Excitatory and inhibitory learning with absent stimuli.

Abstract

Three experiments show that two associatively-activated stimulus representations may engage in excitatory or inhibitory learning, depending on their temporal relationship. Experiment 1a suggested that simultaneously-activated stimulus representations show evidence of inhibitory learning in an acquisition test. Experiment 1b showed similar evidence of inhibition in a summation test. Experiment 2 found that activation of two stimulus representations in a serial compound resulted in excitatory learning between the antecedent and the subsequent (forward), and inhibitory learning between the subsequent and the antecedent (backward). The results show the dynamic influence of temporal contiguity on mediated learning.In a Pavlovian conditioning situation, a stimulus that is repeatedly paired with an unconditioned stimulus (US) comes to elicit a conditioned response. Learning theorists often assume that this learning involves the formation of associations between this stimulus (the conditioned stimulus, CS) and the US, such that subsequent presentations of the CS alone activate the representation of the US. It is this associatively-activated representation that produces much of the conditioned responding that is attributed to the CS. Although this concept is popular among theories of learning, and throughout associative models in psychology, there is some dispute concerning the properties possessed by associatively-activated stimulus representations. They are often assumed to represent at least a portion of the directlyexperienced stimulus, but some theories suggest that an associatively-activated stimulus representation may differ from its directly-activated counterpart in many ways.Investigations conducted by Holland and colleagues elucidated some of the associative properties possessed by associatively-activated stimulus representations. In a conditioned taste aversion preparation with rats, Holland (1981) showed that a taste aversion can be learned in a situation in which the taste CS and the illness-inducing US are never directly paired with each other. Holland (1981, Exp. 1) first paired a tone with a flavored food, and later paired that tone with an illness-inducing injection of LiCl. Rats that received this treatment showed an aversion to the flavored food, compared to rats that received a similar treatment, but with unpaired presentations of the tone and flavor or of the tone and LiCl. Holland (1981) asserted that learning of the food aversion was mediated by the pairing of an associatively-activated representation of that food with illness. There was no evidence of a directly-learned tone-LiCl association, which might otherwise have mediated the expression of the food aversion by a chain of food→tone and tone→illness associations. A related series of experiments conducted by Holland and Forbes (1982) showed that a previously-established flavor aversion could be extinguished if the flavor representation was associatively activated repeatedly in the absence of the illness US. In their experiments, a flavo...

Formation of excitatory and inhibitory associations between absent events.

“…Although simultaneous presentations of CSs and USs have often been found to yield excitatory learning (e.g., Heth, 1976), some studies have observed inhibitory learning (e.g., Heth, 1976; Moscovitch & LoLordo, 1968). Most important, our observation of inhibitory learning when two event representations are simultaneously activated into the A2 sate is consistent with the observations of Wheeler et al (2008). Those authors, using sensory preconditioning procedures, also found inhibitory A2-A2 learning after simultaneous or backward pairings of surrogate events.…”

“…The presence of those noise-tone associations was revealed by subsequent tone-food conditioning, followed by tests of responding to the noise, as in sensory preconditioning experiments. Analogous to the results of the present experiments, Wheeler et al (2008) found excitatory noise-tone associations when noise and tone surrogates were presented in a forward manner, but inhibitory noise-tone associations when they were presented simultaneously or in backward order. Wheeler et al (2008) raised the possibility that their results may have depended on their use of sensory preconditioning procedures, in which both events represented in the A2 state were of relatively neutral value.…”

“…Analogous to the results of the present experiments, Wheeler et al (2008) found excitatory noise-tone associations when noise and tone surrogates were presented in a forward manner, but inhibitory noise-tone associations when they were presented simultaneously or in backward order. Wheeler et al (2008) raised the possibility that their results may have depended on their use of sensory preconditioning procedures, in which both events represented in the A2 state were of relatively neutral value. Miller and Matute (1996) suggested that the results of so-called backward blocking experiments, in which the modification of associative strengths of absent elements is also often asserted to occur, may depend on the biological significance of the events involved.…”

“…It is possible that Wheeler et al’s (2008) observations depended on their use of relatively neutral A2-state events. In the present experiments, we extended Wheeler et al’s (2008) findings by examining the nature of tone-sucrose learning when associatively-activated representations of those events were presented jointly. In Experiment 1 we found evidence for strong excitatory A2-A2 learning, in Experiment 2 we evaluated alternative accounts for those results, and in Experiment 3 we examined the effects of variation in the temporal arrangement of the two associatively-activated event representations on the nature of learning obtained.…”

Pavlovian-to-instrumental transfer: Paradoxical effects of the Pavlovian relationship explained.

“…Holmes et al,, 2010), then these representations of SI and S2 will be activated during later instrumental training when Rl is paired with 01 and R2 is paired with O2, This should allow Sl-Rl and S2-R2 to form. Whatever the order in which Pavlovian and Instrumental training takes place, the process of mediated stimulus-response leaming (see Holland, 1981Holland, , 1983Iordanova, Good, & Honey, 2011;Wheeler, Sherwood, & Holland, 2008; but see, Wagner, 1981) will depend upon the stimuli (or their evoked memories) and responses (or their corresponding motor programs) occurring in close temporal contiguity. Importantly, the influence of the mediated Sl-Rl and S2-R2 associations on instmmental performance will be unaffected by outcome devaluation before the PIT test (Colwill & Rescorla, 1990;Rescorla, 1994;Holland, 2004), Moreover, to the extent that S-R associations are relatively insensitive to extinction, presentations of the stimuli before the PIT test might not infiuence the likelihood of observing outcome-selective PIT in spite of the fact that they should undermine the efficacy of the S-O association during the test (see Delamater, 1996),…”