Fifteen Years of the Australian Imaging, Biomarkers and Lifestyle (AIBL) Study: Progress and Observations from 2,359 Older Adults Spanning the Spectrum from Cognitive Normality to Alzheimer's Disease.

BACKGROUND: The Australian Imaging, Biomarkers and Lifestyle (AIBL) Study commenced in 2006 as a prospective study of 1,112 individuals (768 cognitively normal (CN), 133 with mild cognitive impairment (MCI), and 211 with Alzheimer's disease dementia (AD)) as an 'Inception cohort' who underwent detailed ssessments every 18 months. Over the past decade, an additional 1247 subjects have been added as an 'Enrichment cohort' (as of 10 April 2019). OBJECTIVE: Here we provide an overview of these Inception and Enrichment cohorts of more than 8,500 person-years of investigation. METHODS: Participants underwent reassessment every 18 months including comprehensive cognitive testing, neuroimaging (magnetic resonance imaging, MRI; positron emission tomography, PET), biofluid biomarkers and lifestyle evaluations. RESULTS: AIBL has made major contributions to the understanding of the natural history of AD, with cognitive and biological definitions of its three major stages: preclinical, prodromal and clinical. Early deployment of Aß-amyloid and tau molecular PET imaging and the development of more sensitive and specific blood tests have facilitated the assessment of genetic and environmental factors which affect age at onset and rates of progression. CONCLUSION: This fifteen-year study provides a large database of highly characterized individuals with longitudinal cognitive, imaging and lifestyle data and biofluid collections, to aid in the development of interventions to delay onset, prevent or treat AD. Harmonization with similar large longitudinal cohort studies is underway to further these aims.

Cognitive consequences of high Aß amyloid in mild cognitive impairment and healthy older adults: implications for early detection of Alzheimer's disease.

BACKGROUND: It has been proposed that only mild cognitive impairment (MCI) with high Aß amyloid is indicative of incipient Alzheimer's disease (AD), yet MCI with low Aß amyloid may reflect other neurodegenerative processes. We aimed to determine the extent to which high Aß amyloid influenced cognitive function in healthy older adults and adults with MCI. METHOD: Healthy controls (HC; n = 178) and adults with MCI (n = 56) enrolled in the Australian Imaging, Biomarkers, and Lifestyle study, underwent positron emission tomography neuroimaging for Aß amyloid and completed an extensive neuropsychological battery, assessing the cognitive domains of verbal and visual episodic memory, executive function, visuoconstruction, attention and processing speed, and language at baseline. RESULTS: MCI with low Aß performed worse than MCI with high Aß on measures of executive function, attention, visuoconstruction and language. No differences were observed between HC high and low Aß groups. When compared with HC with low Aß, both MCI high and low Aß groups performed worse on measures of episodic memory. However, only the MCI low Aß group performed worse than HC low Aß on measures of executive function, attention, visuoconstruction, and language. CONCLUSIONS: When compared with HC with low Aß amyloid, MCI with high Aß amyloid present with impairments restricted to episodic memory, and the episodic memory impairments in MCI with low Aß amyloid were accompanied by impairments in executive function, attention, visuoconstruction, and language, suggesting that MCI with high Aß amyloid reflects prodromal AD, although further longitudinal data is required to confirm this.

Pseudoneglect for mental alphabet lines is affected by prismatic adaptation.

While patients with right parietal damage and spatial neglect bisect lines to the right, the general population bisects lines to the left; a phenomenon known as pseudoneglect. The leftward bias also occurs for mental representations, such as number and alphabet lines. Prismatic adaptation can have a dramatic effect on attentional bias and corrects neglect and pseudoneglect for physical and mental number lines. This study examined whether prismatic adaptation can correct leftward bisection biases for alphabet lines, which may have a different spatial arrangement compared to number lines. In pre-adaptation testing, students (n = 42) were shown letter trigrams (e.g. C H P) and judged whether the alphabetical distance before or after the inner-letter was larger. Participants were then split into three groups and were adapted to left-shifting, control or right-shifting prims. After adaptation, the mental alphabet bisection task was re-administered. The length of left side of the alphabet lines was overestimated by all three groups in the pre-adaptation phase. Right-shifting prisms and control spectacles had no effect on the leftward bias whereas exposure to left-shifting prisms corrected the bias. The results replicate an effect observed for mental number lines and demonstrate that low-level sensory-motor shifts can correct attentional biases associated with high-level representations, such as letters.