Anatomical and Functional Plasticity in the Olfactory System

In contrast to the three sensory modalities of vision, audition, and touch, few
studies have explored what impact sensory loss in the chemical senses
(olfaction and gustation) might have on our cortical organization and
behavioral performance. The few studies that have explored cerebral changes
mediated by a loss of olfactory functions demonstrate remarkable little changes
in either morphology or functional remapping.
To date, studies exploring anosmia-related morphological changes have utilized
classical voxel-based GLM analyses where large localized changes is needed to
reach statistically established levels. This project is based on the assumption
that changes within such wide-spread network that encompass only heterogeneous
processing areas should demonstrate subtle but wide-spread alteration rather
than uniquely impacting one specific area. Thus, by using novel multivoxel- and
network-based analyzing techniques, we can define and characterize
anosmia-related neural plasticity in the human brain from a network perspective
rather from than of a single-voxel.
Finally, previous studies exploring blind and deaf individuals have
demonstrated enhancement of sensory functions in remaining sensory modalities
but none have assessed whether sensory loss alters individuals ability to
integrate and utilize information gain from multiple sensory sources, so-called
sensory integration gain.

The overall goal of this project is to define and characterize congenital
anosmia-related neural plasticity in the human brain and its behavioral
consequences. We hypothesize that individuals suffering from congenital anosmia
demonstrate wide-spread morphological changes and that these changes render
them be better at multisensory integration tasks.

We will investigate the following two major issues in the proposed experiments:
1) Are there differences in the basic morphology and functionality of the human
brain between humans who were born with and humans who were born without the
sense of smell?
2) Are there differences in neural processing of other senses (vision and
hearing) between humans who were born with and humans who were born without the
sense of smell?

This is an observational case-control study. Duration of the protocol will be
one session of 2 hours. On the study day participants will perform a
behavioural task (Sniffin' Sticks smell test) as well as engage in an fMRI
session that consists of four subparts:
* Whole brain anatomical image
* Functional resting-state scan
* Multisensory integration task consisting of identifying objects within
degraded stimuli
* Object identification task of clear visual and auditory objects.

The study is non-therapeutic to the participants. No immediate benefits for the
participants are expected from participation in this study. The risk associated
with participation is negligible. The participant*s burden is as follows,
regarding time: the experimental session will take approximately 2hrs: one hour
of behavioral (olfactory) testing, and one hour inside the scanner. MRI is an
eminently safe technique; there are no risks that have been associated with the
acquisition of MRI data per se.
Chance findings of pathology: The MRI-scans in this study are not made with the
intention to diagnose pathologies, however, chance findings of pathology may
occur. Participants will be informed of this possibility and need to be willing
to receive information about incidental findings of pathology, as this is one
of the inclusion criteria. In case of a possible chance finding, a radiologist
will inspect the scans. If any pathology is found or suspected by the
radiologist, the subject will be referred to his/her general physician or a
medical specialist. The participant and her/his general physician will be
informed of the finding.