Effects of corticomotor excitability

Description

It has been shown previously that the corticomotor excitability of hand and arm muscles can be modulated by non-invasive brain stimulation techniques. By contrast, much less is known whether similar effects can be evoked in leg muscles since only one study has been performed previously that mainly focussed on reflex pathway activity (Zuur AT et al. 2009). Motor representations of the hands and legs differ in two important regards:

1. Hand/wrist representations occupy generally a larger area than leg/ankle representations and
2. Hand/wrist muscles are located more dorsally at the crown of the precentral gyrus, while shank representations are located more medially and ventrally, i.e. closer to the cingulate sulcus.

Never the less many neurological diseases affect foot control and gait and further insights into whether motor representations of the lower extremities can be modulated by non-invasive brain stimulation might be of large importance for future interventions in patients. Here we address this question in a series of 3 experiments:

1. we will test whether transcranial magnetic stimulation (TMS) over the leg/ankle representation changes corticomotor excitability of the tibialis anterior, a dorsiflexor of the ankle, to a similar degree as the corticomotor excitability of the index finger.
2. we will test whether TMS stimulation of the leg area modulates behavioural performance as tested by rhythmical ankle tracking task.
3. we will test whether a TMS intervention affects gait, which relies not only on movement control but also on vestibular-visual-tactile-motor integration.

Goal

This projects aims to evaluate the potential of transcranial magnetic stimulation to modulate corticomotor excitability of leg muscles. Furthermore it is aimed to assess the contribution of central motor control on local muscular control of the lower limb. Lastly, the impact of modulated corticomotor excitability on gait variability will be investigated.