Attention-related changes in short-term cortical plasticity help to explain fatigue in multiple sclerosis

Abstract

Short-term and long-term plasticity mechanisms are abnormal in MS possibly owing to widespread changes in ion-channel expression. Fatigue in MS reflects disrupted cortical attentional networks related to movement control.

Abnormal Resting‐State Neural Activity and Connectivity of Fatigue in Parkinson's Disease

“…Coincidentally, a recent study of a patient with right MFG resection clarified that right MFG was a crucial node of attentional circuits, and it controlled over both ventral and dorsal attention networks . What's more, some evidence has already illuminated that attention deficit may be related to the presence of fatigue . For example, Jau‐Shin Lou et al reported PD patients with fatigue had abnormal attention network compared with controls.…”

The Potential Role of Neurophysiology in the Management of Multiple Sclerosis-Related Fatigue

“…Morgante et al (40) found that PwMS have reduced plasticity demonstrated by the lack of MEP increase after the 5-Hz rTMS protocol, without any difference between fatigued and not-fatigued patients. Conte et al (58) found instead that, during an attention-demanding task, the response to 5-Hz rTMS and paired associative stimulation (PAS)-a neuromodulatory protocol consisting of repetitive peripheral nerve stimulation combined with TMS over the contralateral motor cortex (59)significantly differs between PwMS with or without fatigue. Indeed in fatigued patients both PAS and 5-Hz stimulation did not produce the expected changes in cortical excitability, while in not-fatigued patients they both increased the MEP response, although less efficiently than in healthy subjects.…”

“…Indeed single-pulse TMS studies demonstrated that in MS patients the pathogenesis of fatigue is not driven by mechanisms directly related to corticospinal functioning but is due to alterations in structures located upstream to the primary motor cortex (39). In particular, both EEG (34) and TMS studies (37,40,58) pointed out the role of cortical areas involved in movement preparation and attention. For instance, Sandroni et al (83) found that, in PwMS, fatiguing tasks are associated with a change in ERP without significant modifications in MEP parameters, thus suggesting that fatigue affects neural processes acting after stimulus evaluation and before the activation of the primary motor cortex.…”

The use of transcranial magnetic stimulation as a treatment for movement disorders: A critical review

“…TMS can also assess inputs to M1 from other areas by observing how the MEP is modulated by a preceding stimulus, the latter being either a magnetic pulse applied over a different cortical area or a stimulus activating afferents from various sensory modalities . It is also possible to apply repetitive TMS (rTMS) in the form of short or long trains, either regular or patterned, or associated with diverse cortical or sensory stimulation . These protocols can induce long‐term changes in cortical excitability that are the result of changes in synaptic plasticity.…”

“…PAS can increase or decrease MEPs for 30 minutes similarly to rTMS. Novel PAS protocols, using a cortical–cortical approach or different sensory stimuli, have also been applied in humans …”