The aim of the study was to see whether learning a new skill - in this case, juggling - would have an effect on the brains of participants.
The participants for this study were 24 volunteers between the ages of 20 and 24. There were 21 females and 3 males. All participants were non-jugglers at the start of the study. Each participant had an MRI scan at the start of the study to serve as a base rate for grey matter and brain structure.
Participants were allocated to one of two conditions - the jugglers and the non-jugglers. Those that were in the juggling condition were taught a three-ball cascade juggling routine. They were asked to practice this routine and to notify the researchers when they had mastered it. At that point the jugglers had a second MRI scan. After the scan, they were told not to juggle anymore and then a third and final scan was carried out three months later. The non-juggling group served as a control group for the duration of the study.
To analyse the MRI scans, the researchers used voxel-based morphometry [VBM] to determine if there was significant differences in neural density (grey matter) in the brains of jugglers vs. non-jugglers. From the baseline scans, they found no significant regional differences in grey matter between the two conditions. However, the jugglers showed a significantly larger amount of grey matter in the mid-temporal area in both hemispheres - an area associated with visual memory. Three months after the participants stopped juggling - when many were no longer able to carry out the routine - the amount of grey matter in these parts of the brain had decreased.
There was no change over the duration of the study in the non-juggling sample.
Interestingly, it appears that juggling relies more on visual memory - that is, the perception and spatial anticipation of moving objects - than on “procedural memory” which would more likely show change in the cerebellum or basal ganglia.