Transspinal constant-current long-lasting stimulation: a new method to induce cortical and corticospinal plasticity

Area of Science:

• Neuroscience
• Physiology
• Rehabilitation Medicine

Background:

• Functional neuroplasticity is a known outcome of stimulation and motor training.
• Transcutaneous spinal stimulation is primarily used for pain relief but may also influence neuroplasticity due to the spinal cord's role in signal integration.

Purpose of the Study:

• To investigate if long-lasting noninvasive cathodal (c-tsCCS) and anodal (a-tsCCS) transspinal constant-current stimulation over the thoracolumbar enlargement can induce cortical, corticospinal, and spinal neuroplasticity.

Main Methods:

• Twelve healthy subjects received either 40 minutes of c-tsCCS or a-tsCCS in a blinded, randomized manner.
• Measurements included afferent-mediated motor evoked potential (MEP) facilitation, subthreshold transcranial magnetic stimulation (TMS)-mediated flexor reflex facilitation, MEP and transspinal evoked potential (TEP) recruitment curves, and postactivation depression of the soleus H reflex and TEPs before and after stimulation.

Main Results:

• Both c-tsCCS and a-tsCCS reduced afferent-mediated MEP facilitation and altered TMS-mediated flexor reflex facilitation in a polarity-dependent manner.
• Tibialis anterior MEPs increased with both stimulation types, and TEP recruitment curves were altered in a muscle- and polarity-dependent manner.
• Soleus H-reflex postactivation depression decreased after a-tsCCS but not c-tsCCS; TEP postactivation depression remained unchanged.

Conclusions:

• Cathodal and anodal transspinal constant-current stimulation exhibit distinct effects on cortical and corticospinal excitability.
• This noninvasive stimulation method holds potential for inducing targeted neuroplasticity in humans.