IST Austria professor Peter Jonas and team identify computational switch; study published in eLife
Synapses form connections between neurons. Their network is intricate: a single postsynaptic neuron can be connected with thousands of presynaptic neurons. At the synapse, information is transferred from the presynaptic to the postsynaptic neuron. A key factor in information processing is the strength of the synapse.
A 3-D volume reconstruction of an adult hippocampal mossy fiber bouton and its target structure, a dendritic segment of a CA3 pyramidal cell dendrite. Color code: dendrite and spiny excrescences in blue, bouton in transparent yellow, mitochondria in white, synaptic vesicles in green and dense-core vesicles in magenta.
Courtesy of Astrid Rollenhagen and Joachim Lübke; for details see Rollenhagen et al., J. Neurosci. 27: 10434-10444 (2007)
The neuromuscular junction, the connection between neuron and muscle, and the calyx of Held, a synapse in the auditory brainstem, are strong synapses. Also called full detonators, when one of these presynaptic neurons sends out a single activating signal or action potential, the postsynaptic neuron fires.
Whether such detonators also exist in the cortex of the brain has been unclear. In the present study, the authors investigate the synapse between granule cells and CA3 pyramidal cells in the hippocampus, using a recently developed method to simultaneously stimulate the individual presynaptic terminal and record from the connected postsynaptic CA3 neuron.
Under normal conditions, a single action potential from the granule cell does not induce firing in the CA3 neuron. Instead, the granule cells are 'conditional detonators': burst firing of action potentials from a granule cell is required to get the CA3 neuron to fire as well.
But when the researchers altered the synaptic plasticity of the granule cell by stimulating a single presynaptic terminal to fire at high frequency for only one second, causing post-tetanic potentiation (PTP), the picture changes. The granule cell turns into a full detonator: a single action potential causes the CA3 neuron to fire. Peter Jonas explains the significance of their study:
"It is generally thought that individual synapses in the brain are weak, and that tens or hundreds of inputs have to be integrated to activate a neuron. The present paper challenges this view, showing that full detonator synapses exist in the brain. This has important implications for higher order computations in the circuit."
Short-term synaptic plasticity in the form of PTP produces a computational switch at the studied synapse. This change is prolonged, lasting for tens of seconds. This could be critical for information coding, storage and recall in the network formed by granule cells and CA3 neurons, as Nicholas Vyleta points out:
"A single hippocampal mossy fiber synapse can produce an action potential in a postsynaptic pyramidal neuron after activity-dependent enhancement of transmitter release. This computational switch may allow a single piece of highly specific information from the dentate gyrus to be transmitted through the hippocampal formation, and may form the basis of the processing of information in this circuit by pattern separation."
The study was published in eLife, an open access journal for the life sciences and biomedicine. The journal is supported by the Howard Hughes Medical Institute, the Max Planck Society and the Wellcome Trust. For Carolina Borges-Merjane and Nicholas Vyleta, publishing their new findings in the open access journal provides several advantages:
"Publishing our work in eLife maximizes the impact of our research and availability to other scientists. eLife has already been well recognized as a reliable journal, with efficient peer-review by scientists from many fields. Our experiences with reviewers and the editor were fair, efficient and their comments were very constructive. Plus the paper is available freely not just to other scientists, but also the general public, including our families. "
Stefan Bernhardt | EurekAlert!
Could this protein protect people against coronary artery disease?
17.11.2017 | University of North Carolina Health Care
Microbial resident enables beetles to feed on a leafy diet
17.11.2017 | Max-Planck-Institut für chemische Ökologie
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
17.11.2017 | Physics and Astronomy
17.11.2017 | Health and Medicine
17.11.2017 | Studies and Analyses