Mirror visual feedback (MVF) devices.

<p>(A) Mirror glasses: are usable within an MR environment. The optical path was deflected by a prism, which was a 1.5–1.53 45-90-45 angled glass, Barium crown (BK-7, Abbe 63) with quarter wavelength surface tolerance. (B) Mirror box: was a framed glass mirror (size: 35 by 12 centimetres / 13.8 by 4.7 inches) which was placed on the abdomen of the subject providing view on the executing hand as well as the visual reflection of the hand appearing to move in synchrony. During both conditions view on the mirror reflection of the moving limb was provided by means of an additional mirror attached to the head coil. (C) Illustration of the MVF as provided by the mirror glasses: in contrast to the mirror box the users’ view is limited to the mirror reflection of the moving (physical) hand as opposed to seeing both hands (physical hand and visual reflection of the physical hand). The mirror reflection of the physical hand was seen through on eye by means of a prism leading to a total inversion in the left-right dimension (in our setup the right hand movements were seen through the right eye appearing as left hand movements). Furthermore, mirror glasses provide a much larger field of view, allowing the whole limb to be inverted.</p

Task-related brain activation for the mirror glasses and mirror box conditions.

<p>fMRI activations were mapped on a FSL render image. MI/SI = primary motor/somatosensory cortex, ipsi = ipsilateral to the executing (right) hand.</p

Brain regions and peak voxel coordinates showing significant task-related brain activation for the mirror box and mirror glasses conditions.

<p>Areas of significant fMRI-response were determined using clusters identified by a <i>z</i> > 3.0 threshold and a corrected cluster threshold of p = 0.05 assuming a Gaussian random field for the <i>z</i>-statistics. Coordinates are displayed in the Montreal Neurological Institute (MNI152) space.</p><p>Brain regions and peak voxel coordinates showing significant task-related brain activation for the mirror box and mirror glasses conditions.</p

Ratings on the intensity and vividness of mirror illusions for the mirror box and mirror glasses conditions.

<p>Results are reported with Mean ± Standard Deviation of the Mean (<i>M</i> ± <i>SD</i>). Comparisons of the two items between conditions were conducted with paired sample <i>t</i>-tests with Bonferroni adjusted alpha-values of 0.025 (0.05/2). Numerical rating scale ranging from 1 (‘as clear and vivid as a real perceptual experience’) to 7 (‘not at all clear and vivid’).</p><p>Ratings on the intensity and vividness of mirror illusions for the mirror box and mirror glasses conditions.</p

Brain regions showing significant positive psychophysiological interactions (PPI) with the motor representation of the moving hand.

<p>fMRI activations were mapped on a FSL render image. For illustrative purposes the spherical seed region of interest in the left primary motor cortex is also shown as red-colored sphere. MI/SI = primary motor/somatosensory cortex, LOC = lateral occipital cortex, PCC = posterior cingulate cortex, ipsi = ipsilateral to the executing (right) hand.</p

Results for the conjunction analysis.

<p>a) whole brain analysis (<i>p</i><.05, FWE-corrected); the number above each slice indicates the height (z-coordinate in Montreal Neurological Institute [MNI] space); b) analysis for bilateral ventral premotor cortex using regions of interest (<i>p</i><.005, uncorrected); given is the y-coordinate of the slices of peak activity (in MNI space). MOG =  middle occipital gyrus; MTG =  middle temporal gyrus; S2+ =  secondary somatosensory cortex plus its vicinity; PG =  precentral gyrus. Color bars indicate <i>t</i>-values.</p

Illusion vividness ratings.

<p>a) Depicted are the virtual hand illusion (VHI) intensity ratings for each item in each condition. Items # 1–3 represent targets indicating ownership over the virtual hand, and items # 4–9 represent distractors. The number at the base of each target item bar indicates the number of non-responders (i.e., responses  = 0; only given for target items). Asterisks indicate significant differences between the synchronous and distinctly asynchronous conditions (Bonferroni-corrected p-values on item level). Note that there were only significant results for the target items. There were no significant differences between the synchronous and slightly asynchronous conditions for any item.Error bars indicate standard error; b) For illustrative purposes, the ratings of participants who responded minimally (participant # 1–5) or maximally (participant # 21–25) to illusion induction are depicted, arranged according to the proneness to perceive the VHI in the 0 condition (VHI vividness score). Colors indicate the conditions. The 0 condition reflects the visuotactile stimulation in synchrony. Negative signs indicate the temporal delay (in milliseconds), which means that the tactile stimulation was applied prior to the visual stimulation; positive signs indicate that the tactile stimulation was applied after the visual stimulation.</p

Description of the items used to assess the virtual hand illusion. Bold font indicates target items.

<p>Description of the items used to assess the virtual hand illusion. Bold font indicates target items.</p

Setup of the virtual hand illusion.

<p>a) participant's view of the virtual reality environment, including the virtual limb and the stimulating rod at its starting position, b) the same view and rod at its end position touching the virtual finger, c) close-up picture of the pneumatic tactor, d) pneumatic tactor, attached to the participants' left index finger, e) participant lying on the table connected with the magnetic resonance imaging scanner. The participant has given written informed consent, as outlined in the PLOS consent form, to publication of her photograph.</p

Results for the conjunction analysis across all conditions.

<p>Coordinates in MNI space. L =  left; R =  right.</p>**<p><i>p</i><.001 (FWE-corrected) *<i>p</i><.05 (FWE-corrected).</p