A disinhibitory circuit mediates motor integration in the somatosensory cortex
TL;DR: This work used optogenetics to examine the long-range inputs from vM1 to the various neuronal elements in S1 and found that S1-projecting vM2 pyramidal neurons strongly recruited vasointestinal peptide (VIP)-expressing GABAergic interneurons, a subset of serotonin receptor–expressing interneerons.
Abstract: The influence of motor activity on sensory processing is crucial for perception and motor execution. However, the underlying circuits are not known. To unravel the circuit by which activity in the primary vibrissal motor cortex (vM1) modulates sensory processing in the primary somatosensory barrel cortex (S1), we used optogenetics to examine the long-range inputs from vM1 to the various neuronal elements in S1. We found that S1-projecting vM1 pyramidal neurons strongly recruited vasointestinal peptide (VIP)-expressing GABAergic interneurons, a subset of serotonin receptor-expressing interneurons. These VIP interneurons preferentially inhibited somatostatin-expressing interneurons, neurons that target the distal dendrites of pyramidal cells. Consistent with this vM1-mediated disinhibitory circuit, the activity of VIP interneurons in vivo increased and that of somatostatin interneurons decreased during whisking. These changes in firing rates during whisking depended on vM1 activity. Our results suggest previously unknown circuitry by which inputs from motor cortex influence sensory processing in sensory cortex.
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TL;DR: Current understanding of neocortical interneuron diversity and the properties that distinguish cell types are reviewed and it is illustrated how recent advances in the field have shed light onto the mechanisms by which GABAergic inhibition contributes to network operations.
1,358 citations
TL;DR: This perspective emphasizes that the ultimate goal is to dispense with classification criteria and directly define interneuron types by function, and views them as elaborations of a much more finite group of developmentally specified cardinal classes that become further specialized as they mature.
Abstract: 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.
927 citations
TL;DR: Similarities in neocortical circuit organization across areas and species suggest a common strategy to process diverse types of information, including sensation from diverse modalities, motor control and higher cognitive processes.
Abstract: Similarities in neocortical circuit organization across areas and species suggest a common strategy to process diverse types of information, including sensation from diverse modalities, motor control and higher cognitive processes. Cortical neurons belong to a small number of main classes. The properties of these classes, including their local and long-range connectivity, developmental history, gene expression, intrinsic physiology and in vivo activity patterns, are remarkably similar across areas. Each class contains subclasses; for a rapidly growing number of these, conserved patterns of input and output connections are also becoming evident. The ensemble of circuit connections constitutes a basic circuit pattern that appears to be repeated across neocortical areas, with area- and species-specific modifications. Such 'serially homologous' organization may adapt individual neocortical regions to the type of information each must process.
878 citations
TL;DR: These findings establish a cortical circuit for the enhancement of visual response by locomotion and provide a potential common Circuit for the modulation of sensory processing by behavioral state.
841 citations
Cites background or result from "A disinhibitory circuit mediates mo..."
...…while SST neurons are inhibited during locomotion are in good agreement with the current consensus that VIP neuronsmainly innervate SST neurons (Lee et al., 2013; Pfeffer et al., 2013; Pi et al., 2013), although different effects on SST neurons have also been reported (Polack et al., 2013)....
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...Interestingly, it is recently reported that VIP neurons in barrel cortex are strongly activated by vibrissal motor cortex pyramidal neurons (Lee et al., 2013)....
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...Our findings that VIP neurons are activated while SST neurons are inhibited during locomotion are in good agreement with the current consensus that VIP neuronsmainly innervate SST neurons (Lee et al., 2013; Pfeffer et al., 2013; Pi et al., 2013), although different effects on SST neurons have also been reported (Polack et al....
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TL;DR: This comprehensive profiling of neuronal cell types and connections in adult neocortex provides the most complete wiring diagram of neocortical microcircuits to date and should aid efforts to identify specific circuit abnormalities in animal models of brain disease and may eventually provide a path toward the development of comprehensive circuit-based, cell type–specific interventions.
Abstract: Since the work of Ramon y Cajal in the late 19th and early 20th centuries, neuroscientists have speculated that a complete understanding of neuronal cell types and their connections is key to explaining complex brain functions. However, a complete census of the constituent cell types and their wiring diagram in mature neocortex remains elusive. By combining octuple whole-cell recordings with an optimized avidin-biotin-peroxidase staining technique, we carried out a morphological and electrophysiological census of neuronal types in layers 1, 2/3, and 5 of mature neocortex and mapped the connectivity between more than 11,000 pairs of identified neurons. We categorized 15 types of interneurons, and each exhibited a characteristic pattern of connectivity with other interneuron types and pyramidal cells. The essential connectivity structure of the neocortical microcircuit could be captured by only a few connectivity motifs.
786 citations
References
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TL;DR: The spatiotemporal specializations in cortical circuits reveal that cellular diversity and temporal dynamics coemerged during evolution, providing a basis for cognitive behavior.
Abstract: In the cerebral cortex, diverse types of neurons form intricate circuits and cooperate in time for the processing and storage of information. Recent advances reveal a spatiotemporal division of labor in cortical circuits, as exemplified in the CA1 hippocampal area. In particular, distinct GABAergic (γ-aminobutyric acid–releasing) cell types subdivide the surface of pyramidal cells and act in discrete time windows, either on the same or on different subcellular compartments. They also interact with glutamatergic pyramidal cell inputs in a domain-specific manner and support synaptic temporal dynamics, network oscillations, selection of cell assemblies, and the implementation of brain states. The spatiotemporal specializations in cortical circuits reveal that cellular diversity and temporal dynamics coemerged during evolution, providing a basis for cognitive behavior.
1,885 citations
TL;DR: Results suggest that the best stimulus for exciting a cell (that is, a neural code) is coincident bursts, which provide more-precise information than action potentials that arrive singly.
1,345 citations
TL;DR: The universal modulation of these neurons by serotonin and acetylcholine via ionotropic receptors suggests that they might be involved in shaping cortical circuits during specific brain states andbehavioral contexts.
Abstract: An understanding of the diversity of cortical GABAergic interneurons is critical to understand the function of the cerebral cortex. Recent data suggest that neurons expressing three markers, the Ca2+-binding protein parvalbumin (PV), the neuropeptide somatostatin (SST), and the ionotropic serotonin receptor 5HT3a (5HT3aR) account for nearly 100% of neocortical interneurons. Interneurons expressing each of these markers have a different embryological origin. Each group includes several types of interneurons that differ in morphological and electrophysiological properties and likely have different functions in the cortical circuit. The PV group accounts for ∼40% of GABAergic neurons and includes fast spiking basket cells and chandelier cells. The SST group, which represents ∼30% of GABAergic neurons, includes the Martinotti cells and a set of neurons that specifically target layerIV. The 5HT3aR group, which also accounts for ∼30% of the total interneuronal population, is heterogeneous and includes all of the neurons that express the neuropeptide VIP, as well as an equally numerous subgroup of neurons that do not express VIP and includes neurogliaform cells. The universal modulation of these neurons by serotonin and acetylcholine via ionotropic receptors suggests that they might be involved in shaping cortical circuits during specific brain states and behavioral contexts.
1,211 citations
TL;DR: In this article, the authors used optogenetic tools to selectively stimulate VTA dopaminergic neuron action potential firing in freely behaving mammals and found that phasic activation of these neurons was sufficient to drive behavioral conditioning and elicited dopamine transients with magnitudes not achieved by longer, lower-frequency spiking.
Abstract: Natural rewards and drugs of abuse can alter dopamine signaling, and ventral tegmental area (VTA) dopaminergic neurons are known to fire action potentials tonically or phasically under different behavioral conditions. However, without technology to control specific neurons with appropriate temporal precision in freely behaving mammals, the causal role of these action potential patterns in driving behavioral changes has been unclear. We used optogenetic tools to selectively stimulate VTA dopaminergic neuron action potential firing in freely behaving mammals. We found that phasic activation of these neurons was sufficient to drive behavioral conditioning and elicited dopamine transients with magnitudes not achieved by longer, lower-frequency spiking. These results demonstrate that phasic dopaminergic activity is sufficient to mediate mammalian behavioral conditioning.
1,159 citations
TL;DR: The coincidence of a single back-propagating action potential with a subthreshold distal excitatory postsynaptic potential to evoke a burst of axonal action potentials represents a new mechanism by which the main cortical output neurons can associate inputs arriving at different cortical layers.
Abstract: Pyramidal neurons in layer 5 of the neocortex of the brain extend their axons and dendrites into all layers. They are also unusual in having both an axonal and a dendritic zone for the initiation of action potentials. Distal dendritic inputs, which normally appear greatly attenuated at the axon, must cross a high threshold at the dendritic initiation zone to evoke calcium action potentials but can then generate bursts of axonal action potentials. Here we show that a single back-propagating sodium action potential generated in the axon facilitates the initiation of these calcium action potentials when it coincides with distal dendritic input within a time window of several milliseconds. Inhibitory dendritic input can selectively block the initiation of dendritic calcium action potentials, preventing bursts of axonal action potentials. Thus, excitatory and inhibitory postsynaptic potentials arising in the distal dendrites can exert significantly greater control over action potential initiation in the axon than would be expected from their electrotonically isolated locations. The coincidence of a single back-propagating action potential with a subthreshold distal excitatory postsynaptic potential to evoke a burst of axonal action potentials represents a new mechanism by which the main cortical output neurons can associate inputs arriving at different cortical layers.
1,100 citations