Information theoretic interpretation of frequency domain connectivity measures

To provide adequate multivariate measures of information flow between neural structures, modified expressions of Partial Directed Coherence (PDC) and Directed Transfer Function (DTF), two popular multivariate connectivity measures employed in neuroscience, are introduced and their formal relationship to mutual information rates are proved.Comment: 17 pages, 1 figur

Canonical information flow decomposition among neural structure subsets

Partial directed coherence (PDC) and directed coherence (DC) which describe complementary aspects of the directed information flow between pairs of univariate components that belong to a vector of simultaneously observed time series have recently been generalized as bPDC/bDC respectively to portray the relationship between subsets of component vectors (Takahashi, 2009; Faes and Nollo, 2013). This generalization is specially important for neuroscience applications as one often wishes to address the link between the set of time series from an observed ROI (region of interest) with respect to series from some other physiologically relevant ROI. bPDC/bDC are limited, however, in that several time series within a given subset may be irrelevant or may even interact opposingly with respect to one another leading to interpretation difficulties. To address this, we propose an alternative measure, termed cPDC/cDC, employing canonical decomposition to reveal the main frequency domain modes of interaction between the vector subsets. We also show bPDC/bDC and cPDC/cDC are related and possess mutual information rate interpretations. Numerical examples and a real data set illustrate the concepts. The present contribution provides what is seemingly the first canonical decomposition of information flow in the frequency domain

Auditory processing screening test (SCAN) performance profile in seven and eight year-old children living in Cuiabá

OBJETIVO: Caracterizar o perfil de desempenho de crianças normo-ouvintes de sete e oito anos no teste de triagem de processamento auditivo SCAN. MÉTODOS: O trabalho é um estudo observacional descritivo. Foram selecionadas 109 crianças de sete anos e 106 crianças de oito anos da rede regular de ensino na cidade de Cuiabá (MT), utilizando os seguintes critérios de inclusão: portadoras de limiares de audibilidade de até 15 dB NA; ausência de indicativos de distúrbio de processamento auditivo; e ausência de alterações fonológicas. As crianças selecionadas foram avaliadas por meio de um teste de triagem de processamento auditivo SCAN. As pontuações obtidas por essas crianças foram comparadas com a literatura nacional. RESULTADOS: As médias e os desvios-padrões encontrados nos sub-testes fala filtrada, fala no ruído e palavras competitivas na idade de sete anos foram, respectivamente, 24,4±5,1, 33,4±3,4 e 76,5±9,7 pontos, e na idade de oito anos, respectivamente, 24,0±4,8; 34,0±3,0 e 77,5±10,8 pontos. CONCLUSÃO: As pontuações deste estudo no teste de triagem SCAN não podem ser generalizadas como valores de normalidade para todas as crianças brasileiras devido à variabilidade regional. Sendo assim, reforça-se a necessidade de estudos com casuísticas maiores que descrevam o desempenho de crianças de várias faixas etárias e pertencentes a diversas regiões geográficas e condições sociais.PURPOSE: To characterize the performance profile of seven- and eight-year-old children with normal hearing on the SCAN auditory processing screening test. METHODS: This research is a descriptive observational study. One hundred and nine seven-year-old children and 106 eight-year-old children were recruited from the regular school system of Cuiabá (MT, Brazil) through the following criteria: auditory thresholds up to 15 dB NA; absence of auditory processing deficits; and absence of phonological disorders. Selected children were evaluated through SCAN auditory processing screening test. These children's scores were compared to two previous Brazilian studies. RESULTS: Performance averages and standard-deviations for the sub-tests Filtered Words, Auditory Figure Ground and Competitive Words for seven-year-old children were, respectively, 24.4±5.1, 33.4±3.4, and 76.5±9.7 points, and for eight-year-old children were, respectively, 24.0±4.8, 34.0±3.0, and 77.5±10.8 points. CONCLUSION: SCAN test scores obtained for children in the present study cannot be generalized as normality values for Brazilian children, due to regional variability of children's performance in the test. It is emphasized the need for larger multi-centric studies, with greater number os subjects and encompassing children from many geographic regions and social conditions, as well as age ranges

Características espectrais da atividade elétrica hipocampal durante o medo condicionado ao contexto

OBJECTIVE: The hippocampus has an important role in the acquisition and recall of aversive memories. The objective of this study was to investigate the relationship among hippocampal rhythms. METHODS: Microeletrodes arrays were implanted in the hippocampus of Wistar rats. The animals were trained and tested in a contextual fear conditioning task. The training consisted in applying shocks in the legs. The memory test was performed 1 day (recent memory) or 18 days (remote memory) after training. We proposed a measure based on the FFT power spectrum, denominated "delta-theta ratio", to characterize the different behaviors (active exploration and freezing) and the memories types. RESULTS: The delta-theta ratio was able to distinguish recent and remote memories. In this study, the ratio for the 18-day group was smaller than for the 1-day group. Moreover, this measure was useful to distinguish the different behavior states active exploration and freezing. CONCLUSIONS: The results suggest delta-theta oscillations could reflect the demands on information processing during recent and remote memory recalls

GWAS of human bitter taste perception identifies new loci and reveals additional complexity of bitter taste genetics

Human perception of bitterness displays pronounced interindividual variation. This phenotypic variation is mirrored by equally pronounced genetic variation in the family of bitter taste receptor genes. To better understand the effects of common genetic variations on human bitter taste perception, we conducted a genome-wide association study on a discovery panel of 504 subjects and a validation panel of 104 subjects from the general population of São Paulo in Brazil. Correction for general taste-sensitivity allowed us to identify a SNP in the cluster of bitter taste receptors on chr12 (10.88- 11.24 Mb, build 36.1) significantly associated (best SNP: rs2708377, P = 5.31 × 10−13, r2 = 8.9%, β = −0.12, s.e. = 0.016) with the perceived bitterness of caffeine. This association overlaps with—but is statistically distinct from—the previously identified SNP rs10772420 influencing the perception of quinine bitterness that falls in the same bitter taste cluster. We replicated this association to quinine perception (P = 4.97 × 10−37, r2 = 23.2%, β = 0.25, s.e. = 0.020) and additionally found the effect of this genetic locus to be concentration specific with a strong impact on the perception of low, but no impact on the perception of high concentrations of quinine. Our study, thus, furthers our understanding of the complex genetic architecture of bitter taste perceptio

Comprehensive Analysis of Tissue Preservation and Recording Quality from Chronic Multielectrode Implants

Multielectrodes have been used with great success to simultaneously record the activity of neuronal populations in awake, behaving animals. In particular, there is great promise in the use of this technique to allow the control of neuroprosthetic devices by human patients. However, it is crucial to fully characterize the tissue response to the chronic implants in animal models ahead of the initiation of human clinical trials. Here we evaluated the effects of unilateral multielectrode implants on the motor cortex of rats weekly recorded for 1–6 months using several histological methods to assess metabolic markers, inflammatory response, immediate-early gene (IEG) expression, cytoskeletal integrity and apoptotic profiles. We also investigated the correlations between each of these features and firing rates, to estimate the impact of post-implant time on neuronal recordings. Overall, limited neuronal loss and glial activation were observed on the implanted sites. Reactivity to enzymatic metabolic markers and IEG expression were not significantly different between implanted and non-implanted hemispheres. Multielectrode recordings remained viable for up to 6 months after implantation, and firing rates correlated well to the histochemical and immunohistochemical markers. Altogether, our results indicate that chronic tungsten multielectrode implants do not substantially alter the histological and functional integrity of target sites in the cerebral cortex

Sensitivity of Genome-Wide-Association Signals to Phenotyping Strategy: The PROP-TAS2R38 Taste Association as a Benchmark

Natural genetic variation can have a pronounced influence on human taste perception, which in turn may influence food preference and dietary choice. Genome-wide association studies represent a powerful tool to understand this influence. To help optimize the design of future genome-wide-association studies on human taste perception we have used the well-known TAS2R38-PROP association as a tool to determine the relative power and efficiency of different phenotyping and data-analysis strategies. The results show that the choice of both data collection and data processing schemes can have a very substantial impact on the power to detect genotypic variation that affects chemosensory perception. Based on these results we provide practical guidelines for the design of future GWAS studies on chemosensory phenotypes. Moreover, in addition to the TAS2R38 gene past studies have implicated a number of other genetic loci to affect taste sensitivity to PROP and the related bitter compound PTC. None of these other locations showed genome-wide significant associations in our study. To facilitate further, target-gene driven, studies on PROP taste perception we provide the genome-wide list of p-values for all SNPs genotyped in the current study