Brain activation patterns associated with tasting calories independent of sweetness.

Humans easily prefer and select carbohydrate rich foods because of their inborn
preference for sweet taste. However, recently done studies indicate that a
nongustatory factor, caloric content, might also play a role in the formation
of preference for these foods. Nutritive and non-nutritive sweeteners have been
shown to differentially affect brain activation during oral exposure.
Furthermore, oral exposure to a carbohydrate solution during exercise improved
performance, but oral exposure to an artificial sweetener solution did not.
Above findings suggest the existence of an oral carbohydrate receptor that
responds to carbohydrates rather than to sweetness. However, whether this
receptor responds to all carbohydrates or only to specific ones, and whether
energy (carbohydrate) sensing takes place in the absence of sweetness is not
yet known.

The primary objective of this study is to assess whether oral exposure to
caloric and non-caloric stimuli elicits discriminable responses in the brain
independent of sweetness. This knowledge will help us to better understand the
role of energy sensing in the formation of food preferences and food selection.

The 1st secondary objective is to determine the effect of hunger on taste
activation in response to caloric and non-caloric stimuli, i.e. to establish
whether there is an interaction between hunger and stimulus energy content.

The 2nd secondary objective is to establish in how far subject characteristics
like reward sensitivity and impulsivity correlate with brain responses elicited
by tasting caloric and non-caloric stimuli.

The study has a randomized crossover design (within subject design) in which
participants taste a fixed amount of six food stimuli during a scan session on
two occasions, while hungry and while sated. Stimuli are subdivided in (i)
three sweet caloric food-stimuli (solutions of glucose, fructose and
maltodextrin + sucralose), (ii) one non-sweet caloric food-stimulus (solution
of maltodextrin), (iii) one sweet non-caloric food-stimulus (solution of
sucralose) and (iv) one non-sweet non-caloric food-stimulus that is perceived
as neutral (control stimulus: water). The order in which participants are
exposed to these stimuli is randomized and counterbalanced. During a sensory
test subjective ratings for the food stimuli are obtained and individual taste
thresholds are assessed.

There are two interventions:
-Honger and sated; Participants will undergo one scan while sated (a meal will
be offered to the participants by the researchers) and one scan while hungry.
-Exposure to divers types of sugars and sweeteners; during the two scans
different types of sugars and sweeteners will be offered to the participant in
a randomized order.

The study will consist of an intake session (approx. 45 min), a training
session (approx. 30 min), a sensory test (approx. 45 min) and the actual
experiment (hunger scan session: approx. 60 min; sated scan session: approx. 90
min) on separate days. Participants will visit the sensory laboratory in
Wageningen once to take the sensory test. For the fMRI experiment, participants
will visit the MRI facility in Hospital Gelderse Vallei (Ede) twice. During
fMRI subjects will taste the stimuli, and rate their pleasantness (liking),
desirability (wanting) and sweetness. The study is non-therapeutic to the
participants. The risk associated with participation is negligible.