Influence of glial cells on synaptic communication: rather yes, or rather no?
Long time did not take the sword in his hands, but here is such news!
Looks like you'll have to revise recent, but popular concepts!
Within the Neurobiology and Artificial Intelligence Series
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Astrocytes are cells of neuroglia, which were previously assigned the role of auxiliary cells, the functions of which consisted only in delivering useful substances to neurons and removing harmful ones. However, in the past 20 years, many papers have appeared that describe the mechanism of the trilateral synaptic connection, in which astrocytes take an active role in modulating the activity of the synapse. This led to a fairly common opinion that in order to understand how the brain works, it is not enough to consider only neurons, it is also necessary to take into account glial cells.
And just today, in the journal Science a small article appeared in which it is stated that such tripartite interaction is characteristic only of developing organisms, and this is no longer observed in adults.
So what is it and how does it threaten us?
In the early 90s, a theory was advanced that electrically inactive astrocyte cells can “feel” the transmission of signals using glutamate in synapses (glutamatergic synapses). [Let me remind you that in excitatory glutamate synapses, which are considered quite well described, the neurotransmitter glutamate is released from pre-synaptic vesicles and binds to receptors on the post-synaptic membrane, causing its depolarization and, thus, transmitting a signal from one neuron to another. And that was found a lot of evidence. Therefore, many theories have been put forward where it can be used by the brain: from long-term potentiation (the basis of long-term memory?) To higher cognitive functions and sleep.
But comrades from the University of Rochester noticed that most of the work was based on samples taken from young rodents. So for their experiences, they took newborns and adults and compared the results. And the results showed that the genes responsible for such behavior are not expressed in adult rodents (and people too). And it turns out that when glutamate is released in the synapse, astrocytes do not always release calcium ions (which, in fact, could affect the properties of signal transmission in the synapse), but only during a rather short life span. Thus, in the general case, the effect of astrocytes is limited to cases when glutamate is released too actively or in response to a general increase in the concentration of neuromodulators (occurring, for example, when excited or waking up from sleep). It follows that astrocytes cannot actively influence fast synaptic processes that are considered responsible for cognitive functions.
And for theoreticians of AI, this may mean, for example, that it is worthwhile to concentrate on the neurons themselves, rather than trying to describe the interaction of everything with everything. But this means that most likely, it is necessary to invent and develop new theories of the connection of cognitive functions with the activity of neurons, rather than go extensively by inflating the volume of computer simulations.
Looks like you'll have to revise recent, but popular concepts!
Within the Neurobiology and Artificial Intelligence Series
')
Astrocytes are cells of neuroglia, which were previously assigned the role of auxiliary cells, the functions of which consisted only in delivering useful substances to neurons and removing harmful ones. However, in the past 20 years, many papers have appeared that describe the mechanism of the trilateral synaptic connection, in which astrocytes take an active role in modulating the activity of the synapse. This led to a fairly common opinion that in order to understand how the brain works, it is not enough to consider only neurons, it is also necessary to take into account glial cells.
And just today, in the journal Science a small article appeared in which it is stated that such tripartite interaction is characteristic only of developing organisms, and this is no longer observed in adults.
So what is it and how does it threaten us?
In the early 90s, a theory was advanced that electrically inactive astrocyte cells can “feel” the transmission of signals using glutamate in synapses (glutamatergic synapses). [Let me remind you that in excitatory glutamate synapses, which are considered quite well described, the neurotransmitter glutamate is released from pre-synaptic vesicles and binds to receptors on the post-synaptic membrane, causing its depolarization and, thus, transmitting a signal from one neuron to another. And that was found a lot of evidence. Therefore, many theories have been put forward where it can be used by the brain: from long-term potentiation (the basis of long-term memory?) To higher cognitive functions and sleep.
But comrades from the University of Rochester noticed that most of the work was based on samples taken from young rodents. So for their experiences, they took newborns and adults and compared the results. And the results showed that the genes responsible for such behavior are not expressed in adult rodents (and people too). And it turns out that when glutamate is released in the synapse, astrocytes do not always release calcium ions (which, in fact, could affect the properties of signal transmission in the synapse), but only during a rather short life span. Thus, in the general case, the effect of astrocytes is limited to cases when glutamate is released too actively or in response to a general increase in the concentration of neuromodulators (occurring, for example, when excited or waking up from sleep). It follows that astrocytes cannot actively influence fast synaptic processes that are considered responsible for cognitive functions.
And for theoreticians of AI, this may mean, for example, that it is worthwhile to concentrate on the neurons themselves, rather than trying to describe the interaction of everything with everything. But this means that most likely, it is necessary to invent and develop new theories of the connection of cognitive functions with the activity of neurons, rather than go extensively by inflating the volume of computer simulations.
Source: https://habr.com/ru/post/165399/
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