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Cortical information processing is thought to be facilitated by the resonant properties of individual neurons and neuronal networks, which selectively amplify inputs at specific frequencies. We used optogenetics to test how different input frequencies are encoded by excitatory cells and parvalbumin-expressing (PV) interneurons in mouse V1. Spike phase-locking and power increased with frequency, reaching a broad peak around 80-100Hz. This effect was observed only for Chronos, a fast-kinetic opsin, but not for Channelrhodopsin-2. Surprisingly, neurons did not exhibit narrow-band resonance in specific frequency-ranges, and showed reliably phase-locking up to 140Hz. Strong phase-locking at high frequencies reflected non-linear input/output transformations, with neurons firing only in a narrow part of the cycle. By contrast, low-frequency inputs were encoded in a more continuous manner. Correspondingly, spectral coherence and firing rates showed little dependence on frequency and did not reflect transferred power. To investigate whether strong phase-locking facilitated the reliable encoding of inputs, we analyzed various spike-train distances and Fano factor. Interestingly, responses to lower rather than higher frequencies had more globally reliable spike-counts and timing structure. These findings have various practical implications for understanding the effects of optogenetic stimulation and choice of opsin. Furthermore, they show both PV and excitatory neurons respond with more local precision, i.e. phase-locking, to high-frequency inputs, but have more globally reliable responses to low-frequency inputs, suggesting differential coding regimes for these frequencies.

Who writes the news in the Chilean press according to gender? Who are the sources, male or female, in the Chilean press? Is there a relationship between the gender of journalists and the gender of the sources in the Chilean press? This article studies the gender of the Chilean newsroom and their sources in 12,113 news through a quantitative method with a computational social science approach. This method combines web scraping and natural language processing techniques to gather and preprocess data, facilitating the exploration of complex social phenomena. Results show important biases in journalists and source gender. From a sample of 158 journalists, 99 were men (63%) and 59 women (37%). Also, from 12,113 news, 7,565 (62%) were written by male and 4,548 (38%) by female journalists. Of the 12,334 sources mentioned in the news, 9,771 were men (79%) and 2,563 were women (21%). A significant finding is that equality in the newsroom is related to how female and male journalists choose their sources. In other words, when a media has a newsroom with gender equality, the sources of the journalists are more equitable too. These results have important insights to discuss within the journalism schools, to make students aware of the gender bias in the profession. Furthermore, if the presence of female – journalists or sources- increased in the media, it would allow them to grow their media power and status. ¿Quién escribe las noticias en la prensa chilena según el género? ¿Las fuentes son masculinas o femeninas en la prensa chilena? ¿Existe una relación entre el género de los y las periodistas y el género de las fuentes en la prensa chilena? Este artículo estudia el género de los y las periodistas y sus fuentes en 12.113 noticias, a través de un método cuantitativo con enfoque de ciencias sociales computacionales. Este método combina técnicas de procesamiento de lenguaje natural y web scraping para recopilar y pre-procesar datos. Los resultados muestran sesgos importantes en los y las periodistas y el género de la fuente. De una muestra de 158 periodistas, 99 eran hombres (63%) y 59 mujeres (37%). De 12.113 noticias, 7.565 (62%) fueron escritas por hombres y 4.548 (38%) por mujeres periodistas. De las 12.334 fuentes mencionadas en la noticias, 9.771 eran hombres (79%) y 2.563 eran mujeres (21%). Un hallazgo significativo es que la igualdad en la sala de redacción está relacionada con la forma en que los y las periodistas eligen sus fuentes. Es decir, parece ser que cuando un medio tiene una redacción con igualdad de género, las fuentes de los y las periodistas también son más equitativas. Estos resultados son importantes para ser discutidos dentro de las escuelas de periodismo, para concientizar a los y las estudiantes sobre el sesgo de género en la profesión. Si aumentara la presencia de mujeres – como periodistas y como fuentes de información- en los medios, les permitiría aumentar su poder y estatus mediático.

Neural coding and memory formation depend on temporal spiking sequences that span high-dimensional neural ensembles. The unsupervised discovery and characterization of these spiking sequences requires a suitable dissimilarity measure to spiking patterns, which can then be used for clustering and decoding. Here, we present a new dissimilarity measure based on optimal transport theory called SpikeShip, which compares multineuron spiking patterns based on all the relative spike-timing relationships among neurons. SpikeShip computes the optimal transport cost to make all the relative spike-timing relationships (across neurons) identical between two spiking patterns. We show that this transport cost can be decomposed into a temporal rigid translation term, which captures global latency shifts, and a vector of neuron-specific transport flows, which reflect inter-neuronal spike timing differences. SpikeShip can be effectively computed for high-dimensional neuronal ensembles, has a low (linear) computational cost that has the same order as the spike count, and is sensitive to higher-order correlations. Furthermore SpikeShip is binless, can handle any form of spike time distributions, is not affected by firing rate fluctuations, can detect patterns with a low signal-to-noise ratio, and can be effectively combined with a sliding window approach. We compare the advantages and differences between SpikeShip and other measures like SPIKE and Victor-Púrpura distance. We applied SpikeShip to large-scale Neuropixel recordings during spontaneous activity and visual encoding. We show that high-dimensional spiking sequences detected via SpikeShip reliably distinguish between different natural images and different behavioral states. These spiking sequences carried complementary information to conventional firing rate codes. SpikeShip opens new avenues for studying neural coding and memory consolidation by rapid and unsupervised detection of temporal spiking patterns in high-dimensional neural ensembles.

Cities have been compared to social reactors constrained by the communication and coordination possibilities offered by an urban environment that has only grown since the advent of the industrial age. We attempt to provide a first description of human interactions in the urban environment using Call Detailed Records (CDR) of the major mobile phone communication network operator in Chile. We build communication networks for 145 Chilean cities to describe and characterize the communication behavior of urban dwellers. We center our analysis in observed indicators of social activity, such as the number of contacts, number of calls and total communication time in each city and evaluate their scaling relationship with the number of mobile phones assigned to each city as an approximation of city size. Interestingly, the values of scaling exponents closely match recent explanations proposed in the literature. The topologies of voice-call networks among cities of increasing sizes are slightly assortative, albeit assortativeness decreases with size. Additionally, they show small average path length relative to their sizes, a typical feature of small-world networks. However, they decrease instead of growing when size is taken into account, unlike other complex networks. Different transitivity indices show mixed results. Average Watts-Strogatz clustering coefficient increases in larger cities much more than expected by pure chance as it has been shown in other social networks. On the other hand, the fact that classic transitivity index decreases seem to exhibit a regime change with a decreasing relation with size and an unexpected growth in larger cities. Both transitivity indices, as a whole, could describe among those who are making new interactions as the city grows. All these results indicate that while tightly knit human communities seem to lose cohesion as they grow, such community properties may progressively disappear among the three to four largest urban centers in Chile where the coordination of complex functions requires each city dweller to reach out to a larger network of people and speak for longer periods of time as compared to smaller cities. Finally, although these results are valid for all networks, there is a division into two regimes when networks reach a critical size of ~10,000 nodes, which raises the possibility of an empirical definition of city for Chile.