PhD defence Nele Zickert
Nele Zickert (EvolGen)
Promotor: Prof. A.G.G. Groothuis; copromotor: Dr R.H. Geuze (UMCG)
Functional and evolutionary aspects of lateralization
This thesis examines functional and evolutionary aspects of brain lateralization and behavioural lateralization. In order to test hypotheses on why certain cognitive functions are lateralized in the human brain, we measured lateralization of a language task and a spatial orientation task with functional transcranial Doppler in a group of participants while also recording the performance of these tasks. We then tested if strength, direction, and pattern of lateralization were related to task performance. A subset of these participants underwent a structural MRI scan of their brain. From these images we extracted thickness measurements of the corpus callosum – the white matter structure connecting the hemispheres. We analyzed if corpus callosum thickness had an influence on lateralization and task performance.
Left-handedness in humans is associated with several popular myths and hypotheses, since it persists in a stable minority of about 10% compared to right-handedness. We tested a selection of hypotheses in a large Dutch sample based on an online survey. We tested the relation of hand preference to fitness-related traits like health problems, creativity, aggression, and number of offspring. We furthermore tested the association of the same fitness-related traits with hand skill, based on a test of fine motor skills. One hypothesis on why humans are largely sharing the same hand preference states, that it might be easier to learn motoric skills from a teacher with the same hand preference. We tested this hypothesis by analyzing the success of replicating a nautical knot from a teacher of the same or opposite handedness.