Rebecca G. Deason

Music-based memory enhancement in Alzheimer's disease: promise and limitations.

In a previous study (Simmons-Stern, Budson & Ally, 2010), we found that patients with Alzheimers disease (AD) better recognized visually presented lyrics when the lyrics were also sung rather than spoken at encoding. The present study sought to further investigate the effects of music on memory in patients with AD by making the content of the song lyrics relevant for the daily life of an older adult and by examining how musical encoding alters several different aspects of episodic memory. Patients with AD and healthy older adults studied visually presented novel song lyrics related to instrumental activities of daily living (IADL) that were accompanied by either a sung or a spoken recording. Overall, participants performed better on a memory test of general lyric content for lyrics that were studied sung as compared to spoken. However, on a memory test of specific lyric content, participants performed equally well for sung and spoken lyrics. We interpret these results in terms of a dual-process model of recognition memory such that the general content questions represent a familiarity-based representation that is preferentially sensitive to enhancement via music, while the specific content questions represent a recollection-based representation unaided by musical encoding. Additionally, in a test of basic recognition memory for the audio stimuli, patients with AD demonstrated equal discrimination for sung and spoken stimuli. We propose that the perceptual distinctiveness of musical stimuli enhanced metamemorial awareness in AD patients via a non-selective distinctiveness heuristic, thereby reducing false recognition while at the same time reducing true recognition and eliminating the mnemonic benefit of music. These results are discussed in the context of potential music-based memory enhancement interventions for the care of patients with AD.

Gist-based conceptual processing of pictures remains intact in patients with amnestic mild cognitive impairment.

OBJECTIVE The picture superiority effect, better memory for pictures compared to words, has been found in young adults, healthy older adults, and, most recently, in patients with Alzheimers disease and mild cognitive impairment. Although the picture superiority effect is widely found, there is still debate over what drives this effect. One main question is whether it is enhanced perceptual or conceptual information that leads to the advantage for pictures over words. In this experiment, we examined the picture superiority effect in healthy older adults and patients with amnestic mild cognitive impairment (MCI) to better understand the role of gist-based conceptual processing. METHOD We had participants study three exemplars of categories as either words or pictures. In the test phase, participants were again shown pictures or words and were asked to determine whether the item was in the same category as something they had studied earlier or whether it was from a new category. RESULTS We found that all participants demonstrated a robust picture superiority effect, better performance for pictures than for words. CONCLUSIONS These results suggest that the gist-based conceptual processing of pictures is preserved in patients with MCI. While in healthy older adults preserved recollection for pictures could lead to the picture superiority effect, in patients with MCI it is most likely that the picture superiority effect is a result of spared conceptually based familiarity for pictures, perhaps combined with their intact ability to extract and use gist information.

Source Memory for Self and Other in Patients With Mild Cognitive Impairment due to Alzheimer’s Disease

OBJECTIVES The present study examined the role of enactment in source memory in a cognitively impaired population. As seen in healthy older adults, it was predicted that source memory in people with mild cognitive impairment due to Alzheimers disease (MCI-AD) would benefit from the self-reference aspect of enactment. METHOD Seventeen participants with MCI-AD and 18 controls worked in small groups to pack a picnic basket and suitcase and were later tested for their source memory for each item. RESULTS For item memory, self-referencing improved corrected recognition scores for both MCI-AD and control participants. The MCI-AD group did not demonstrate the same benefit as controls in correct source memory for self-related items. However, those with MCI-AD were relatively less likely to misattribute new items to the self and more likely to misattribute new items to others when committing errors, compared with controls. DISCUSSION The enactment effect and self-referencing did not enhance accurate source memory more than other referencing for patients with MCI-AD. However, people with MCI-AD benefited in item memory and source memory, being less likely to falsely claim new items as their own, indicating some self-reference benefit occurs for people with MCI-AD.

Alzheimer’s disease and memory-monitoring impairment: Alzheimer’s patients show a monitoring deficit that is greater than their accuracy deficit

We assessed the ability of two groups of patients with mild Alzheimers disease (AD) and two groups of older adults to monitor the likely accuracy of recognition judgments and source identification judgments about who spoke something earlier. Alzheimers patients showed worse performance on both memory judgments and were less able to monitor with confidence ratings the likely accuracy of both kinds of memory judgments, as compared to a group of older adults who experienced the identical study and test conditions. Critically, however, when memory performance was made comparable between the AD patients and the older adults (e.g., by giving AD patients extra exposures to the study materials), AD patients were still greatly impaired at monitoring the likely accuracy of their recognition and source judgments. This result indicates that the monitoring impairment in AD patients is actually worse than their memory impairment, as otherwise there would have been no differences between the two groups in monitoring performance when there were no differences in accuracy. We discuss the brain correlates of this memory-monitoring deficit and also propose a Remembrance-Evaluation model of memory-monitoring.

A critical boundary to the left-hemisphere advantage in visual-word processing

Two experiments explored boundary conditions for the ubiquitous left-hemisphere advantage in visual-word recognition. Subjects perceptually identified words presented directly to the left or right hemisphere. Strong left-hemisphere advantages were observed for UPPERCASE and lowercase words. However, only a weak effect was observed for AlTeRnAtInG-cAsE words, and a numerical reversal of the typical left-hemisphere advantage was observed for words in a visual prototype font (a very unfamiliar word format). Results support the theory that dissociable abstract and specific neural subsystems underlie visual-form recognition and fail to support the theory that a visual lexicon operates in the left hemisphere.

Visual Antipriming: Evidence for Ongoing Adjustments of Superimposed Visual Object Representations

A fundamental question of memory is whether the representations of different items are stored in localist/discrete or superimposed/overlapping manners. Neural evidence suggests that neocortical areas underlying visual object identification utilize superimposed representations that undergo continual adjustments, but there has been little corroborating behavioral evidence. We hypothesize that the representation of an object is strengthened, after it is identified, via small representational changes; this strengthening is responsible for repetition priming for that object, but it should also be responsible for antipriming of other objects that have representations superimposed with that of the primed object. Functional evidence for antipriming is reported in young adults, amnesic patients, and matched control participants, and neurocomputational models. The findings from patients dismiss explicit memory explanations, and the models fit the behavioral performance exceptionally well. Putative purposes of priming and comparisons with other theories are discussed. Priming and antipriming may reflect ongoing adjustments of superimposed representations in neocortex.

Hemispheric Asymmetries in Visual Word-Form Processing: Progress, Conflict, and Evaluating Theories.

The ubiquitous left-hemisphere advantage in visual word processing can be accounted for in different ways. Competing theories have been tested recently using cAsE-aLtErNaTiNg words to investigate boundary conditions for the typical effect. We briefly summarize this research and examine the disagreements and commonalities across the theoretical perspectives. This work may provide a good example why a multi-level, multi-method, and multi-paradigm approach holds the greatest promise for rapid theoretical progress.

Identifying objects impairs knowledge of other objects: A relearning explanation for the neural repetition effect

Different items in long-term knowledge are stored in the neocortex as partially overlapping representations that can be altered slightly with usage. This encoding scheme affords well-documented benefits, but potential costs have not been well explored. Here we use functional magnetic resonance imaging (fMRI), neurocomputational modeling, and electrophysiological measures to show that strengthening some visual object representations not only enhances the subsequent ability to identify those (repeated) objects-an effect long known as repetition priming-but also impairs the ability to identify other (non-repeated) objects-a new effect labeled antipriming. As a result, the non-repeated objects elicit increased neural activity likely for the purpose of reestablishing their previously weakened representations. These results suggest a novel reevaluation of the ubiquitously observed repetition effect on neural activity, and they indicate that maintenance relearning may be a crucial aspect of preserving overlapping neural representations of visual objects in long-term memory.

Destruction of White Matter Integrity in Patients With Mild Cognitive Impairment and Alzheimer Disease

Background Accumulating evidence shows that gradual loss of white matter integrity plays an important role in the development of Alzheimer disease (AD). Objective The aim of this research was to study the microstructural integrity of white matter in AD in vivo. Methods Global fractional anisotropy, global axial diffusivity (AxD), and global radial diffusivity (RD) were analyzed in subjects with normal controls (NC), mild cognitive impairment (MCI), and AD using Alzheimer’s Disease Neuroimaging Initiative data (total N = 210). We further compared specific white matter tracts among the 3 groups. Results Compared with the NC group, the MCI group had significantly increased global AxD and global RD. Compared with the NC and MCI groups, the AD group had significantly decreased global fractional anisotropy, increased global AxD, and increased global RD. With regard to specific white matter tracts, in the MCI group, we found increased AxD and increased RD in the external capsule, part of the lateral cholinergic pathway, in addition to the tracts connecting the limbic regions, predominantly in the left hemisphere. In the AD group, white matter abnormalities were widespread, including in the external capsule (cholinergic pathway) and limbic region tracts as well as tracts connecting anterior to posterior regions bilaterally. Conclusions The radiographic manifestation of damaged white matter microstructural integrity in the cholinergic pathway in MCI patients may provide a rational basis for the use of cholinesterase inhibitor drugs in the MCI stage of AD.

Separability of Abstract-Category and Specific-Exemplar Visual Object Subsystems: Evidence from fMRI Pattern Analysis

Previous research indicates that dissociable neural subsystems underlie abstract-category (AC) recognition and priming of objects (e.g., cat, piano) and specific-exemplar (SE) recognition and priming of objects (e.g., a calico cat, a different calico cat, a grand piano, etc.). However, the degree of separability between these subsystems is not known, despite the importance of this issue for assessing relevant theories. Visual object representations are widely distributed in visual cortex, thus a multivariate pattern analysis (MVPA) approach to analyzing functional magnetic resonance imaging (fMRI) data may be critical for assessing the separability of different kinds of visual object processing. Here we examined the neural representations of visual object categories and visual object exemplars using multi-voxel pattern analyses of brain activity elicited in visual object processing areas during a repetition-priming task. In the encoding phase, participants viewed visual objects and the printed names of other objects. In the subsequent test phase, participants identified objects that were either same-exemplar primed, different-exemplar primed, word-primed, or unprimed. In visual object processing areas, classifiers were trained to distinguish same-exemplar primed objects from word-primed objects. Then, the abilities of these classifiers to discriminate different-exemplar primed objects and word-primed objects (reflecting AC priming) and to discriminate same-exemplar primed objects and different-exemplar primed objects (reflecting SE priming) was assessed. Results indicated that (a) repetition priming in occipital-temporal regions is organized asymmetrically, such that AC priming is more prevalent in the left hemisphere and SE priming is more prevalent in the right hemisphere, and (b) AC and SE subsystems are weakly modular, not strongly modular or unified.