Interneurons

Curator: Tamas Freund. Eugene M.

Federal government websites often end in. The site is secure. Understanding brain neural circuits begins with understanding their component parts, the cells that form them. GABAergic interneurons, although a minority of cells within the brain, are critical in the control of inhibition. While understanding their diversity has been a central goal of neurobiologists, this amazing cell type has to date defied a generalized classification system. Here we review data that supports that interneuron complexity within the telencephalon can simplified by viewing them as elaborations of a much more finite group of developmentally specified cardinal classes. Within the forebrain, interneurons possess the largest diversity in morphology, connectivity, and physiological properties 1.

Interneurons

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. The cortical microcircuit seems to be a stereotyped unit that has been replicated and adapted to serve specific computational functions in different regions of the neocortex. An important element of this microcircuit is the wide variety of interneurons, most of which are inhibitory. Interneurons share several common features, but also show considerable diversity. Morphologically, interneurons can be divided into several groups: basket cells large, small or nest basket cells ; chandelier cells; Martinotti cells; bipolar cells; double bouquet cells; bitufted cells; neurogliaform cells; and layer I interneurons. However, the morphology of an interneuron does not define it; within a given morphological type, interneurons can show widely varying electrical or molecular properties. Interneurons can also be divided according to their steady-state or initial responses to stimuli.

Nevertheless we argue this complexity arises from a small number of non-overlapping cardinal classes, interneurons, which represent developmental genetic ground states that possess the ability to further specialize through their later interactions with other neurons. Schuurmans C, Guillemot F. IS cells are relatively scarce; interneurons vast majority of interneurons selectively innervate different compartments of interneurons cells besides establishing a small number of synaptic contacts with other interneurons.

Interneurons also called internuncial neurons , relay neurons , association neurons , connector neurons , intermediate neurons or local circuit neurons are neurons that connect to brain regions, i. Interneurons are the central nodes of neural circuits , enabling communication between sensory or motor neurons and the central nervous system CNS. Interneurons can be further broken down into two groups: local interneurons and relay interneurons. An effective means of identifying coetaneous interneurons is neuronal birthdating. In , a nomenclature for the features of GABAergic cortical interneurons was proposed, called Petilla terminology. However, excitatory interneurons using glutamate in the CNS also exist, as do interneurons releasing neuromodulators like acetylcholine.

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. An Author Correction to this article was published on 24 November Primates and rodents, which descended from a common ancestor around 90 million years ago 1 , exhibit profound differences in behaviour and cognitive capacity; the cellular basis for these differences is unknown. Here we use single-nucleus RNA sequencing to profile RNA expression in , individual interneurons across homologous brain regions from three primates human, macaque and marmoset , a rodent mouse and a weasel ferret. Homologous interneuron types—which were readily identified by their RNA-expression patterns—varied in abundance and RNA expression among ferrets, mice and primates, but varied less among primates. In the primate neocortex, dozens of genes showed spatial expression gradients among interneurons of the same type, which suggests that regional variation in cortical contexts shapes the RNA expression patterns of adult neocortical interneurons. We also found a notable subcortical innovation: an abundant striatal interneuron type in primates that had no molecularly homologous counterpart in mice or ferrets.

Interneurons

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Understanding brain circuits begins with an appreciation of their component parts — the cells. Although GABAergic interneurons are a minority population within the brain, they are crucial for the control of inhibition. Determining the diversity of these interneurons has been a central goal of neurobiologists, but this amazing cell type has so far defied a generalized classification system. Interneuron complexity within the telencephalon could be simplified by viewing them as elaborations of a much more finite group of developmentally specified cardinal classes that become further specialized as they mature. Our perspective emphasizes that the ultimate goal is to dispense with classification criteria and directly define interneuron types by function.

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They are multipolar, just like motor neurons. The CGE produces the relatively rarer subtypes including the neurogliaform, bipolar and VIP-expressing multipolar interneurons Copy Download. Tamas Freund and Szabolcs Kali , Scholarpedia, 3 9 They have horizontal dendrites that remain in str. Behavioral correlates of interneurons: the flow control hypothesis Alternatively, it is possible that the function of some interneuron types is better described with reference to behavioral events. S2CID Modified from Freund and Katona, ; Neuron Tiesinga P, Sejnowski TJ. Fogarty M, et al. The functionally relevant classification based on afferent and efferent connectivity is easier to determine in the hippocampus, where afferent pathways and cellular compartments are confined to different laminae. As the name suggests, interneurons are the ones in between - they connect spinal motor and sensory neurons. This shows that PV interneurons, at least in mouse frontal regions, can be thought as a functional unit.

Curator: Tamas Freund.

In this light, the observations that some interneuron types are recruited at specific behavioral events may seem puzzling. They are multipolar, just like motor neurons. For instance, the CCK basket cells, while a large population within the cortex and hippocampus, do not appear to be present within other brain areas Hence the tools to genetically target cardinal classes will prove invaluable for parsing the function of the different and quite exotic interneuron subtypes they ultimately give rise to. Calcium electrogenesis in distal apical dendrites of layer 5 pyramidal cells at a critical frequency of back-propagating action potentials. Similarly, in the hippocampus, dendritic inhibition by SST neurons controls burst firing 90 , 91 , Accordingly, the 6-layered neocortex, as the center of the highest nervous functions such as conscious perception or cognition, has the largest number of interneuron types. Wang, Y. This is a preview of subscription content, access via your institution. Dendritic inhibition may also control various forms of synaptic and cellular-level plasticity through its interaction with active dendritic processes. How is neuronal diversity created?