FMRI of space, number and time processing networks across the senses

Large areas of the human brain are involved in sensory processing, motor
processing and multisensory integration. To understand mechanisms of human
brain function in health, it is desirable to understand the response properties
of neural populations involved in sensory and multisensory processing, and how
these change between brain areas. Functional magnetic resonance imaging (fMRI)
is an excellent tool to establish the functional architecture of the brain, and
is increasingly used to quantify neural response properties. Therefore, we
propose to present visual stimuli, auditory stimuli, somatosensory stimuli,
and/or cues to perform motor actions to healthy participants while recording
fMRI responses to these stimuli. We will then use advanced fMRI analyses to
quantify the response properties of each recording site, and how these response
properties are organised. We hypothesise that the responses of individual
recording sites are selective for particular timings and spatial distributions
of sensory and motor events, forming networks of interacting topographic maps
of space and time that support multisensory perception. These experiments will
therefore reveal the neural mechanisms involved in sensory and multisensory
processing.

To evaluate the quantifiable spatial representation of space, time and number
in the normal human brain.

Determining how fMRI voxels respond to the temporal and spatial distribution of
sensory stimulation is a descriptive study design. The aim of the study is to
quantify and compare fMRI responses for a number of stimuli and tasks. To
measure and model fMRI responses, healthy volunteer will undergo T1-weighted
structural MRI scans and T2-weighted fMRI scans. In different scanning
sessions, several series of functional brain scans be acquired while
participant perform the following tasks.

- Visual field mapping: Participants will view visual stimuli that change their
visual field position. Periods of spatially-specific visual stimulation are
alternated with blank display periods. Participant fixate (look at) a colored
dot in the center of the display and press a button when in changes color, to
ensure they maintain attention to a specific location. The task lasts for 7
minutes. This task is repeated several times to increase signal-to-noise ratio
(SNR).
- Visual numerosity and object size mapping: Participants will view visual
stimuli projected on a screen in the scanner. These stimuli will contain
objects that change their numbers and/or sizes. Participant press a button when
these objects change color, to ensure they maintain attention to the stimulus.
The task lasts for 7 minutes. The task will be repeated several times to
increase signal-to-noise ratio (SNR).
- Sensory time mapping: Participants will be presented with visual stimuli
(flashed dots projected on a screen in the scanner), auditory stimuli (tones
played through MRI-compatible headphones) and/or somatosensory stimuli (air
puffs to the hand). The numbers, durations and appearance of these sensory
events will change through the scanning run. Participants press a button when
the visual stimuli change colour, the auditory stimuli change tone, or the
somatosensory stimuli change location. The task lasts for 7 minutes. The task
will be repeated several times to increase signal-to-noise ratio (SNR).
- Motor time mapping: Participants will view visual cues (symbolic numbers or
flashed dots) projected on a screen in the scanner. They will respond to these
cues by performing hand movements with numbers or durations specified by the
cues, which will change through the scanning run. Participants will wear an
MRI-compatible data glove to record these movements. The task lasts for 7
minutes. The task will be repeated several times to increase signal-to-noise
ratio (SNR).
- Resting state: During a period of 500 seconds (i.e. 8 minutes 20 seconds),
the participant is instructed to close their eyes, lie still and think of
nothing in particular.

Healthy volunteers are asked to fill out several questionnaires and visit the
UMC Utrecht. During the visit to the UMC Utrecht the tasks will be practiced
and the fMRI scans session will be performed. There are no known risks of fMRI
as it does not make use of contrast agents, etc. The fMRI procedure is painless
and not uncomfortable. Participants will be asked to lay still for a maximum of
90 minutes, which has been shown to be an acceptable duration for fMRI
experiments.