Neocortex | EPFL Graph Search

The neocortex, also called the neopallium, isocortex, or the six-layered cortex, is a set of layers of the mammalian cerebral cortex involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, spatial reasoning and language. The neocortex is further subdivided into the true isocortex and the proisocortex. In the human brain, the cerebral cortex consists of the larger neocortex and the smaller allocortex. The neocortex is made up of six layers, labelled from the outermost inwards, I to VI. Etymology
The term is from cortex, Latin, "bark" or "rind", combined with neo-, Greek, "new". Neopallium is a similar hybrid, from Latin pallium, "cloak". Isocortex and allocortex are hybrids with Greek isos, "same", and allos, "other". Anatomy The neocortex is the most developed in its organisation and number of layers, of the cerebral tissues. The neocortex consists of the grey matter, or neuronal cell bodies and unmyelinated

Spike frequency adaptation supports network computations on temporally dispersed information

Anand Subramoney

For solving tasks such as recognizing a song, answering a question, or inverting a sequence of symbols, cortical microcircuits need to integrate and manipulate information that was dispersed over time during the preceding seconds. Creating biologically realistic models for the underlying computations, especially with spiking neurons and for behaviorally relevant integration time spans, is notoriously difficult. We examine the role of spike frequency adaptation in such computations and find that it has a surprisingly large impact. The inclusion of this well-known property of a substantial fraction of neurons in the neocortex - especially in higher areas of the human neocortex - moves the performance of spiking neural network models for computations on network inputs that are temporally dispersed from a fairly low level up to the performance level of the human brain.

ELIFE SCIENCES PUBLICATIONS LTD2021

Molecular heterogeneity of the ganglionic eminence and its relationship to the birth of neocortical interneurons

Susan Willi Monnerat

Neocortical function and malfunction depends critically on a spectrum of inhibitory interneurons. To gain novel insight in normal brain function and mechanisms leading to diseases, such as epilepsy or schizophrenia, the knowledge about the specific functions of each interneuron type appears crucial. To date, the mystery about the diversity of neocortical interneurons remains still unresolved, even though much effort was devoted to the characterization of mature interneurons in the neocortex. Ten years ago, the discovery of the ganglionic eminence (GE) as origin of neocortical interneurons allowed a novel approach to assess their various identities, and thus prompted researchers to follow the fate of cells accommodated in this region. Despite the knowledge of the source location and its subdivision into three GEs, their molecular identity remained unknown apart from few genes, and consequently unabled the specific isolation of precursor cells. To this purpose, we performed extensive microarray analysis of the three GEs at various developmental timepoints to reveal their molecular heterogeneity and identify novel precursor cell surface markers that would enable their prospective isolation by flow cytometry and subsequent fate assessment in vitro and in vivo. Surprisingly, molecular heterogeneity of the three GEs was restricted to few differentially expressed genes. However, the differences in gene expression became more apparent at late developmental stage that may reflect the increased specification during development. Among the three GEs, the LGE and CGE resembled molecularly each other most, while the MGE and CGE were most distantly related to each other. Furthermore, our genome-wide expression study suggested that the CGE, a structure of so far controversial nature, was rather a unique structure than a fusion of the MGE and LGE. Analysis across developmental timepoints revealed that the MGE underwent tremendous changes in gene expression when compared to the differential expression existing between the homochronic MGE and cerebral cortex. In our microarray screen, we could identify Boc as a novel marker of LGE/CGE-resident precursor cells. Taking advantage of Boc that encodes a cell surface molecule, we could isolate the Boc+ cells from the GE by flow cytometry, and demonstrate that in contrast to Boc– cells, they self-renewed and differentiated into oligodendrocytes, astrocytes, and neurons, and thus identify them as progenitor cells. Furthermore, immunohistochemical studies suggested that Boc+ GE cells may correspond to radial glia, the embryonic neural stem cells. The specific expression of Boc in the LGE and CGE, but not in the MGE during their entire lifetime suggested that Boc is a reliable marker for LGE/CGE-resident precursor cells. To assess the fate of Boc+ GE cells, we performed homotypic transplantations of Boc+ and Boc– cells onto organotypic slice cultures, and observed that in contrast to Boc– cells, Boc+ cells did not migrate from the GE to the neocortex suggesting that Boc+ precursor cells of the GE do not generate neocortical interneurons. In future, additional fate-mapping studies of Boc+ GE cells, such as in vivo transplantation, should shed more light on the ability of Boc+ LGE/CGE precursor cells to generate neocortical interneurons, and dependent on the outcome serve to construct a cell-lineage tree of neocortical interneurons. Thus, Boc will remain a useful tool to investigate developmental processes underlying the generation of neocortical and/or other neurons, such as striatal neurons.

EPFL2007

Voltage-sensitive dye imaging of mouse neocortex during a whisker detection task

Matthieu Pierre Auffret, Alexandros Kyriakatos, Alessandro Motta, Carl Petersen, Vijay Sadashivaiah, Yifei Zhang

Sensorimotor processing occurs in a highly distributed manner in the mammalian neocortex. The spatiotemporal dynamics of electrical activity in the dorsal mouse neocortex can be imaged using voltage-sensitive dyes (VSDs) with near-millisecond temporal resolution and similar to 100-mu m spatial resolution. Here, we trained mice to lick a water reward spout after a 1-ms deflection of the C2 whisker, and we imaged cortical dynamics during task execution with VSD RH1691. Responses to whisker deflection were highly dynamic and spatially highly distributed, exhibiting high variability from trial to trial in amplitude and spatiotemporal dynamics. We differentiated trials based on licking and whisking behavior. Hit trials, in which the mouse licked after the whisker stimulus, were accompanied by overall greater depolarization compared to miss trials, with the strongest hit versus miss differences being found in frontal cortex. Prestimulus whisking decreased behavioral performance by increasing the fraction of miss trials, and these miss trials had attenuated cortical sensorimotor responses. Our data suggest that the spatiotemporal dynamics of depolarization in mouse sensorimotor cortex evoked by a single brief whisker deflection are subject to important behavioral modulation during the execution of a simple, learned, goal-directed sensorimotor transformation. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.

SPIE-Intl Soc Optical Eng2017

Molecular heterogeneity of the ganglionic eminence and its relationship to the birth of neocortical interneurons

Susan Willi Monnerat

EPFL2007