Dopamine decline underlies episodic memory decline in old age

December, 2012

Findings supporting dopamine’s role in long-term episodic memory point to a decline in dopamine levels as part of the reason for cognitive decline in old age, and perhaps in Alzheimer’s.

The neurotransmitter dopamine is found throughout the brain and has been implicated in a number of cognitive processes, including memory. It is well-known, of course, that Parkinson's disease is characterized by low levels of dopamine, and is treated by raising dopamine levels.

A new study of older adults has now demonstrated the effect of dopamine on episodic memory. In the study, participants (aged 65-75) were shown black and white photos of indoor scenes and landscapes. The subsequent recognition test presented them with these photos mixed in with new ones, and required them to note which photos they had seen before. Half of the participants were first given Levodopa (‘L-dopa’), and half a placebo.

Recognition tests were given two and six hours after being shown the photos. There was no difference between the groups at the two-hour test, but at the six-hour test, those given L-dopa recognized up to 20% more photos than controls.

The failure to find a difference at the two-hour test was expected, if dopamine’s role is to help strengthen the memory code for long-term storage, which occurs after 4-6 hours.

Individual differences indicated that the ratio between the amount of Levodopa taken and body weight is key for an optimally effective dose.

The findings therefore suggest that at least part of the reason for the decline in episodic memory typically seen in older adults is caused by declining levels of dopamine.

Given that episodic memory is one of the first and greatest types of memory hit by Alzheimer’s, this finding also has implications for Alzheimer’s treatment.

Caffeine improves recognition of positive words

Another recent study also demonstrates, rather more obliquely, the benefits of dopamine. In this study, 200 mg of caffeine (equivalent to 2-3 cups of coffee), taken 30 minutes earlier by healthy young adults, was found to improve recognition of positive words, but had no effect on the processing of emotionally neutral or negative words. Positive words are consistently processed faster and more accurately than negative and neutral words.

Because caffeine is linked to an increase in dopamine transmission (an indirect effect, stemming from caffeine’s inhibitory effect on adenosine receptors), the researchers suggest that this effect of caffeine on positive words demonstrates that the processing advantage enjoyed by positive words is driven by the involvement of the dopaminergic system.

Recent posts at Mynd

</

Creating amyloid-beta...

A Finnish study involving moderately obese adult patients with mild obstructive sleep apnea (OSA) has found that even a modest weight loss (5%)...

Data from a survey of 20,000 people across the UK has found that people who cycle, walk, or take public transport to work had a lower risk of...

A Swedish study of some 4,000 60-year-olds has found that regular “non-exercise” physical activity such as gardening or DIY...

An 11-week trial involving 54 young, healthy men and women engaging in an endurance training program, has found that markers for the production of...

A mouse study has found that long-term physical activity increased levels of two proteins...

Data from 133,479 women in the California Teachers Study has found that those who reported doing moderate physical activity (such as brisk walking...

It’s well established that performing both cardio- and resistance training in the same session is decidedly better than doing them...

A year-long study involving 424 sedentary, mobility-limited seniors aged 70-89, has found that variants in a specific gene (the ACE I/D gene)...

Brain scans have revealed that those who regularly practiced yoga had larger brain volume in the somatosensory cortex...

A four-year study involving 1,502 healthy older adults (50+) has found that the frequency of negative interactions with family members (not...

A year-long study involving young adults has compared those who engaged in either tai chi or brisk walking or no exercise. Those who practiced tai...

Data from the very large U.S. National Health and Nutrition Examination Survey (NHANES), involving 23,168 people, has found a significant...

A study involving 12 rhesus macaques, of whom some were given access to alcohol, has found that those who drank moderately showed enhanced...

A mouse study suggests that resveratrol...

A study involving 74 older adults (70+), of whom 3 had mild dementia, 33 were cognitively normal and 38 had mild cognitive impairment...