Unpresented Words Research Articles

Dissociating Semantic Integration and Inhibitory Control in the Remote Associates Test: A tDCS-EEG Study

ABSTRACT Neuromodulation was utilized here to investigate the distinct involvement of two recognized cortical hubs for semantic integration (the left anterior temporal lobe, lATL) and inhibitory control (the right dorsolateral prefrontal cortex, rDLPFC) in creative problem-solving. Participants were presented with a list of category-exemplar words, selectively recalled some of them, and then solved a set of RAT problems. Selective retrieval was introduced to trigger inhibitory control over competitors. Critically, some RAT problems could be solved with words from the previous phases of the experiment, including words that might be less accessible due to inhibition. Other problems, however, could only be solved with unpresented words. Experiment 1 showed that anodal tDCS over the lATL had a negative effect on the production of correct responses to baseline RAT problems, but not on those that required inhibited solutions. Experiment 2 produced the reverse pattern with cathodal tDCS over the rDLPFC. Resting-state EEG recordings were obtained before and after delivering tDCS, which also revealed specific tDCS-induced changes in frequency bands depending on the site of stimulation. Overall, these findings provide support for the involvement of semantic and control processes in creative problem solving that are linked to different brain networks.

Spreading of phonological activation in dyslexia throughout life

We studied the developmental course of the spreading of phonological activation in individuals with and without dyslexia by means of a phonological version of the Deese/Roediger-McDermott false memory task. The false memory effect is assumed to reflect the spreading of activation from the presented stimuli to similar words in the lexicon. We assessed 35 volunteers with dyslexia and a group of matched controls with ages ranging from 6 to 58 years. They were first presented with six lists of ten two-syllable words each, all of which shared one syllable with a reference unpresented word. Then, they answered a recognition questionnaire including 24 presented words, 18 phonologically related unpresented words, and 12 unrelated unpresented words. False recognition of phonologically related words increased with age in the control group but stayed at very low levels in the dyslexia group. Our study indicates the existence of a deficit in the spreading of phonological activation in individuals with dyslexia throughout life.

Variations in Pupil Size Related to Memory for Recently Presented Words and Event Related Potentials.

Pupillometry has been found to be correlated with activity of cholinergic and noradrenergic neuromodulator systems. These systems regulate the level of cortical arousal and therefore perception, attention, and memory. Here, we tested how different types of pupil size variance (prestimulus baseline and prestimulus hippus power) may correlate with behavioral and event-related potentials (ERPs). We recorded pupil size and ERPs while participants were presented with a series of words and then asked whether the words had been in the initial list when they were later presented intermixed with unpresented words. We found that a smaller prestimulus baseline pupil size during the study phase was associated with better memory performance. Study items also evoked a larger P3 response at presentation and a greater old/new memory ERP effect at test when prestimulus pupil size was small rather than large. Prestimulus hippus power was found to be a between-subjects factor affecting the robustness of memory encoding with less power being associated with a greater old/new memory ERP effect. These results provide evidence relating memory and ERPs to variables defined on pupil size that are thought to reflect varying states of parasympathetic and sympathetic arousal.

It's about time: Adding processing to neuroemergentism

Alzheimer's disease (AD) patients are known to present semantic memory impairments, and semantic processing plays a crucial role in the formation of false memories. We assessed 40 early stage AD patients and 35 matched healthy volunteers with an emotional version of the Deese-Roediger-McDermott paradigm, which allows the study of false memory formation. Participants were presented with three negative, three neutral and three positive lists of words, each semantically associated to a critical unpresented word. After the presentation of the lists the volunteers were asked to respond to a recognition questionnaire stating whether these critical lures, as well as other presented and unpresented words, had been previously shown or not. We replicate the pattern of decreased discriminability between list-related and -unrelated items for AD patients compared to healthy seniors observed in previous studies. Moreover, like control participants, AD patients displayed enhanced true recognition for emotional materials, both positive and negative. With regards to false recognition, our data show decreased discriminability between related and unrelated lures for positive material. These results point out differential involvement of semantic-based information during memory formation in AD patients compared to healthy seniors. Nevertheless, our data indicate that emotional content effects over semantic-based false memory formation persist in this population, at least at early stages of disease development.

Differential effects of negative and positive emotional content over veridical and false recognition in aging and Alzheimer's disease

Abstract Alzheimer's disease (AD) patients are known to present semantic memory impairments, and semantic processing plays a crucial role in the formation of false memories. We assessed 40 early stage AD patients and 35 matched healthy volunteers with an emotional version of the Deese-Roediger-McDermott paradigm, which allows the study of false memory formation. Participants were presented with three negative, three neutral and three positive lists of words, each semantically associated to a critical unpresented word. After the presentation of the lists the volunteers were asked to respond to a recognition questionnaire stating whether these critical lures, as well as other presented and unpresented words, had been previously shown or not. We replicate the pattern of decreased discriminability between list-related and -unrelated items for AD patients compared to healthy seniors observed in previous studies. Moreover, like control participants, AD patients displayed enhanced true recognition for emotional materials, both positive and negative. With regards to false recognition, our data show decreased discriminability between related and unrelated lures for positive material. These results point out differential involvement of semantic-based information during memory formation in AD patients compared to healthy seniors. Nevertheless, our data indicate that emotional content effects over semantic-based false memory formation persist in this population, at least at early stages of disease development.

The influence of theme identifiability

In the present study, we used the Deese/Roediger-McDermott paradigm to analyze the relationship between theme identifiability of word lists and false memories in adults and children. We conducted two normative studies to determine the identifiability levels for critical unpresented words in 40 associative lists in adults and in 16 associative lists in children. Then, in three experiments, false memories for critical words that were either easy or hard to identify were analyzed in adults and in children 4-5 years old and 11-12 years old. Opposite results were found for adults and children. Lists with highly identifiable critical words produced fewer false memories for adults but more false memories for children. These results suggest that, if they can identify critical words, adults use an identify-to-reject strategy to edit out false memories, whereas, in children, theme identification does not lead to the use of such a monitoring strategy.

Semantic processing in “associative” false memory

We studied the semantic properties of a class of illusions, of which the Deese/Roediger-McDermott (DRM) paradigm is the most prominent example, in which subjects falsely remember words that are associates of studied words. We analyzed DRM materials for 16 dimensions of semantic content and assessed the ability of these dimensions to predict interlist variability in false memory. For the more general class of illusions, we analyzed pairs of presented and unpresented words that varied in associative strength for the presence of these same 16 semantic properties. DRM materials proved to be exceptionally rich in meaning, as indexed by these semantic properties. Variability in false recall, false recognition, and backward associative strength loaded on a single semantic factor (familiarity/meaningfulness), whereas variability in true recall loaded on a quite different factor (imagery/concreteness). For word association generally, 15 semantic properties varied reliably with forward or backward association between words. Implications for semantic versus associative processing in this class of illusions, for dual-process theories, and for semantic properties of word associations are discussed.

Going beyond a single list: Modeling the effects of prior experience on episodic free recall

We present an extension of the search of associative memory (SAM) model that simulates the effects of both prior semantic knowledge and prior episodic experience on episodic free recall. The model incorporates a memory store for preexisting semantic associations, a contextual drift mechanism, a memory search mechanism that uses both episodic and semantic associations, and a large lexicon including both words from prior lists and unpresented words. These features enabled the model to successfully account for the effects of prior semantic knowledge and prior episodic learning on the pattern of correct recalls and intrusions observed in free recall experiments.

Forward Association, Backward Association, and the False-Memory Illusion.

In the Deese-Roediger-McDermott false-memory illusion, forward associative strength (FAS) is unrelated to the strength of the illusion; this is puzzling, because high-FAS lists ought to share more semantic features with critical unpresented words than should low-FAS lists. The authors show that this null result is probably a truncated range artifact. When FAS and its complement, backward associative strength (BAS), were independently manipulated in factorial designs, they both affected illusion strength. Moreover, their effects did not interact and were of comparable magnitude. Conjoint-recognition analyses were used to pinpoint the influence of BAS and FAS on retrieval processes that support or suppress false-memory responses. Although the variables affected both types of processes, their effects on suppressive processes were larger and more consistent. This research also provided the first clear evidence that subjects often use suppressive processes inappropriately to reject studied items that preserve the gist of experience.

False recognition without intentional learning.

Asked to memorize a list of semantically related words, participants often falsely recall or recognize a highly related semantic associate that has not been presented (the critical lure). Does this false memory phenomenon depend on intentional word reading and learning? In Experiment 1, participants performed a color identification task on distractor words from typical false memory lists. In Experiment 2, participants read the same words. In both experiments, the primary task was followed by a surprise recognition test for actually presented and unpresented words, including the critical lures. False alarms to critical lures were robust and quite equivalent across the two experiments. These results are consistent with an activation/monitoring account of false memory, in which processing of semantic associates can evoke false memories even when that processing is incidental.

Hemispheric Asymmetries in Memory Processes as Measured in a False Recognition Paradigm

Although memory differs in important ways between the left and right cerebral hemispheres, the nature of these differences remains controversial. We examined this issue in two experiments using a false memory paradigm that allowed novel tests of two theories that have not been assessed in a common paradigm previously. Lists of semantically related words (e.g., bed, rest, wake…), all highly associated to one “critical” word (e.g., sleep), were presented auditorily during a study phase. Memory for both the related words and the critical words was measured in a subsequent old/new recognition test using divided-visual- field word presentations. The most important results were that the ability to correctly reject previously unpresented words was greater when test items were presented to the right visual field/left hemisphere (RVF/LH) than to the left visual field/right hemisphere (LVF/RH) and that participants were more confident in correctly rejecting unpresented words when test items were presented to the RVF/LH than to the LVF/RH. Results were in line with the theory that associative activation of semantic information is restricted in the left hemisphere but diffuse in the right; however, these results contrasted with the theory that memory traces are interpretive in the left hemisphere but veridical in the right. A potential resolution to the seemingly contradictory theories of asymmetries in memory processing is briefly discussed.