A detailed somatotopic map of the speech articulators: a 7T fMRI study

Communication through speech is an important aspect in our daily life. People
with severe motor impairment (Locked-In Syndrome, LIS), caused by neurological
disorders such as brainstem stroke or amyotrophic lateral sclerosis (ALS), are
unable to speak or communicate effectively. Brain computer interfaces (BCIs)
may offer a solution to this problem by using voluntarily induced signal
changes in the sensorimotor areas of the brain recorded with implanted
electrodes that are converted to control signals for a communication device.
These signal changes can be produced by the attempt to move a body part, for
example the hand or speech articulators (i.e., the tongue, lips, jaws). An
important remaining challenge for sensorimotor BCIs is the long training time
needed for reliable and independent control. Somatosensory feedback about the
attempted movements, through electrical stimulation of the brain, seems to be a
promising step to reduce training time and improve performance of BCIs in
people with LIS. To determine where to apply electrical stimulation to the
somatosensory cortex for improved BCI training and performance, it is necessary
to understand the underlying brain processes of tactile perception. Previous
research found that the hand and fingers are represented in the somatosensory
cortex in an orderly manner. However, the organization of the speech
articulators, another important BCI control strategy, remains unknown.

The overall goal of this study is to investigate the detailed representation of
the speech articulators in the somatosensory cortex.

This is an observational study in healthy volunteers, involving 7 Tesla (7T)
functional magnetic resoncance imaging (fMRI) with pneumatic stimulation of the
speech articulators using a device that produces air puffs.

The risks and burden of this study are minimal. There are no known risks
associated with fMRI acquisition. The technique does not require any contrast
agents or ionizing radiation administration. The Utrecht research group has
ample experience with fMRI scanning (approx. 400 sessions per year done on the
7 Tesla MRI scanner). The fMRI procedure is painless, but some discomfort may
occur due to peripheral nerve stimulation during scanning and prolonged time
lying still with head and upper body in a confined tunnel-like device.

The pneumatic device is developed by the Medical Technology department of the
University Medical Center (UMC) Utrecht, based on a previously reported design,
which was shown to be safe to use in an MRI environment (Nazarian et al., 2022;
Wienbruch et al., 2006). Intensity of air puffs delivered by the pneumatic
device will be extensively tested before the start of the study, to prevent any
discomfort for the participant. The device uses clean medical air from the UMC
Utrecht and bacterial filters to prevent skin or respiratory tract irritation
related to the minimal chance of particles detaching from components in the
device. After each participant the device will be cleaned and the tip of the
tube that stimulates the tongue plus filter, will be replaced for each
participant.