Researchers from the Institute of Neuroscience and the Institute of Biophysics of the Shanghai Academy of Biological Sciences, Chinese Academy of Sciences used a new two-color calcium imaging method to reveal the mechanism of selective information conversion of neuronal microcircuits and odor generation in specific functional areas of the brain The research results were published in the PNAS journal. Leading this research was Academician Guo Aike of the Institute of Neuroscience, Shanghai Academy of Biological Sciences. Academician Guo was called a "Drosophila Academician". This famous scholar established China's first The laboratory of evaluation paradigm also served as the first article published in Science magazine by the Chinese neuroscience community, introducing that fruit flies have higher cognitive behavior than learning and memory.
In most cases, a single neuron receives input from many presynaptic neurons and integrates these input signals into a single output signal. Therefore, the response characteristics of a single neuron to external stimuli are largely converted by the response characteristics of the presynaptic neurons it receives. If the response characteristics of the presynaptic neurons received by a neuron can be measured one by one and compared with the response characteristics of the neuron itself, you can get a clear understanding of the loop calculation involved in this neuron. However, due to the extremely complicated structure of the neural circuit, there has not been an effective strategy to find the presynaptic neurons of a neuron one by one, and conduct detailed functional research. In this article, the researchers introduced a new strategy based on two-color calcium imaging and applied it to the mushroom body neurons (KC) of Drosophila, thereby stimulating the olfactory stimulation of a single mushroom body neuron in Drosophila How is the response characteristic of the project is converted by the projection neurons of the previous stage.
The researchers used the green calcium indicator protein G-CaMP to mark a single KC, and the red calcium indicator protein R-GECO to mark many pre-projected neurons (PN); through structural tracking, you can distinguish a single KC from Which PN axon tips receive input and use functional imaging to measure the response of this KC and the PN axon tips it receives to odor one by one.
Using this strategy, the researchers found that the selectivity of a single KC's response to odor can be largely predicted from the odor response of the PN axon tip it receives. As long as the odor responses of these PN axon tips are linearly added, and the obtained results are compared with a preset threshold, it is possible to predict more accurately which odors a single KC will react to. This shows that the selectivity of KC's response to odor is mainly determined by the response characteristics of the presynaptic PN it receives. Even if a certain odor cannot activate the output of KC, a calcium response spatially restricted to the postsynaptic site can often be observed on the dendrites of the KC. This local calcium response probably corresponds to the subthreshold excitatory post-synaptic potential caused by the activation of a single PN axon terminal in KC. The size of a single local calcium response and its corresponding pre-synaptic PN axon tip often have a linear correlation, allowing the authors to measure the strength of a single synaptic site. In addition, the number of PN axon terminals received by a single KC has an inverse relationship with the average strength of these PN-KC synapses.
The strategy introduced in this work provides a new perspective on the process of information transmission and integration in Drosophila mushroom bodies, and to a certain extent reveals the source of the odor coding characteristics of mushroom body neurons. In the future, this strategy may be applied to many other loops to reveal how more complex neuronal response characteristics are generated.
At present, drawing human "intelligence blueprints" has become the commanding height of international life science research and future development. In February 2013, US President Barack Obama proposed the "BrainActivityMap Plan" (BrainActivityMap) in the National Report of Congress. The goal of the plan is to make "every electric pulse on every nerve cell" in the brain in a living state. Map. After years of discussion, organization, and refining goals, the Chinese Academy of Sciences took the lead in launching the strategic pilot science and technology project "Brain Function Connection Map" in November 2012 (B). The main difference between this project and the US "brain activity atlas program" is that it selectively describes the functional connection and operation between special types of nerve cell groups in various brain regions, and chooses according to the development trend of brain science and the latest technical conditions. Several important brain functions (sensation, emotion, learning and memory, decision-making) strive to completely describe the structure and operation mechanism of these neural network connections that bear important functions under normal physiological and pathological states.
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