Imaging Real-Time Tactile Interaction With Two-Person Dual-Coil fMRI

Abstract

Studies of brain mechanisms supporting social interaction are demanding because real interaction only occurs when persons are in contact. Instead, most brain imaging studies scan subjects individually. Here we present a proof-of-concept demonstration of two-person blood oxygenation dependent (BOLD) imaging of brain activity from two individuals interacting inside the bore of a single MRI scanner. We developed a custom 16-channel (8 + 8 channels) two-helmet coil with two separate receiver-coil pairs providing whole-brain coverage, while bringing participants into a shared physical space and realistic face-to-face contact. Ten subject pairs were scanned with the setup. During the experiment, subjects took turns in tapping each other's lip versus observing and feeling the taps timed by auditory instructions. Networks of sensorimotor brain areas were engaged alternatingly in the subjects during executing motor actions as well as observing and feeling them; these responses were clearly distinguishable from the auditory responses occurring similarly in both participants. Even though the signal-to-noise ratio of our coil system was compromised compared with standard 32-channel head coils, our results show that the two-person fMRI scanning is feasible for studying the brain basis of social interaction.

Keywords: functional magnetic resonance imaging; motor; somatosensory; touch; two-person neuroscience.

Figure 1

Coil and subject setup. (A, B) Illustration of the dual coil and its arrangement in the scanner. (C, D) Subject setup inside the scanner.

Figure 2

Experimental design. Subjects took 30-s turns in tapping the top of each other’s lip with their index finger, resulting in alternating tapping-feeling boxcar design with complete antiphase across the subjects. Turns were indicated with commands relayed via headphones.

Figure 3

Representative single-dyad T1 (A) and T*2 (B) -weighted images acquired with the dual coil. (C) tSNR for the dual coil and (D) conventional Siemens 32-channel head coil. Note that in due to preprocessing, the data from the dual coil pairs in panel (C) are further away from each other than they actually are (c.f. panel B).

Figure 4

Main effects of auditory cue (A) and the touching task (B) for the actor and receiver subjects. The data are thresholded at p < 0.05, FDR corrected.

Figure 5

Cumulative map of the binarized (active / inactive) single-pair level activation maps for the auditory cues and touching task. Color bar indicates the number of subjects where significant activations were observed in the first-level analyses. Note that this analysis does not differentiate which subject was active in the tapping task.

Figure 6

(A) Two representative independent components (ICs) and (B) their time courses extracted from the data.