Update: A new way to improve AD memory disorder? Scientists have discovered a new type of memory imprinted cell.

Learn about the latest progress in neuroscience ● click on the blue word to focus on us ● picture quoted in: memory is the recollection or reproduction of things experienced, and scientists have been deciphering how memory is formed.current studies have shown that memory is formed through synaptic plasticity, and specific memories are stored in memory trace cells. Different memories have different imprinted cell groups, but may overlap.in recent years, there are more and more researches on memory trace cells. At present, we mainly use the gene encoding activity report genes Fos and arc to label the neurons of imprinted cells.in patients with Alzheimer's disease (AD), declarative memory decreased.this symptom is related to the pathophysiological changes of hippocampal CA1 region in AD patients (1).inhibition of memory imprinting cells in CA1 region impairs memory retrieval, and activation of these imprinted cells can perform memory retrieval even under amnesia or ad like symptoms (2).however, the specific mechanism of imprinted cells in hippocampal CA1 region involved in AD related memory impairment is still unknown.June 9, 2020, Martin Fuhrmann research team of German neurodegenerative disease center published an article in the journal Nature Neuroscience, and found a new type of memory imprinted cells. Under normal conditions, the memory impairment occurs after activating this type of cells, and inhibits this type of cells in ad to improve memory impairment.How can we dynamically observe the dynamic changes of imprinted cells in hippocampus under the pathological state of ad? The researchers hybridized the early gene FOS tool mice carrying green fluorescence with AD transgenic mice (called fosgfp – AD mice), so that we can observe the imprinted cell population in the brain region of Hippo under pathological conditions, and continuously observe the dynamic changes of imprinted cells by embedding GRIN lens in this brain area.the researchers skillfully use the fluorescence expression of Fos to divide the neurons into three types in the dynamic observation time window: the neurons with FOS fluorescence expression are called on neurons, the neurons without FOS fluorescence expression are called off neurons, and the neurons maintaining FOS fluorescence expression are called con neurons (this wave operation is really high, playing a wave of Fos fluorescence) In fact, it corresponds to the newly formed imprinted cells, the disappeared imprinted cells and the remaining imprinted cells.the mice were trained in two different groups. After 2 days of electric stimulation in environment a, the memory retrieval experiment was carried out in environment a; after 2 days of electric stimulation in environment a, memory retrieval was performed in environment B. they found that less than 1% of imprinted cells were inhibitory neurons, indicating that almost all imprinted cells in CA1 area were excitatory neurons.in normal mice, the rate of stiffness increased when they were directly used in memory retrieval without fear dissipation training.however, it was found that the stiffness rate of fosgfp – AD mice was significantly reduced after memory retrieval in environment a, but no change was found in the stiffness rate of mice in environment B, indicating the presence of memory impairment.although fosgfp – AD mice had memory impairment, the number of on neurons increased significantly during the memory consolidation period, indicating that the function of newly formed imprinted cells in AD mice was normal and there was no impairment.What's more surprising is that the researchers listed 15 expression patterns of fosgfp through mathematical permutation and combination, and calculated the relative frequency of these fosgfp expression patterns. Overall, about 20% of on neurons were reactivated in the memory retrieval stage, and less than 10% of con neurons were activated in the memory retrieval stage 。from the local point of view, the proportion of AD mice reactivated in the memory retrieval stage was similar to that of the normal control group, which was 15%.in addition, the researchers also found a kind of "novelty like" imprinted cells, which are imprinted cells formed by memory retrieval in environment B.quoted from 3, the role of "novelty like" imprinted cells in normal and pathological conditions. In general, this paper revealed that the ability of AD mice to form imprinted cells was not impaired from the perspective of development and change, and further found that a new type of imprinted cells can improve learning and memory.References: 1. Kerchner, G. A. et al. Hippocampal CA1 apical neuropil atrophy in cold Alzheimer disease visualized with 7-T MRI. Neurology 75, 1381 – 1387 (2010) 2. Roy, D. S. et al. Memory retrieval by activating engram cells in mouse models of early Alzheimer's disease. Nature 531, 508–512 (2016)3. Memory trace interference impairs recall in a mouse model of Alzheimer’s disease，