Drifting Assemblies for Persistent Memory

Change is ubiquitous in living beings. In particular, the connectome and neural representations can change. Nevertheless behaviors and memories often persist over long times. In a standard model, memories are represented by assemblies of strongly interconnected neurons. For faithful storage these assemblies are assumed to consist of the same neurons over time. Here we propose a contrasting memory model with complete temporal remodeling of assemblies, based on experimentally observed changes of connections and neural representations. The assemblies drift freely as spontaneous synaptic turnover or random activity induce neuron exchange. The gradual exchange allows activity dependent and homeostatic plasticity to conserve the representational structure and keep inputs, outputs and assemblies consistent. This leads to persistent memory. Our findings explain recent experimental results on the temporal evolution of fear memory representations and suggest that memory systems need to be understood in their completeness as individual parts may constantly change.

Induction of Activity Synchronization among Primed Hippocampal Neurons out of Random Dynamics is Key for Trace Memory Formation and Retrieval

Memory is thought to be encoded by sparsely distributed neuronal ensembles in memory-related regions. However, it is unclear how memory-eligible neurons react incrementally during learning to encode trace fear memory, and how they respond to cues to retrieve the memory. We implemented fiber-optic confocal fluorescence endoscopy to directly visualize calcium dynamics of hippocampal CA1 neurons in freely behaving mice, which were subjected to trace fear conditioning. Here we report that the overall activity levels of CA1 principal neurons showed a right-skewed lognormal-like distribution. A small portion of highly active neurons (termed Primed Neurons) exhibited high sensitivity to sensory stimuli and marked activity plasticity. The Primed Neurons maintained random activity status for at least 5 hours in multiple contexts, including those prior to training and prior to recall. Repetitive training induced Primed Neurons to shift from random activity to a well-tuned synchronization. Importantly, the emergence of activity synchronization coincided with the appearance of mouse freezing behaviors. In recall, a partial synchronization among the same population of Primed Neurons was induced from originally random activity, which also coincided with mouse freezing behaviors. Additionally, training-induced synchronization facilitated robust calcium entry into individual Primed Neurons. In contrast, most CA1 neurons stayed silent and did not respond significantly to tone and foot-shock throughout the training and recall testing cycles. In conclusion, highly active Primed Neurons are preferably recruited to encode trace fear memory, and induction of activity synchronization among Primed Neurons out of random dynamics is critical for trace memory formation and memory retrieval.Significance StatementThe overall activity levels of hippocampal principal CA1 neurons show a right-skewed lognormal-like distribution.A small portion of CA1 neurons (termed Primed Neurons) exhibit high activity and marked activity plasticity during learning and recall.Primed Neurons in the hippocampus are preferably recruited to encode trace fear memory, whereas the majority of CA1 neurons show little activity and little activity change during fear conditioning and recall testing.Induction of activity synchronization among Primed Neurons out of random dynamics is critical for trace memory formation and memory retrieval.Training-induced synchronization drastically increases calcium entry into Primed Neurons, which may promote memory consolidation.

STUDI PERBANDINGAN PEMASANGAN MATERIAL WATERPROOFING JENIS SELF ADHESIVE MEMBRANE DENGAN CRYSTALLINE

Pekerjaan waterproofing pada suatu bangunan sangat penting terutama pada lantai basement. Dalam pekerjaan pemasangan waterproofing terdapat banyak jenis material waterproofing yang ditawarkan dengan harga dan durasi pekerjaan yang beragam. Dalam studi ini dibandingkan material dari segi harga dan durasi pekerjaan. Untuk perhitungan harga dihitung jumlah harga material terpasang. Untuk durasi pekerjaan dibandingkan luas daerah yang telah tertutupi waterproofing selama waktu pengamatan. Dua jenis waterproofing yang dibandingkan adalah jenis self adhesive membrane dan crystalline. Setelah ditentukan jenis waterproofing yang digunakan, agar suatu proyek berjalan tepat waktu maka perlu diperhitungkan tingkat produktivitas pekerjaannya. Pada analisis ini juga dibandingkan tingkat produktivitas pekerjaan pemasangan waterproofing pada kedua proyek dimana tiap waterproofing tersebut dipasang. Pengambilan sampel dilakukan dengan cara random activity sampel dan perhitungan produktivitas menggunakan metode work sampling dan metode labor utilization rate (LUR). Dari hasil perhitungan, untuk produktivitas dan efektivitas didapat nilai produktivitas proyek A tempat terpasangnya self adhesive membrane waterproofing sebesar 30,07 m2/orang-hari dengan nilai LUR sebesar 88,18 % dan total harga adalah sebesar Rp 550.000,00 per m2-hari. Sementara untuk crystalline waterproofing pada proyek B didapat hasil perhitungan produktivitas sebesar 40,39 m2/orang-hari dengan nilai LUR sebesar 80,23 % dan total harga sebesar Rp 150.000,00. Luas daerah yang telah tertutupi waterproofing untuk proyek A dan B masing-masing seluas 7981,55 m2 dan 8707,5 m2.

Development of a Decision-Making Algorithm for Determination of the Optimal Land Use Function

Although the arrangement of urban space use functions is the outcome of the activity of many different entities, it is not a random activity, as there are general principles guiding the creation process of such a structure. The correct selection and arrangement of areas in a city for different types of use is of significant importance for the fulfillment of economic, functional and planning needs of the city. The concept of land division therefore has a decisive effect on the spatial structure of every city. The growing shortage of free urban space causes, or even forces, its optimal use. The optimization of land use functions in a city aims to verify mismatched land functions and replace them with functions best matched to the present natural and anthropogenic features. Adaptation of problem areas generating “spatial conflicts” should be based on the opinion of the city’s residents to reflect their current needs as well as on economic calculations. This paper presents a procedure for determining optimal states of land use as a tool in the urban space management process. The developed algorithm is designed to form the basis for conducting spatial monitoring, serving to analyze and verify individual land management forms in order to minimize the costs of transformation and maximize income.