Effects of masking tasks on differential eyelid conditioning: a distinction between knowledge of stimulus contingencies and attentional or cognitive activities involving them

Awareness and differential eyeblink conditioning: effects of manipulating auditory CS frequencies

The role of awareness in differential delay eyeblink conditioning (EBC) has been a topic of much debate. We tested the idea that awareness is required for differential delay EBC when two cues are perceptually similar. The present study manipulated frequencies of auditory conditioned stimuli (CS) to vary CS similarity in three groups of participants. Our findings indicate that awareness was not necessary for differential delay EBC when two tones are easily discriminable, awareness was also not needed for relatively similar tones but may facilitate earlier conditioning, and awareness alone was not sufficient for differential delay EBC.

Awareness is essential for differential delay eyeblink conditioning with soft-tone but not loud-tone conditioned stimuli

The role of awareness in differential delay eyeblink conditioning (DEC) remains controversial. Here, we investigated the involvement of awareness in differential DEC with a soft or a loud tone as the conditioned stimulus (CS). In the experiment, 36 participants were trained in differential DEC with a soft tone (60 dB) or a loud tone (85 dB) as the CS, paired with a corneal air-puff as the unconditioned stimulus (US). After conditioning, awareness of the relationship between the CS and the US was assessed with a 17-item true/false questionnaire. Interestingly, during differential DEC with a soft-tone CS, a higher proportion of differential conditioned responses (CRs) was evident in participants who were aware than those who were unaware. In contrast, when a loud tone was used as the CS, the proportion of differential CRs of the aware participants did not differ significantly from those who were unaware over any of the blocks of 20 trials. In unaware participants, the percentage of differential CRs with a loud-tone CS was significantly higher than that with a soft-tone CS; however in participants classified as aware, the percentage of differential CRs with a loud-tone CS did not differ significantly from that with a soft-tone CS. The present findings suggest that awareness is critical for differential DEC when the delay task is rendered more difficult.

Effects of noun imagery and awareness of the discriminative cue upon differential eyelid conditioning to grammatical and ungrammatical phrases

Two differential eyelid conditioning studies employed grammatically correct and incorrect adjective-noun phrases as conditioned stimuli. For different groups of subjects, the nouns were either high or low in imagery. The hypothesis that congruency between grammatical correctness and reinforcement consequences (i.e., the aversive stimulus contingent upon presence of incorrect rather than correct grammar) would facilitate conditioned discrimination was not supported, but the hypothesis that high noun imagery would facilitate differential response to syntax received strong support. Cognitive awareness of the syntactic discriminandum was also related to effective differential responding, as well as being implicated as a mediating mechanism in the imagery effects. Finally, performance was also significantly related to conditioned-response topography, with better conditioned discrimination by voluntary-form (V) than by conditioned-form (C) responders, and also evidence of more effective utilization of contingency awareness by Vs than by Cs.

The role of contingency awareness in single-cue human eyeblink conditioning

Single-cue delay eyeblink conditioning is presented as a prototypical example of automatic, nonsymbolic learning that is carried out by subcortical circuits. However, it has been difficult to assess the role of cognition in single-cue conditioning because participants become aware of the simple stimulus contingency so quickly. In this experiment (n = 166), we masked the contingency to reduce awareness. We observed a strong relationship between contingency awareness and conditioned responding, with both trace and delay procedures. This finding suggests that explicit associative knowledge and anticipatory behavior are regulated by a coordinated system rather than by functionally and neurally distinct systems.

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.

Awareness is necessary for differential trace and delay eyeblink conditioning in humans

Squire et al. have proposed that trace and delay eyeblink conditioning procedures engage separate learning systems: a declarative hippocampal/cortical system associated with conscious contingency awareness, and a reflexive sub-cortical system independent of awareness, respectively (Clark and Squire, 1998; Smith et al., 2005). The only difference between these two procedures is that the conditioned stimulus (CS) and the unconditioned stimulus (US) overlap in delay conditioning, whereas there is a brief interval (e.g., 1s) between them in trace conditioning. In two experiments using the same procedure as Clark and Squire's group, we observed differential conditioning only in participants who showed contingency awareness in a post-experimental questionnaire, with both trace and delay procedures. We interpret these results to suggest that, although there may be multiple brain regions involved in learning, these regions are organized as a coordinated system rather than as separate, independent systems.

Experience-dependent eye movements, awareness, and hippocampus-dependent memory

We asked what kind of memory is operating when eye movements change as the result of experience. Participants viewed scenes that were either novel, repeated, or manipulated (i.e., a change was introduced in one region of the scene). Eye movements differed depending on the past viewing history of each scene. Participants made fewer fixations and sampled fewer regions when scenes were repeated than when scenes were novel. When scenes were altered, participants made more fixations in the altered region, spent more time looking at the altered region, and made more transitions into and out of the altered region than in unchanged (matched) regions in the repeated scenes. Importantly, these effects occurred only when individuals were aware that a change had occurred. Participants who were unaware that the scene had been altered looked at the changed scenes in the same way that they looked at repeated scenes. Thus, there was no indication that eye movements could reveal an unaware (unconscious) form of memory. Instead, eye movements reflected conscious memory of whether the scene was repeated or manipulated. The findings were the same when awareness was assessed after viewing all the scenes (experiment 1) and when awareness was assessed after each scene was presented (experiment 2). In experiment 3, memory-impaired patients with damage limited to the hippocampus were impaired at deciding whether scenes were novel, repeated, or manipulated. Thus, the ability to consciously recollect recent encounters with scenes reflects a form of hippocampus-dependent memory. The findings show that experience-dependent eye movements in response to altered scenes reflect conscious, declarative memory, and they support the link between aware memory, declarative memory, and hippocampus-dependent memory.

Acquisition of differential delay eyeblink classical conditioning is independent of awareness

There has been debate about whether differential delay eyeblink conditioning can be acquired without awareness of the stimulus contingencies. In 4 experiments, the authors reexamined this question. Older participants were tested with a tone and white noise (Experiment 1) or with 2 tones (Experiment 2). In addition, younger participants were tested with 2 tones (Experiment 3) or with 2 tones plus the parameters from an earlier study that had reported a relationship between conditioning and awareness (Experiment 4). Participants who were designated aware of the stimulus contingencies and participants who were designated unaware exhibited equivalent levels of differential eyeblink conditioning. Awareness of stimulus contingencies is not required for differential delay eyeblink conditioning when simple conditioned stimuli are used.

The importance of awareness for eyeblink conditioning is conditional: theoretical comment on Bellebaum and Daum (2004)

Eyeblink conditioning entails a variety of paradigms that differ in terms of the brain systems that support conditioning and the importance of awareness. In this issue, C. Bellebaum and I. Daum (2004) that reports that conditional discrimination learning depends on awareness. Their findings, along with other recent work, suggest a framework whereby the temporal features of the conditioning paradigm are critical in determining the ability of the cerebellum to support conditioning and, as a result, the role of awareness in conditioning.

Impact of healthy aging on awareness and fear conditioning

Fear conditioning has provided a useful model system for studying associative emotional learning, but the impact of healthy aging has gone relatively unexplored. The present study investigated fear conditioning across the adult life span in humans. A delay discrimination task was employed using visual conditioned stimuli and an auditory unconditioned stimulus. Awareness of the reinforcement contingencies was assessed in a postexperimental interview. Compared with young adult participants, middle-aged and older adults displayed reductions in unconditioned responding, discriminant conditioning, and contingency awareness. When awareness and overall arousability were taken into consideration, there were no residual effects of aging on conditioning. These results highlight the importance of considering the influence of declarative knowledge when interpreting age-associated changes in discriminative conditioned learning.

Classical conditioning, awareness, and brain systems

Memory is composed of several different abilities that are supported by different brain systems. The distinction between declarative (conscious) and nondeclarative (non-conscious) memory has proved useful in understanding the nature of eyeblink classical conditioning - the best understood example of classical conditioning in vertebrates. In delay conditioning, the standard procedure, conditioning depends on the cerebellum and brainstem and is intact in amnesia. Trace conditioning, a variant of the standard procedure, depends additionally on the hippocampus and neocortex and is impaired in amnesia. Recent studies have sharpened the contrast between delay and trace conditioning by exploring the importance of awareness. We discuss these new findings in relation to the brain systems supporting eyeblink conditioning and suggest why awareness is important for trace conditioning but not for delay conditioning.