Cognitive tuning of corticospinal excitability during human gait: adaptation to the phase

Abstract

The aim of this study was to investigate how the cognitive tuning of corticospinal (CS) excitability adapts to the type of evoked-movement (Flexion vs. Extension) during human gait. Transcranial magnetic stimulation (TMS) was used both as a central perturbation evoking a movement and as a tool for quantifying the CS excitability of the muscles under study (RF/BF). In the first condition (Dst), the TMS occurred at mid-stance, inducing hip extension, whereas in the second condition (Dsw), the TMS occurred at the beginning of the swing phase, inducing hip flexion. In both conditions, the subjects were asked to cognitively prepare to either not intervene (NINT) or to compensate (COMP) for the evoked-movements. The results showed that, regardless of the type of evoked-movement, preparing to compensate resulted in a selective increase in the CS excitability to those muscles that would be involved in counteracting the possible central perturbation, i.e. the hip extensor muscle (BF) to compensate for an evoked flexion during the swing phase or the hip flexor muscle (RF) to compensate for an evoked extension during the stance phase. This latter result offers the first evidence of a modulation in CS excitability to the proximal muscles during the stance phase. In conclusion, the cognitive tuning of CS excitability was found to adapt to the gait phases. Moreover, the same selective preparation strategy was observed whether the central perturbation occurred during the stance or the swing phase of the step cycle.

Task-specific changes in motor evoked potentials of lower limb muscles after different training interventions

“…For such immediate effects, transcranial magnetic stimulation (TMS) studies identified predominantly cortical plasticity such as increased motor cortex excitability and enlargement of motor cortical representation (Classen et al, 1998;Pascual-Leone et al, 1994, 1995. Analogous to hand function, gait and postural control are highly adaptable and underlie specific cortical control (Bonnard et al, 2002;Camus et al, 2004;Christensen et al, 2001;Schubert et al, 1999;Taube et al, 2006). Likewise, short-term motor skill training in the leg muscles induces increased motor cortex excitability, which is consistent with findings in the upper limb suggesting a similar underlying principle (Perez et al, 2004).…”

Training with robot-applied resistance in people with motor-incomplete spinal cord injury: Pilot study

“…Indeed, it has been shown that corticospinal excitability is tuned according to the level of cognitive engagement during gait [67][68]. In addition, the improvement in locomotor control in people with m-iSCI is associated with increased corticospinal drive to leg muscles [69][70].…”

Weak motor cortex contribution to the quadriceps activity during human walking

“…As compared to ankle muscles, which are involved in foot placement during locomotion for which the corticospinal control is crucial [1], Quadriceps may be involved in the postural control, which, in the light of the present results, could be assigned to sub-cortical structures. However, the present results were obtained during treadmill locomotion, without perturbation, and we assume that the cortical contribution to Quadriceps activity might be reinforced during volitional step control [5,25,26].…”