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Optogenetic decomposition of inhibitory micro-circuits in the mouse V1 and S1

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Interneuron properties

Understanding how different neurons interact with each other in the central nervous system is of paramount importance. Towards this goal, European scientists in collaboration with American scientists worked to delineate the role of interneurons in neuronal circuits.

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GABAergic interneurons play a key role in shaping sensory processing and plasticity of the mature and developing brain. Interneurons can be divided into classes with distinct molecular, morphological and functional properties such as parvalbumin-expressing (PV) and somatostatin-expressing (SOM) interneurons. Although their dysfunction leads to several neurological disorders, the precise role of specific interneuron subtypes is yet to be elucidated. In general, neuronal operations rely on two basic arithmetic computations – division and subtraction. Response division takes place when the function performed by a neuron is scaled down, while subtraction homogeneously reduces the firing pattern of a cell regardless of the sensory stimulus. It has been suggested that different cortical inhibitory cell classes provide distinct combinations of divisive or subtractive inhibition during sensory stimulation of cortical networks. The EU-funded INTERNEURONS (Optogenetic decomposition of inhibitory micro-circuits in the mouse V1 and S1) project employed a combination of genetically engineered mouse lines alongside advanced imaging and optogenetic tools to precisely manipulate the activity of PV or SOM neurons while recording the response of their targets. Results showed that depending on the sensory context, these interneurons displayed very contrasting response modes. Experimental and computational modelling data indicated that PV and SOM interneurons adapted to the stimulus and had a divisive or subtractive effect on their target cells. For instance, SOM interneurons responded in a divisive manner when large stimuli were displayed and became subtractive for smaller stimuli. These results provide a fundamental overview of interneuron function in the mouse cortex. Extrapolation of this information to the human brain will help decipher the role of complex neuronal circuits and understand the underlying mechanisms of various neurological disorders.


Interneuron, central nervous system, neuronal circuits, GABA, PV, SOM, neurological disorder, optogenetic

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