Imagery encoding and false recognition errors: Examining the role of imagery process and imagery content on source misattributions

Is it all in the details? Description content and false recognition errors

In three experiments, we examined the effect of embellished content on memory errors for thematically related items as well as whether an encoding manipulation, specifically instructions to visualize content, further affects those errors. Using a modified Deese-Roediger-McDermott (DRM) paradigm, participants listened to subsets of DRM items embedded within scene descriptions. Some descriptions embellished item connections, weaving them into cohesive scenes. Other descriptions only made general reference to scenes, mentioning the items in list-like format. Listening to more detailed descriptions, compared to general scene references, elicited higher false recognition errors (Experiments 1 and 3). However, when description details varied within the same encoding series, as expected, false recognition errors did not differ significantly (Experiments 2 and 3). Results further suggest that more detailed content was more vividly imagined, providing one possible mechanism for increases in false recognition (Experiment 3). Implications for theoretical discussions of encoding task effects on false recognition errors are discussed.

Lateral parietal contributions to memory impairment in posterior cortical atrophy

Objective

Posterior cortical atrophy (PCA) is a neurodegenerative syndrome characterised by progressive impairment in visuospatial and perceptual function. Recent findings show that memory functioning can also be compromised early in the course of disease. In this study, we investigated the neural basis of memory impairment in PCA, and hypothesised that correlations would be observed with parietal cortex rather than classic medial temporal memory structures.

Methods

Eighteen PCA patients, 15 typical Alzheimer's disease (tAD) patients and 21 healthy controls underwent memory testing with the Rey Auditory Verbal Learning Test (RAVLT) word list and MRI. Voxel-based morphometry (VBM) was used to identify regions in the parietal and medial temporal lobes that correlated with memory performance.

Results

Compared with controls, PCA patients were impaired at learning, immediate and delayed recall and recognition of the RAVLT. Learning rate and immediate recall was significantly better in PCA compared to tAD, whereas there was no difference in delayed recall. Recognition memory also was not statistically different between patient groups, but PCA patients made significantly more false positive errors than tAD patients. VBM analysis in the PCA patients revealed a significant correlation between total learning and grey matter density in the right supramarginal gyrus, right angular gyrus and left postcentral gyrus. The left post central gyrus also significantly correlated with immediate and delayed recall and with recognition memory. No correlations were detected in the medial temporal lobe.

Conclusions

The findings provide novel evidence that early verbal memory impairment is frequently observed in PCA, and is associated with damage to lateral parietal structures. The results have implications for the diagnosis and management of PCA.

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PCA patients were impaired in learning, recall and recognition memory.

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Deficits were evident in the early stages of disease.

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Memory impairment was associated with damage to lateral parietal structures.

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No correlations were detected in the medial temporal lobe.

Boundary Extension in Face Processing

Boundary extension is a common false memory error, in which people confidently remember seeing a wider angle view of the scene than was viewed. Previous research found that boundary extension is scene-specific and did not examine this phenomenon in nonscenes. The present research explored boundary extension in cropped face images. Participants completed either a short-term or a long-term condition of the task. During the encoding, they observed photographs of faces, cropped either in a forehead or in a chin area, and subsequently performed face recognition through a forced-choice selection. The recognition options represented different degrees of boundary extension and boundary restriction errors. Eye-tracking and performance data were collected. The results demonstrated boundary extension in both memory conditions. Furthermore, previous literature reported the asymmetry in amounts of expansion at different sides of an image. The present work provides the evidence of asymmetry in boundary extension. In the short-term condition, boundary extension errors were more pronounced for forehead, than for chin face areas. Finally, this research examined the relationships between the measures of boundary extension, imagery, and emotion. The results suggest that individual differences in emotional ability and object, but not spatial, imagery could be associated with boundary extension in face processing.

Visual Imagery and False Memory for Pictures: A Functional Magnetic Resonance Imaging Study in Healthy Participants

Background

Visual mental imagery might be critical in the ability to discriminate imagined from perceived pictures. Our aim was to investigate the neural bases of this specific type of reality-monitoring process in individuals with high visual imagery abilities.

Methods

A reality-monitoring task was administered to twenty-six healthy participants using functional magnetic resonance imaging. During the encoding phase, 45 words designating common items, and 45 pictures of other common items, were presented in random order. During the recall phase, participants were required to remember whether a picture of the item had been presented, or only a word. Two subgroups of participants with a propensity for high vs. low visual imagery were contrasted.

Results

Activation of the amygdala, left inferior occipital gyrus, insula, and precuneus were observed when high visual imagers encoded words later remembered as pictures. At the recall phase, these same participants activated the middle frontal gyrus and inferior and superior parietal lobes when erroneously remembering pictures.

Conclusions

The formation of visual mental images might activate visual brain areas as well as structures involved in emotional processing. High visual imagers demonstrate increased activation of a fronto-parietal source-monitoring network that enables distinction between imagined and perceived pictures.

Deficits in metaphor but not in idiomatic processing are related to verbal hallucinations in patients with psychosis

There is scant evidence that the verbal cognitive deficits observed in patients with psychosis are related to auditory verbal hallucinations. The understanding of metaphors and idiomatic expressions was investigated in a cohort of 90 patients with active psychosis, and in 44 healthy controls. The Psychotic Symptom Rating Scales (PSYRATS: verbal hallucinations subscale) was used to measure the current verbal hallucinations episode; a subscore of the Launay-Slade Hallucination Scale was used to measure long-term propensity to auditory verbal hallucination-like experiences (HLEs) in the sample. The concurrent influence of education, IQ, and cognitive functioning in memory, attention, fluency, and processing speed on metaphor and idioms processing was investigated. Patients performed worse than healthy controls on all neuropsychological measures. Metaphor, but not idioms processing was poorer in patients with verbal hallucinations (n=46) when compared to patients without verbal hallucinations in the current episode (n=44). By taking into account confounding variables, the ability to produce explanations of metaphors was related to scores on the verbal HLEs in the whole sample of patients. Metaphor-comprehension deficit was related to the occurrence of auditory verbal hallucinations in patients with psychosis, suggesting that abnormal pragmatic inferential abilities have an impact on the mechanisms that cause hallucinatory experiences.

Source misattributions and false recognition errors: examining the role of perceptual resemblance and imagery generation processes

In three experiments, we examine the extent to which participants' memory errors are affected by the perceptual features of an encoding series and imagery generation processes. Perceptual features were examined by manipulating the features associated with individual items as well as the relationships among items. An encoding instruction manipulation was included to examine the effects of explicit requests to generate images. In all three experiments, participants falsely claimed to have seen pictures of items presented as words, committing picture misattribution errors. These misattribution errors were exaggerated when the perceptual resemblance between pictures and images was relatively high (Experiment 1) and when explicit requests to generate images were omitted from encoding instructions (Experiments 1 and 2). When perceptual cues made the thematic relationships among items salient, the level and pattern of misattribution errors were also affected (Experiments 2 and 3). Results address alternative views about the nature of internal representations resulting in misattribution errors and refute the idea that these errors reflect only participants' general impressions or beliefs about what was seen.