Structure and function of the human subthalamic nucleus

The overall aim of this thesis was to study the structure and function of the human STN. The first part of this thesis focused on describing several anatomical features of the STN using ultra-high field 7T MRI. The results of Chapter 2 show that it is feasible to manually segment the BG but that the choice of MRI sequence influences the visibility of the structure and that the anatomical variability is large. Chapter 3 showed that healthy aging has an effect on the location of the STN that highlights the need to develop atlases that take aging into account. Chapter 4 reviewed the empirical literature regarding the number of subdivisions in the STN and, contrary to popular believes, comes to the conclusion that there is no clear empirical evidence for well defined "limbic", "cognitive", and "motor" subparts. Chapter 5 presents the results from an empirical study providing clear evidence for a gradual organization of iron in the STN. The findings of chapter 4 and 5 are in favour of a theoretical model of the BG in which cognitive, motor, and limbic information are integrated instead of segregated.
The second part of this thesis focused on the function of the STN and its role in perceptual decision-making. First, an fMRI meta-analysis was conducted. The fMRI meta-analysis, which is described in Chapter 6, showed that there is some evidence for the involvement of the BG in decision-making but did not provide any evidence for the involvement of the STN. This was in direct contrast to the findings described in Chapter 7 where evidence is provided for the involvement of the STN in perceptual decision-making.
Finally, chapter 8 summarizes the empirical findings and discusses how anatomy in combinations with neurocomputational models can help understand the brain.