As we age, our memories of autobiographical events often fade but some individuals are much better at remembering than others. A new study explores how our genetics result in some of these individual differences in memory retention – and finds that certain genes play an increasingly larger role in how much we forget as we get older.
“In previous studies, it has been difficult to identify factors that predict forgetting of ‘episodic’ information across long timescales,” says Goran Papenberg of the Max Planck Institute for Human Development in Germany. “This was surprising to me, given that there are actually considerable differences in rates of forgetting among individuals.”
To better understand these differences, he and colleagues turned to a specific set of genes related to dopamine signaling in the brain. A large body of research has found that the neurotransmitter dopamine affects our ability to recall specific past events, so called “episodic memory.” In people, for example, researchers have found that having a greater density of dopamine receptors in the hippocampus results in better episodic memory. In animals, researchers recently have found that dopamine assists in the long-term storage of episodic memories.
Papenberg’s study wanted to find out if dopamine also affects the long-term storage of episodic memories in humans and how that differs based on age. In 433 adults aged 20 to 31 years old and 690 adults aged 59 to 71 years old, they looked at genotypes of three genes that affect different components of the dopamine system in memory-related brain regions. Two of the genes influence the density of dopamine receptors and a third gene influences the amount of dopamine available for the transmission of a signal.
The researchers showed the participants a variety of color images and tested their recall after 2.5 hours and brought them back in a week later to see how well they recalled the images. The older adults carrying more genotypes associated with higher dopamine receptor density and more available dopamine were better able to recall the pictorial information a week later compared to older individuals carrying only one or none of the beneficial genotypes. The researchers did not find these genetic effects in the younger participants or after only 2.5 hours, as reported in the Journal of Cognitive Neuroscience.
“Our findings suggest that common genetic variance may be one contributing factor to the higher between-person differences in older age,” Papenberg says. But, he says, that genetic factors are only one piece of the puzzle. “They account for individual differences in forgetting to some extent,” he says. “We know that our genes also interact with our lifestyle and other health risk factors in predicting cognition.”
Papenberg’s team would like to use longitudinal studies to identify some of these other factors that interact with our genetics to predict aging-related cognitive decline. This work could eventually help to develop targeted interventions for aiding memory and other cognitive skills in older adults.
–Lisa M.P. Munoz
Dopaminergic Gene Polymorphisms Affect Long-term Forgetting in Old Age: Further Support for the Magnification Hypothesis, Journal of Cognitive Neuroscience, Goran Papenberg et al., online Jan. 30, 2013.
Media contact: Lisa M.P. Munoz, CNS Public Information Officer, firstname.lastname@example.org