Sex Differences in Cortical Thickness and Neuropsychiatric Symptom Burden Based on APOE4 Homozygosity in Alzheimer's Disease.

Sex differences in patterns of cortical thickness and neuropsychiatric symptom (NPS) burden were examined among individuals with Alzheimer's disease (AD) and two copies (homozygote carriers) of the e4 allele of the apolipoprotein gene (APOE). A total of 752 participants with a clinical etiologic diagnosis of AD were selected from the National Alzheimer's Coordinating Center (NACC) database. Bayesian multilevel regression was used to examine both the within- and between-sex differences in gray-matter cortical thickness and total NPS burden associated with APOE homozygosity. Female homozygote carriers displayed a high probability of having reduced cortical thickness primarily in medial-lateral temporal regions and a greater burden of NPS, relative to both non-homozygous females and homozygous males. These findings support the notion that APOE4 status affects cortical thickness and symptom burden in men and women with AD differentially, with females showing more pronounced effects in brain areas known to be vulnerable in early AD. Future investigations should attempt to elucidate the proposed pattern of decline longitudinally.

Neural Basis of Long-term Musical Memory in Cognitively Impaired Older Persons.

OBJECTIVE: The objective of this study was to determine whether exposure to long-known music would evoke more extensive activation of brain regions minimally affected by Alzheimer disease (AD) pathology and outside traditional memory networks using a functional magnetic resonance imaging paradigm involving listening to long-known and recently-learned music in older adults with cognitive impairment to provide insight into mechanisms of long-term musical memory preservation in cognitively impaired older persons. METHODS: Seventeen subjects with a diagnosis of mild AD or mild cognitive impairment were recruited for this study. Subjects were scanned using functional magnetic resonance imaging while they performed a music listening task, which included short clips of personally selected music from the patient's past and newly-composed music heard for the first time 60 minutes before scanning. From this task, we obtained group-level maps comparing brain areas associated with long-known and recently-heard music in all subjects. RESULTS: Exposure to long-known music preferentially activated brain regions including the medial prefrontal cortex, precuneus, anterior insula, basal ganglia, hippocampus, amygdala, and cerebellum relative to recently-heard music. These areas are involved in autobiographical memory and associated emotional responses. In addition, they are minimally affected by early stage AD pathology, thus providing a neural basis for long-known musical memory survival. CONCLUSIONS: Long-known music activates a bilateral network of prefrontal, emotional, motor, auditory, and subcortical regions (cerebellum, putamen, limbic structures). This extensive activation, relative to recently-heard music, may offer structural and functional clues as to why long-term musical memory appears to be relatively preserved among cognitively impaired older persons.

Association Between Neuropsychiatric Symptom Trajectory and Conversion to Alzheimer Disease.

INTRODUCTION: Neuropsychiatric symptoms (NPS) are both common in mild cognitive impairment and Alzheimer disease (AD). Studies have shown that some NPS such as apathy and depression are a key indicator for progression to AD. METHODS: We compared Neuropsychiatric Inventory (NPI) total score and NPI subdomain score between mild cognitive impairment-converters (MCI-C) and mild cognitive impairment-nonconverters (MCI-NC) longitudinally for 6 years using the Alzheimer's Disease Neuroimaging Initiative (ADNI) database. In addition to the NPI, Mini-Mental State Examination (MMSE) scores were also compared to find out if MMSE scores would differ between different NPI groups. Lastly, a linear regression model was done on MMSE and NPI total score to establish a relationship between MMSE and NPI total score. RESULTS: The results in this study showed that NPI total scores between MCI-C and MCI-NC differed significantly throughout 6 years. MCI-C subjects had a higher mean NPI total score and lower MMSE score compared with MCI-NC subjects. In addition, MMSE scores were significantly different between the 3 groups of NPI total score. Subjects who have a high NPI score have the lowest mean MMSE score, thus demonstrating that NPI scores do indeed affect MMSE scores. Further analyses using a regression model revealed that a unit change in NPI total score lead to 0.1 to 0.3 decrease in MMSE. DISCUSSION: On the basis of the findings, this study showed evidence that increase in NPS burden (reflected by increase in NPI) over time predicts conversion to AD, whereas stability of symptoms (reflected by stable NPI score) favors nonconversion. Further study should investigate the underlying mechanisms that drive both NPS burden and cognitive decline.

Delusional Severity Is Associated with Abnormal Texture in FLAIR MRI.

Background: This study examines the relationship between delusional severity in cognitively impaired adults with automatically computed volume and texture biomarkers from the Normal Appearing Brain Matter (NABM) in FLAIR MRI. Methods: Patients with mild cognitive impairment (MCI, n = 24) and Alzheimer's Disease (AD, n = 18) with delusions of varying severities based on Neuropsychiatric Inventory-Questionnaire (NPI-Q) (1­mild, 2­moderate, 3­severe) from the Alzheimer's Disease Neuroimaging Initiative (ADNI) were analyzed for this task. The NABM region, which is gray matter (GM) and white matter (WM) combined, was automatically segmented in FLAIR MRI volumes with intensity standardization and thresholding. Three imaging biomarkers were computed from this region, including NABM volume and two texture markers called "Integrity" and "Damage". Together, these imaging biomarkers quantify structural changes in brain volume, microstructural integrity and tissue damage. Multivariable regression was used to investigate relationships between imaging biomarkers and delusional severities (1, 2 and 3). Sex, age, education, APOE4 and baseline cerebrospinal fluid (CSF) tau were included as co-variates. Results: Biomarkers were extracted from a total of 42 participants with longitudinal time points representing 164 imaging volumes. Significant associations were found for all three NABM biomarkers between delusion level 3 and level 1. Integrity was also sensitive enough to show differences between delusion level 1 and delusion level 2. A significant specified interaction was noted with severe delusions (level 3) and CSF tau for all imaging biomarkers (p < 0.01). APOE4 homozygotes were also significantly related to the biomarkers. Conclusion: Cognitively impaired older adults with more severe delusions have greater global brain disease burden in the WM and GM combined (NABM) as measured using FLAIR MRI. Relative to patients with mild delusions, tissue degeneration in the NABM was more pronounced in subjects with higher delusional symptoms, with a significant association with CSF tau. Future studies are required to establish potential tau-associated mechanisms of increased delusional severity.

Long-Known Music Exposure Effects on Brain Imaging and Cognition in Early-Stage Cognitive Decline: A Pilot Study.

BACKGROUND: Repeated exposure to long-known music has been shown to have a beneficial effect on cognitive performance in patients with AD. However, the brain mechanisms underlying improvement in cognitive performance are not yet clear. OBJECTIVE: In this pilot study we propose to examine the effect of repeated long-known music exposure on imaging indices and corresponding changes in cognitive function in patients with early-stage cognitive decline. METHODS: Participants with early-stage cognitive decline were assigned to three weeks of daily long-known music listening, lasting one hour in duration. A cognitive battery was administered, and brain activity was measured before and after intervention. Paired-measures tests evaluated the longitudinal changes in brain structure, function, and cognition associated with the intervention. RESULTS: Fourteen participants completed the music-based intervention, including 6 musicians and 8 non-musicians. Post-baseline there was a reduction in brain activity in key nodes of a music-related network, including the bilateral basal ganglia and right inferior frontal gyrus, and declines in fronto-temporal functional connectivity and radial diffusivity of dorsal white matter. Musician status also significantly modified longitudinal changes in functional and structural brain measures. There was also a significant improvement in the memory subdomain of the Montreal Cognitive Assessment. CONCLUSION: These preliminary results suggest that neuroplastic mechanisms may mediate improvements in cognitive functioning associated with exposure to long-known music listening and that these mechanisms may be different in musicians compared to non-musicians.