Neocortex

…and learning in the adult mammalian neocortex. The Brain and Cognitive Sciences colloquium is followed by a reception.

…encoding individual episodes and the neocortex slowly extracting regularities over days, months, and years. But this do

…of work have elucidated how sensory neocortex processes physical stimulus features. In contrast, examining how memory-related-top-down information is encoded and integrated with bottom-up signals has long been challenging. Here, I will discuss our recent work pinpointing the outermost layer 1 of neocortex as a central hotspot for processing of experience-dependent top

…In the mammalian neocortex, inhibitory neurons are diverse. They are characterized by a variety of cellular attributes that enable their specialized roles in regulating information processing. It is increasingly clear that the major subtype specification of inhibitory neurons is given by their molecular identity, defined by techniques such as gene expression profiling. However, the molecular class alone provides limited insight into the anatomical, physiological, and connectivity properties of

To resolve the fundamental question of how the mammalian neocortex learns to create complex hierarchical representations, two main competing theories that intersect ideas from neuroscience and machine learning are currently debated. The first theory draws inspiration from artificial neural networks, suggesting the brain approximates error backpropagation (BP), where neurons adjust synapses to minimize a backpropagated error. The second approach, target learning (TL), proposes that neurons learn by reducing feedback needed to achieve desired activity patterns. While both theories are computati

The neocortex is considered to be the seat of higher cognitive functions in humans. During its evolution, most notably in humans, the neocortex has undergone considerable expansion, which is reflected by an increase in the number of neurons. Neocortical neurons are generated during development by neural stem and progenitor cells. Epigenetic mechanisms play a pivotal role in orchestrating the behaviour of stem cells during development. We are interested in the mechanisms that regulate gene expression in neural stem cells, which have implications for our understanding of neocortex development an

The neocortex is built up from homologous neuron types, but neurons exhibit between-species differences in gene expression, molecular profile, and electrical function. Purpose of these specializations is not well understood. In human neocortex, fast-spiking interneurons have high electrical excitability compared to their rodent counterparts. This slows down time course for cell membrane potential changes, and in theory, makes human fast-spiking neurons slower than rodent cells to process electrical input signals and generate action potential (AP). However, human neurons are nearly as fast with

The neocortex is stereotypically organized into layers of excitatory neurons arranged in a precise parallel orientation. Here we show that dynamic adhesion both preceding and following radial migration is essential for this organization. Neuronal adhesion is regulated by the Mowat-Wilson syndrome-associated transcription factor Zeb2 (Sip1/Zfhx1b) through direct repression of independent adhesion pathways controlled by Neuropilin-1 (Nrp1) and Cadherin-6 (Cdh6). We reveal that to initiate radial migration, neurons must first suppress adhesion to the extracellular matrix. Zeb2 regulates the multi

…macroglia cells that form the mature neocortex. Precisely regulated mechanisms are crucial for the proper development of this structure, from the generation of neural cells to their correct migration and establishment of specific connections. Among the many genes described to regulate its proper development, cell-cell adhesion molecules such as Cdh2 or its associated protein Afadin play important roles. Inactivation of these genes in the dorsal tele

…the hippocampus and transferred to the neocortex for long-term storage during sleep. These processes involve brain-wide plastic changes, heralded by macroscopic brain activities that occur upon changes in the neuromodulatory activity of the brainstem. The brainstem prompts periods of both enduring and transient changes of neuronal excitability that modify the activity of other sub-structures in a precise manner. Thus, brainstem activity may play a critical role in memory formation. However, the specific neural mechanisms that a

Epilepsy provides a unique opportunity to study human cellular electrophysiology through in vivo and in vitro approaches. In vivo recordings offer advantages in action potential pattern reconstruction and connection preservation, while in vitro studies allow broader tissue exploration within a confined space of cut connections, yet coherent investigation in these distinct conditions is lacking. This study compared single-neuron firing properties in four epileptic patients using identical 24-channel laminar microelectrodes with 150 μm inter-contact distance for both their in vivo and in vitro i

The processing of sensory information by the neocortex is at the heart of conscious perception and is known to involve a dynamic interaction between synaptically connected GABAergic inhibitory interneurons (INs) and excitatory principal neurons (PNs). One hypothesis is that sensory feature encoding in PNs is supported by different IN types performing specific functional roles. Here we address this hypothesis in the mouse thermal cortex. The thermal system is a fundamental pathway required for accurate object identification, pain perception and body temperature regulation and one that is highly

Projections from basal forebrain cholinergic neurons (BFCNs) densely innervate neocortex, releasing acetylcholine to regulate arousal, sensory processing and learning. Although the cholinergic system is one of the extensively studied neuromodulatory system, its impact on cortical processing remains unclear. Earlier studies have shown that BFCNs in rostral and caudal basal forebrain nuclei respond largely similar to reward and punishment despite their non-overlapping cortical projections, suggesting that BFCNs act as a unified broadcasting system. In contrast, more recent findings revealed dist

…field potential (LFP) across the whole neocortex in freely behaving rats using high-density flexible surface and translaminar arrays using active transistors. 3D tracking and spatio-spectral analysis of recordings over long sessions enabled automatic and accurate brain and behavioral

Loss of function mutations in genes encoding lysine methyltransferases responsible for trimethylation of histone 3 on lysine 4 (H3K4me3) are associated with a range of neurodevelopmental conditions. Intriguingly, mutations of H3K4me3-specific lysine demethylases (KDMs) are also associated with autism and intellectual disability. Mutations in KDM5B have been reported in patients with autism, intellectual disability and developmental delay. We hypothesised that a deficiency in the demethylation activity of KDM5B will lead to a dysregulated H3K4me3 epigenome, abnormal neurodevelopmental gene expr

…between the hippocampus and neocortex. It is therefore important to assess the developmental timeline of

…neuronal population in the mammalian neocortex, which largely disappears at the time of postnatal somatosensory maturation. In this study, we used mouse genetics, anatomical, functional and behavioral approaches to explore the impact of the early postnatal death of CRs in the maturation of the cortical circuit. We find that CRs apoptosis plays a crucial role in facilitating the proper development of inhibitory connectivity from

…are progressively transferred to the neocortex, where they are reorganised and stabilised to become long-term memories. This consolidation process is believed to occur concurrently with neuronal oscillations such as sleep spindles. Spindles are waxing-and-waning oscillations in the 10-16 Hz frequency range recorded from the brain's surface, originating in the thalamus and transmitted to the neocortex via thalamo-cortical projections. Several types of spindles have been identified, but how they are linked to specific consolidation proc

Principal neurons with dendritic axon origins offer privileged pathways for information flow through the hippocampal network and between brain hemispheres. Traditionally overshadowed in research, the GABAergic interneurons play a crucial role in modulating network activity. Our research leverages genetic and immunofluorescent markers to dissect the morphological variance among inhibitory neuron subpopulations, focusing on the axon initial segments (AIS) — key sites for action potential generation. Our study captures the extensive diversity of proximal interneuron morphologies within the murine

…patterns of neural activity in the neocortex. These patterns arise from synchronous synaptic activity and are often detected in particular frequency bands in the cortical field potential. However, cortical activity is highly variable on multiple timescales (milliseconds to hundreds of seconds). Identifying discrete neural events underlying patterned activity within highly dynamic cortical network fluctuations thus remains a critical challenge. Here, we develop a novel ana

…between the hippocampus and neocortex. The hippocampus encodes novel episodes using sparse and orthogonal neural representations, which form and stabilize within ~10 minutes in a novel environment. Recent studies have shown that several neocortical areas, including the retrosplenial cortex (RSC), primary somatosensory cortex (S1), and primary visual cortex (V1) contain sparse neural coding correlated to spatial location in one-dimensional environments. This spatial coding depends on an intact hipp

…and progressively consolidate in the neocortex. During sleep and rest periods, neuronal traces are reactivated at the time of hippocampal sharp-wave ripples (SWRs) thought to mediate memory consolidation. Though SWRs have been widely studied within the hippocampus, the ongoing activity within the rest of the brain remains elusive, because technically challenging: electrophysiology cannot easily resolve the whole brain and optical recording techniques have limited access to deep tissue. In a 2012 study, Logothetis and colleague

…primates) with the larger neocortex, an evolutionary newer region of the cerebral cortex, than in species with smaller neocortex (e.g. mice). Therefore, it can be hypothesized that morphotype diversification of bRG is a feature gained in species with expanded neocortex during evolution. To examine this hypothesis, the present study analyzed the morphotypes of bRG in the evolutionary older regi

…very early hippocampal homolog but no neocortex. Whereas behavioral studies suggest that lizards are able to perform similar hippocampus-dependent cognitive tasks as mammals, it is not known whether the functional organization in reptiles is the same as in mammals. One way to probe functional architecture is to investigate neural representations across different subregions, e.g. by immediate early gene imaging, which visualizes genomic responses of activated neuronal popula