The Olympic brain. Does corticospinal plasticity play a role in acquisition of skills required for high-performance sports?

Abstract

Non-invasive electrophysiological and imaging techniques have recently made investigation of the intact behaving human brain possible. One of the most intriguing new research areas that have developed through these new technical advances is an improved understanding of the plastic adaptive changes in neuronal circuitries underlying improved performance in relation to skill training. Expansion of the cortical representation or modulation of corticomotor excitability of specific muscles engaged in task performance is required for the acquisition of the skill. These changes at cortical level appear to be paralleled by changes in transmission in spinal neuronal circuitries, which regulate the contribution of sensory feedback mechanisms to the execution of the task. Such adaptive changes also appear to be essential for the consolidation of a memory of performance of motor tasks and thus for the lasting ability of performing highly skilled movements such as those required for Olympic sports.

Figure 1. The purpose of this figure is to depict schematically some of the many different ways in which plasticity in the human motor cortex can be studied physiologically in health and disease

TMS application over the hand representation of M1 (Yousry et al. 1997) in a representative subject showing: A, maximum calculated induced field for this particular 8-shaped coil (light red dot) and position (green oval) using a stereotactic TMS device (Nexstim in this case) which localizes the target scalp position (in this case M1) on the same subject anatomical MRI; B, representative distribution of the motor map for a hand muscle (scalp locations which, upon TMS stimulation, elicited MEP responses from the target hand muscles) before training in a normal volunteer; C, centrifugal enlargement of the motor map (increase in the number of scalp positions which, upon stimulation, evoked MEP in target hand muscles) in a healthy volunteer, often described after motor training (see text). Note that a similar result in terms of centrifugal expansion of a motor map could be induced by an expansion in the motor cortical representation of that muscle or by an increase in motor cortical or spinal excitability of a topographically unchanged motor cortical representation (Ridding & Rothwell, 1995); D, enlargement in the motor map that is directionally more specific, showing a medial expansion of a hand muscle representation in M1 towards the upper arm representations, a more precise example of representational plasticity, as shown for example in amputees with phantom limb pain (Karl et al. 2001). For a detailed discussion of the differences between C and D see Ridding & Rothwell (1995), Ziemann et al. (1998, ; E, example of situations in which responses from a left hand or forearm muscles can be obtained by stimulation of the contralesional left M1 in cases of hemispherectomy (red posterior circle in the intact hemisphere) or even from the contralesional dorsal premotor cortex (red anterior circle) in patients with more severe forms of stroke (Benecke et al. 1991; Cohen et al. 1991; Johansen-Berg et al. 2002). The black oval depicts in diagrammatic form a large stroke or hemispherectomy engaging the right hemisphere; F, example of the involvement of ipsilesional dorsal premotor cortex, anterior to M1, in motor control of the paretic hand in patients with less severe stroke (Fridman et al. 2004).