Conflict Adaptation and Cue Competition during Learning in an Eriksen Flanker Task.

Two experiments investigated competition between cues that predicted the correct target response to a target stimulus in a response conflict procedure using a flanker task. Subjects received trials with five-character arrays with a central target character and distractor flanker characters that matched (compatible) or did not match (incompatible) the central target. Subjects' expectancies for compatible and incompatible trials were manipulated by presenting pre-trial cues that signaled the occurrence of compatible or incompatible trials. On some trials, a single cue predicted the target stimulus and the required target response. On other trials, a second redundant, predictive cue was also present on such trials. The results showed an effect of competition between cues for control over strategic responding to the target stimuli, a finding that is predicted by associative learning theories. The finding of competition between pre-trial cues that predict incompatible trials, but not cues that predict compatible trials, suggests that different strategic processes may occur during adaptation to conflict when different kinds of trials are expected.

Learned Irrelevance and Cue Competition Using an Eriksen Flanker Task.

Many studies have examined competition between cues for learning. Research examining cue competition has used cues that predict the occurrence of an outcome, or, in some rare cases, competition between cues that predict the absence of an outcome (predicting that an outcome explicitly will not occur). Alternatively, learned irrelevance occurs when a cue lacks the ability to predict the occurrence or absence of an outcome. Using an Eriksen flanker task, the present study evaluated competition among cues that do not have predictive value, that is, competition for learning that an outcome is unpredictable. Subjects' inability to predict the occurrence of compatible and incompatible trials was manipulated by presenting cues that were uncorrelated with these trial types. Accuracy results showed competition between cues possessing a lack of predictive ability. The results are discussed in terms of propositional and associative theories of learning.

Strategic behavior without awareness? Effects of implicit learning in the Eriksen flanker paradigm.

This experiment investigated whether subjects' selection and use of strategies in detecting a target letter in a flanker task requires intention. Subjects' expectancies for compatible and incompatible trials (trials on which the response to the flanker stimulus was consistent or inconsistent with the target response) were manipulated by presenting cues that signaled the occurrence of these types of trials. Three groups of subjects received explicit, partially explicit, or implicit instructions about the meaning of the cues. By the end of the experiment, all the groups were able to select and use strategies based on the cues to improve their performance. However, this strategy selection developed slowly with practice in the latter two groups, whereas it was present from the outset in the first group. In addition, forced choice tests performed after the experiment showed that the subjects in the implicit condition could not intentionally indicate which stimuli were most likely to follow a given cue. Thus, the data suggest that the selection of strategies occurred outside the subjects' awareness, and without their intention.

MPEP, a selective metabotropic glutamate receptor 5 antagonist, attenuates conditioned taste aversion in rats.

Metabotropic glutamate receptors (mGluRs) have been implicated in several types of cognitive and associative learning. Although recent evidence indicates an influence of mGluRs in conditioned taste aversion (CTA), the subtype-specific involvement of mGluRs in this learning paradigm remained to be determined. The aim of this study was to examine the role of Group I mGluR subtypes in CTA using a selective mGluR5 antagonist (2-methyl-6-(phenylethynyl)-pyridine, MPEP) and a selective mGluR1 antagonist (1-aminoindan-1,5-dicarboxylic acid, AIDA). Male, water-deprived, Sprague-Dawley rats were injected i.p. with 6 or 12 mg/kg MPEP or saline. Twenty-five minutes later, all rats received 15-min access to a 0.1% saccharin solution (Sac) immediately followed by an injection of 0.15M LiCl at 1.33% body weight. The animals were tested with 15-min access to Sac on each of four test days. MPEP-treated animals consumed more Sac on the test trials than saline-treated rats. In another experiment, controlled access to Sac was used by infusing the solution on the conditioning trial. Consistent with the above results, MPEP attenuated the degree of CTA. Similar experiments using the mGluR1 antagonist AIDA, have found no effect on CTA learning. These results suggest that the two subtypes of Group I mGluRs are differentially involved in taste aversion learning.