results in the development of inhibition (e.g., Cole & Miller, 1999;Chang, Blaisdell, & Miller, 2003;Delamater, Lolordo, & Sosa, 2003;Heth, 1976;Williams & Overmier, 1988), often after a brief period of excitatory learning.By contrast, within the MSOP account outlined previously, the temporal arrangement of noise and tone in Phase 2 might have little effect on whether noise forms an excitatory or inhibitory association with sucrose. In all cases, pairings of two associatively-activated event representations would result in excitatory learning between those representations.…”

Dominance, the bidirectional hypothesis, and Pavlovian backward conditioning in the US-US paradigm

“…Pavlov's (1927, p. 393) revised view that the backward CR is transitory and limited to the early stages of training finds support in current research with conditioned suppression (Heth, 1976;Mahoney & Ayres, 1976). In contrast, however, both Beritoff (1965) and Asratyan (1972) have reported that the backward CR may benefit from extended training-a view that finds some support in research with the Pavlovian procedure (Harlow, 1939;Wagner & Terry, 1975).…”