Cortical plasticity induced by different degrees of peripheral nerve injuries: a rat functional magnetic resonance imaging study under 9.4 Tesla

Abstract

BackgroundMajor peripheral nerve injuries not only result in local deficits but may also cause distal atrophy of target muscles or permanent loss of sensation. Likewise, these injuries have been shown to instigate long-lasting central cortical reorganization.MethodsCortical plasticity changes induced after various types of major peripheral nerve injury using an electrical stimulation technique to the rat upper extremity and functional magnetic resonance imaging (fMRI) were examined. Studies were completed out immediately after injury (acute stage) and at two weeks (subacute stage) to evaluate time affect on plasticity.ResultsAfter right-side median nerve transection, cortical representation of activation of the right-side ulnar nerve expanded intra-hemispherically into the cortical region that had been occupied by the median nerve representation After unilateral transection of both median and ulnar nerves, cortical representation of activation of the radial nerve on the same side of the body also demonstrated intra-hemispheric expansion. However, simultaneous electrical stimulation of the contralateral uninjured median and ulnar nerves resulted in a representation that had expanded both intra- and inter-hemispherically into the cortical region previously occupied by the two transected nerve representations.ConclusionsAfter major peripheral nerve injury, an adjacent nerve, with similar function to the injured nerve, may become significantly over-activated in the cortex when stimulated. This results in intra-hemispheric cortical expansion as the only component of cortical plasticity. When all nerves responsible for a certain function are injured, the same nerves on the contralateral side of the body are affected and become significantly over-activated during a task. Both intra- and inter-hemispheric cortical expansion exist, while the latter dominates cortical plasticity.

Experimentelle Modelle für selektive Nerventransfers der oberen Extremität: Modellbeschreibung und neurophysiologische Effekte

“…Außerdem ist der sensomotorische Ausfall nach UN-Transfer geringer als beim N. medianus, was vor allem im Rattenmodell relevant ist, da so Autotomien verhindert werden können [17]. Dieses Problem, welches in der UE sehr häufig auftritt, stellt bei der OE kein Problem dar, da das sensible Innervationsgebiet des N. ulnaris in der Rattenpfote verhältnismäßig gering ist [18]. Durch etliche Synergien im physiologischen Bewegungsablauf zwischen MCN und UN, was in nur wenigen Nervengruppen an der OE gegeben ist, zeigte sich postoperativ eine schnelle kortikale Re-edukation der Ratte.…”

Neuroplasticity and MRI: A perfect match

“…Several other experimental models displaying cross-modal plasticity have been investigated using fMRI and resting state fMRI (rsfMRI ; Table 1) (Pelled, Chuang et al 2007, Pawela, Biswal et al 2010, Yu, Wang et al 2010, Li, Hettinger et al 2013 or DTI to shed light on alterations in structural connectivity e.g. (Ramu, Herrera et al 2008, Wrigley, Gustin et al 2009).…”

Clinical and neurobiological advances in promoting regeneration of the ventral root avulsion lesion

“…This observation was confirmed in rat neonates where, following a spinal root lesion, the adjacent intact C7 motoneuron contribution to the biceps muscle increased four-fold . Using functional MRI imaging of the sensory motor cortex or spinal electrophysiological measurements it was shown that, after nerve injury, adjacent spinal cord segments and corresponding cortical areas may become significantly over-activated, compensating for the loss of function (Havton & Kellerth, 2004;Li et al, 2013). These results suggest that intact axons from adjacent segments could potentially take over the innervation as a result of sprouting.…”