Nav: Home

Full detonation in the hippocampus

November 09, 2016

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. 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. "
-end-


Institute of Science and Technology Austria

Related Neurons Articles:

How do we get so many different types of neurons in our brain?
SMU (Southern Methodist University) researchers have discovered another layer of complexity in gene expression, which could help explain how we're able to have so many billions of neurons in our brain.
These neurons affect how much you do, or don't, want to eat
University of Arizona researchers have identified a network of neurons that coordinate with other brain regions to influence eating behaviors.
Mood neurons mature during adolescence
Researchers have discovered a mysterious group of neurons in the amygdala -- a key center for emotional processing in the brain -- that stay in an immature, prenatal developmental state throughout childhood.
Astrocytes protect neurons from toxic buildup
Neurons off-load toxic by-products to astrocytes, which process and recycle them.
Connecting neurons in the brain
Leuven researchers uncover new mechanisms of brain development that determine when, where and how strongly distinct brain cells interconnect.
More Neurons News and Neurons Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#537 Science Journalism, Hold the Hype
Everyone's seen a piece of science getting over-exaggerated in the media. Most people would be quick to blame journalists and big media for getting in wrong. In many cases, you'd be right. But there's other sources of hype in science journalism. and one of them can be found in the humble, and little-known press release. We're talking with Chris Chambers about doing science about science journalism, and where the hype creeps in. Related links: The association between exaggeration in health related science news and academic press releases: retrospective observational study Claims of causality in health news: a randomised trial This...