Biology subjects

Vervaeke, K.

Publications and source records attributed to Vervaeke, K..

8 recordsLinked to original sources

bioRxiv2025

Sparsening and decorrelation of granule cell activity in the dentate gyrus by noradrenaline

The dentate gyrus in the hippocampus makes important contributions to the acquisition of episodic memories by transforming synaptic inputs from the entorhinal cortex into sparse and decorrelated activity patterns of its principal neurons, the granule cells. However, the underlying mechanism remains unclear. Using a combination of electrophysiological and optical recordings, together with optogenetic and pharmacological manipulations, we demonstrate that the release of noradrenaline plays a key role in this specialization via an enhancement of feedforward inhibition generated by cholecystokinin-expressing interneurons. By imposing coincidence detection with milliseconds temporal resolution onto granule cells, this enhancement of feedforward inhibition makes granule cell activity sparser and their firing patterns decorrelated. Since decorrelation contributes to efficient memory storage during auto-associative learning, these findings reveal a circuit mechanism by which an arousal signal facilitates memory formation in the hippocampus.

neuroscience↗

bioRxiv2025

VIP interneurons control hippocampal place cell remapping through transient disinhibition in novel environments.

Hippocampal place cells dynamically reorganize their activity, or "remap", to encode novel spatial environments, a process tightly regulated by inhibitory networks. Here, we identify vasoactive intestinal peptide (VIP)-expressing interneurons as key regulators of this plasticity. Using all-optical methods in mice navigating virtual reality, we show that novel environments trigger a transient increase in VIP interneuron activity, which facilitates rapid place field formation and stable spatial map construction. Bidirectional optogenetic manipulation --suppressing or upregulating VIP interneuron activity-- modulates the speed of spatial map formation and alters signatures of behavioral timescale plasticity (BTSP), a mechanism critical for place field induction. Both insufficient and excessive VIP interneuron activity impair reward-seeking behavior specifically in novel environments, revealing that a precise balance of VIP activity is essential for spatial learning. Our findings demonstrate that VIP interneurons gate a temporal window for place cell plasticity, mediating the impact of environmental novelty on hippocampal remapping and spatial memory.

neuroscience↗

bioRxiv2022

Representations of tactile object location in the retrosplenial cortex

Little is known about how animals use tactile sensation to detect important objects and remember their location in a worldbased coordinate system. Here, we hypothesized that retrosplenial cortex (RSC), a key network for contextual memory and spatial navigation, represents the location of objects based on tactile sensation. We studied mice that palpate objects with their whiskers while running on a treadmill in a tactile virtual reality in darkness. Using two-photon Ca2+ imaging, we discovered a population of neurons in agranular RSC that signal the location of tactile objects. Tactile object location responses do not simply reflect the sensory stimulus. Instead, they are highly task- and context-dependent and often predict the upcoming object before it is within reach. In addition, most tactile object location neurons also maintain a memory trace of the objects location. These data show that RSC encodes the location and arrangement of tactile objects in a spatial reference frame.

neuroscience↗

bioRxiv2022

Diverse long-range projections convey position information to the retrosplenial cortex.

Neuronal signals encoding the animals position, originally discovered in the hippocampus, widely modulate neocortical processing. While it is assumed that these signals depend on hippocampal output, their origin has not been investigated directly. Here, we asked which brain region sends position information to the retrosplenial cortex (RSC), a key circuit for navigation and memory. Using two-photon axonal imaging in head-fixed mice performing a spatial task, we performed a comprehensive functional characterization of long-range inputs to agranular RSC. Surprisingly, most long-range pathways convey position information, but with key differences. We found that axons from the secondary motor cortex transmit the most position information. By contrast, axons from the posterior parietal-anterior cingulate- and orbitofrontal cortex and thalamus convey substantially less position information. Axons from the primary- and secondary visual cortex make a negligible contribution. These data show that RSC is a node in a widely distributed ensemble of networks that share position information in a projection-specific manner.

neuroscience↗

bioRxiv2021

Parvalbumin interneuron dendrites enhance gamma oscillations

Dendrites are important determinants of the input-output relationship of single neurons, but their role in network computations is not well understood. Here, we used a combination of dendritic patch-clamp recordings and in silico modeling to determine how dendrites of parvalbumin (PV)-expressing basket cells contribute to network oscillations in the gamma frequency band. Simultaneous soma-dendrite recordings from PV basket cells in the dentate gyrus revealed that the slope, or gain, of the dendritic input-output relationship is exceptionally low, thereby reducing the cells sensitivity to changes in its input. By simulating gamma oscillations in detailed network models, we demonstrate that the low gain is key to increase spike synchrony in PV neuron assemblies when cells are driven by spatially and temporally heterogeneous synaptic input. These results highlight the role of dendritic computations in synchronized network oscillations.

neuroscience↗

bioRxiv2021

Cell-type-specific silence in thalamocortical circuits precedes hippocampal sharp-wave ripples.

Memory consolidation requires the encoding of neocortical memory traces, which is thought to occur during hippocampal oscillations called sharp-wave ripples (SWR). Evidence suggests that the hippocampus communicates memory-related neural patterns across distributed cortical circuits via its major output pathways. Here, we sought to understand how this information is processed in the retrosplenial cortex (RSC), a primary target circuit. Using patch-clamp recordings from mice during quiet wakefulness, we found that SWR-aligned synaptic modulation is widespread but weak, and that spiking responses are sparse. However, using cell type and projection-specific two-photon calcium imaging and optogenetics, we show that, starting 1-2 seconds before SWR, superficial inhibition in RSC is reduced, along with thalamocortical input. We propose that pyramidal dendrites experience a period of decreased local inhibition and subcortical interference in a seconds-long time window preceding hippocampal SWR. This may aid communication of weak and sparse SWR-aligned excitation between the hippocampus and neocortex, and promote the selective strengthening of memory-related connections.

neuroscience↗

bioRxiv2021

Mapping vestibular and visual contributions to angular head velocity tuning in the cortex

Neurons that signal the direction and angular velocity of head movements (AHV cells) are critically important to process visual and spatial information. However, it has been challenging to isolate the sensory modality that drives them and to comprehensively map their cortical distribution. To address this, we developed a method that enables rotating awake, head-fixed mice under a two-photon microscope in a visual environment. Starting in layer 2/3 of the retrosplenial cortex, a key area for vision and navigation, we found that a significant fraction of rotation-sensitive neurons report AHV. These tuning properties depend on vestibular input because they persist in darkness and are reduced when replaying visual flow to stationary animals. When mapping the spatial extent, we found AHV cells in all cortical areas that we explored, including motor, somatosensory, visual- and posterior parietal cortex. Notably, the vestibular and visual contributions to AHV are area dependent. Thus, many cortical circuits have access to AHV, enabling a diverse integration with sensorimotor and cognitive information.

neuroscience↗

bioRxiv2019

Ca2+ signaling in astrocytes is sleep-wake state specific and modulates sleep

Astrocytic Ca2+ signaling has been intensively studied in health and disease but remains uncharacterized in sleep. Here, we employed a novel activity-based algorithm to assess astrocytic Ca2+ signals in the barrel cortex of awake and naturally sleeping mice while monitoring neuronal Ca2+ activity, brain rhythms and behavior. We discovered that Ca2+ signaling in astrocytes exhibits distinct features across the sleep-wake cycle and is reduced in sleep compared to wakefulness. Moreover, an increase in astrocytic Ca2+ signaling precedes transitions from slow-wave sleep to wakefulness, with a peak upon awakening exceeding the levels during whisking and locomotion. Genetic ablation of a key astrocytic Ca2+ signaling pathway resulted in fragmentation of slow-wave sleep, yet increased the frequency of sleep spindles. Our findings suggest a role for astrocytic Ca2+ signaling in modulating sleep.

neuroscience↗