This innovative protocol is relevant for the study of group interpersonal interactions in ecological settings. It is designed to access differences in brain and behavior interpersonal responses in quartets during different drawing tasks. This protocol offers easy to implement procedures and a reliable paradigm using fNIRS to simultaneously measure the hemodynamic responses of a group of four individuals interacting.
To prepare for the study, remove all potential eye distractors from the scene. Turn off all electrical devices such as air conditioning during the experimental condition. Ensure that the room has sufficient lighting for people to observe and draw.
Upon setting up, position all fNIRS wires such that they remain stable during the experimental task. Position the quartet on the table two by two so that each individual can observe the other three individuals. To perform the drawing paradigm, which is the social condition, have participants draw the forehead and eye area on the top strip of all the paper sheets.
Have each paper represent a fully drawn portrait of a participant. Also have the face of each participant depicted in a collaborative way by their partners. For the connect the dots game, which is the non-social condition, ask the participants to connect the numbers in an ascendant way.
Select a commercially available 360 degree scene camera and position it on the table so that the eye and head movements of all the participants can be perceived simultaneously. Check for possible interferences on fNIRS reception. Before fNIRS calibration, start the equipment, check the interface, and set the recording mode.
For data analysis, select a synchronized view or analysis platform that allows the transcription and coding of several video contents simultaneously such as the INTERACT software. To refine observational data, set parameters that enable the search for patterns or sequences such as individual gaze behavior metrics, head and eye movement, hand movement, facial expressions, and talking behavior. After analysis, start by downloading the video from all cameras in MP4 format and load them into INTERACT.
Segment the video data for coding and further analysis. For data extraction, mark the video sections manually and provide them with codes. Click on Define Codes to create the first tier by dividing the block sections into social and non-social conditions and resting periods.
Then create a second tier by dividing the behavioral data from the participants along with social conditions. Observe details and determine drawing metrics by counting the details drawn during the experiment. Use the NIRSite tool to locate the optodes over the PFC regions.
Configure the distribution of optodes on the caps such that the channels are positioned above the regions of interest on the head of the participant. Divide the optodes among four participants for the simultaneous acquisition of signals. Before setting the fNIRS apparatus, measure the brain perimeters of the four participants like the distances between the nasion and the inion around the head to determine the cap size of each participant.
Then fit the sources and detectors to the cap according to the predetermined settings. Put the caps on the head of the participant and position the cap so that the central midline is at the top of the head. Further ensure that the cap is positioned correctly by measuring the distance between the left and right ear above the top of the head and positioning the central midline at the middle of the measure.
Then connect the wires of the optodes to the amplifiers and connect both NIRSport 1 and 2 to the computer. After setting up the equipment, enabled the software to acquire the fNIRS data. Click on Configure Hardware on the menu bar.
Select the option Tandem Mode on the hardware specification tab to perform the hyper scanning. On the configure hardware tab, select a montage and check the settings in channel masking, topo layout, and channel setup. Perform an automatic calibration by clicking Calibrate on the display panel.
When ready to start the procedure, click on Preview to have a preview of how the signals are being received. Then start recording the signals by clicking on Record. Open the blocks programming software NIRStim and start the presentation of the programmed blocks by clicking on Run.
NIRStim will close at the end of the experiment. Stop recording in NIRStar. Close the software and verify the file is saved correctly.
This method was applied to a quartet composed of women postgraduate students aged 24 to 27 years. The fNIRS preliminary results showed typical brain activation for participants one, two, and three in both the social and non-social drawing conditions. This was observed in both channels located in the left and right hemispheres, although the activation patterns were distinct.
On the other hand, participant four showed atypical brain activation. The oxyhemoglobin signal was significantly synchronized between subjects only during the last part of the task both in the connecting the dots condition and in the collaborative drawing condition. This method can provide insights into neuroscience, art, art therapy, and social interaction research areas in general.
