Altered cortical and subcortical connectivity due to infrasound administered near the hearing threshold – Evidence from fMRI

In the present study, the brain’s response towards near- and supra-threshold infrasound (IS) stimulation (sound frequency < 20 Hz) was investigated under resting-state fMRI conditions. The study involved two consecutive sessions. In the first session, 14 healthy participants underwent a hearing threshold—as well as a categorical loudness scaling measurement in which the individual loudness perception for IS was assessed across different sound pressure levels (SPL). In the second session, these participants underwent three resting-state acquisitions, one without auditory stimulation (no-tone), one with a monaurally presented 12-Hz IS tone (near-threshold) and one with a similar tone above the individual hearing threshold corresponding to a ‘medium loud’ hearing sensation (supra-threshold). Data analysis mainly focused on local connectivity measures by means of regional homogeneity (ReHo), but also involved independent component analysis (ICA) to investigate inter-regional connectivity. ReHo analysis revealed significantly higher local connectivity in right superior temporal gyrus (STG) adjacent to primary auditory cortex, in anterior cingulate cortex (ACC) and, when allowing smaller cluster sizes, also in the right amygdala (rAmyg) during the near-threshold, compared to both the supra-threshold and the no-tone condition. Additional independent component analysis (ICA) revealed large-scale changes of functional connectivity, reflected in a stronger activation of the right amygdala (rAmyg) in the opposite contrast (no-tone > near-threshold) as well as the right superior frontal gyrus (rSFG) during the near-threshold condition. In summary, this study is the first to demonstrate that infrasound near the hearing threshold may induce changes of neural activity across several brain regions, some of which are known to be involved in auditory processing, while others are regarded as keyplayers in emotional and autonomic control. These findings thus allow us to speculate on how continuous exposure to (sub-)liminal IS could exert a pathogenic influence on the organism, yet further (especially longitudinal) studies are required in order to substantialize these findings

Neural coding tools, based on Information Theory, applied to discrete time series: from electrophysiology to neuroethology

This work is supported by Brazilian agencies Fapesp, CAPES and CNP

26th Annual Computational Neuroscience Meeting (CNS*2017): Part 3 - Meeting Abstracts - Antwerp, Belgium. 15–20 July 2017

This work was produced as part of the activities of FAPESP Research,\ud Disseminations and Innovation Center for Neuromathematics (grant\ud 2013/07699-0, S. Paulo Research Foundation). NLK is supported by a\ud FAPESP postdoctoral fellowship (grant 2016/03855-5). ACR is partially\ud supported by a CNPq fellowship (grant 306251/2014-0)

Modelling human choices: MADeM and decision‑making

Research supported by FAPESP 2015/50122-0 and DFG-GRTK 1740/2. RP and AR are also part of the Research, Innovation and Dissemination Center for Neuromathematics FAPESP grant (2013/07699-0). RP is supported by a FAPESP scholarship (2013/25667-8). ACR is partially supported by a CNPq fellowship (grant 306251/2014-0)

Study of electrocomunication in gymnotus carapo and gnathonemus petersii for long time using realistic stimulation protocols

A bioeletrogenese tem atraído a atenção da ciência desde a antiguidade. Capazes de produzir campos elétricos e também de sentir estes campos, os peixes elétricos pulsadores de campo fraco são um modelo de estudo praticamente com características únicas em neuroetologia, ja que permitem ao experimentador medir de maneira não invasiva os sinais espaco-temporais envolvidos em pelo menos duas capacidades complexas do sistema nervoso do animal: a eletrolocalizacao (em que e produzida uma imagem elétrica das proximidades) e a eletrocomunicacao (em que os padrões de pulsos são usados para identificar conspecificos, seu sexo, tamanho, resolver disputas de território, etc). Entretanto, como os pulsos geralmente são idênticos em indivíduos de uma mesma espécie e a amplitude do sinal medido depende da distancia dos animais aos eletrodos usados, experimentos com animais livres para se movimentar são muito difíceis de realizar, mais ainda experimentos com mais de um animal interagindo. Por isso, na maioria dos trabalhos encontrados na literatura o comportamento elétrico dos animais e registrado durante curtos intervalos de tempo em que seus movimentos eram bastante restritos ou limitados a agua bem rasa. Além disso, os estímulos eram geralmente compostos por pulsos quadrados ou períodos senoidais apresentados a intervalos regulares. Os protocolos experimentais usados eram sempre unidirecionais, ou seja, não dependiam nem se adaptavam a atividade dos peixes. Para lidar com estas limitações, que acreditamos tornarem o comportamento dos animais muito diferente do que ocorre na natureza, desenvolvemos aparatos experimentais para registrar e estudar o comportamento elétrico e motor de peixes elétricos pulsadores nadando livremente por longos períodos de tempo e que podem ser facilmente adaptados para o estudo de diversas espécies. Utilizamos técnicas de interação em tempo real entre computadores e sistema nervoso vivo, adaptado de protocolos do tipo dynamic clamp, para produzir estímulos elétricos realistas e também estímulos luminosos. Mostramos protocolos de estimulação clássicos unidirecionais bem como bidirecionais, dependentes da atividade dos animais. Aplicamos técnicas de analise de dados baseadas na teoria da informação que permitiram associar a entropia da serie de pulsos do órgão elétrico a movimentação do animal. Aplicamos estes aparatos e técnicas para estudar peixes elétricos de campo fraco de espécies que pertencem a ordens diferentes e, portanto, são o resultado de historias evolutivas distintas: o peixe sul americano G. carapo, da ordem dos Gymnotiformes e o peixe africano G. petersii, da ordem dos Mormyriformes. Obtivemos evidencias de comunicação dos animais e estudamos quais os padrões mais prováveis de disparo em diferentes condições. Uma das espécies apresentou um longo transiente quando exposta a um novo ambiente, evidenciando que as técnicas tradicionais de restringir periodicamente o movimento do peixe não são adequadas para o estudo do comportamento desta espécie. Nossos resultados apresentaram varias evidencias de que os animais são capazes de distinguir estímulos realistas (gravados de conspecificos), de estímulos aleatórios com propriedades estatísticas semelhantes e que há 2 valores de echo response validando a necessidade dos métodos de estimulo desenvolvidos. Também pudemos mostrar que protocolos de estimulação em tempo real bidirecionais, são mais efetivos em interagir com o código do peixe quando comparados com os protocolos unidirecionais tradicionais e que os animais são capazes de aprender a controlar seu comportamento motor e também sua frequência de disparo para evitar estímulos indesejados.Bioloelectrogenesis is known since ancient times. Weakly electric fish are a wonderful model in Neuroethology because they produce and sense eletric fields. These unique features allow non invasive experiments to access complex spatio-temporal signals involved in 2 tasks called electrocommunication and electrolocation. Electrolocation is the ability to see the surrounding areas /objects by analyzing changes in the fish\'s own electric field and electrocommunication is the ability to identify conspecifics, fight for dominance etc. In this last task fish have their electric field distorted by conspecifics\' eletric organ discharges. Usually, within species, pulse-type weakly electric fish discharge pulses with similar waveform and the amplitude of the pulse depends on the distance to the recording electrodes being very difficult to measure the discharges in freely swimming animals, specially when 2 or more animals are interacting. For these reasons, most studies found in the literature are done with restrained animals or in shallow tanks. The most commom stimuli used are square/sine waves or very short pre-recorded discharges in classic protocol where the stimuli do not depend on the fish\'s activity. To overcome these issues trying to perform more naturalistic experiments, we developed experimental setups to record the electric and motor behavior in freely pulse-type electric fish for long periods. Our setups have also the advantage of being easy to adapt making possible to study several species. We performed real time experiments with realistic electric and light stimuli using dynamic clamp techniques adapted to Neuroethology. We show both classic unidirectional protocols as well as bidirectional closed loop interaction, taking into account the fish\'s dynamic activity. Analyzes based on Information Theory revealed that the entropy of the electric organ discharges are correlated to the their movement. We performed experiments using the setups and techniques mentioned before in 2 species that have evolved independently: G. Carapo (Gymnotidae) from South America and G. petersii (Mormyridae) from Africa. We show evidence of real communication and we study the inter pulse discharge probability in different behavioral circumstances. One specie showed a long transient behavior when introduced in new environment, hence, the traditional experiments with restrained animals might not be suitable to study natural behavior. Our results show several evidences that the fish can distinguish between realist stimuli from conspecifics and random ones, that there are 2 values of echo response instead of 1, demonstrating the importance of our new setup and protocols. We could also show that closed loop protocols were more effective to stimulate and interact with the fish\'s activity and that the animals are able to control their motor and electric behavior avoiding possibly harmful stimulation

Experimental study of electrocommunication in weakly electric fish from the Gymnotus carapo species - an application of Information Theory

Construímos um aparato experimental para medir os instantes de disparo do órgão elétrico de peixes elétricos de campo fraco da espécie Gymnotus carapo, que produz estes pulsos para localizar objetos dentro da água e para se comunicar socialmente. O aparato foi desenvolvido de maneira a iisolar o animal de perturbações externas como vibrações mecânicas, sons, campos elétricos e variações de luminosidade do ambiente. A principal característica de nosso aparato é um conjunto de eletrodos, distribuídos nos vértices do tanque de experimentos, que permitem obter as medidas (longas séries de instantes de disparo) sem restringir os movimentos do peixe e até mesmo inferir a sua posição comparando as amplitudes em diferentes eletrodos, o que possibilita relacionar a posteriori os padrões de disparo ao comportamento do animal. Desenvolvemos um programa de computador em linguagem C que, através de uma interface digital­analógica reproduz a série temporal da voltagem de um pulso de um peixe verdadeiro e utilizamos este sinal elétrico para estimular os animais. Os pulsos artificiais foram aplicados a um dipolo elétrico que imita a geometria do órgão elétrico de um peixe e os intervalos entre pulsos foram produzidos por diferentes distribuições: aleatória, intervalos gravados previamente do próprio ou de outro peixe, sequências manipuladas para repetir determinados trechos reais intercalados com trechos aleatórios, etc. Um segundo computador foi utilizado para detectar os instantes dos pulsos de estímulo e resposta e armazenar estas sequências em arquivos. Posteriormente utilizamos estas sequências para calcular a informação mútua média entre os sinais e verificamos que diferentes peixes reconhecem e reagem (alterando seus disparos elétricos) a determinados trechos da série de estímulo real de maneira bastante reprodutível. Também desenvolvemos outro programa de controle para detectar os pulsos do peixe em um dos aquários e estimular, em tempo real, o peixe de outro aquário e vice­versa. Assim, a única forma de interação entre os peixes é através dos pulsos elétricos e esta interação ocorre de modo bidirecional. Os dados destes experimentos também foram analisados utilizando o cálculo da informação mútua média entre os padrões dos dois peixes e encontramos evidências de que neste caso o fluxo de informação é maior que nos experimentos unidirecionais. Nosso aparato permitiu utilizar com sucesso a teoria da informação para estudar a dinâmica de disparo durante a interação elétrica entre peixes e possibilita diversos experimentos futuros em que pretendemos relacionar os padrões elétricos ao comportamento social dos animais e a sua interação com o meio ambiente.We built an experimental apparatus to measure the electric organ discharge times from weakly electric fishes of the Gymnotus carapo species. Such fishes use these pulses to actively locate objects in water as well as in social communication. Our apparatus was designed to allow such measures in the absence of some external perturbations the fishes are sensitive to, such as mechanical vibrations, electric fields and changes in the laboratory luminosity. A set of eight electrods were installed in the corners of the experimental tank and allows to obtain the discharge times without need to restrain the movements of the fish. Actually, from the maximal amplitudes of the discharge in different elecrodes we can infer the position and movements of the fish and relate its electrical dynamics to its behavior. A computer program (C language) was written to use a digital to analog interface to reproduce the time series of a discharge pulse from a real fish (recorded previously) and this electrical signal was used to stimulate the animals. The artificial pulses were applied to an electrical dipole built to mimic the geometry of the electrical organ of a living fish. The intervals between discharges were chosen from sequences obtained from different distributions: random, sequencies from real living fishes, handled sequencies where we repeated some real patterns with random patterns in between, etc. The detection of the stimuli and response pulses were done in another computer with the software Dasylab and the discharge times sequencies were recorded in harddisk for further analysis. Both sequencies were used to compute the average mutual information between the signals and we verified that different fishes recognize and react (changing their pulse interval pattterns) to the same regions of the real stimuli sequence. We also developed another control program (C language) to detect the discharges of a fish in one tank and to stimulate, in real time, a fish in another tank with those pulses, and vice­versa, in a bidirectional way. In this way, the only interaction between the fishes is through their electric pulses. The data analysis also consisted in obtaining the average mutual information between the sequencies of the two fishes and we found evidences that the flow of information is higher than that found in unidirectional experiments. Our apparatus allowed us to succesfully apply information theory to study the dynamics of the discharge intervals when the fishes are interacting. In the future we intend to extensivelly use such experiments to relate the electrical patterns to social behavior and to the interaction of these fishes with their environment

Delay-Dependent Response in Weakly Electric Fish under Closed-Loop Pulse Stimulation.

In this paper, we apply a real time activity-dependent protocol to study how freely swimming weakly electric fish produce and process the timing of their own electric signals. Specifically, we address this study in the elephant fish, Gnathonemus petersii, an animal that uses weak discharges to locate obstacles or food while navigating, as well as for electro-communication with conspecifics. To investigate how the inter pulse intervals vary in response to external stimuli, we compare the response to a simple closed-loop stimulation protocol and the signals generated without electrical stimulation. The activity-dependent stimulation protocol explores different stimulus delivery delays relative to the fish's own electric discharges. We show that there is a critical time delay in this closed-loop interaction, as the largest changes in inter pulse intervals occur when the stimulation delay is below 100 ms. We also discuss the implications of these findings in the context of information processing in weakly electric fish

Corresponding fish and delays used in this study.

<p>Corresponding fish and delays used in this study.</p