Vicarious function within the human primary motor cortex?: A longitudinal fMRI stroke study

 I can't find any definition of vicariate that isn't religious, so go ask your competent? doctor how this will get you recovered.

But this does exist; Vicariation is the ability of one part of the brain to take over the function of another, especially after an injury:

Vicarious function within the human primary motor cortex?: A longitudinal fMRI stroke study

Assia Jaillard, 1,4 Chantal Delon Martin, 4 Katia Garambois, 1 Jean Franc ¸ois Lebas 2,4 and Marc Hommel 1,3,4 Correspondence to: Dr Assia Jaillard, De ´partement de Neurologie—Unite ´ Neuro-vasculaire, Centre Hospitalier Universitaire de Grenoble, BP 217-38043 Grenoble Cedex 9, France E-mail: AJaillard@chu-grenoble.fr 1 Department of Neurology, Stroke Unit, 2 Unite ´ de RMN Service of Neuroradiology, 3 Inserm, CIC 003, University Hospital and 4 Inserm, U594-University Joseph Fourier, Grenoble, France 

Summary 

While experimental studies in the monkey have shown that motor recovery after partial destruction of the hand motor cortex was based on adjacent motor reorganization, functional MRI (fMRI) studies with isolated primary motor cortical stroke have not yet been reported in humans. Based on experimental data, we designed a study to test if recovery after stroke within primary motor cortex (M1) was associated with reorganization within the surrounding motor cortex, i.e. the motor cortex was able to vicariate. Since motor recovery is time-dependent and might be inflected according to the tested task, the delay after stroke and two motor tasks were included in our design. We examined four patients with one ischaemic stroke limited to M1, and four sex- and age-matched healthy controls in a temporally balanced prospective longitudinal fMRI study over three sessions: <20 days, 4 months and 2 years after stroke. The paradigm included two motor tasks, finger tapping (FT) and finger extension (FE). Distinct patterns of motor activation were observed with time for FT and FE. At the first session, FT-related activation was lateralized in the ipsilateral hemisphere while FE-related activation was contralateral, involving bilateral cerebellar regions for both tasks. From 4 months, skilled motor recovery was associated with contralateral dorsal premotor and sensorimotor cortex and ipsilateral cerebellum motor-related activations, leading to lateralzed motor patterns for both tasks. For the left recovered hand, FT and FE-related activations within M1 were more dorsal in patients than in controls. This dorsal shift progressively increased over 2 years, reflecting functional reorganization in the motor cortex adjacent to the lesion. In addition, patients showed a reverse representation???of FT and FE within M1, corresponding to a greater dorsal shift for FT than for FE. This functional dissociation might reflect the structural subdivision of M1 with two distinct finger motor representations within M1. Recovery of FT, located within the lesioned depth of the rolandic sulcus in controls, might be related to the re-emergence of a new representation in the intact dorsal M1, while FE, located more dorsally, underwent minor reorganization. This is the first fMRI study of humans presenting with iso- lated M1 stroke comparable with experimental lesions in animals. Despite the small number of patients, our findings showing the re-emergence of a fingers motor task in the intact dorsal M1 instead of in ventral M1 are consistent with ‘vicariation’ models of stroke recovery.