Generalization from correlated sets of patterns in the perceptron

Generalization is a central aspect of learning theory. Here, we propose a framework that explores an auxiliary task-dependent notion of generalization, and attempts to quantitatively answer the following question: given two sets of patterns with a given degree of dissimilarity, how easily will a network be able to "unify" their interpretation? This is quantified by the volume of the configurations of synaptic weights that classify the two sets in a similar manner. To show the applicability of our idea in a concrete setting, we compute this quantity for the perceptron, a simple binary classifier, using the classical statistical physics approach in the replica-symmetric ansatz. In this case, we show how an analytical expression measures the "distance-based capacity", the maximum load of patterns sustainable by the network, at fixed dissimilarity between patterns and fixed allowed number of errors. This curve indicates that generalization is possible at any distance, but with decreasing capacity. We propose that a distance-based definition of generalization may be useful in numerical experiments with real-world neural networks, and to explore computationally sub-dominant sets of synaptic solutions

Using machine-learning modelling to understand macroscopic dynamics in a system of coupled maps

Machine learning techniques not only offer efficient tools for modelling dynamical systems from data, but can also be employed as frontline investigative instruments for the underlying physics. Nontrivial information about the original dynamics, which would otherwise require sophisticated ad-hoc techniques, can be obtained by a careful usage of such methods. To illustrate this point, we consider as a case study the macroscopic motion emerging from a system of globally coupled maps. We build a coarse-grained Markov process for the macroscopic dynamics both with a machine learning approach and with a direct numerical computation of the transition probability of the coarse-grained process, and we compare the outcomes of the two analyses. Our purpose is twofold: on the one hand, we want to test the ability of the stochastic machine learning approach to describe nontrivial evolution laws, as the one considered in our study; on the other hand, we aim at gaining some insight into the physics of the macroscopic dynamics by modulating the information available to the network, we are able to infer important information about the effective dimension of the attractor, the persistence of memory effects and the multi-scale structure of the dynamics.Comment: 17 pages, 13 figure

Selection and validation of a set of reliable reference genes for quantitative RT-PCR studies in the brain of the Cephalopod Mollusc Octopus vulgaris

<p>Abstract</p> <p>Background</p> <p>Quantitative real-time polymerase chain reaction (RT-qPCR) is valuable for studying the molecular events underlying physiological and behavioral phenomena. Normalization of real-time PCR data is critical for a reliable mRNA quantification. Here we identify reference genes to be utilized in RT-qPCR experiments to normalize and monitor the expression of target genes in the brain of the cephalopod mollusc <it>Octopus vulgaris</it>, an invertebrate. Such an approach is novel for this taxon and of advantage in future experiments given the complexity of the behavioral repertoire of this species when compared with its relatively simple neural organization.</p> <p>Results</p> <p>We chose <it>16S</it>, and <it>18S </it>rRNA, <it>actB</it>, <it>EEF1A</it>, <it>tubA </it>and <it>ubi </it>as candidate reference genes (housekeeping genes, HKG). The expression of <it>16S </it>and <it>18S </it>was highly variable and did not meet the requirements of candidate HKG. The expression of the other genes was almost stable and uniform among samples. We analyzed the expression of HKG into two different set of animals using tissues taken from the central nervous system (brain parts) and mantle (here considered as control tissue) by BestKeeper, geNorm and NormFinder. We found that HKG expressions differed considerably with respect to brain area and octopus samples in an HKG-specific manner. However, when the mantle is treated as control tissue and the entire central nervous system is considered, NormFinder revealed <it>tubA </it>and <it>ubi </it>as the most suitable HKG pair. These two genes were utilized to evaluate the relative expression of the genes <it>FoxP</it>, <it>creb, dat </it>and <it>TH </it>in <it>O. vulgaris</it>.</p> <p>Conclusion</p> <p>We analyzed the expression profiles of some genes here identified for <it>O. vulgaris </it>by applying RT-qPCR analysis for the first time in cephalopods. We validated candidate reference genes and found the expression of <it>ubi </it>and <it>tubA </it>to be the most appropriate to evaluate the expression of target genes in the brain of different octopuses. Our results also underline the importance of choosing a proper normalization strategy when analyzing gene expression by qPCR taking into appropriate account the experimental setting and variability of the sample of animals (and tissues), thus providing a set of HGK which expression appears to be unaffected by the experimental factor(s).</p

Trimetazidine Reduces Endogenous Free Fatty Acid Oxidation

INTRODUCTION: The metabolic modulator trimetazidine (TMZ) has been suggested to induce a metabolic shift from myocardial fatty acid oxidation (FAO) to glucose utilization, but this mechanism remains unproven in humans. The oxidation of plasma derived FA is commonly measured in humans, whereas the contribution of FA from triglycerides stored in the myocardium has been poorly characterized. AIMS: To verify the hypothesis that TMZ induces a metabolic shift, we combined positron emission tomography (PET) and magnetic resonance spectroscopy ((1)H-MRS) to measure myocardial FAO from plasma and intracellular lipids, and myocardial glucose metabolism. Nine obese subjects were studied before and after 1 month of TMZ treatment. Myocardial glucose and FA metabolism were assessed by PET with (18)F-fluorodeoxyglucose and (11)C-palmitate. (1)H-MRS was used to measure myocardial lipids, the latter being integrated into the PET data analysis to quantify myocardial triglyceride turnover. RESULTS: Myocardial FAO derived from intracellular lipids was at least equal to that of plasma FAs (P = NS). BMI and cardiac work were positively associated with the oxidation of plasma derived FA (P ≤ 0.01). TMZ halved total and triglyceride-derived myocardial FAO (32.7 ± 8.0 to 19.6 ± 4.0 μmol/min and 23.7 ± 7.5 to 10.3 ± 2.7 μmol/min, respectively; P ≤ 0.05). These changes were accompanied by increased cardiac efficiency since unchanged LV work (1.6 ± 0.2 to 1.6 ± 0.1 Watt/g × 10(2), NS) was associated with decreased work energy from the intramyocardial triglyceride oxidation (1.6 ± 0.5 to 0.4 ± 0.1 Watt/g × 10(2), P = 0.036). CONCLUSIONS: In obese subjects, we demonstrate that myocardial intracellular triglyceride oxidation significantly provides FA-derived energy for mechanical work. TMZ reduced the oxidation of triglyceride-derived myocardial FAs improving myocardial efficiency

Construction of an adult barnacle (Balanus amphitrite) cDNA library and selection of reference genes for quantitative RT-PCR studies

De Gregoris TB, Borra M, Biffali E, et al. Construction of an adult barnacle (Balanus amphitrite) cDNA library and selection of reference genes for quantitative RT-PCR studies. BMC Molecular Biology. 2009;10(1):62.BACKGROUND: Balanus amphitrite is a barnacle commonly used in biofouling research. Although many aspects of its biology have been elucidated, the lack of genetic information is impeding a molecular understanding of its life cycle. As part of a wider multidisciplinary approach to reveal the biogenic cues influencing barnacle settlement and metamorphosis, we have sequenced and annotated the first cDNA library for B. amphitrite. We also present a systematic validation of potential reference genes for normalization of quantitative real-time PCR (qRT-PCR) data obtained from different developmental stages of this animal. RESULTS: We generated a cDNA library containing expressed sequence tags (ESTs) from adult B. amphitrite. A total of 609 unique sequences (comprising 79 assembled clusters and 530 singlets) were derived from 905 reliable unidirectionally sequenced ESTs. Bioinformatics tools such as BLAST, HMMer and InterPro were employed to allow functional annotation of the ESTs. Based on these analyses, we selected 11 genes to study their ability to normalize qRT-PCR data. Total RNA extracted from 7 developmental stages was reverse transcribed and the expression stability of the selected genes was compared using geNorm, BestKeeper and NormFinder. These software programs produced highly comparable results, with the most stable gene being mt-cyb, while tuba, tubb and cp1 were clearly unsuitable for data normalization. CONCLUSION: The collection of B. amphitrite ESTs and their annotation has been made publically available representing an important resource for both basic and applied research on this species. We developed a qRT-PCR assay to determine the most reliable reference genes. Transcripts encoding cytochrome b and NADH dehydrogenase subunit 1 were expressed most stably, although other genes also performed well and could prove useful to normalize gene expression studies

Anterior Intraparietal Area: a Hub in the Observed Manipulative Action Network.

Current knowledge regarding the processing of observed manipulative actions (OMAs) (e.g., grasping, dragging, or dropping) is limited to grasping and underlying neural circuitry remains controversial. Here, we addressed these issues by combining chronic neuronal recordings along the anteroposterior extent of monkeys\u2019 anterior intraparietal (AIP) area with tracer injections into the recorded sites. We found robust neural selectivity for 7 distinct OMAs, particularly in the posterior part of AIP (pAIP), where it was associated with motor coding of grip type and own-hand visual feedback. This cluster of functional properties appears to be specifically grounded in stronger direct connections of pAIP with the temporal regions of the ventral visual stream and the prefrontal cortex, as connections with skeletomotor related areas and regions of the dorsal visual stream exhibited opposite or no rostrocaudal gradients. Temporal and prefrontal areas may provide visual and contextual information relevant for manipulative action processing. These results revise existing models of the action observation network, suggesting that pAIP constitutes a parietal hub for routing information about OMA identity to the other nodes of the network

InSEA Project: Initiatives in Supporting the consolidation and enhancement of the EMSO infrastructure and related Activities

The observation of the phenomena occurring on our planet was in the past based mainly on ground monitoring with both temporal and spatial approaches. On the other hand, in the part covered by the oceans until a few years ago the monitoring was carried out through discrete measurement campaigns in time and space with the disadvantage of not having information on the variability of oceanic processes. Only more recently, since the 90s of the last century, technology has allowed the installation of multidisciplinary systems on the seabed for long periods (years), even at great depths (thousands of meters). From the circumscribed campaigns in space and time, we have therefore moved on to the installation of observatories on the seabed, to record in a continuous way the physical and chemical parameters, in order to know the state of the oceans and of the whole planet. This produces two advantages: A spatial improvement of the observations, because they extend from land to the 1. previously less known and more extensive part of the planet, i.e. the oceans that cover seventenths of the Earth’s surface; A scientific improvement, because the oceans represent a fundamental element in the 2. processes at the base of the Earth’s climate, whose knowledge on large time scales makes it possible to understand the future evolution of these processes [e.g. Favali et al., 2015].PublishedRome6IT. Osservatori non satellitar

Occupational Exposure to Solar UV Radiation of a Group of Fishermen Working in the Italian North Adriatic Sea

Occupational solar radiation exposure is a relevant heath risk in the fishing sector. Our aim was to provide a detailed evaluation of individual UV exposure in three different fishing activities in Italy, with personal UV dosimeters and a simple formula to calculate the fraction of ambient erythemal UV dose received by the workers. The potential individual UV exposure of the fishermen was between 65 and 542 Joules/m2. The percentages of the ambient exposure were estimated between 2.5% and 65.3%. Workers\u2019 UV exposure was mainly influenced by the characteristics of the work activity, the postures adopted, and the type of boats. Overall, our data showed that 43% of the daily measurements could result largely above the occupational limits of 1\u20131.3 standard erythemal dose (i.e., 100 Joules/m2) per day, in case of exposure of uncovered skin areas. Measurements of individual UV exposure are important not only to assess the risk but also to increase workers\u2019 perception and stimulate the adoption of preventive measures to reduce solar UV risk. Furthermore, the simple method proposed, linking ambient erythemal UV dose to the workers\u2019 exposure, can be a promising tool for a reliable assessment of the UV risk, as time series of environmental UV dose are widely availabl

BCIAUT-P300: A Multi-Session and Multi-Subject Benchmark Dataset on Autism for P300-Based Brain-Computer-Interfaces

There is a lack of multi-session P300 datasets for Brain-Computer Interfaces (BCI). Publicly available datasets are usually limited by small number of participants with few BCI sessions. In this sense, the lack of large, comprehensive datasets with various individuals and multiple sessions has limited advances in the development of more effective data processing and analysis methods for BCI systems. This is particularly evident to explore the feasibility of deep learning methods that require large datasets. Here we present the BCIAUT-P300 dataset, containing 15 autism spectrum disorder individuals undergoing 7 sessions of P300-based BCI joint-attention training, for a total of 105 sessions. The dataset was used for the 2019 IFMBE Scientific Challenge organized during MEDICON 2019 where, in two phases, teams from all over the world tried to achieve the best possible object-detection accuracy based on the P300 signals. This paper presents the characteristics of the dataset and the approaches followed by the 9 finalist teams during the competition. The winner obtained an average accuracy of 92.3% with a convolutional neural network based on EEGNet. The dataset is now publicly released and stands as a benchmark for future P300-based BCI algorithms based on multiple session data

Consensus Paper: The Role of the Cerebellum in Perceptual Processes

Various lines of evidence accumulated over the past 30 years indicate that the cerebellum, long recognized as essential for motor control, also has considerable influence on perceptual processes. In this paper, we bring together experts from psychology and neuroscience, with the aim of providing a succinct but comprehensive overview of key findings related to the involvement of the cerebellum in sensory perception. The contributions cover such topics as anatomical and functional connectivity, evolutionary and comparative perspectives, visual and auditory processing, biological motion perception, nociception, self-motion, timing, predictive processing, and perceptual sequencing. While no single explanation has yet emerged concerning the role of the cerebellum in perceptual processes, this consensus paper summarizes the impressive empirical evidence on this problem and highlights diversities as well as commonalities between existing hypotheses. In addition to work with healthy individuals and patients with cerebellar disorders, it is also apparent that several neurological conditions in which perceptual disturbances occur, including autism and schizophrenia, are associated with cerebellar pathology. A better understanding of the involvement of the cerebellum in perceptual processes will thus likely be important for identifying and treating perceptual deficits that may at present go unnoticed and untreated. This paper provides a useful framework for further debate and empirical investigations into the influence of the cerebellum on sensory perception