Both trace and delay conditioned eyeblink responding can be dissociated from outcome expectancy

Squire and colleagues have proposed that trace and delay eyeblink conditioning are fundamentally different kinds of learning: trace conditioning requires acquisition of a conscious declarative memory for the stimulus contingencies whereas delay conditioning does not. Declarative memory in trace conditioning is thought to generate conditioned responding through the activation of a conscious expectancy for when the unconditioned stimulus (US) is going to occur. Perruchet (1985) has previously shown that in a 50% partial reinforcement design it is possible to dissociate single cue delay eyeblink conditioning from conscious expectancy for the US by examining performance over runs of reinforced and nonreinforced trials. Clark, Manns, and Squire (2001) claim that this dissociation does not occur in trace eyeblink conditioning. In the present experiment we examined the Perruchet effect for short, moderate, and long trace intervals (600, 1000, and 1400 ms) and for the equivalent interstimulus intervals (ISIs) in a delay conditioning procedure. We found evidence for a dissociation of eyeblink CRs and US expectancy over runs regardless of whether there was a delay or a trace arrangement of cues. The reasons for the Perruchet effect are still unclear, but the present data suggest that it does not depend on a separate nondeclarative system of the type proposed by Squire and colleagues.     

Parallel acquisition of awareness and differential delay eyeblink conditioning

There is considerable debate about whether differential delay eyeblink conditioning can be acquired without awareness of the stimulus contingencies. Previous investigations of the relationship between differential-delay eyeblink conditioning and awareness of the stimulus contingencies have assessed awareness after the conditioning session was finished using a post-experimental questionnaire. In two experiments, the point at which contingency awareness developed during the conditioning session was estimated from a button-press measure of expectancy of the unconditioned stimulus (US). In both experiments, knowledge of the stimulus contingencies and acquisition of differential delay eyeblink conditioning developed approximately in parallel. In Experiment 1 it was shown that predicting the US facilitated eyeblink conditioning compared with predicting the eyeblink response. In Experiment 2, a masking task was used that slowed down the emergence of awareness, and it was shown that differential conditioning only occurred in participants who were able to predict the US. The current findings challenge the hypothesis that differential delay eyeblink conditioning is entirely mediated by a functionally and neurally distinct nondeclarative learning system.     

Reaction time task as unconditional stimulus

The present study was conducted to demonstrate classic conditioning in electrodermal (ED) and heart rate (HR) responses by using a nonaversive reaction time (RT) task as unconditional stimulus (US). Three groups of 12 subjects each were studied to test the efficacy of this US procedure by varying the essential components of the RT task-US between groups. Eight seconds differential delay conditioning was applied in each group. Simple geometric features (square, cross) displayed on a TV screen were used as CS+ and CS−. RT task consisted of a nonaversive tone (72 dBA, 1000 or 1200 Hz) and a motor response (pressing a button with the left index finger). Subjects were asked to respond as soon as the tone stimulus was presented. The three groups received different stimulus sequences during the 16-trial acquisition phase only. In one group (Group C1), CS+ was followed by a tone to which subjects were to respond, whereas CS− was not followed by a tone. Similarly, in a second group (Group H), CS+ was followed by a tone, whereas CS− was not; however, subjects of Group H (habituation group) were not required to respond to the tone. In a third group, (Group C2) CS+ was followed by a tone to which subjects were to respond, while CS− was followed by a different tone requiring no response. According to analysis of Group C1 data, differential conditioning was obtained in each response measure. Group H displayed habituation in each response measure obtained. In Group C2, differential conditioning was obtained in the second latency window of ED responses only. In all trials, first-interval anticipatory ED responses and HR responses did occur during acquisition, but were not differentiated with respect to the CS conditions. Although the results of Group C2 need further exploration, differential conditioning of HR and in all latency windows of ED responses was demonstrated by the use of a nonaversive RT task as US.     

Dissociating expectancy of shock and changes in skin conductance: an investigation of the Perruchet effect using an electrodermal paradigm

Is human Pavlovian conditioning driven by a unitary, propositional system (as claimed by Mitchell, De Houwer, & Lovibond, 2009) or by dual systems; one under conscious control, symbolic in nature, and requiring effort to deploy, and the other utilizing associative processes and automatic in its operation (McLaren, Green, & Mackintosh, 1994)? Past research has suggested that for electrodermal conditioning to occur in humans, conscious awareness of the contingencies is necessary to produce conditioned responding (e.g., Hinchy, Lovibond, & Ter-Horst, 1995), as predicted by single process theories that attribute the conditioned response (CR) to conscious expectancy of the shock. In this article, the authors examined the Perruchet effect (Perruchet, 1985), using an electrodermal paradigm to determine whether there is any role for associative processes in human electrodermal conditioning. The authors attempted to replicate the basic effect, whereby expectancy of an unconditioned stimulus (US) increases over a run of nonreinforced trials while the CR to the conditional stimulus (CS) declines, and the complementary pattern in which expectancy decreases over a run of reinforced trials while the CR to the CS grows in strength. In line with these patterns, the change in skin conductance response (our CR) as a function of US run length was found to follow a linear trend opposite to that of conscious expectancy of shock with respect to US run length. This dissociation supports a dual-processing system account of human Pavlovian conditioning, with conscious, controlled processes governing expectancy (and subject to the gambler's fallacy), whereas automatic, associative processes determine at least some of the strength of the CR to the CS.     

Reward priming of temporal preparation

Recent studies have demonstrated a strong impact of reward on the expectancy of future target locations or features. In this study, we examined whether reward would have similar effects on temporal preparation. In two experiments, participants completed a reaction time task with a variable interval between a warning stimulus and the target stimulus. After each trial they were awarded either low or high reward which was converted to cash after the experiment. Crucially, reward magnitude was assigned randomly and was unrelated to task performance. Nevertheless, across experiments, the results revealed that reward modified future temporal preparation, especially in participants that could be identified as highly motivated. These findings generalize the principles of reward priming to the temporal domain.     

The Effect of Counterconditioning on Evaluative Responses and Harm Expectancy in a Fear Conditioning Paradigm

In fear conditioning, extinction targets harm expectancy as well as the fear response, but it often fails to eradicate the negative affective value that is associated with the conditioned stimulus. In the present study, we examined whether counterconditioning can serve to reduce evaluative responses within fear conditioning. The sample consisted of 70 nonselected students, 12 of whom were men. All participants received acquisition with human face stimuli as the conditioned stimuli and an unpleasant white noise as the unconditioned stimulus. After acquisition, one third of the sample was allocated to an extinction procedure. The other participants received counterconditioning with either a neutral stimulus (neutral tone) or a positive stimulus (baby laugh). Results showed that counterconditioning (with both neutral and positive stimuli), in contrast to extinction, successfully reduced evaluative responses. This effect was found on an indirect measure (affective priming task), but not on self-report. Counterconditioning with a positive stimulus also tended to enhance the reduction of conditioned skin conductance reactivity. The present data suggest that counterconditioning procedures might be a promising approach in diminishing evaluative learning and even expectancy learning in the context of fear conditioning.     

Mental fatigue and temporal preparation in simple reaction-time performance

Performance decrements attributed to mental fatigue have been found to be especially pronounced in tasks that involve the voluntary control of attention. Here we explored whether mental fatigue from prolonged time on task (TOT) also impairs temporal preparation for speeded action in a simple reaction-time task. Temporal preparation is enabled by a warning signal presented before the imperative stimulus and usually results in shorter reaction time (RT). When the delay between warning and imperative stimuli - the foreperiod (FP) - varies between trials, responses are faster with longer FPs. This pattern has been proposed to arise from either voluntary attentional processes (temporal orienting) or automatic trial-to-trial learning (trace conditioning). The former account suggests a selective RT increase on long-FP trials with fatigue; the latter account suggests no such change. Over a work period of 51 min, we found the typical increase in overall RT but no selective RT increase after long FPs. This additivity indicates that TOT-induced mental fatigue generally reduces cognitive efficiency but leaves temporal preparation under time uncertainty unaffected. We consider this result more consistent with the trace-conditioning account of temporal preparation.     

EYEBLINK CLASSICAL CONDITIONING AND AWARENESS REVISITED

Abstract— Dual-task performance was assessed in 140 adults during eyeblink classical conditioning (EBCC) and one of several secondary tasks (timed-interval tapping, recognition memory choice reaction time, video viewing). Four groups received paired-EBCC stimulus presentation and three groups received explicitly unpaired EBCC stimuli. Although the subjects were not laid about the conditioning task, they acquired conditioned responses (CRs) as normal levels. Postsession interviews probed participants' awareness of EBCC stimulus contingencies and production of CRs. Reported awareness of paired-EBCC stimulus contingencies and CK production was not related to actual EBCC performance Twenty-seven percent of the participants receiving explicitly unpaired stimuli reported a stimulus contingency when none existed. The dissociation between awareness and performances provides additional support for the categorization of simple EBCC as a form of nondeclarative learning.     

Insensitivity to stimulus validity in human pavlovian conditioning

Four experiments investigated the role of information value, or stimulus validity, in human electrodermal conditioning. Conditioned stimuli (CSs) were long, variable duration (10-50-sec) slides or sounds, the unconditioned stimulus (US) was shock, and the primary measures were change in tonic skin conductance level and self-report expectancy of shock. In Experiment 1 electrodermal responding to a target stimulus was marginally lower in a blocking group than in a superconditioning group. This difference failed to occur in Experiment 2, despite increased sensitivity of the electrodermal measure. Explicit instructions to pay attention to the relationship between each stimulus and shock improved learning, but did not lead to group differences (Experiment 3). In Experiment 4 expectancy ratings in a blocking group were lower than in an overshadowing group, but no electrodermal differences occurred. The results were interpreted in terms of non-additive learning processes such as occasion-setting, in addition to a general lack of transfer of learning about a stimulus from one context to another (element to compound or vice versa). It was suggested that sensitivity to stimulus validity might be observed if conditioning were embedded in a causally familiar task, as in contingency judgement research.     

Unawareness is more than a chance event: comment on Lovibond and Shanks (2002)

P. F. Lovibond and D. R. Shanks (2002) suggested that expectancy of the unconditional stimulus and emotional ratings are valid indexes of awareness in Pavlovian conditioning and that participants are aware if they can discriminate the conditional stimuli. However, research suggests that processes that are irrelevant to awareness affect these measures. Further, as awareness refers to conscious experience, a valid measures needs to index subjective state rather than discrimination ability. In support, research using subjective measures has demonstrated qualitatively different effects depending on whether participants reported being aware or unaware of the stimuli. In this research, participants reported being unaware of the stimuli even though they were clearly able to discriminate the stimuli. These findings question the validity of Lovibond and Shanks' concept of awareness and their suggestion of a close association between conditioning and awareness.     

The role of timing deviations and target position uncertainty on temporal attending in a serial auditory pitch discrimination task

Listeners were presented with sequences of tones that ascended in semitone intervals. On each trial a single target tone in the sequence was displaced in pitch, and listeners were required to indicate whether the target tone was higher or lower than its normal pitch. Task constraints, specifically target serial position uncertainty and the probabilistic relationship between time deviations and target tones, were varied in order to determine the impact of task constraints on temporal attending strategy. When listeners had no advance knowledge of the serial position of the target, and early and late targets provided information regarding target serial position, performance was better for early and late target trials than for on-time target trials (Experiment 1). When listeners had no advance knowledge of the serial position of the target, and early and late temporal deviations provided no information regarding target serial position, performance for late target trials was superior to that for early and on-time target trials (Experiment 2). Finally, when target serial position uncertainty was eliminated, performance was equivalent across all three levels of target timing (early, on time, late). The results indicate that performance profiles based on stimulus timing properties are affected by various task constraints as well as by stimulus properties.     

Consciousness of attention and expectancy as reflected in event-related potentials and reaction times

The effects of conscious expectancies and attention on event-related potentials (ERP) and choice reaction times (RT) and their modulation by stimulus sequence were studied. Subjects retrospectively reported their expectancy of, and attention to, the terminal tones of short series. ERPs and RTs showed the usual sequential effects that were modulated by practice. As ratings were affected by only a few of the stimulus sequence, conscious access to sequence-based expectancy or attention appears to be fragmentary. Increased P300 amplitude with attention indicates conscious access to processing capacity. RTs and P300 latencies suggest stimulus processing time to decrease with sequence-based and consciously accessible expectancy. Differential effects of stimulus sequences and conscious expectancies on P300 amplitude indicate influences of two varieties of expectancy.     

Effects of fimbria lesions on trace two-way active avoidance acquisition and retention in rats

The fimbria-fornix (FF) is the main subcortical input to the hippocampus. It has been shown that FF lesions facilitate performance on a standard-delay two-way active avoidance task (AA2), thought to involve implicit memory. The hippocampal region is required for explicit or relational memory. It has been proposed that the hippocampus and related structures might associate events that are separated in space or time and detect elements shared in common by such discontiguous episodes. Therefore, FF lesions would be expected to impair performance on a trace paradigm, which introduces an interval between the CS (conditioned stimulus) and the US (unconditioned stimulus) and is generally considered a model of explicit memory. We predicted that FF lesions would impair memory in a trace AA2 procedure, while the same lesions would facilitate memory in a standard delay version of the task. To test this hypothesis, two experiments were carried out in 102 male Wistar rats. The first experiment characterized the trace paradigm using this kind of conditioning and demonstrated that control rats were able to acquire and retrieve (24 h and 11 days postacquisition) the association between the CS (tone) and the US (electric foot shock) when a trace interval (5, 10, or 20 s) was interposed between both stimuli. In the second experiment, we investigated the effects of FF electrolytic lesions on the same task using delay and trace (10-s trace interval) paradigms. Surprisingly, FF lesions facilitated the acquisition and the 24-h retention of the AA2 not only on the standard delay paradigm, but also with the trace paradigm. We suggest that facilitative effects could be a result of impairment in contextual learning.     

The role of awareness in delay and trace fear conditioning in humans

Expression of conditional fear without awareness has been previously demonstrated during delay conditioning, a procedure in which the conditioned stimulus (CS) and unconditioned stimulus (UCS) overlap. However, less is known about the role of awareness in trace fear conditioning, where an interval of time separates the CS and UCS. The present study assessed skin conductance response (SCR) and UCS expectancy during delay and trace conditioning. UCS predictability was varied on a trial-bytrial basis by presenting perithreshold auditory CSs. Differential UCS expectancies were demonstrated only on perceived delay and trace trials. Learning-related SCRs were observed during both perceived and unperceived delay CSs. In contrast, differential SCRs were demonstrated only for perceived trace CSs. These data suggest that awareness is necessary for conditional responding during trace, but not delay, fear conditioning.     

Aversive conditioning under conditions of restricted awareness: Effects on spatial cueing

In the literature on aversive conditioning there is still debate on the role of awareness. According to some authors, affective learning can occur with or without contingency learning (dual-process model), whereas others argue that a single process produces both affective responses and contingency knowledge. Although many studies have investigated these models, the results to date are inconclusive. Based on a review of the literature, a new series of experiments was designed to examine aversive conditioning in the absence of contingency awareness. In the present study we examined the effects of subliminal aversive conditioning on a spatial cueing task. Awareness was stringently tested after conditioning. Three kinds of awareness were distinguished: contingency awareness (awareness of the CS?US contingencies, where CS is the conditioned stimulus, and US is the unconditioned stimulus), perceptual awareness (awareness of the perceptual differences between the CSs), and US expectancy (awareness of a threat feeling when confronted with the CS+, but not when confronted with the CS?). The results of three experiments demonstrated that responses on the spatial cueing task were modulated by subliminal aversive conditioning. Importantly, none of the participants was contingency aware or able to perceptually discriminate between the conditioned stimuli. However, in Experiment 3, only those participants showing some level of postconditioning expectancy awareness exhibited conditioning effects. These experiments suggest that subliminal aversive conditioning produces small but significant effects, which may be modulated by expectancy awareness.     

Measuring consciousness: task accuracy and awareness as sigmoid functions of stimulus duration

When consciousness is examined using subjective ratings, the extent to which processing is conscious or unconscious is often estimated by calculating task performance at the subjective threshold or by calculating the correlation between accuracy and awareness. However, both these methods have certain limitations. In the present article, we propose describing task accuracy and awareness as functions of stimulus intensity (thus obtaining an accuracy and an awareness curve) as suggested by Koch and Preuschoff (2007). The estimated lag between the curves describes how much stimulus intensity must increase for awareness to change proportionally as much as accuracy and the slopes of the curves are used to assess how fast accuracy and awareness increases and whether awareness is dichotomous. The method is successfully employed to assess consciousness characteristics on data from four different awareness scales.     

Under what conditions can human affective conditioning occur without contingency awareness? Test of the evaluative conditioning paradigm

The role of conscious cognitive processes in human affective conditioning remains controversial, with several theories arguing that such conditioning can occur without awareness of the conditioned stimulus (CS)-unconditioned stimulus (UCS) contingency. One specific type of affective conditioning in which unaware conditioning is said to occur is "evaluative conditioning." The present experiment tested the role of contingency awareness by embedding an evaluative conditioning paradigm in a distracting masking task while obtaining, in addition to subjective ratings of affect, both psychophysiological (skin conductance and startle eyeblink) and indirect behavioral (affective priming) measures of conditioning, along with a trial-by-trial measure of awareness from 55 college student participants. Aware participants showed conditioning with all of the measures; unaware participants failed to show conditioning with all measures. The behavioral, neurophysiological, and therapeutic implications of these findings are discussed.     

The neural correlates of implicit and explicit sequence learning: Interacting networks revealed by the process dissociation procedure

In two H2(15)O PET scan experiments, we investigated the cerebral correlates of explicit and implicit knowledge in a serial reaction time (SRT) task. To do so, we used a novel application of the Process Dissociation Procedure, a behavioral paradigm that makes it possible to separately assess conscious and unconscious contributions to performance during a subsequent sequence generation task. To manipulate the extent to which the repeating sequential pattern was learned explicitly, we varied the pace of the choice reaction time task-a variable that is known to have differential effects on the extent to which sensitivity to sequence structure involves implicit or explicit knowledge. Results showed that activity in the striatum subtends the implicit component of performance during recollection of a learned sequence, whereas the anterior cingulate/mesial prefrontal cortex (ACC/MPFC) supports the explicit component. Most importantly, we found that the ACC/MPFC exerts control on the activity of the striatum during retrieval of the sequence after explicit learning, whereas the activity of these regions is uncoupled when learning had been essentially implicit. These data suggest that implicit learning processes can be successfully controlled by conscious knowledge when learning is essentially explicit. They also supply further evidence for a partial dissociation between the neural substrates supporting conscious and nonconscious components of performance during recollection of a learned sequence.     

Retrospective perceptual distortion of position representation does not lead to delayed localization

Previous studies have reported retrospective influences of visual events that occur after target events. In the attentional attraction effect, a position cue presented after a target stimulus distorts the target’s position towards that of the cue. The present study explored the temporal relationship between stimulus presentation and reaction time (RT) in this effect in two experiments. Participants performed a speeded localization task on two vertical lines, the positions of which were to be distorted by an additional attentional cue. No significant difference in RTs was found between the conditions with simultaneous and delayed cues. RTRT was modulated by the perceived (rather than physical) alignment of the lines. In Experiment 2, we manipulated the strength of attentional capture by modulating the color relevance of the cue to the target. Trials with cues producing stronger attentional capture (with cues of a different color from the targets) were found to induce apparently stronger distortion effects. This result favors the notion that the observed repulsion and attraction effects are driven by attentional mechanisms. Overall, the results imply that the attentional shift induced by the cue might occur rapidly and complete before the establishment of conscious location representation of the cue and the target without affecting overall response time.     

Emotional conditioning to masked stimuli and modulation of visuospatial attention

Two studies investigated the effects of conditioning to masked stimuli on visuospatial attention. During the conditioning phase, masked snakes and spiders were paired with a burst of white noise, or paired with an innocuous tone, in the conditioned stimulus (CS)+ and CS- conditions, respectively. Attentional allocation to the CSs was then assessed with a visual probe task, in which the CSs were presented unmasked (Experiment 1) or both unmasked and masked (Experiment 2), together with fear-irrelevant control stimuli (flowers and mushrooms). In Experiment 1, participants preferentially allocated attention to CS+ relative to control stimuli. Experiment 2 suggested that this attentional bias depended on the perceived aversiveness of the unconditioned stimulus and did not require conscious recognition of the CSs during both acquisition and expression.