In what seems like a debatable outcome of interest, our brain exemplifies one of its capabilites - plasticity. In multiple studies researchers compared the grey matter (neuronal cell bodies) as well as white matter (composed of dendritic processes of neuronal cell bodies, commonly referred to as nerves) of people actively training juggling and control groups who don’t. With magnet resonance imaging (MRI)[ voxel based morphometry, VBM for black matter and Diffusion Tension Imaging, DTI) the participants’ brains were assessed and screened for changes.
In fact, both white and black matter in thee regions hMT/V5+ and the area around the intraparieteal sulcus showed an increase in density. These two areas are immediately connected to the occipital lobe and in this with the visual system. In fact, the two centeres are spacial representations of concept of gravity and the ability to follow moving objects leaving our field of vision 1. Interestingly, one group of researches also assessed the density of black matter three months after the obligatory training sessions. The results indicated a loss of the acquired density 2.
Explainations for these changes of density remain matter of debate. In terms of white matter 3 an increased degree of myelinization of the nerve fiber or an increase of the axon caliber may be accountable. Potential explainations for an increase in density of the assessed black matter may be a mere swelling of the neuron body or a better dendritic interconnectivity.
The mentioned results indicate structural changes induced by training. Interestingly, the finding of black matter changes occured in relation of hours invested in training regardless of actual success. Of further interest would be the precise time when the measured changes begin to degrade and further in what time intervals does one have to reassess those skills in order to prevent loss. The findings lead to a “use it or lose it” conclusion.
Interestingly, similar neuronal plasticity has also been reported in the development of a taxi driver’s map of London. To acquire a licence taxi drivers are - among others - oblidged to prensent their skills of orientation. The usual time span required to build up this map of London is 2 years (!). After this period, increased volume of grey matter can be detected in the right posterior hippocampus ( a region deep within out hemisphere).4 This finding seems to be especially striking since the hippocampus was thought to only be involved transiently in the process of memory.
In case you wanted to to learn how to juggle now, great 🎆! I highly recommend the tutorials of “Tailor Tries”5
Changes in grey matter induced by training, Arne May Univ. Regensburg, Nature (2014) ↩︎
De Sá Teixeira NA, Bosco G, Delle Monache S, Lacquaniti F. The role of cortical areas hMT/V5+ and TPJ on the magnitude of representational momentum and representational gravity: a transcranial magnetic stimulation study. Exp Brain Res. 2019 Dec;237(12):3375-3390. doi: 10.1007/s00221-019-05683-z. Epub 2019 Nov 14. PMID: 31728598. ↩︎
Scholz, J., Klein, M., Behrens, T. et al. Training induces changes in white-matter architecture. Nat Neurosci 12, 1370–1371 (2009). doi: 10.1038/nn.2412 ↩︎
Eleanor A. Maguire*†, David G. Gadian‡, Ingrid S. Johnsrude; Navigation-related structural change in the hippocampi of taxi drivers; Maguire et al. 1999 ↩︎