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Sensory cortical re-mapping following upper-limb amputation and subsequent targeted reinnervation: A case report

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      Abstract

      This case study demonstrates the change of sensory cortical representations of the residual parts of the arm in an individual who underwent a trans-humeral amputation and subsequent targeted reinnervation (TR). As a relatively new surgical technique, TR restores a direct neural connection from amputated sensorimotor nerves to specific target muscles. This method has been successfully applied to upper-limb and lower-limb amputees, and has shown effectiveness in regaining control signals via the newly re-innervated muscles. Correspondingly, recent study results have shown that motor representations for the missing limb move closer to their original locations following TR. Besides regaining motor control signals, TR also restores the sensation in the re-innervated skin areas. We therefore hypothesize that TR causes analogous cortical sensory remapping that may return closer to their original locations. In order to test this hypothesis, cortical activity in response to sensory-level electrical stimulation in different parts of the arm was studied longitudinally in one amputated individual before and up to 2 years after TR. Our results showed that 1) before TR, the cortical response to sensory electrical stimulation in the residual limb showed a diffuse bilateral pattern without a clear focus in either the time or spatial domain; and 2) 2 years after TR, the sensory map of the reinnervated median nerve reorganized, showing predominant activity over the contralateral S1 hand area as well as moderate activity over the ipsilateral S1. Therefore, this work provides new evidence for long-term sensory cortical plasticity in the human brain after TR.

      Highlights

      • We studied sensory cortical mapping before and after targeted reinnervation (TR).
      • EEG was recorded when stimulating the intact finger and the residual nerve.
      • The experiment was repeated longitudinally through 2 years in a single subject.
      • The missing finger representation changed back to a more normal pattern post-TR.
      • Neural mechanisms underlying TR-induced sensory cortical remapping are discussed.

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      Most cited references 31

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      Low resolution electromagnetic tomography: a new method for localizing electrical activity in the brain.

      This paper presents a new method for localizing the electric activity in the brain based on multichannel surface EEG recordings. In contrast to the models presented up to now the new method does not assume a limited number of dipolar point sources nor a distribution on a given known surface, but directly computes a current distribution throughout the full brain volume. In order to find a unique solution for the 3-dimensional distribution among the infinite set of different possible solutions, the method assumes that neighboring neurons are simultaneously and synchronously activated. The basic assumption rests on evidence from single cell recordings in the brain that demonstrates strong synchronization of adjacent neurons. In view of this physiological consideration the computational task is to select the smoothest of all possible 3-dimensional current distributions, a task that is a common procedure in generalized signal processing. The result is a true 3-dimensional tomography with the characteristic that localization is preserved with a certain amount of dispersion, i.e., it has a relatively low spatial resolution. The new method, which we call Low Resolution Electromagnetic Tomography (LORETA) is illustrated with two different sets of evoked potential data, the first showing the tomography of the P100 component to checkerboard stimulation of the left, right, upper and lower hemiretina, and the second showing the results for the auditory N100 component and the two cognitive components CNV and P300. A direct comparison of the tomography results with those obtained from fitting one and two dipoles illustrates that the new method provides physiologically meaningful results while dipolar solutions fail in many situations. In the case of the cognitive components, the method offers new hypotheses on the location of higher cognitive functions in the brain.
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        Functional imaging with low-resolution brain electromagnetic tomography (LORETA): a review.

        This paper reviews several recent publications that have successfully used the functional brain imaging method known as LORETA. Emphasis is placed on the electrophysiological and neuroanatomical basis of the method, on the localization properties of the method, and on the validation of the method in real experimental human data. Papers that criticize LORETA are briefly discussed. LORETA publications in the 1994-1997 period based localization inference on images of raw electric neuronal activity. In 1998, a series of papers appeared that based localization inference on the statistical parametric mapping methodology applied to high-time resolution LORETA images. Starting in 1999, quantitative neuroanatomy was added to the methodology, based on the digitized Talairach atlas provided by the Brain Imaging Centre, Montreal Neurological Institute. The combination of these methodological developments has placed LORETA at a level that compares favorably to the more classical functional imaging methods, such as PET and fMRI.
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          The reorganization of somatosensory cortex following peripheral nerve damage in adult and developing mammals.

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            Author and article information

            Affiliations
            [a ]Department of Physical Therapy and Human Movement Sciences, Northwestern University, IL, USA
            [b ]Department of Biomedical Engineering, Northwestern University, IL, USA
            [c ]Department of Physical Medicine and Rehabilitation, Northwestern University, IL, USA
            [d ]Center for Bionic Medicine, Rehabilitation Institute of Chicago, IL, USA
            Author notes
            [* ]Corresponding author at: Room 1113, 645 N Michigan Ave Physical Therapy and Human Movement Sciences Department, Northwestern University, Chicago, IL 60611, USA. Tel.: +1 312 908 9060; fax: +1 312 908 0741. j-yao4@ 123456northwestern.edu
            Contributors
            Journal
            Neuroimage Clin
            Neuroimage Clin
            NeuroImage : Clinical
            Elsevier
            2213-1582
            20 January 2015
            2015
            20 January 2015
            : 8
            : 329-336
            4473101
            S2213-1582(15)00011-X
            10.1016/j.nicl.2015.01.010
            © 2015 The Authors. Published by Elsevier Inc.

            This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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