Cortical activation during voluntary contraction in spinal cord injured subjects

After human spinal cord injury (SCI), muscles are usually weak and fatigable,
characteristics that severely limit their function. An ability to maintain
adequate voluntary drive to muscles over time, termed central fatigue, is a
prevalent component of the functional deficits seen after SCI. While motor
evoked potentials represent one way to examine central fatigue, the afferent
contributions to the declines in muscle force have not been evaluated.

In humans with SCI, we propose to use functional magnetic resonance imaging
(fMRI) to: 1) examine the cortical areas that are activated during voluntary
contractions, and 2) evaluate how cortical activation patterns change as a
muscle is fatigued. We hypothesize that more areas of the brain are activated
during voluntary contractions performed by spinal cord injured subjects
compared to control subjects. In SCI subjects, we expect that the brain areas
activated during voluntary contractions will include areas related to muscles
that remain under voluntary control and areas that used to be activated during
contractions of muscles that are now paralyzed by SCI. With respect to central
fatigue, maintained contractions result in an increase in the intensity of the
active brain areas in control subjects. How brain activity in SCI subjects is
influenced by prolonged contractions is unknown. Thus, these fMRI studies are a
powerful way to explore in vivo changes in cortical function in SCI individuals
as they perform functional tasks.

Subjects perform contractions in an MR-scanner. During the contractions EMG and
brain activity is measured.

Subjects perform contractions and a fatigue test in an MR-scanner

Subjects produce force in an MR-scanner, no risks are known. During the
contraction the muscle is stimulated. The stiimulation could be a litle
painfull.