Reward and the brain of healthy young adults and healthy older adults.

To perform optimally in daily life we use knowledge about success and failure
in the past. This knowledge is continuously updated based on the feedback we
receive from our environment. Based on this feedback we learn which behaviour
in response to stimuli or events was successful or rewarding and which
behaviour was not, that is, we learn to associate certain stimuli or events
with rewards. These stimulus-reward associations will subsequently influence
future behaviour. For instance, previous studies examined neural responses to
symbols that had a higher probability of reward (i.e. probability for losing or
gaining money). However, these studies did not look at how the learning of
stimulus-specific reward associations was implemented on a neural level and how
these stimulus-reward associations would be updated. In the present study we
aim to identify those neural underpinnings of learning and updating of
stimulus-reward associations.

The present study aims to identify processes underlying feedback related
updating of stimulus-reward associations.

The study will combine behavioural and event*related fMRI measures. While in
the scanner, participants will place a bet on either a face or a house. In a
block of 20 trials either the face or the house has a higher probability of
gaining money. To maximize their earnings, the participants has to learn which
one has a higher probability of losing or gaining money. After 20 trials the
probability is shuffled and the learning process starts over until a total of
24 blocks is completed. Behaviourally, we can track the learning progress
within each block, additionally we can map when participants decide to switch
from betting on houses to faces or vice versa (e.g., choice sequence: house,
house, house, face). The design is double blind; neither the participants nor
researcher knows which stimulus is associated with a higher probability of
gaining or losing money. Participants will be fully informed about the nature
and parameters of the study and paradigm before the experimental session.

In the MRI-scanner participants will be exposed to a field-strenght of 3 Tesla
and scanner noise. Thus far there is no evidence to suggest that exposing
humand to a magentic field of this strength has a negative influence on health.
With regard to the noise earplugs and headphones will be provided. Subjects
will not benefit directly from participating in the study, however the data
collected during this study will enhance understanding of the neural basis of
learning by young and elderly individuals.