Aging

A rhesus monkey study has revealed which dendritic spines are lost with age, providing a new target for therapies to help prevent age-association cognitive impairment. It appears that it is the thin, dynamic spines in the dorsolateral prefrontal cortex, which are key to learning new things, establishing rules, and planning, that are lost. Learning of a new task was correlated with both synapse density and average spine size, but was most strongly predicted by the head volume of thin spines.

An imaging study reveals why older adults are better at remembering positive events. The study, involving young adults (ages 19-31) and older adults (ages 61-80) being shown a series of photographs with positive and negative themes, found that while there was no difference in brain activity patterns between the age groups for the negative photos, there were age differences for the positive photos. In older adult brains, but not the younger, two emotion-processing regions (the ventromedial prefrontal cortex and the amygdala) strongly influenced the memory-encoding hippocampus.

Examination of the brains from 9 “super-aged” — people over 80 whose memory performance was at the level of 50-year-olds — has found that some of them had almost no tau tangles. The accumulation of tau tangles has been thought to be a natural part of the aging process; an excess of them is linked to Alzheimer’s disease. The next step is to work out why some people are immune to tangle formation, while others appear immune to the effects. Perhaps the first group is genetically protected, while the others are reaping the benefits of a preventive lifestyle.

An imaging study involving 79 volunteers aged 44 to 88 has found lower volumes of gray matter and faster rates of decline in the frontal and medial temporal lobes of those who ranked high in neuroticism traits, compared with those who ranked high in conscientious traits. These are brain regions particularly affected by aging. The idea that this might occur derived from the well-established effects of chronic stress on the brain. This is the first study to investigate whether the rate and extent of cognitive decline with age is influenced by personality variables.

A new study provides more support for the idea that cognitive decline in older adults is a product of a growing inability to ignore distractions. Moreover, the study, involving 21 older adults (60-80) shown random sequences of pictures containing faces and scenes and asked to remember only the scene or the face, reveals that being given forewarning about which specific pictures would be relevant (say the second, or the fourth) did not help.

The role of the catechol-O-methyltransferase (COMT) gene in cognitive function has been the subject of some debate. The gene, which affects dopamine, comes in two flavors: Val and Met. One recent study found no difference between healthy carriers of these two gene variants in terms of cognitive performance, but did find differences in terms of neural activity. Another found that, although the gene did not affect Alzheimer’s risk in its own, it acted synergistically with the Alzheimer’s gene variant to do so.