1,322 research outputs found
Olfactory Sensor Processing in Neural Networks: Lessons from Modeling the Fruit Fly Antennal Lobe
The insect olfactory system can be a model for artificial olfactory devices. In particular, Drosophila melanogaster due to its genetic tractability has yielded much information about the design and function of such systems in biology. In this study we investigate possible network topologies to separate representations of odors in the primary olfactory neuropil, the antennal lobe. In particular we compare networks based on stochastic and homogeneous connection weight distributions to connectivities that are based on the input correlations between the glomeruli in the antennal lobe. We show that moderate homogeneous inhibition implements a soft winner-take-all mechanism when paired with realistic input from a large meta-database of odor responses in receptor cells (DoOR database). The sparseness of representations increases with stronger inhibition. Excitation, on the other hand, pushes the representation of odors closer together thus making them harder to distinguish. We further analyze the relationship between different inhibitory network topologies and the properties of the receptor responses to different odors. We show that realistic input from the DoOR database has a relatively high entropy of activation values over all odors and receptors compared to the theoretical maximum. Furthermore, under conditions in which the information in the input is artificially decreased, networks with heterogeneous topologies based on the similarity of glomerular response profiles perform best. These results indicate that in order to arrive at the most beneficial representation for odor discrimination it is important to finely tune the strength of inhibition in combination with taking into account the properties of the available sensors
Sobre um bom texto : algumas liçÔes de Steven Pinker
Trabalho de ConclusĂŁo de Curso (graduação)âUniversidade de BrasĂlia, Instituto de Letras, Departamento de LinguĂstica, LĂnguas ClĂĄssicas e PortuguĂȘs, 2019.Este trabalho aborda algumas liçÔes de Steven Pinker publicadas em seu livro âGuia de Escrita â Como escrever um texto com clareza, precisĂŁo e elegĂąnciaâ. A edição tomada como base, de 2016, traduzida por Rodolfo Ilari, compreende cinco capĂtulos, os quais somente dois foram aqui comentados com detalhes: o capĂtulo âEscrever bemâ, - que elenca algumas qualidades que o autor vĂȘ nos bons textos e as prĂĄticas e truques dos bons escritores -, e o capĂtulo âA rede, a ĂĄrvore e a sequĂȘnciaâ, - que aborda a boa escrita Ă luz da ciĂȘncia da linguĂstica. Os demais capĂtulos mereceram aqui resumos ligeiros, face Ă exiguidade do tempo disponĂvel para feitura deste trabalho acadĂȘmico. O prĂłlogo de Pinker foi examinado com vagar, nĂŁo sĂł por abrir o livro-base, como em razĂŁo de sua densidade enquanto tema para reflexĂŁo do estudante
Neural activity tracking identity and confidence in social information
Humans learn about the environment either directly by interacting with it or indirectly by seeking information about it from social sources such as conspecifics. The degree of confidence in the information obtained through either route should determine the impact that it has on adapting and changing behaviour. We examined whether and how behavioural and neural computations differ during non-social learning as opposed to learning from social sources. Trial-wise confidence judgements about non-social and social information sources offered a window into this learning process. Despite matching exactly the statistical features of social and non-social conditions, confidence judgements were more accurate and less changeable when they were made about social as opposed to non-social information sources. In addition to subjective reports of confidence, differences were also apparent in the Bayesian estimates of participants' subjective beliefs. Univariate activity in dorsomedial prefrontal cortex and posterior temporoparietal junction more closely tracked confidence about social as opposed to non-social information sources. In addition, the multivariate patterns of activity in the same areas encoded identities of social information sources compared to non-social information sources
Identification and disruption of a neural mechanism for accumulating prospective metacognitive information prior to decision-making
More than one type of probability must be considered when making decisions. It is as necessary to know one's chance of performing choices correctly as it is to know the chances that desired outcomes will follow choices. We refer to these two choice contingencies as internal and external probability. Neural activity across many frontal and parietal areas reflected internal and external probabilities in a similar manner during decision-making. However, neural recording and manipulation approaches suggest that one area, the anterior lateral prefrontal cortex (alPFC), is highly specialized for making prospective, metacognitive judgments on the basis of internal probability; it is essential for knowing which decisions to tackle, given its assessment of how well they will be performed. Its activity predicted prospective metacognitive judgments, and individual variation in activity predicted individual variation in metacognitive judgments. Its disruption altered metacognitive judgments, leading participants to tackle perceptual decisions they were likely to fail
Neural mechanisms for learning self and other ownership
The sense of ownership â of which objects belong to us and which to others - is an important part of our lives, but how the brain keeps track of ownership is poorly understood. Here, the authors show that specific brain areas are involved in ownership acquisition for the self, friends, and strangers
Ageing is associated with disrupted reinforcement learning whilst learning to help others is preserved.
Funder: Wellcome Trust (Wellcome); doi: https://doi.org/10.13039/100004440Funder: DH | National Institute for Health Research (NIHR); doi: https://doi.org/10.13039/501100000272Funder: Christ Church Junior Research Fellowship Christ Church Research Centre GrantReinforcement learning is a fundamental mechanism displayed by many species. However, adaptive behaviour depends not only on learning about actions and outcomes that affect ourselves, but also those that affect others. Using computational reinforcement learning models, we tested whether young (age 18-36) and older (age 60-80, total nâ=â152) adults learn to gain rewards for themselves, another person (prosocial), or neither individual (control). Detailed model comparison showed that a model with separate learning rates for each recipient best explained behaviour. Young adults learned faster when their actions benefitted themselves, compared to others. Compared to young adults, older adults showed reduced self-relevant learning rates but preserved prosocial learning. Moreover, levels of subclinical self-reported psychopathic traits (including lack of concern for others) were lower in older adults and the core affective-interpersonal component of this measure negatively correlated with prosocial learning. These findings suggest learning to benefit others is preserved across the lifespan with implications for reinforcement learning and theories of healthy ageing
Causal manipulation of self-other-mergence in dorsomedial prefrontal cortex
To navigate social environments, people must simultaneously hold representations about their own and othersâ abilities. During self-other-mergence, people estimate othersâ abilities not only on the basis of the othersâ past performances, but in addition the estimates are also influenced by their own performances. For example, if we ourselves perform well, we overestimate the abilities of those we are co-operating with and underestimate competitors. Self-other mergence is associated with specific activity patterns in dorsomedial prefrontal cortex (dmPFC). Using a combination of non-invasive brain stimulation, functional magnetic resonance imaging and computational modelling, we show that dmPFC neurostimulation silences these neural signatures of self-other-mergence in relation to the estimation of othersâ abilities. In consequence, self-other-mergence behavior increases and our assessments of our own performance are increasingly projected onto other people. This suggests an inherent tendency to form interdependent social representations and a causal role for dmPFC in separating self and other representations
Extraordinary rocks from the peak ring of the Chicxulub impact crater: P-wave velocity, density, and porosity measurements from IODP/ICDP Expedition 364
Joint International Ocean Discovery Program and International Continental Scientific Drilling Program Expedition 364 drilled into the peak ring of the Chicxulub impact crater. We present P-wave velocity, density, and porosity measurements from Hole M0077A that reveal unusual physical properties of the peak-ring rocks. Across the boundary between post-impact sedimentary rock and suevite (impact melt-bearing breccia) we measure a sharp decrease in velocity and density, and an increase in porosity. Velocity, density, and porosity values for the suevite are 2900â3700 m/s, 2.06â2.37 g/cm3, and 20â35%, respectively. The thin (25 m) impact melt rock unit below the suevite has velocity measurements of 3650â4350 m/s, density measurements of 2.26â2.37 g/cm3, and porosity measurements of 19â22%. We associate the low velocity, low density, and high porosity of suevite and impact melt rock with rapid emplacement, hydrothermal alteration products, and observations of pore space, vugs, and vesicles. The uplifted granitic peak ring materials have values of 4000â4200 m/s, 2.39â2.44 g/cm3, and 8â13% for velocity, density, and porosity, respectively; these values differ significantly from typical unaltered granite which has higher velocity and density, and lower porosity. The majority of Hole M0077A peak-ring velocity, density, and porosity measurements indicate considerable rock damage, and are consistent with numerical model predictions for peak-ring formation where the lithologies present within the peak ring represent some of the most shocked and damaged rocks in an impact basin. We integrate our results with previous seismic datasets to map the suevite near the borehole. We map suevite below the Paleogene sedimentary rock in the annular trough, on the peak ring, and in the central basin, implying that, post impact, suevite covered the entire floor of the impact basin. Suevite thickness is 100â165 m on the top of the peak ring but 200 m in the central basin, suggesting that suevite flowed downslope from the collapsing central uplift during and after peak-ring formation, accumulating preferentially within the central basin
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