Neuroscientists have long wondered how individual connections between brain cells remain diverse and "fit" enough for storing new memories. Reported in the prestigious science journal Neuron, a new study led by Dr. Inna Slutsky of the Sackler School of Medicine at Tel Aviv University describes what makes some memories stick.
The key is GABA (ã-Aminobutyric acid), a natural molecule that occurs in the brain, which could be the main factor in regulating how many new memories we can generate, the new study has found. The understanding of these mechanisms might lead to the development of new memory enhancers and new treatments for neurodegenerative diseases such as Alzheimer's.
Memories, Dr. Slutsky says, are stored in synaptic connections between neurons in our brain. In the past, other teams, including her own, have demonstrated that the strength of individual synapses is highly variable, even at the single neuron level. This variability ultimately determines if and how new memories are stored, and the key to this variability is GABA, a naturally-occurring chemical found in the brain.
In the hippocampus, one of the main areas of the brain involved in learning and memory, the strength of neuronal connections is known to be highly variable. Some neurons are tightly connected to others, while some appear to be "lone rangers."
The new paper, which examines individual synapses in the hippocampus, demonstrates that this process is regulated by GABA, the main inhibitory neurotransmitter in our brain. "We determined that variations in the local level of GABA in the vicinity of individual synapses are responsible for the differences or 'heterogeneity' of synaptic strength. And this heterogeneity may facilitate the formation of new memories," Dr. Slutsky explains.
Looking at the brain at rest
While looking at the brain in its basal state — when the activity was "at rest" before attempting to memorize a list of items or after a memory had been stored — Dr. Slutsky's team could actually "see" where synapses differ at different dendritic branches in the neuronal network. Those branches of neurons close to a cell body displayed a larger number of weak synapses, while the most distant branches were composed of a smaller number of strong synapses.
"Why the difference?" they asked. GABA was the answer. Higher concentrations of GABA near a synapse induced a stronger activation of its receptors, weakening basal synapse strength. As a result, GABA makes this synapse more liable to the formation of new memories, the researchers propose.
Dr. Slutsky, who previously discovered a basal-state regulator molecule, says that the research may also have implications for treating diseases of the mind. "We found that amyloid-beta, a well-known hallmark of Alzheimer's disease, regulates basal synapse strength in an opposite way to GABA," she notes, suggesting that an increase in the basal activity of synapses may initiate memory decline in Alzheimer's and other neurodegenerative disorders.
Experiments in the study were done using neuronal cultures and brain slices of rats subjected to molecular biology, optical imaging and electrophysiological techniques. The study also constituted a technical achievement, since it used advanced imaging techniques such as fluorescence resonance energy transfer (FRET) spectroscopy that looked at protein-to-protein interactions in the brain at the 10 nanometer scale. In the past, such fine resolution was impossible — brain scientists could only investigate interactions at the level of entire tissues, not between molecules at individual synapses.
George Hunka | EurekAlert!
The personality factor: How to foster the sharing of research data
06.09.2017 | ZBW – Leibniz-Informationszentrum Wirtschaft
Europe’s Demographic Future. Where the Regions Are Heading after a Decade of Crises
10.08.2017 | Berlin-Institut für Bevölkerung und Entwicklung
Controlling electronic current is essential to modern electronics, as data and signals are transferred by streams of electrons which are controlled at high speed. Demands on transmission speeds are also increasing as technology develops. Scientists from the Chair of Laser Physics and the Chair of Applied Physics at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have succeeded in switching on a current with a desired direction in graphene using a single laser pulse within a femtosecond ¬¬ – a femtosecond corresponds to the millionth part of a billionth of a second. This is more than a thousand times faster compared to the most efficient transistors today.
Graphene is up to the job
At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.
Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
26.09.2017 | Life Sciences
26.09.2017 | Physics and Astronomy
26.09.2017 | Information Technology