Body Integrity Identity Disorder: abnormal processing in the primary sensory cortex, superior parietal lobule and insula?

Body Integrity Identity Disorder (BIID) is characterised by a wish for
amputation of a perfectly healthy body part, most often part of a leg or arm.
Patients have the feeling the limb does not belong to their body and they can
only feel complete after the unwanted limb has been removed. No treatment is
available yet and surgeons refuse to operate on these patients, so not seldomly
patients take matters in their own hands and resort to drastic measures:
self-amputation with possibly fatal outcome.


It has been suggested that problems with integrating sensory information
underlie the sense of reduced body ownership, but little research has been
done. A magnetoencephalography study showed that sensory stimulation of the
unwanted limb resulted in reduced activity compared to stimulation of the
wanted limb in the superior parietal lobule, an area involved in body image and
integration of sensory information from multiple regions. Also, abnormal
activity in the ipsilateral primary sensory cortex during stimulation of the
unwanted but not the wanted limb was found (Brang, McGeoch &Ramachandran,
2007). These results point to abnormal white matter connectivity in the sensory
cortex. Additionally, the right posterior insula is thought to be involved in
body ownership. Stroke victims with lesions in this area show a disturbed
sensation of limb ownership (Baier & Karnath, 2008) and studies creating the
illusion of perceiving a rubber hand as one's own also show activation in this
region (Tsakiris et al., 2007).

In the current study we hope to find whether BIID is related to abnormal
functioning of the sensory cortex, superior parietal lobule and insula. We also
want to investigate if any problems with integration of sensory information
also occur on the level of integration of motor information. Furthermore we
want evaluate whether these potential differences are related to abnormalities
in the brain structure (especially in white matter tracts) of BIID patients
compared to healthy controls.

Therefore, neural responses to sensory stimuli and to a motor task are
investigated in 4 patients with BIID and 10 healthy matched controls using
functional Magnetic Resonance Imaging. The sensory stimuli are applied to the
legs (below and above the desired line of amputation) with a brush for 20
seconds followed by 20 seconds of no stimulation in a randomly alternating
manner. In the motor task participants are asked to wiggle toes or fingers of
one limb in a block consisting of 20 seconds of movement followed by 20 of
seconds rest in randomized blocks. Additionally structural differences between
BIID patients and healthy controls are investigated. White matter tracts will
be analyzed using diffusion tensor imaging-based fiber tracking and grey matter
differences are examined using Voxel Based Morphometry.

The participants will fill out a questionnaire which will take a maximum of 10
minutes. Thereafter participants will lie in the MRI scanner for 50 minutes
during which they perform a motor task and undergo tactile stimulation on the
legs. During the structural scans participants only need to lay still. The MRI
scan will cause the most inconvenience to the participants since they need to
lay as still as possible for 50 minutes (except during the motor task when they
are asked to move fingers or toes but need to keep the rest of the body as
still as possible).
The risks of this study are limited to the risks of an MRI scan.