The feel-good hormone dopamine improves long-term memory. This is the finding of a team lead by Emrah Düzel, neuroscientist at the German Center for Neurodegenerative Diseases (DZNE) and the University of Magdeburg.
The researchers investigated test subjects ranging in age from 65 to 75 years, who were given a precursor of dopamine. Treated subjects performed better in a memory test than a comparison group, who had taken a placebo.
The study provides new insights into the formation of long lasting memories and also has implications for understanding why memories fade more rapidly following the onset of Alzheimer’s disease. The results appear in the “Journal of Neuroscience”.
Dopamine is a multi-faced neurotransmitter. It provides communication between nerve cells as well as between nerve and muscle cells. If this signal transmission becomes disturbed, the consequences can be dramatic. This is illustrated by Parkinson’s disease, whose symptoms – akinesia and other movement disorders – can be traced back to a lack of dopamine. On the other hand, when someone is pleased or motivated, a flood of dopamine is released in the brain, which is why the term “feel-good hormone“ has become popular.
There have already been indications of the special role of dopamine in forming long-lasting memories for some time. The signs came from various studies and also from the fact that rewarding incidents and other important events can usually be remembered for a long time. Researchers led by Düzel, who is also affiliated with University College London, have now been able to confirm this effect in older people.
“Our investigations for the first time prove that dopamine has an effect on episodic memory. This is the part of long-term memory, which allows us to recall actual events. Occurrences in which we were personally involved,“ Düzel says. The Site Speaker of the DZNE in Magdeburg and Director of the Institute of Cognitive Neurology and Dementia Research at the University of Magdeburg adds: “Episodic memory is that part of our capacity to remember, which is first affected in Alzheimer’s dementia. This is why our results can contribute to a better understanding of the disease.“
In particular animal studies have indicated that to store experiences permanently the brain has to release dopamine. Düzel and his colleagues examined whether this also applies to humans: the task of the test subjects ranging in age from 65 to 75 years was to recognise photos which they had been shown previously. Half of the test participants had first taken a placebo and the remainder had taken Levodopa. This substance, also known as L-DOPA, is able to reach the brain from the bloodstream, and there it is converted into dopamine. In this way the researchers could exercise a targeted influence over dopamine levels in the brains of the test subjects. “Neurons, which produce dopamine, decline with age,“ Düzel says. “Increasing dopamine levels in these elderly subjects, should show a clear effect.“ The neuroscientist mentions another reason for undertaking the study with older people: „In old age the episodic memory declines. This is why the topic we are investigating is particularly relevant for elderly people.“
The participants were first shown black and white photos of indoor scenes and landscapes. They were to differentiate these images from others, which they had not seen before. When they first viewed the pictures brain activity of the participants was monitored using fMRT, a special form of magnetic resonance tomography. The photos which triggered hardly any activity in the memory centre were of particular interest to the neuroscientists. The reason: If this brain area is only slightly active, then it should cause little or no dopamine release. “In such cases the memory of these pictures should gradually fade. As they have been encoded only weakly,“ Düzel says, “we wanted to find out whether the memory of these pictures could nevertheless persist.“
Effect after six hours
Two and six hours after the participants had memorized the photos, they were requested to recognise and distinguish them from new images.
In the test after two hours there was no significant difference between participants who had taken Levodopa and those who had consumed a placebo. However, after six hours memory performance changed. Test subjects with Levodopa recognised up to 20 per cent more photos than the members of the comparison group. The ratio between the amount of Levodopa taken and the body weight of the test subjects proved to be decisive for an optimal dose. “This confirms our assumption that dopamine contributes to anchoring memories in the brain on a permanent basis. You might say it improves the survival chances of memory content,“ Düzel indicates. “Our study also shows that the survival of memories can be regulated, regardless of how strong these were originally encoded. This is a new finding.“
But why did the effect emerge only after six hours? Düzel sees the cause in the way in which the brain stores memories. “When memories are encoded, certain changes take place at the nerve endings, the so-called synapses,“ he explains. “This activation is however only temporary, and afterwards the state of synapses change back again. This is unless dopamine is available so that newly formed synapses can be stabilised over a long period of time.“ The test after two hours must still have taken place during the period of short-term synaptic activation, according to the neuroscientist. Both test subject groups therefore had similarly good results. However, at the later time the memories of the test participants with the placebo had already started to fade. Now, the influence of the dopamine was noticeable for the other test subjects.
In this study participants had taken the dopamine precursor before memorizing. The finding that the persistence of memories can be influenced – independent of whether memory encoding was weak or strong – might open the way to further investigation. “It is conceivable that participants might receive the supplement at a later stage,“ Düzel says. “The idea is that they learn something, then take dopamine afterwards and still don’t forget what they have learnt.“
In addition, the study gives food for thought for the treatment of Alzheimer’s dementia. “The episodic memory suffers substantially when affected by Alzheimer’s. Our results show that in addition to current forms of treatment, which chiefly target certain protein deposits in the brain, other aspects should also be taken into consideration“, Düzel says. “Here dopamine and the so-called neuromodulatory systems, which release chemical messengers into the brain are of particular importance. But so far, research into this topic is still in its infancy.“Original publication:
The German Center for Neurodegenerative Diseases (DZNE) investigates the causes of diseases of the nervous system and develops strategies for prevention, treatment and care. It is an institution of the Helmholtz Association with sites in Berlin, Bonn, Dresden, Göttingen, Magdeburg, Munich, Rostock/Greifswald, Tübingen and Witten. The DZNE cooperates closely with universities, their clinics and other research facilities. Co-operation partners in Magdeburg are the Otto-von-Guericke University, the University Clinic and the Leibniz-Institute for Neurobiology. Website: http://www.dzne.deContacts
Cancer diagnosis: no more needles?
25.05.2018 | Christian-Albrechts-Universität zu Kiel
Less is more? Gene switch for healthy aging found
25.05.2018 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)
The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.
Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...
A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.
The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...
At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.
At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...
There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?
At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
25.05.2018 | Event News
02.05.2018 | Event News
13.04.2018 | Event News
25.05.2018 | Event News
25.05.2018 | Machine Engineering
25.05.2018 | Life Sciences