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Ohkawa, N.

Publications and source records attributed to Ohkawa, N..

2 recordsLinked to original sources

Automatic sorting system for large calcium imaging data

It has become possible to observe neural activity in freely moving animals via calcium imaging using a microscope, which could not be observed previously. However, it remains difficult to extract the dynamics of nerve cells from the recorded imaging data. In this study, we greatly improved the stability, and robustness of the cell activity estimation method via non-negative matrix decomposition with shrinkage estimation of the baseline. In addition, by improving the initial state of the iterative algorithm using a newly proposed method to extract the shape of the cell via image processing, a solution could be obtained with a small number of iterations. These methods were applied to artificial and real data, and their effectiveness was confirmed.

neuroscience

Adult Neurogenesis Conserves Hippocampal Learning Capacity

Memory coding strengthens synaptic efficacy in the hippocampus via a long-term potentiation (LTP)-like mechanism. Given that animals are able to store memories of everyday experiences, hippocampal circuits should be able to avoid saturation of overall synaptic weight to preserve learning capacity. However, the underlying mechanism for this is still poorly understood. Here, we show that adult neurogenesis in rats plays a crucial role in the maintenance of the hippocampal learning capacity for learning. Artificial saturation with hippocampal LTP impaired learning capacity in contextual fear conditioning, which then completely recovered after 14 days, when LTP had decayed to the basal level. Ablation of neurogenesis by X-ray irradiation delayed the recovery of learning capacity, while enhancement of neurogenesis using running wheel sped up the recovery. Thus, one benefit of ongoing adult neurogenesis is the maintenance of hippocampal learning capacity through homeostatic renewing of hippocampal memory circuits. Decreased neurogenesis in aged animals may underlie declines in cognitive function with aging.

neuroscience