Page 11 - Shimadzu Journal vol.5 Issue1

Neuroscience

Cap design for optimal brain coverage The new neuroscience of two or more
Optode placements for corresponding hemispheres on two subjects Recent investigations of interpersonal interactions between two or
are illustrated in Fig 4. Table 1 includes an example of the more persons have demonstrated the efficacy of NIRS technology,
anatomical locations for each channel (single subject), as represented which now leads the way toward a new neuroscience of natural
in standard anatomical coordinates using the current Montreal cross-person communication (Babiloni & Astolfi, 2014; Scholkmann
Neurological Institute system (ICBM152, Mazziota et al., 2001). Since et al., 2013). Breakthroughs in technology, computational
NIRS does not provide structural information, as in the case of MRI, algorithms, and experimental paradigms promise a quantum leap in
standard brain atlases are employed to relate channel locations to future advances for developing a theoretical framework of the social
known anatomical structures. brain, and for treating the many psychiatric and neurological
conditions in which social functioning is often compromised. An
Optodes are positioned in similar head locations on both subjects to emerging basis for a new neuroscience originates with advanced
obtain cortical signals from nearly corresponding brain regions. The computational approaches to observe cross-brain synchrony
probes are positioned on each participant’s head, aligned to the associated with specific functions. For example, coherence between
midline defined as the arc running from the nasion through Cz to frontal cortical signals during cooperation on a computer task has
the inion. The position of the probes is based on the 10-20 been measured using wavelet analysis and showed greater
international coordinate system (Jasper, 1958), which provides an coherence between subjects who were competing on the same task,
accurate relationship with the cortical anatomy (Koessler et al., suggesting a neurophysiological substrate sensitive to interpersonal
2009). A 3D magnetic digitizer such as the PATRIOT Polhemus cues that are specific for cooperation (Cui et al., 2013). A similar
(Colchester, VT) is frequently used to identify the optode locations frontopolar finding using simultaneous recordings of individuals in
and, therefore, the channel positions for each subject, which are groups of four was reported during a cooperative word game
normalized by shape and size of the subject’s skull (Singh et al., (Nozawa et al., 2016). The emergence of leaders and followers has
2003). Three-dimensional coordinates of anatomical landmarks on been studied in groups using simultaneous NIRS recordings of left
the head are recorded in addition to locations of the individual frontal and parietal brain areas. Findings revealed that the
optodes (Okamoto et al., 2004). These coordinates are used to emergence of a group leader was associated with increased neural
estimate the position of each channel as defined by an synchronization between the leader and the follower relative to
emitter-detector optode pair using standard software packages such synchronization between followers (Jiang et al., 2015). These
as NIRS-SPM (http://www.fil.ion.ucl.ac.uk/spm/), a MATLAB-based findings suggest that neural mechanisms for leadership may be
application. understood in the future using hyperscanning methodologies and
NIRS. Increased neural synchronization observed between left
hemisphere signals across brains during face-to-face communication
relative to back-to-back communication suggest that facial cues
contribute specific neural signals employed during interpersonal
communication, and point the way toward the investigation of live
facial cues as a fundamental component of natural interpersonal
interaction (Jiang et al., 2012). Synchrony between premotor areas
of two brains participating in an imitation task of finger tapping was
Table 1 Example of MNI coordinates for channel locations greater than a control task in which the task was performed by
Channel Centroid Locations: MNI Coords
self-pacing (Holper et al., 2012). Eye-to-Eye contact also increases
coherence between brains (Hirsch et al, 2017). Additional examples
include cooperative button pressing (Funane et al., 2011) and the
4 n-back task (Dommer et al., 2012). Together, these findings
contribute to the growing documentation that cross-brain effects are
specific to neural regions, and that coherence is increased under
varied conditions of interpersonal engagement. These foundational
findings are early entry points that document the potential
significance of a new hyperscanning technology based on NIRS, and
the forward trajectory is moving at a very fast pace.

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Fig. 4 Channel distributions for both cerebral hemispheres applied for two subjects

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