Biology subjects

Kobayakawa, R.

Publications and source records attributed to Kobayakawa, R..

4 recordsLinked to original sources

bioRxiv2022

The Temporal and Contextual Stability of Activity Levels in Hippocampal CA1 Cells

Recent long-term optical imaging studies have demonstrated that the activity levels of hippocampal neurons in a familiar environment change on a daily to weekly basis. However, it is unclear whether there is any time-invariant property in the cells neural representations. In this study, using miniature fluorescence microscopy, we measured the neural activity of the mouse hippocampus in four different environments every 3 days. Although the activity level of hippocampal neurons fluctuated greatly in each environment across days, we found a significant correlation between the activity levels for different days, and the correlation was higher for averaged activity levels across multiple environments. When the number of environments used for averaging was increased, a higher activity correlation was observed. Furthermore, the number of environments in which a cell showed activity was preserved. Cells that showed place cell activity in many environments had greater spatial information content, and thus carried a higher amount of information about the current position. In contrast, cells that were active only in a small number of environments provided sparse representation for the environment. These results suggest that each cell has not only an inherent activity level but also play a characteristic role in the coding of space. Significance StatementRecent studies have revealed that place cell activity in the hippocampal CA1 cells exhibit instability on a daily to weekly scale. However, it is unclear whether there is any invariant property in the activity of the cells. In this study, we found that, although the activity level of CA1 neurons fluctuated greatly in one environment, the mean activity level across multiple environments was more stable. Furthermore, the number of environments in which a cell showed activity was preserved over time. These results suggest that even though the spatial code changes dynamically, each cell has an inherent activity level and plays a characteristic role in spatial coding.

neuroscience↗

bioRxiv2021

Large-scale calcium imaging with a head-mount axial scanning 3D fluorescence microscope

Miniaturized fluorescence microscopes are becoming more important for deciphering the neural codes underlying various brain functions. With gradient index (GRIN) lenses, these devices enable recording neuronal activity in deep brain structures. However, to minimize any damage to brain tissues and local circuits, the diameter of the GRIN lens should be 0.5-1 mm, resulting in a small field of view. Volumetric imaging capability might increase the number of neurons imaged through the lenses considering the three-dimensional (3D) structure of neural circuits in the brain. To observe 3D calcium dynamics, we developed a miniaturized microscope with an electrically tunable lens and a novel CNMF-based neural signal extraction algorithm for wide-field 3D imaging data. By combining the hardware and software, approximately 1000 neurons were imaged from the cortices of freely behaving mice. Compared with the state-of-the-art 2D imaging technique, the proposed 3D method imaged 1.7-2.6 times more cells with a higher separation of cellular signals.

neuroscience↗

bioRxiv2020

Thiazoline-related TRPA1 agonist odorants orchestrate survival fate in mice

Therapeutic hypothermia protects the brain after cardiopulmonary arrest. Innate fear has evolved to orchestrate protective effects in life-threatening situations. Thus, strong fear perception may induce a specialized life-protective metabolism based on hypothermia/hypometabolism; however, such phenomena and their inducers are yet to be elucidated. Here, we report that thiazoline-related fear odors (tFOs), which are TRPA1 agonists and induce robust innate fear in mice, induced hibernation-like systemic hypothermia/hypometabolism, accelerated glucose uptake in the brain, and suppressed aerobic metabolism via phosphorylation of pyruvate dehydrogenase, thereby enabling long-term survival in a lethal hypoxic environment. In contrast to hibernation, during which immune functions are generally suppressed, tFO-stimulation induced a crisis-response immune state characterized by potentiated innate immune functions but suppressed inflammation with anti-hypoxic ability. Collectively, these responses exerted potent therapeutic effects in cutaneous and cerebral ischemia/reperfusion injury models. Whole brain mapping and chemogenetic activation revealed that sensory representation of tFOs orchestrate survival fate via brain stem Sp5/NST to midbrain PBN pathway. TFO-induced strong crisis perception maximizes latent life-protective effects by shifting metabolism to a crisis response mode characterized by hypothermia, hypometabolism and crisis immunity.

physiology↗

bioRxiv2019

Spontaneous activity generated within the olfactory bulb establishes the discrete wiring of mitral cell dendrites

In developing brains, activity-dependent remodeling facilitates the formation of precise neuronal connectivity. Synaptic competition is known to facilitate synapse elimination; however, it has remained unknown how different synapses compete to each other within a postsynaptic cell. Here we investigate how a mitral cell in the olfactory bulb prunes all but one primary dendrite during the developmental remodeling process. We find that spontaneous activity generated within the olfactory bulb is essential. We show that strong glutamatergic inputs to one dendrite trigger branch-specific changes in RhoA activity to facilitate the pruning of the remaining dendrites: NMDAR-dependent local signals suppress RhoA to protect it from pruning; however, the subsequent neuronal depolarization induces neuron-wide activation of RhoA to prune non-protected dendrites. NMDAR-RhoA signals are also essential for the synaptic competition in the barrel cortex. Our results demonstrate a general principle whereby activity-dependent lateral inhibition across synapses establishes a discrete receptive field of a neuron.

neuroscience↗