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The Brain Imaging Data Structure (BIDS) is a community-driven standard for the organization of data and metadata from a growing range of neuroscience modalities. This paper is meant as a history of how the standard has developed and grown over time. We outline the principles behind the project, the mechanisms by which it has been extended, and some of the challenges being addressed as it evolves. We also discuss the lessons learned through the project, with the aim of enabling researchers in other domains to learn from the success of BIDS.

The Brain Imaging Data Structure (BIDS) is a community-driven standard for the organization of data and metadata from a growing range of neuroscience modalities. This paper is meant as a history of how the standard has developed and grown over time. We outline the principles behind the project, and the mechanisms by which it has been extended. We also discuss the lessons learned through the project, with the aim of enabling researchers in other domains to learn from the success of BIDS.

When acting together, we may represent not only our own individual goals but also a collective goal. Although behavioural evidence suggests that agents' motor plans might be related to collective goals, direct neurophysiological evidence of whether collective goals are motorically represented is still scarce. The aim of the present transcranial magnetic stimulation (TMS) study is to begin to fill this gap. A participant and a confederate were asked to sequentially perform a two-choice reaction time task by acting on pressure sensors. In their own turn, they saw a cue indicating whether to lift their fingers from (or to press them on) a pressure sensor to shoot a ball across the screen as fast as possible. The confederate responded with the right hand, the participant with the left hand. While the confederate acted on the sensor, the participant's motor evoked potentials (MEPs) were collected from the right Extensor Carpi Ulnaris. If participants represent their own and the confederate's actions as being directed to a collective goal, MEPs amplitude should be modulated according to the action the confederate should perform. To test this conjecture, we contrasted three conditions: a Joint condition, in which both players worked together with their collective goal being to shoot the ball to get it to a common target, a Parallel condition, in which the players performed exactly the same task but received independent outcomes for their performance, and a Competitive condition, in which the outcome of the game still depended on the other player performance, but without the collective goal feature. Results showed no MEPs modulation according to the confederate's action in the Joint condition. Post-hoc exploratory analyses both provide some hints about this negative finding and also suggest possible improvements (i.e., adopting a different dependent variable, avoiding task-switching between conditions) for testing our hypothesis that collective goal can be represented motor

Transcranial magnetic stimulation (TMS)-evoked potentials (TEPs) are a promising proxy for measuring effective connectivity, that is, the directed transmission of physiological signals along cortico-cortical tracts, and for developing connectivity-based biomarkers. A crucial point is how stimulation parameters may affect TEPs, as they may contribute to the general variability of findings across studies. Here, we manipulated two TMS parameters (i.e. current direction and pulse waveform) while measuring (a) an early TEP component reflecting contralateral inhibition of motor areas, namely, M1-P15, as an operative model of interhemispheric cortico-cortical connectivity, and (b) motor-evoked potentials (MEP) for the corticospinal pathway. Our results showed that these two TMS parameters are crucial to evoke the M1-P15, influencing its amplitude, latency, and replicability. Specifically, (a) M1-P15 amplitude was strongly affected by current direction in monophasic stimulation; (b) M1-P15 latency was significantly modulated by current direction for monophasic and biphasic pulses. The replicability of M1-P15 was substantial for the same stimulation condition. At the same time, it was poor when stimulation parameters were changed, suggesting that these factors must be controlled to obtain stable single-subject measures. Finally, MEP latency was modulated by current direction, whereas non-statistically significant changes were evident for amplitude. Overall, our study highlights the importance of TMS parameters for early TEP responses recording and suggests controlling their impact in developing connectivity biomarkers from TEPs. Moreover, these results point out that the excitability of the corticospinal tract, which is commonly used as a reference to set TMS intensity, may not correspond to the excitability of cortico-cortical pathways.

Transcranial magnetic stimulation (TMS) has been widely used in both clinical and research practice. However, TMS might induce unintended sensations and undesired effects as well as serious adverse effects. To date, no shared forms are available to report such unintended effects. This study aimed at developing a questionnaire enabling reporting of TMS unintended effects. A Delphi procedure was applied which allowed consensus among TMS experts. A steering committee nominated a number of experts to be involved in the Delphi procedure. Three rounds were conducted before reaching a consensus. Afterwards, the questionnaire was publicized on the International Federation of Clinical Neurophysiology website to collect further suggestions by the wider scientific community. A last Delphi round was then conducted to obtain consensus on the suggestions collected during the publicization and integrate them in the questionnaire. The procedure resulted in a questionnaire, that is the TMSens_Q, applicable in clinical and research settings. Routine use of the structured TMS questionnaire and standard reporting of unintended TMS effects will help to monitor the safety of TMS, particularly when applying new protocols. It will also improve the quality of data collection as well as the interpretation of experimental findings.

Existing literature on sensory deprivation suggests that short-lasting periods of dark adaptation (DA) can cause changes in visual cortex excitability. DA cortical effects have previously been assessed through phosphene perception, i.e., the ability to report visual sensations when a transcranial magnetic stimulation (TMS) pulse is delivered over the visual cortex. However, phosphenes represent an indirect measure of visual cortical excitability which relies on a subjective report. Here, we aimed at overcoming this limitation by assessing visual cortical excitability by combining subjective (i.e., TMS-induced phosphenes) and objective (i.e., TMS-evoked potentials - TEPs) measurements in a TMS-EEG protocol after 30 min of DA. DA effects were compared to a control condition, entailing 30 min of controlled light exposure. TMS was applied at 11 intensities in order to estimate the psychometric function of phosphene report and explore the relationship between TEPs and TMS intensity. Compared to light adaptation, after DA the slope of the psychometric function was significantly steeper, and the amplitude of a TEP component (P60) was lower, only for high TMS intensities. The perceptual threshold was not affected by DA. These results support the idea that DA leads to a change in the excitability of the visual cortex, accompanied by a behavioral modification of visual perception. Furthermore, this study provides a first valuable description of the relationship between TMS intensity and visual TEPs

Clinical manifestations of Alzheimer's disease (AD)are associated with a breakdown in large-scale communication, such that AD may be considered as a “disconnection syndrome.” An established method to test effective connectivity is the combination of transcranial magnetic stimulation with electroencephalography (TMS–EEG)because the TMS-induced cortical response propagates to distant anatomically connected regions. To investigate whether prefrontal connectivity alterations may predict disease severity, we explored the relationship of dorsolateral prefrontal cortex connectivity (derived from TMS–EEG)with cognitive decline (measured with Mini Mental State Examination and a face–name association memory task)in 26 patients with AD. The amplitude of TMS–EEG evoked component P30, which was found to be generated in the right superior parietal cortex, predicted Mini Mental State Examination and face–name memory scores: higher P30 amplitudes predicted poorer cognitive and memory performances. The present results indicate that advancing disease severity might be associated with effective connectivity increase involving long-distance frontoparietal connections, which might represent a maladaptive pathogenic mechanism reflecting a damaged excitatory–inhibitory balance between anterior and posterior regions.

In this study we assessed changes in phosphene perception and transcranial magnetic stimulation (TMS)-evoked potentials (TEPs) after light and dark adaptation. The primary aim was to link a direct neurophysiological correlate of cortical excitability (i.e., TEPs) to the subjective report (i.e., phosphene perception) in order to evaluate whether environmental light changing induced modifications in visual cortex excitability or only at retinal level, as previously reported. Ten young healthy participants underwent three conditions: baseline (environmental light), 30 minutes of light adaptation (LA) and 30 minutes of and dark adaptation (DA) in counterbalanced order. After each condition, we assessed the TMS-induced phosphenes perception by single pulse TMS over the visual cortex (V1) while 32-channels electroencephalogram (EEG) was recorded. Coil position was maintained stable across conditions through a stereotaxic neuronavigation system. Phosphenes threshold was calculated through the method of constant stimuli, in which TMS pulses were delivered at different TMS intensities ranging from 46 to 76% of the maximal stimulator output. The participants were asked to report whether they perceived or not a phosphene after each TMS pulse. A Weibull function was fitted to phosphenes report for each condition and participant separately, in order to estimate the threshold and slope of the psychometric functions. Results confirmed that dark adaptation modulated visual perception: the slope of the psychometric function after dark adaptation significantly increased (p<0.05) compared to light adaptation and baseline, whilst the estimated threshold for phosphene perception did not change across conditions. A preliminary analysis of TMS-EEG data shows a reduction of TEPs amplitude after DA compared to LA, thus suggesting that a period of prolonged dark adaptation is able to decrease cortical excitability. This modulation could explain the reduction of sensitivity indexed by the inc

A growing body of evidence has shown that prestimulus M/EEG power and phase in the alpha band account for a significant portion of trial-to-trial variability in visual perception. However, up to now the neural mechanisms related to ongoing alpha activity are not fully understood; moreover, only few studies have investigated the effects of prestimulus oscillations by evaluating the full psychometric function, which provides valuable information on the functional mechanisms involved. In the present work we describe a formal model with the aim of exploring possible neural mechanisms associated with the effects of ongoing alpha activity on visual perception, by linking the response probability of sensory neurons with the psychometric function at the behavioural level. We identified three possible mechanisms through which alpha activity may regulate sensory processing: it may alter (1) the amplitude of subthreshold oscillations, (2) the degree of synchronization, and (3) the input to sensory neurons. According to the model, each mechanism has a specific effect on the response probability function, by affecting (1) the slope, (2) the upper asymptote and (3) the threshold. Therefore, we hypothesized that selective modifications of the psychometric function could provide suggestions on the associated neural mechanisms, which cannot be distinguished non-invasively.

Background: One of the most important functions of the visual system is the sensitivity to variation of the environment light. In the present study we aimed at assessing cortical modulation as a function of environmental light adaptation through directly linking subjective report (i.e., phosphene perception) with neurophysiological correlates (i.e., transcranial magnetic stimulation (TMS)-evoked potentials, TEPs). Methods: Ten young healthy participants underwent 30 minutes of light and 30 minutes of dark adaptation in counterbalanced order. We measured TMS-induced phosphene perception through the method of constant stimuli (11 TMS intensities from 46 to 76% of the maximal stimulator output) after each condition while 32-channels electroencephalogram (EEG) was continuously recorded. A Weibull function was fitted to phosphene report in order to estimate threshold and slope of the psychometric functions. Results: Dark adaptation modulated visual perception: the slope of the psychometric function after dark adaptation significantly increased compared to light adaptation. A preliminary analysis of TMS-EEG data shows a modulation of TEPs amplitude after dark adaptation.

Recent studies have shown that the stimulation-dependent model is unable to account for the complex experimental evidence observed when applying transcranial electrical stimulation (tES) outside the motor cortex. An alternative model refers to the concept of stochastic resonance. It is based on the assumption that the injected electric field in the brain is unspecific; therefore, it can be defined as noise induction in a non-linear system (Miniussi et al., 2013). According to the model, the interaction between the injected noise and the ongoing activity of the system (in terms of signal to noise ratio, SNr) is a key factor in determining behavioral effects. The SNr in neural networks may change depending on task demands; consequently, also the response of the system to brain stimulation is expected to vary. However, up to now only few studies have considered elements which may affect the state of the system, such as performance level and interindividual variability. The present study aims to investigate whether the stochastic resonance framework can account for behavioral outcomes when an excitatory type of tES is applied (Paulus 2011; Woods et al. 2016). 36 young healthy participants were asked to perform a visual orientation discrimination task while receiving anodal transcranial direct current stimulation or high frequency transcranial random noise stimulation (hf-tRNS) on the primary visual cortex. In Experiment 1 subjects were presented with a large range of angular differences between the reference and the target stimulus. In Experiment 2 task difficulty was manipulated according to individual performance previously recorded, in order to control for intersubjects variability. Different levels of performance were obtained in a between subjects design. Half of the subjects received sham stimulation. In Experiment 1 an increased performance was observed in the experimental group only for hf-tRNS, while for Experiment 2 no main effect of stimulation was present fo

Background: Anodal transcranial direct current stimulation (A-tDCS) is a non-invasive technique in which cortical polarization can be used to increase excitability and facilitate learning through the modulation of neuroplasticity. Although the facilitatory effects of A-tDCS are well documented, there is evidence that they are not always present and may even be reversed during task execution. Objective: In this study, we explored the interaction between A-tDCS and task execution. We aimed to test how the excitability induced by the task interacts with the excitability induced by A-tDCS and determines the behavioral outcome. Methods: We performed an experiment in which A-tDCS or a control stimulation (Ctrl) were combined with one of two motor practices (MP), one inducing learning and increasing cortical excitability (F-MP) and the other neither inducing learning nor changing cortical excitability (S-MP). Six blocks of MP were performed while the primary motor cortex was stimulated. Moreover, one block of F-MP was performed before the stimulation (baseline) and one after. In an additional experiment, motor evoked potentials (MEPs) were recorded before the baseline block (TMS-pre) and after the MP (TMS-post). Results: We observed that A-tDCS reduced learning when participants performed the F-MP and facilitated learning for the S-MP. MEPs data paralleled behavioral results, confirming that the effects generated by A-tDCS depend on the excitability changes induced by the task. Conclusions: Our results demonstrate that tDCS-induced plasticity is task-dependent, and the concurrent combination of A-tDCS with another excitability-increasing event, e.g., motor practice, may trigger non-additive mechanisms, hindering neuroplasticity.