Biology subjects

Kuroki, S.

Publications and source records attributed to Kuroki, S..

7 recordsLinked to original sources

bioRxiv2025

Grid cells encode reward distance during path integration in cue-rich environments

The medial entorhinal cortex supports both path integration and landmark anchoring, but how these computations interact during goal-directed navigation is unclear. We show that grid cells dissociate from landmarks and instead encode reward distance when mice perform a path integration task on a cue-rich treadmill. Grid cell population activity reset at rewards and shifted coherently across trials, consistent with continuous attractor dynamics realigned by rewards. Furthermore, grid cells exhibited reduced spatial scales, broadened theta frequency distributions, and altered temporal coordination. These phenomena were captured by a theta interference model incorporating cell competition and two sets of theta oscillating inputs whose frequencies shifted apart. Switching to cue-based navigation stabilized the firing fields and partially restored grid scale, theta frequencies and temporal structure. These results demonstrate that MEC circuits flexibly reset to encode goal-directed trajectories, and suggest that continuous attractor and interference mechanisms normally cooperate but can decouple under path integration demands.

neuroscience↗

bioRxiv2024

Synchronicity transitions determine connection fluctuations in a model of coupled oscillators with plasticity

Sleep and rest, characterized by synchronized neuronal activity that emerges under large shifts in the excitation-inhibition balance, are crucial for synaptic reorganization in the brain. However, the network dynamics that permit rewiring without erasing stable connections remain unclear. To address this question, we extended a Kuramoto framework with excitation-inhibition balance by adding Hebbian and homeostatic plasticity. The resulting model showed that networks with robust inhibition consistently exhibited desynchronized dynamics and stable couplings. In contrast, networks with weaker inhibition exhibited a bistable regime, in which couplings of intermediate strengths fluctuated while strong couplings remained stable. These findings suggest that the dynamic interplay between network activity and plasticity selectively stabilizes stronger connections while permitting flexible reorganization of weaker ones, providing a potential mechanism for network reorganization during sleep and rest.

neuroscience↗

bioRxiv2023

CA3 circuit model compressing sequential information in theta oscillation and replay

The hippocampus compresses the sequential information in a theta oscillation cycle and short-term sequential activities during sharp-wave ripple while sleeping or resting; these processes are known as theta sequence and replay, respectively. The theta sequence is based on theta phase precession patterns of individual neurons. However, how these sequential neuronal activities are generated and how they store information about the outside environment remains unknown. We developed a hippocampal cornu ammonis (CA)3 computational model based on the biological CA3 circuits anatomical and electrophysiological evidence to address these. The model comprises theta rhythm inhibition, place input, and CA3-CA3 plastic recurrent connection. The model could compress the sequence of the external inputs and reproduce theta phase precession and replay, learn additional sequences, and reorganize previously learned sequences. A gradual increase in synaptic inputs, controlled by interactions between theta-paced inhibition and place inputs, explained the mechanism for sequence acquisition. This model highlights the crucial role of plasticity in the CA3 recurrent connection and theta oscillational dynamics, and hypothesizes how the CA3 circuit acquires, compresses, and replays sequential information.

neuroscience↗

bioRxiv2020

Distributed sensory coding by cerebellar complex spikes in units of cortical segments

Sensory processing is essential for motor control. Climbing fibers from the inferior olive transmit sensory signals to Purkinje cells, but how the signals are represented in the cerebellar cortex remains elusive. We examined the olivocerebellar organization of the mouse brain by optically measuring complex spikes (CSs) evoked by climbing fiber inputs over the entire dorsal surface of the cerebellum. We discovered that the surface was divided into approximately 200 segments each composed of [~]100 Purkinje cells that fired CSs synchronously. Our in vivo imaging of evoked responses revealed that whereas stimulation of four limb muscles individually similar global CS responses across nearly all segments, the timing and location of a stimulus were derived by Bayesian inference from coordinated activation and inactivation of multiple segments on a single trial basis. Our findings suggest that the cerebellum performs segment-based distributed population coding by assembling probabilistic sensory representation in individual segments.

neuroscience↗

bioRxiv2019

Haptic metameric textures

Humans sense spatial patterns through their eyes and hands. Past studies have revealed differences (as well as similarities) between vison and touch in texture processing (e.g., eye is good at detecting texture boundaries, while hand can discriminate subtle texture differences), but the underlying computational differences remains poorly understood. Here we transcribed various textures as surface relief patterns by 3D-printing, and analyzed the tactile discrimination performance regarding the sensitivity to image statistics. The results suggest that touch is sensitive to texture differences in lower-order statistics (e.g., statistics of local amplitude spectrum), while may not to those in the higher-order statistics (e.g., joint statistics of local orientations). In agreement with this, we found that pairs of synthesized textures differing only in higher-order statistics were nearly indiscriminable (metameric) by touch, while easily discriminable by vision. Our findings show that touch and vision sense spatial information using different and complementary computational strategies.

neuroscience↗

bioRxiv2017

Common features in plastic changes rather than constructed structures in recurrent neural network prefrontal cortex models

We have flexible control over our cognition depending on the context or surrounding environments. The prefrontal cortex (PFC) controls this cognitive flexibility; however, the detailed underlying mechanisms remain unclear. Recent developments in machine learning techniques have allowed simple recurrent neural network PFC models to perform human- or animal-like behavioral tasks. These systems allow us to acquire parameters, which we could not in biological experiments, for performing the tasks. We compared four models, in which a flexible cognition task, called context-dependent integration task, was performed; subsequently, we searched for common features. In all the models, we observed that high plastic synapses were concentrated in the small neuronal population and the more concentrated neuronal units contributed further to the performance. However, there were no common properties in the constructed structures. These results suggest that plastic changes can be more general and important to accomplish cognitive tasks than features of the constructed structures.

neuroscience↗

bioRxiv2017

Caspase-8, RIPK1, and RIPK3 Coordinately Regulate Retinoic Acid-Induced Cell Differentiation and Necroptosis

Caspase-8, which is essential for death receptor-mediated apoptosis, inhibits necroptosis by suppressing the function of RIPK1 and RIPK3 to activate MLKL. We show that knockdown of caspase-8 expression in embryoid bodies derived from ES cells markedly enhances retinoic acid (RA)-induced cell differentiation and necroptosis, both of which are dependent on Ripkl and Ripk3. RA treatment obviously enhanced the expression of RA-specific genes having a retinoic acid response element (RARE) to induce cell differentiation, and induced marked expression of RIPK1, RIPK3 and MLKL to stimulate necroptosis. Caspase-8 knockdown induced RA receptor (RAR) to form a complex with RIPK1 and RIPK3 in the nucleus, and RAR interacting with RIPK1 and RIPK3 showed much stronger binding activity to RARE than RAR without RIPK1 or RIPK3. In Caspase-8-deficient mouse embryos, expression of RA-specific genes was obviously enhanced. Thus, caspase-8, RIPK1, and RIPK3 regulate RA-induced cell differentiation and necroptosis both in vitro and in vivo.

cell biology↗