Self-recognition of one's own fall recruits the genuine bodily crisis-related brain activity.

While bipedalism is a fundamental evolutionary adaptation thought to be essential for the development of the human brain, the erect body is always an inch or two away from falling. Although the neural mechanism for automatically detecting one's own body instability is an important consideration, there have thus far been few functional neuroimaging studies because of the restrictions placed on participants' movements. Here, we used functional magnetic resonance imaging to investigate the neural substrate underlying whole body instability, based on the self-recognition paradigm that uses video stimuli consisting of one's own and others' whole bodies depicted in stable and unstable states. Analyses revealed significant activity in the regions which would be activated during genuine unstable bodily states: The right parieto-insular vestibular cortex, inferior frontal junction, posterior insula and parabrachial nucleus. We argue that these right-lateralized cortical and brainstem regions mediate vestibular information processing for detection of vestibular anomalies, defensive motor responding in which the necessary motor responses are automatically prepared/simulated to protect one's own body, and sympathetic activity as a form of alarm response during whole body instability

Brain activity in the DU vs. DS contrast for self and others.

<p><b>A:</b> Brain regions significantly activated for the Self DU vs. Self DS contrast, and the eigenvariate values (parameter estimates, mean ± standard error) in the spherical region of interest (ROI; radius, 5 mm) whose center was the peak voxel at each cluster showing significant activity in the above contrast, in each of the Self DU (S-DU) and Self DS (S-DS) comparisons. <b>B:</b> Brain regions significantly activated for the Others DU vs. Others DS contrast, and the eigenvariate values in the spherical ROI (radius, 5 mm) whose center was the peak voxel at each cluster showing significant activity in the above contrast, in each of the Others DU (O-DU) and Others DS (O-DS) comparisons. R: right, L: left, PMd: dorsal premotor area, PIVC: parieto-insular vestibular cortex, TPJ: temporo-parietal junction, IPL: inferior parietal lobe, aSMG: anterior supramarginal gyrus, EBA: extrastriate body area, SPL: superior parietal lobe.</p

Brain activity in the DU vs. DS contrast for self and others.

<p>Brain regions significantly activated for the Self DU vs. Self DS contrast (upper) and Others DU vs. Others DS contrast (lower).</p><p>BA: Brodmann area, MNI: Montreal Neurological Institute, PMd: dorsal premotor area, PIVC: parieto-insular vestibular cortex, TPJ: temporo-parietal junction, IPL: inferior parietal lobe, aSMG: anterior supramarginal gyrus, SPL: superior parietal lobe, EBA: extrastriate body area.</p><p>Brain activity in the DU vs. DS contrast for self and others.</p

Subjective ratings of motion pattern (A) and emotion (B).

<p>There were significant main effects of conditions (DU, DS, and SS), and no significant main effects of performers. DU: dynamically unstable, DS: dynamically stable, SS: statically stable.</p

Self-specific brain activity in the DU vs. DS contrast.

<p>Brain regions which were significantly activated for the Self (DU vs. DS) vs. Others (DU vs. DS) contrast and whose averaged ROI eigenvariate for the Self (DU vs. DS) contrast was positive. The ROI eigenvariates including those for the Others (DU vs. DS) contrast are shown for illustration.</p><p>BA: Brodmann area, MNI: Montreal Neurological Institute, RLPFC: rostrolateral prefrontal cortex, PMv: ventral premotor area, IFJ: inferior frontal junction, pINS: posterior insula, PBN: parabrachial nucleus.</p><p>Self-specific brain activity in the DU vs. DS contrast.</p