Subjective feeling of control during fNIRS-based neurofeedback targeting the DL-PFC is related to neural activation determined with short-channel correction

Figures

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  Fig 1. Experimental design and installation of the participant during real-time neurofeedback training. A. Protocol design. Each NF session consisted in 15 trials of 30 seconds of NF with the colored gauge, alternating with 15 rest periods with a moving blue circle to help the participants to disengage from the task. During the baseline period, the blue circle also appeared on the computer screen of the participants. B. Layout of the NIRS cap with the positions of sources and detectors. C. Schematic representation of the installation of the participant in a dedicated dark room (to avoid light noise). The experimenter was hidden behind the participant’s computer screen. The NIRScout system was connected to the experimenter’s computer to launch the software used for data acquisition and signal feedback. During rest periods, the experimenter could still see the gauge and raw signals, as well as cardiac and breathing rhythms. The task was computed and launched through ©Psychopy and extended on the LCD computer screen (HP Compaq LA2045wg, 1680x1050, 59.94 Hz) placed approximately 80 cm in front of the participant.

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  Fig 2. Number of activated channels as a function of the best-selected trials of the 30 participants (all 15, or only 10 or 5) and two different BP filters. A. Frontal view of the functional near-infrared spectroscopy (fNIRS) layout with the region of interest (ROI) neurofeedback (NF) channels (n = 4) used for feedback calculation covering the dorsolateral prefrontal cortex (DL-PFC, green). The layout consisted of a coupling of eight sources and seven detectors; Detector 8 was used to collect the short-channel (SC) signal for all sources (purple circle). The respective locations of sources (red) and detectors (blue), as well as the labels of sources, detectors and SC detectors are indicated. B. Block-average on activated channels within the NF channels from an individual who succeeded in NF training. Red lines represent mean HbO2 concentration and blue lines represent mean HbR concentration. See S1 Fig for the block-average on the 30 individuals for the average signal in the four DL-PFC NF channels for the 10 best trials. Distribution of the participants according to the number of activated channels within the four NF channels for the entire 15 trials, or the 10 and 5 best trials,…

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  Fig 3. Characterization of the neurofeedback (NF) signal. A. Frontal view of the functional near-infrared spectroscopy (fNIRS) layout with (i) the NF channels (n = 4) used for feedback presentation covering the DL-PFC (green), (ii) other frontal channels (n = 12) covering the frontal area (brown), and (iii) one channel covering the motor area in the temporal lobe (black). The layout consisted in the coupling of eight sources and seven detectors; Detector 8 was used to collect the short-channel (SC) signal for all sources (purple circle). The respective locations of sources (red) and detectors (blue) are indicated. B. For each BP filtering and for each volunteer, the number of activated channels within the four NF channels with (DL-PFC+SC) and without (DL-PFC) SC regression (i.e. exclusion or inclusion of the scalp physiological signal, respectively), as well as the number of activated channels in other frontal (Other frontal+SC) and motor areas (Motor+SC) with SC regression. C. For each BP filtering, influence of the scalp physiological signal on the NF channels activation (comparison of subjects identified as having 0 or at least ≥ 1 activated channel between the DL-PFC+SC and the…

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  Fig 4. NF channel activation based on the DL-PFC+SC analysis with the BP 0.01–0.09 Hz filter in relation with A. the gauge control feeling (Control vs. No Control), and B. the strategy used by the participants to control the gauge. Cheering strategies (e.g. self-encouragement); Concentration (e.g. being focused on something); Visualization strategies, (e.g. visual imagination); Anger (e.g. getting angry towards the gauge or himself/herself). Participants who had a positive gauge control feeling are in red while participants with no control feeling are in blue. The number of subjects for each condition is indicated in the pie charts. Chi-square comparison control vs. no control, *p<0.05.