Inhibitory neurons

…and maturation of excitatory and inhibitory

Over the years, excitatory neurons received much attention for their role in brain dynamics, while the inhibitory neurons were understood to play more of a support, stabilizing role. However, recent advances have revealed that memories are encoded both by excitatory and inhibitory neurons (EI engrams), adding to the evidence of the functional importance of inhibitory neurons beyond mere stability. Still, the computations enabled by such EI engrams are unclear, and the synaptic plasticity rules that could create and sustain them are unknown. Here, we explore in silico a mechanism for EI engram

The dynamic interplay of inhibitory and excitatory neurons drives the cortical functional repertoire. 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

Classical views suggest that memories are stored in assemblies of excitatory neurons that become strongly interconnected during learning. However, recent experimental and theoretical results have challenged this view, leading to the hypothesis that memories are encoded in assemblies containing both excitatory (E) and inhibitory (I) neurons. Understanding the effects of these E-I assemblies on memory function is therefore essential. Using a biologically constrained model of an olfactory memory network, I will first describe how introducing E-I assemblies reorganizes odor-evoked activity pattern

Activity-dependent structural plasticity (ADSP) plays a significant role in the homeostatic regulation of neuronal connectivity and activity in developing neuronal networks. This process involves intricate activity-dependent interaction between neuronal growth and migration, which shapes synaptic connections and results in network architectures with varying levels of clustering and modularity, influenced by the initial conditions. While excitatory interactions are essential for early network formation, the timely maturation of inhibition is also considered essential for stable activity dynamic

Inhibitory neurons (I), akin to their excitatory (E) counterparts, adjust synaptic efficacies in response to neural activity. Contrary to the traditional view of inhibition as a purely global activity modulator, recent studies highlighted the importance of specificity in (E/I) wiring and motif structures. These motifs, encompassing mutual and lateral inhibition, take essential functional roles in tuning of receptive fields, learning of representations, predictive coding, and in the regulation of the degrees of freedom of the network’s dynamics (i.e. the network dimensionality). Despite numero

Coherent oscillations of neural activity are ubiquitous across brain spatial and temporal scales and have been associated with the formation of sensory or behavioral representations [1]. Refined experimental techniques report today a new complexity of this oscillatory activity, especially in the gamma (30-100 Hz) band. Indeed, the frequency of these oscillations shows a large variability through time [2], questioning the classical view of γ oscillations being separated into different frequency bands. Oscillations appear instead in bursts characterised by rapid, synchronous neuronal firing. Thi

The hippocampus plays a central role in memory processing. In order to avoid deleterious interference between stored and ongoing experience, theoretical considerations require a separation between phases of memory encoding and recall within the same neural circuit, putatively controlled by hippocampal theta oscillations [1]. However, the neural mechanisms subserving this separation remain unknown. Classical models either remain moot about these mechanisms [2], or assume purpose-built neuromodulatory interactions that are in conflict with biologically realistic timescales of synaptic modulation

Prolonged reduction in blood flow leads to stroke, a devastating neurological insult leading cause of adult disability worldwide. One of the early features of stroke is the disruption of neuronal activity that results from the reduction of metabolic supply. Changes in oscillatory brain patterns have been observed in several neurological disorders, including stroke. Evoked neural oscillations in the gamma range have recently shown the ability to restore and maintain intrinsic homeostatic processes in the brain. However, the causal relationship between stimulation and restoration of function is

…subpopulations of GABAergic interneurons. However, the underlying molecular mechanisms linking these observations are not fully understood. The activity-regulated gene Arc/Arg3.1 is rapidly up-regulated by acquiring novel experience, learning and memory, and synaptic plasticity-inducing stimuli1,2. Acute stress has also been reported to elevate the levels of Arc/Arg3.1 mRNA o

During hunger onset, animals need to reprioritize the behaviours they express to maximize the chance of finding food. Selecting the appropriate actions requires them to gauge their internal hunger-state but also to weigh up the value of inputs coming from their external environment. The neural mechanisms that underlie this survival-linked perceptual decision-making are of significant interest, but poorly understood.To identify the underlying neural mechanisms of these motivational state dependent decisions, we used the mollusc, Lymnaea stagnalis, whose behaviours have been extensively characte

Neurons in sensory areas are tuned to various input features, and tuning properties reveal essential aspects of the computation performed by the neuronal population. In the post-subiculum (PoSub), neurons are modulated by the animal’s head-direction (HD), and most pyramidal neurons are fine tuned to a specific direction. Other cell types, especially fast-spiking neurons, are less specifically tuned but are generally still modulated by HD. By recording from ensembles of neurons in the PoSub in freely moving mice with linear silicon probes, making it possible to determine precise anatomical loca

…pathologies, little is known about inhibitory neurons properties themselves and whether specific inhibitory subpopulations are preferentially altered in chronic pain conditions.We used the Spared Nerve Injury (SNI) neuropathic pain model on Gad67-GFP transgenic mice, which specifically labels dorsal horn inhibitor

Multiple studies suggest that inhibitory neurons are involved in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). ALS and FTD are two devastating, frequently co-occurring neurodegenerative disorders. While ALS primarily affects motor neurons, causing rapid progressive paralysis and premature death, FTD affects frontal and temporal lobes, leading to severe changes in personality, behaviour, or language skills. To characterise the contribution of inhibitory neurons to these phenotypes, we generated a mouse model based on the expression of mutant Fused in Sarcoma (FUS) selec

…is generally robust despite loss of neurons during aging, and even the accelerated loss during prodromal phases of neurodegeneration. Here, we probed the robustness of the representational map against the permanent removal of specific neurons and tested in how far its structure is stabilized by homeostatic network mechanisms. We combined longi

…can be encoded by both excitatory and inhibitory neurons (EI engrams), adding to the evidence of the functional importance of inhibitory neurons beyond mere stabilization. The functional consequence of such EI engrams is unclear, and the synaptic plasticity rules that could sustain them are unknown. Here, we explore in silico a mechanism for EI engrams storage and recall to glean possible computational benefits of such engrams ove

…span several millimeters and connect neurons that encode different portions of the visual space [1], while connections in the granular layers remain local.We presented disks of varying radii and annuli of varying inner radii to anesthetized cats to investigate laminar differences in spatial integration of the stimuli i

…Cross-species analysis revealed that inhibitory neurons and inhibitory neuron-enriched subnuclei of the amygdala were well-conserved i

…Recent evidence suggests that inhibitory neurons (INs) are key regulators of neocortical states.Here we investigate how neocortical long-range INs that co-express somatostatin (SST) and neuronal nitric oxide synthase (nNOS) (“SST/nNOS cells”), control patterns of synchronous neocortical activity and arousal states in mice. While the in-vivo function of SST/nNOS cells

Inhibitory neurons are pivotal in shaping neural dynamics, acting as a regulatory mechanism to maintain network stability and enhance sensory processing. Their interplay within neural circuits affects stimulus selectivity, temporal precision, and memory functions. On the other hand, mounting evidence suggests that neural responses to sensory stimuli change over time – a phenomenon termed representational drift. Yet, how inhibitory neurons contribute to representational drift remains largely unknown.Here, we examined the collective statistics of inhibitory and excitatory neurons in layers 2/3 o

…can arise from locally connected neurons through multi-synaptic interactions. Here we seek to map the structure of cortical lateral interactions through localised perturbations in vivo.We first constructed a rectified recurrent neural netwo

…Inhibitory neurons, or Interneurons (IN), play a critical role in shaping neuronal networks by selectively gating signal flow. Parvalbumin-IN (PV-IN) is one of the predominant interneurons and is known to be involved in memory consolidation and development. However, its role in maintaining memory specificity is still elusive. Here, we perturbed PV-IN activity and found that the activity of PV-IN is needed to maintain recent memory specificity. Interestingl

…In this brain state, cortical neurons alternate between hyperpolarized Down states and depolarized Up states, which will travel from their source through cortico-cortical connections along the whole cortex. This makes the SWO an ideal model to understand cortico-cortical communication and disentangle local properties from those that are controlled by the network state.In this project, we built a computational model of coupled cortical populations under the

Calcium imaging is a key method to record from identified neurons in the living brain. To infer spiking activity from neuronal calcium signals, we have previously developed CASCADE, a method based on supervised deep learning1. To train the algorithm, we assembled a database of simultaneous calcium and electrophysiological recordings from the same neurons in several brain regions in mouse and zebrafish1. Here, we provide additional datasets and analyses. First, we now include ground truth datasets recorded from excitatory and inhibitory neurons of mouse spinal cord. A CASCADE model for spike in