Flexible Adaptive Paradigms for fMRI Using a Novel Software Package ‘Brain Analysis in Real-Time’ (BART)

In this work we present a new open source software package offering a unified framework for the real-time adaptation of fMRI stimulation procedures. The software provides a straightforward setup and highly flexible approach to adapt fMRI paradigms while the experiment is running. The general framework comprises the inclusion of parameters from subject’s compliance, such as directing gaze to visually presented stimuli and physiological fluctuations, like blood pressure or pulse. Additionally, this approach yields possibilities to investigate complex scientific questions, for example the influence of EEG rhythms or fMRI signals results themselves. To prove the concept of this approach, we used our software in a usability example for an fMRI experiment where the presentation of emotional pictures was dependent on the subject’s gaze position. This can have a significant impact on the results. So far, if this is taken into account during fMRI data analysis, it is commonly done by the post-hoc removal of erroneous trials. Here, we propose an a priori adaptation of the paradigm during the experiment’s runtime. Our fMRI findings clearly show the benefits of an adapted paradigm in terms of statistical power and higher effect sizes in emotion-related brain regions. This can be of special interest for all experiments with low statistical power due to a limited number of subjects, a limited amount of time, costs or available data to analyze, as is the case with real-time fMRI

4MOST: Project overview and information for the First Call for Proposals

We introduce the 4-metre Multi-Object Spectroscopic Telescope (4MOST), a new high-multiplex, wide-field spectroscopic survey facility under development for the four-metre-class Visible and Infrared Survey Telescope for Astronomy (VISTA) at Paranal. Its key specifications are: a large field of view (FoV) of 4.2 square degrees and a high multiplex capability, with 1624 fibres feeding two low-resolution spectrographs ($R = \lambda/\Delta\lambda \sim 6500$), and 812 fibres transferring light to the high-resolution spectrograph ($R \sim 20\,000$). After a description of the instrument and its expected performance, a short overview is given of its operational scheme and planned 4MOST Consortium science; these aspects are covered in more detail in other articles in this edition of The Messenger. Finally, the processes, schedules, and policies concerning the selection of ESO Community Surveys are presented, commencing with a singular opportunity to submit Letters of Intent for Public Surveys during the first five years of 4MOST operations

Main effect of emotion.

<p>All subjects’ t-map results for the second level analysis of ‘negative > neutral’ contrast.</p

Comparison of experiment timing adapted and non-adapted condition.

<p>Individual rates of the amount of trials reached as valid regarding the fixation compliance (A); Overall comparison of time that was needed to reach a certain amount of valid trials. For 95% and 100% valid trials none of the subjects reached these amounts in the non-adapted manner, therefore comparison is not shown (B); Exemplarily, the individual results for this with the threshold of 70% valid trials. 7 out of 17 subjects did not reach this amount of valid trials in the non-adapted condition. 9 out of the 10 remaining subjects need less time in the adapted condition (C). In summary, the adaption of the stimulation can help to minimize measurement time and dropout of subjects.</p

Behavioral results.

<p>The post-hoc analysis of eye tracking data shows the correct functionality of the software by 100% fixations for all subjects in the adapted condition. In addition, it shows difference in fixation compliance and gaze distance from the center of the screen for the non-adapted picture presentation. Due to the bimodal distribution of this parameter, subjects were divided into subgroups.</p

Schematic overview of the software package BART.

<p>Shown are the modules each running as a separate and independent process, responsible for the inclusion of behavioral/physiological parameters, the adaptation of the stimulation, design generation (blue arrows), and fMRI data processing (orange arrows). In the context of the presented study, we used an eye tracker to adapt visually presented emotional pictures according to subjects’ fixation on the center of the screen. The plugin mechanism also allows for straightforward and flexible extension to other devices, like ECG, pulse or EEG.</p

Activation network for the main effect of emotion (‘negative > neutral’ IAPS pictures; all subjects included).

<p>*p < 0.001 (uncorr.), Abbreviations: L—left, R- right, MDN—Medial Dorsal Nuclei</p><p>Activation network for the main effect of emotion (‘negative > neutral’ IAPS pictures; all subjects included).</p

Exemplarily results for the increase of effect sizes due to adaption.

<p>In the ROI analysis for non-adapted vs. adapted picture presentations based on regions involved in emotional processing (main effect of emotion, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0118890#pone.0118890.g006" target="_blank">Fig. 6</a>) we found enhanced brain responses for adapted trials in Low-Compliant which, due to the adaptation, met the activation levels in High-Compliant. This picture shows this exemplarily for the right pulvinar and insula, the results are summarized in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0118890#pone.0118890.t002" target="_blank">Table 2</a>.</p

Experimental paradigm.

<p>The experiment’s paradigm consisted of 60 negative and 60 neutral IAPS pictures, each presented in adapted and non-adapted manner over the course of the experiment. Each picture was presented for 500 ms with a fixation cross in between. In the adapted condition the picture presentation was shifted in time until subjects directed their gaze position toward the center of the screen and hence fixated the center of the subsequently presented picture. The main purpose of the study was to investigate the benefits of this trial adaptation.</p

Main effect of adaptation.

<p>Low-Compliant’ t-map results for the second level analysis of ‘adapted-non > adapted’ contrast.</p