Neuronal ensembles

The analysis of neuronal ensembles often suffers from low spiking activity. As statistical analysis relies on sufficiently large samples, rare joint events in neuronal ensembles usually fail to reach statistical significance. We show that statistical power can be enhanced considerably by careful preselection of specific, separated temporal stripes distributed throughout the whole time series in which spiking is more likely to occur. In a data set of two-photon calcium imaging from the visual cortex of mice (Cleppien et al., 2024+), we identified short temporal stripes of interest from the un

Neuronal ensembles encoding a specific memory have been shown to be distributed across multiple brain regions. However, the computational principles behind the distributed nature of such memory engrams are unknown. Here we propose that distributed engrams support functional flexibility and versatility. We investigated whether distributed engrams can differentially regulate memory discrimination and generalization, opposing and complementary computations that must be balanced for adaptive memory-guided behavior. For instance, while animals need to discriminate between threat-predictive and neut

Neuronal cultures are an excellent experimental tool to study the collective behaviour of neuronal ensembles in a controlled environment. However, neurons cultured on flat surfaces present limitations in terms of their functionality, as they exhibit a synchronous dynamic behaviour that differs from the much richer repertoire of brain activity [1].In order to address this limitation, we studied the capacity to break the isotropy in connectivity and enrich dynamics by modulating the spatial arrangement of neurons in the substrate they grow. Specifically, we cultured neurons on polydimethylsiloxa

Neuronal ensembles, groups of simultaneously active neurons, are considered to be one of basic forms of information representation in the mammalian cortex. However, the mechanisms underlying the modulation of neuronal ensembles yet remain to be fully understood. Here, we investigated external input-dependent modulation of neuronal ensembles in cultured neuronal networks with modular connectivity mimicking the mammalian cortex. The modular neuronal networks were fabricated by growing cultured rat cortical neurons in microfluidic devices. A fraction of the neurons was stimulated using optogeneti

…of associative memories are encoded in neuronal ensembles within and across distinct prefrontal subregions and the role of these representations in the encoding and retrieval of emotional memories. In this study, we aim to elucidate the interplay between prefrontal subregions a

…it is hypothesized that downstream neuronal ensembles are stabilized in diverse cortical regions. The stability of neuronal ensembles across several months has not been

Memories have been suggested to be stored in groups of neurons known as neuronal ensembles, or “engrams”, and neuroplasticity is believed to be the underlying mechanism that allows the formation or remodeling of these ensembles, thus allowing memory modifications. Critically, the hippocampus has been described as a central hub for neuronal ensembles. In the context of fear memory, the representation of the hippocampal neuronal ensemble has been characterized, while little is known about the neuronal ensemble within the hippocampus and the upstream circuits in spatial learning and memory. With

Breaking the neural code requires the systematic identification and characterization of neuronal ensembles related to specific brain functions. Recent research suggests that neuronal ensembles underlie brain functions such as perception, movement, and memory processes. However, the standardization of different mathematical algorithms that allow the identification and characterization of the properties of neuronal ensembles is still lacking in the systems neuroscience field. Our work addresses this gap by introducing an open-source Graphic User Interface (GUI) designed for researchers intereste

…the salience of social stimuli as ensembles of neurons with individual stimuli preferences. Correct evaluation of prediction errors, defined as the difference between expectation and result, is critical f

…dynamics and the network topology of neuronal ensembles across different levels of consciousness, focusing on wakefulness, anesthesia, and awakening. The data were acquired by two chronically implanted multielectrode arrays (Utah 96), placed in the dorsal prefrontal cortex (dPFC) and dorsal premotor cortex (PMd) of two

…However, the neuronal networks underpinning this memory are only just being identified. Effectively modelled through object-in-place (OIP) tasks, associative recognition memory can be represented by the time mice spend exploring novel compared to familiar objects and configurations. During learning, active neurons are recruited into neuronal ensembles making an engram, the neural representation of

…showed that the brain also forms neuronal representations of specific immune responses. We termed these representations as immunengrams. Chemogenetic reactivation of the neuronal ensembles that compromise these immunengrams, specifically in the insular cortex, were sufficient to re-create the original inflammatory state. These findings have major implications for our understanding of how the brain can induce disease based on a mental (sensory or cognitive) trigger. However, critical to our understanding of

…sparsely distributed neurons, called neuronal ensembles. Here, we explored the role of neuronal ensembles in alcohol-memory reconsolidation and relapse and characterized their transcriptional signature. Upon retrieving alcohol-related memories, we observed increased neuronal activation in the nucleus accumb

…the refinement and stabilisation of neuronal ensembles. This study aimed to examine the effect of noradrenergic regulation of dorsal hippocampal neuronal activity during spatial learning. For this, we used wide-field calcium imaging as a method to study B-AR modulation of the activity of visualised hippocampal CA1 neurons during item-place learning that is known to trigger hippocampal long-term depression (LTD) (doi: 10.109

…To allow lifelong tracking of neuronal populations recruited during early-life stress we used FosTRAP2 mice in a juvenile (P21) social defeat model (jSD), in which neuronal

…memories are deposited in discrete neuronal ensembles in the hippocampus, amygdala and other brain regions involved in memory formation. However, the creation of a brain-wide map for engram formation and stability has proven to be a challenging endeavor that has been only partially solved. Among the methods to label active neurons, the Targeted Recombination in Active Populations v2 (TRAP2) mouse strain sticks out for enabling t

Continuous attractor networks support various cognitive functions yet the neuronal dynamics and circuits supporting these dynamics in vivo remain unclear. The HD circuit is a canonical example of such network and HD cells each fire for a specific direction of the animal’s head. In the anterodorsal nucleus of the thalamus (ADn), HD cells maintain their mutual coordination during sleep, when sensory inputs are virtually absent, supporting the view of an attractor-driven system. The rigid organization of HD cell activity in the ADN begs the question of the origin of these structured patterns. Th

…To study how neuronal ensembles might support memory-updating, we used a hippocampus-dependent spatial reversal task to measure hippocampal ensemble dynamics when mice switched navigational goals. Using Miniscope calcium imaging, we identified neuronal ensembles (co-active neurons) in dorsal CA1 that were spatially tuned and stable across training sessions. When reward locations were moved during a

…in time are encoded by overlapping neuronal ensembles, but whether dendritic plasticity plays a role in linking memories is unknown. Using activity-dependent labeling and manipulation, as well as longitudinal one- and two-photon imaging of RSC somatic and dendritic compartments, we show that memory linking is not only dependent on ensemble overlap in the retrosplenial cortex, but also on branch-specific dendritic alloc

Accumulating data indicate that the brain can affect immunity, as evidenced, for example, by the effects of stress, stroke, and reward system activity on the peripheral immune system. However, our understanding of this neuroimmune interaction is still limited. Importantly, we do not know how the brain evaluates and represents the state of the immune system. In this talk, I will present our latest study from our lab, designed to test the existence of immune-related information in the brain and determine its relevance to immune regulation. We hypothesized that the InsCtx, specifically the poster

The hippocampal dentate gyrus (DG) to CA3 pathway plays a key role in encoding new experiences that are ultimately consolidated in the anterior cingulate cortex (ACC). Experience-dependent changes among excitatory neurons in the DG ‒ CA3 circuit have been intensely studied. However, DG cell axons innervate not only CA3 pyramidal neurons but also inhibitory, parvalbumin positive interneurons (PV IN) to provide strong feed-forward inhibition (FFI) onto CA3 pyramidal neurons. Following learning, FFI onto CA3 is temporarily increased which may be a key element for consolidation and long-term memor

…to spatial representations, yet the neuronal dynamics and circuits supporting these dynamics in vivo remain unclear. One example of such networks is the head-direction (HD) circuit, a crucial signal for navigation. It is represented by HD cells, which each fire for a specific direction of the animal’s head, and is transmitted to the cortex by the anterodorsal nucleus (ADN) of the thalamus where a vast majority of neurons are modulated by HD. ADn HD cells maintain their mutual coordination dur

…interested in studying the activity of neuronal ensembles in behaving animals, and how it changes with learning. We have recently set up a paradigm where mice learn to associate sensory information (two different odors) to motor outputs (lick vs no-lick) under head-fixation. We combined this with two-photon calcium imaging, which can monitor the activity of a microcircuit of many tens of neurons simultaneously from a small area of the

…image and manipulate the activity of neuronal populations in 3D in vivo (2). Using them we find that groups of synchronous neurons (neuronal ensembles) dominate the evoked and spontaneous activity of mouse primary visual cortex (3). Ensembles can be optogenetically imprinted for several days and some of their neurons