Biomarkers in subtypes of mild cognitive impairment and subjective cognitive decline.

OBJECTIVES: Preclinical Alzheimers disease (AD) patients may or may not show cognitive impairment on testing. AD biomarkers are central to the identification of those at low, intermediate, or high risk of later dementia due to AD. We investigated biomarker distribution in those identified as subjective cognitive decline (SCD), amnestic (aMCI), and nonamnestic (naMCI) mild cognitive impairment (MCI) subtypes. In addition, the clinical groups were compared with controls on downstream neuroimaging markers. MATERIALS AND METHODS: Cerebrospinal fluid (CSF) amyloid-ß42 (A ß42) and total tau (t-tau), phosphorylated tau (p-tau), fluorodeoxyglucose (FDG), positron-emission tomography (PET), and MRI neuroimaging measures were collected from 116 memory clinic patients. They were characterized as SCD, aMCI, and naMCI according to comprehensive neuropsychological criteria. ANOVAs were used to assess differences when biomarkers were treated as continuous variables and chi square analyses were used to assess group differences in distribution of biomarkers. RESULTS: We did not find any between group differences in Aß42, nor in p-tau, but we observed elevated t-tau in aMCI and SCD relative to the naMCI group. Significantly lower cortical glucose metabolism (as measured by FDG PET) was found in aMCI relative to SCD and controls, and there was a trend for lower metabolism in naMCI. Significant thinner entorhinal cortex (ERC) was found in aMCI and SCD. As expected biomarkers were significantly more frequently pathological in aMCI than in naMCI and SCD, whereas the naMCI and SCD groups displayed similar pathological biomarker burden. CONCLUSIONS: aMCI cases show the most pathologic biomarker burden. Interestingly naMCI and SCD subjects show similar levels of pathological biomarkers albeit the former displayed neuropsychological deficits. That the latter group may represent a risk group is supported by our observation of both elevated CSF tau and thinner ERC relative to controls.

The Combination of Dysexecutive and Amnestic Deficits Strongly Predicts Conversion to Dementia in Young Mild Cognitive Impairment Patients: A Report from the Gothenburg-Oslo MCI Study.

BACKGROUND/AIMS: The present study aimed to add to the knowledge of mild cognitive impairment (MCI) by studying the prognosis in a relatively young cohort of patients characterized by neuropsychological criteria. METHODS: PATIENTS (MEAN AGE: 63 years) with cognitive complaints and MCI (n = 302) were recruited from two university clinics and followed for 2 years. RESULTS: Pure dysexecutive MCI occurred in 11.7% of the neuropsychologically impaired patients, while 59.3 and 29.0% were characterized as having pure amnestic MCI or multidomain MCI. During the study period, the state of 2 (10.5%) of the patients with single-domain dysexecutive MCI converted to dementia, while 28 (29.2%) of the patients with pure amnestic MCI became demented. Of the patients with both executive and amnestic deficits, 28 (59.6%) became demented. CONCLUSION: The results suggest that dysexecutive symptoms in combination with amnestic symptoms constitute a strong risk factor for dementia in young MCI patients. A significant number of patients in all subgroups showed normal test results at follow-up, indicating that a neuropsychological diagnosis needs to be supported by imaging or biomarker data.

Increased theta and alpha EEG activity during nondirective meditation.

OBJECTIVES: In recent years, there has been significant uptake of meditation and related relaxation techniques, as a means of alleviating stress and maintaining good health. Despite its popularity, little is known about the neural mechanisms by which meditation works, and there is a need for more rigorous investigations of the underlying neurobiology. Several electroencephalogram (EEG) studies have reported changes in spectral band frequencies during meditation inspired by techniques that focus on concentration, and in comparison much less has been reported on mindfulness and nondirective techniques that are proving to be just as popular. DESIGN: The present study examined EEG changes during nondirective meditation. The investigational paradigm involved 20 minutes of acem meditation, where the subjects were asked to close their eyes and adopt their normal meditation technique, as well as a separate 20-minute quiet rest condition where the subjects were asked to close their eyes and sit quietly in a state of rest. Both conditions were completed in the same experimental session with a 15-minute break in between. RESULTS: Significantly increased theta power was found for the meditation condition when averaged across all brain regions. On closer examination, it was found that theta was significantly greater in the frontal and temporal-central regions as compared to the posterior region. There was also a significant increase in alpha power in the meditation condition compared to the rest condition, when averaged across all brain regions, and it was found that alpha was significantly greater in the posterior region as compared to the frontal region. CONCLUSIONS: These findings from this study suggest that nondirective meditation techniques alter theta and alpha EEG patterns significantly more than regular relaxation, in a manner that is perhaps similar to methods based on mindfulness or concentration.