Restorative Neurology and Neuroscience - Volume 30, issue 6

Authors: Shi, Xue-feng F. | Xu, Li-min | Li, Yao | Wang, Ting | Zhao, Kan-xing | Sabel, Bernhard A.

Article Type: Research Article

Abstract: Purpose: Amblyopia develops during a critical period in early visual development and is characterized by reduced visual sensory functions and structural reorganization of the brain. However, little is known about oculomotor functions in amblyopes despite the special role of eye movements in visual perception, task execution and fixation. Therefore, we studied the relationship of visual deficits in anisometropic amblyopia and fixational saccadic eye movements. Methods: We recruited twenty-eight anisometropic amblyopes and twenty-eight age-matched control subjects. Using a high-speed eye-tracker, fixational eye-movements of both eyes were recorded. A computerized fixational saccadic component analysis of eye-movement waveforms was developed to quantify the …parameters of fixational saccades (FSs) and a simulation model was developed to help explain the FS performances. Results: Amblyopic eyes, but not control eyes, showed fewer FSs, but these had increased amplitudes, increased peak velocities, and longer inter-saccadic intervals. The reduced FSs occurred mainly in the 0- to 0.6-degree amplitude range, and the probability of FSs with larger amplitudes and longer inter-saccadic intervals was significantly higher than in controls. A new simulation model analysis suggests that an excitatory-inhibitory activity imbalance in superior colliculus may explain these FSs changes. Conclusions: We propose that the abnormal visual processing and circuitry reorganization in anisometropic amblyopia has an impact on the fixational saccade generation. We see two possible interpretations: (i) altered FSs may be an attempt of the visual system to adapt to the deficit, trying to capture more information from a broader spatial domain of the visual world so as to enhance the contrast sensitivity to low spatial frequencies viewed by the amblyopic eye, or (ii) it may be the cause of amblyopia or a contributing factor to the original deficit that aggravates the early deprivation. Show more

Keywords: Anisometropic amblyopia, fixational eye movements, microsaccade, amplitude, inter-saccadic interval, excitation-inhibition balance

DOI: 10.3233/RNN-2012-129000

Citation: Restorative Neurology and Neuroscience, vol. 30, no. 6, pp. 445-462, 2012

Authors: Keilhoff, Gerburg | Wiegand, Stefan | Fansa, Hisham

Article Type: Research Article

Abstract: Purpose: The regeneration of adult peripheral nerves is a complex, multi-step process that is often incomplete, resulting in pain and/or loss of muscle innervation. Success is based on a fine-tuned interplay of neurons, Schwann cells, fibrocytes and macrophages realizing Wallerian degeneration, fiber regrowth and revascularization. Following trauma, the nerves distal to the injury site undergo Wallerian degeneration, an event that includes the phagocytosis of debris and the formation of Schwann cell scaffolds that guide the sprouting nerve fibers. The actin cytoskeleton is critical to all of these processes; therefore, activators of the cytoskeleton such as Rho GTPases and RhoGEFS such …as Vav2 and Vav3 represent attractive targets for therapeutic intervention. Methods: Sciatic nerve segments were surgically resected and reconstructed, and the degenerative/regenerative outcomes were compared in wild-type and Vav2/3 double knockout mice. Results: Vav2/3 knockout nerves showed delayed Wallerian degeneration and revascularization, a broadly control-like morphometry of the regenerated nerves including remyelination, and contradictory motor function recovery, whereby impaired toe spreading was accompanied by enhanced muscle weight recreation. Conclusions: The data suggest that Vav2 and Vav3 are required for normal peripheral nerve degeneration/regeneration, revascularization and functional recovery. Functional redundancy, compensatory mechanisms, and muscle (pseudo)hypertrophy, however, impede the understanding of and intervention in Vav-mediated processes. Show more

Keywords: Nerve graft, regeneration, revascularization, sciatic nerve, Vav2/3 knockout mice, Wallerian degeneration

DOI: 10.3233/RNN-2012-120230

Citation: Restorative Neurology and Neuroscience, vol. 30, no. 6, pp. 463-479, 2012

Authors: Bianco, Giovanni | Feurra, Matteo | Fadiga, Luciano | Rossi, Alessandro | Rossi, Simone

Article Type: Research Article

Abstract: Purpose: To investigate whether repeated sessions of motor imagery and action observation modulate corticospinal excitability (CE) over time, whether these processes are susceptible of any training effect and if such effect might be different for the dominant and non dominant hemisphere. Methods: 11 subjects underwent three sessions, spaced 5–7 days, of single-pulse Transcranial Magnetic Stimulation (TMS) of right and left primary motor cortex. Subjects were asked to imagine or observe pinch-grip actions with either hand. Motor evoked potentials (MEPs) were recorded bilaterally from the First Dorsal Interosseus muscle (FDI), acting as main agonist during precision grip. Results: Motor imagery consistently …enhanced CE with respect to action observation, regardless of hemispheric lateralization and of separate testing sessions. However, motor imagery increased CE only when measured over the non-dominant hemisphere, during the third session with respect to the first one. The increase of CE induced by action observation in the first session was not further modified throughout the remaining two sessions, in either hemisphere. Conclusions: Results suggest that motor imagery is sustained by a cortical network susceptible to training effects only for the non-dominant hemisphere. Such an effect was lacking for action observation, likely because of the innateness of these mechanisms. Results might have implications for rehabilitative purposes. Show more

Keywords: Transcranial magnetic stimulation, learning, motor imagery, actions observation, mirror neurons

DOI: 10.3233/RNN-2012-120241

Citation: Restorative Neurology and Neuroscience, vol. 30, no. 6, pp. 481-489, 2012

Authors: Sun, Fen | Xie, Lin | Mao, XiaoOu | Hill, Justin | Greenberg, David A. | Jin, Kunlin

Article Type: Research Article

Abstract: Purpose: Clinical studies suggest a correlation between changes in activity of the contralesional cerebral cortex and spontaneous recovery from stroke, but whether this is a causal relationship is uncertain. Methods: Young adult Sprague-Dawley male rats underwent unilateral or bilateral permanent distal middle cerebral artery occlusion (dMCAO). Infarct volume was determined by 2,3,5-triphenyltetrazolium chloride (TTC) staining 24 hr after dMCAO, and functional outcome was assessed 1–28 days after dMCAO using the ladder rung walking and limb placing tests. Results: Infarct volume was unchanged, but functional neurological deficits were reduced 1 day after bilateral compared to unilateral dMCAO. Conclusions: Activity in the …contralesional cerebral cortex may inhibit functional motor recovery after experimental stroke. Show more

Keywords: Stroke, ischemia, recovery, rat

DOI: 10.3233/RNN-2012-120254

Citation: Restorative Neurology and Neuroscience, vol. 30, no. 6, pp. 491-495, 2012

Authors: Pellegrino, G. | Tomasevic, L. | Tombini, M. | Assenza, G. | Bravi, M. | Sterzi, S. | Giacobbe, V. | Zollo, L. | Guglielmelli, E. | Cavallo, G. | Vernieri, F. | Tecchio, F.

Article Type: Research Article

Abstract: Purpose: In the chronic phase of stroke brain plasticity plays a crucial role for further motor control improvements. This study aims to assess the brain plastic reorganizations and their association with clinical progresses induced by a robot-aided rehabilitation program in chronic stroke patients. Methods: 7 stroke patients with an upper limb motor impairment in chronic phase underwent a multi-modal evaluation before starting and at the end of a 12-week upper-limb neurorehabilitation program. Fugl-Meyer Assessment (FMA) Scale scores and performance indices of hand movement performance (isometric pinch monitored through a visual feedback) were collected. Cerebral reorganizations were characterized by 32-channel electroencephalography …(EEG) focusing on ipsilesional and contralesional resting state properties investigating both bipolar derivations overlying the middle cerebral artery territory and the primary somatosensory sources (S1) obtained through the Functional Source Separation (FSS) method. Power Spectral Density (PSD) and interhemispheric coherence (IHCoh) at rest were measured and correlated with clinical and hand control robot-induced improvements. Results: After the robotic rehabilitation we found an improvement of FMAS scores and hand motor control performance and changes of brain connectivity in high frequency rhythms (24–90 Hz). In particular, the improvement of motor performance correlated with the modulation of the interhemispheric S1 coherence in the high beta band (24–33 Hz). Conclusions: Recently it has been shown that an upper limb robot-based rehabilitation improves motor performance in stroke patients. We confirm this potential and demonstrate that a robot-aided rehabilitation program induces brain reorganizations. Specifically, interhemispheric connectivity between primary somatosensory areas got closer to a ‘physiological level’ in parallel with the acquisition of more accurate hand control. Show more

Keywords: Chronic stroke, robotic rehabilitation, resting state EEG, primary somatosensory hand area (S1), interhemispheric coherence, Functional Source Separation (FSS)

DOI: 10.3233/RNN-2012-120227

Citation: Restorative Neurology and Neuroscience, vol. 30, no. 6, pp. 497-510, 2012

Authors: Mohammad-Gharibani, Payam | Tiraihi, Taki | Mesbah-Namin, Seyed Alireza | Arabkheradmand, Jalil | Kazemi, Hadi

Article Type: Research Article

Abstract: Purpose: Deficits involving GABAergic neurons have been reported in aging, central nervous trauma and neurodegenerative disorders; bone marrow stromal cells (BMSCs) have been proposed as a feasible source of donor cells in replacement cell therapy. In this study, the effects of creatine on transdifferentiating BMSCs into GABAergic-like neurons were evaluated in vitro. Methods: The BMSCs were isolated from adult rats, preinduced by β-mercaptoethanol (BME) and retinoic acid (RA), and then induced by creatine into GABAergic-like neurons. The cells were characterized using different differentiation markers. The functionality of the differentiated cells was evaluated using FM1-43. Results: The isolated cells expressed Oct-4 …and were immunoreactive to fibronectin and CD44. The highest percentages of cells immunoreactive to nestin and neurofilament-68 were found at the second day of preinduction. At the induction stage, there were increases in the number of cells immunoreactive to neurofilament-200, MAP-2, synapsin I, synaptophysin, and NeuN. The percentages of the immunoreactive cells to GABAergic neuron markers increased. The optimal induction dose was 5 mM. The dose of 10 mM showed a decline in the expression of most of these markers. The functionality test indicated that the synaptic vesicles were released upon stimulation. Conclusion: Creatine can induce the differentiation of BMSCs to the GABAergic neuronal phenotype within one week. Show more

Keywords: BMSCs, GABAergic-like neurons, induction, creatine

DOI: 10.3233/RNN-2012-100155

Citation: Restorative Neurology and Neuroscience, vol. 30, no. 6, pp. 511-525, 2012

Article Type: Correction

DOI: 10.3233/RNN-2012-129001

Citation: Restorative Neurology and Neuroscience, vol. 30, no. 6, pp. 527-528, 2012

Article Type: Other

Citation: Restorative Neurology and Neuroscience, vol. 30, no. 6, pp. 529-533, 2012