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P22.6 Rapid reorganization of a forearm flexor but not a forearm extensor representation in human motor cortex during ischemic nerve block
S158 subjects (7 male, mean age 28.4±5.0 years) before and following (0, 15 min) a period of cycling at two intensities. Exercise consisted of two 15 minute periods (separated by 5 mins) of cycling at a heart rate of either (180 resting heart rate [RHR])·0.4 + RHR or (180 RHR)·0.8 + RHR. Results: Compared to baseline, there was significantly less SICI at both 0 and 15 mins post exercise (ANOVA, P = 0.003). Furthermore, there was a significant conditioning intensity effect (ANOVA, P = 0.001) but no significant difference between exercise intensities (ANOVA, P = 0.13). Significance: These findings provide evidence that an acute exercise bout, even at relatively low intensity, can transiently reduce intracortical inhibition. This reduction in inhibition might provide a mechanism by which neuroplastic processes can be facilitated. Reference(s) [1] Cirillo, J., et al., J. Physiol, 2009. 587, 5831 5842. [2] Ziemann, U., B. Corwell, and L.G. Cohen. J. Neurosci., 1998. 18, 1115 1123. P22.5 Extremely low frequency magnetic fields (ELF-MF) produce functional changes in human brain F. Capone1 , M. Dileone1 , P. Profice1 , F. Pilato1 , G. Musumeci1 , F. Ranieri1 , R. Cadossi1 , L. Florio1 , R. Di Iorio1 , V. Di Lazzaro1 1 Institute of Neurology, Universita’ Cattolica del Sacro Cuore, Rome, Italy Introduction: Experimental data in animals and humans have demonstrated behavioral and neurophysiological changes after exposure to extremely low frequency magnetic fields (ELF-MF). The physiological bases of these effects are not clear. In vitro studies on neuronal cultures showed that ELF-MF applied in pulsed mode (PEMFs) produce an increase in excitatory neurotransmission. Methods: Using transcranial magnetic stimulation, we studied noninvasively the effect of PEMFs on cortical excitability in 22 healthy volunteers, in 14 of them we also evaluated the effects of sham field exposure. Results: After 45 min of PEMF exposure, intracortical facilitation produced by paired pulse brain stimulation was significantly increased of about 20%, while other parameters of cortical excitability remained unchanged. Sham exposure did not produce any effect. Discussion: The intracortical facilitation is a physiological parameter related to cortical glutamatergic activity. Our data suggest that PEMFs exposure may produce an enhancement in cortical excitatory neurotransmission. This study suggests that PEMFs may produce functional changes in human brain. P22.6 Rapid reorganization of a forearm flexor but not a forearm extensor representation in human motor cortex during ischemic nerve block A.-M. Vallence1 , K. Reilly2 , G. Hammond1 1 School of Psychology, University of Western Australia, Perth, Australia, 2 Centre de Neuroscience Cognitive, CNRS, Lyon, France Introduction: The human primary motor cortex (M1) is capable of rapid and long-lasting reorganization. This reorganization is evident both at a global level, in the form of shifts in body part representations, as well as at the level of individual muscles in the form of changes in corticospinal excitability. Representational shifts provide an overview of how various body parts reorganize relative to each other but are unable to tell us whether all muscles in a given body part reorganize in the same manner and to the same extent. Transcranial magnetic stimulation (TMS) provides specific information about individual muscles and can therefore inform us about the uniformity of plastic changes within a given body part. Objectives: We used TMS to investigate changes in corticospinal excitability of both a forearm flexor and extensor during ischemic nerve block (INB), a model of reversible, short-term reorganization. Methods: Motor evoked potential (MEP) amplitudes and input/output (I/O) curves were obtained before and during INB from a forearm flexor and extensor simultaneously when a blood pressure cuff induced a nerve block at the wrist. Several experiments were conducted in which total time of nerve block, cuff inflation pressure, and stimulation site and intensity were varied. Results: In all experiments flexor MEP amplitude increased very rapidly following cuff inflation while extensor MEP amplitude showed no systematic change, and the slope of flexor but not extensor I/O curves increased after INB.
Poster presentations: Poster session 22. Neuroplasticity Conclusions: This finding shows that forearm flexors and extensors differ in their potential to reorganize, and highlights the importance of investigating how experimentally-induced reorganization affects anatomically close, but functionally distinct, muscle groups. It also suggests that rehabilitation interventions that aim to alter cortical organization should take into account the differential sensitivity of various muscle groups to reorganizational processes. P22.7 Outlasting cortical plasticity changes induced by 25 Hz whole-hand mechanical stimulation M. Christova1 , D. Rafolt2 , S. Golaszewski3 , E. Gallasch4 Institute of physiology, Medical University, Graz, Austria, 2 Center for Medical Physics and Biomedical Engineering, Medical University, Vienna, Austria, 3 Department of Neurology, Paracelsus Medical University, Salzburg, Austria, 4 Institute of Physiology, Medical University, Graz, Austria Introduction: Studies have shown that a period of pure sensory stimulation increases corticomotor excitability for a period outlasting the stimulation. Objectives: The study aims to investigate if whole-hand mechanical stimulation (MSTIM) in the tapping-flutter frequency range induces outlasting post-stimulus changes in the hand motor cortical region. Methods: MSTIM was delivered to 12 healthy subjects for 20 min using a therapeutic stimulation device. Frequencies of 10 and 25 Hz were tested in separate sessions, and for control the foot sole was stimulated at 25 Hz. Motor evoked potentials (MEPs) after single (recruitment curves) and paired-pulse transcranial magnetic stimulation (TMS) were recorded from FDI and APB muscles of the right hand. TMS assessments were carried out at baseline, immediately after, 30 min, 1 h and 2 h after end of MSTIM. Additionally the effect of MSTIM with 25 Hz was examined with fMRI at pre- and post-stimulation on 22 subjects. Results: After MSTIM with 25 Hz, MEP recruitment curves were increased at all post stimulation assessments in both muscles. The most significant effect was achieved after 1h. Intracortical inhibition was decreased within the first hour, while the intracortical facilitation was increased at all post stimulation assessments. No significant effects were found following MSTIM with 10 Hz and following foot-vibration. Cortical activation in the sensorimotor area was significantly increased in the post stimulation fMRI sessions. Conclusions: We conclude that 20 min MSTIM with a frequency of 25 Hz induces outlasting plastic changes in the primary motor cortex. These results could be of relevance for hemiplegic patients with motor deficits, to improve the rehabilitation outcome with vibration exercise in combination with motor training. 1
P22.8 The effect of preceding muscle activity on reaction time e3 J.M. Castellote1 , M. van den Berg2 , J. Valls Sol´ 1 National School of Occupational Medicine, Carlos III Institute of Health; Physical Medicine and Rehabilitation Dpt., Universidad Complutense de Madrid, Madrid, Spain, 2 National School of Occupational Medicine, Carlos III Institute of Health, Madrid, Spain, 3 Unidad de EMG y Control Motor, Servei de Neurologia, Hospital Clínico, Universidad de Barcelona, Barcelona, Spain Introduction: The speed in the execution of a ballistic movement involving joint displacement vary according to the motor set. We reasoned that premotor and movement times may be influenced by whether the muscle has been previously in a resting position or maintaining a tonic contraction. Objectives: To establish the effect of preceding muscle activation on reaction time. Methods: Subjects wearing surface EMG recording electrodes in the anterior deltoid and triceps brachii muscles and a sensor of arm movement were requested to react to the presentation of a visual stimulus by performing a ballistic upper limb abduction in one of the following conditions: resting quietly (control trials) and immediately after maintaining a tonic contraction of about 50% of the maximum force for a variable period of time (test trials). We measured onset of EMG activity to assess premotor time (PT), onset of joint displacement to assess movement time (MT) and the difference between both, to assess the electromechanical coupling time (emCT). Results: There were no differences in PT, MT or emCT between control and test trials during the first minute, but there was a significant
Poster presentations: Poster session 22. Neuroplasticity Conclusions: This finding shows that forearm flexors and extensors differ in their potential to reorganize, and highlights the importance of investigating how experimentally-induced reorganization affects anatomically close, but functionally distinct, muscle groups. It also suggests that rehabilitation interventions that aim to alter cortical organization should take into account the differential sensitivity of various muscle groups to reorganizational processes. P22.7 Outlasting cortical plasticity changes induced by 25 Hz whole-hand mechanical stimulation M. Christova1 , D. Rafolt2 , S. Golaszewski3 , E. Gallasch4 Institute of physiology, Medical University, Graz, Austria, 2 Center for Medical Physics and Biomedical Engineering, Medical University, Vienna, Austria, 3 Department of Neurology, Paracelsus Medical University, Salzburg, Austria, 4 Institute of Physiology, Medical University, Graz, Austria Introduction: Studies have shown that a period of pure sensory stimulation increases corticomotor excitability for a period outlasting the stimulation. Objectives: The study aims to investigate if whole-hand mechanical stimulation (MSTIM) in the tapping-flutter frequency range induces outlasting post-stimulus changes in the hand motor cortical region. Methods: MSTIM was delivered to 12 healthy subjects for 20 min using a therapeutic stimulation device. Frequencies of 10 and 25 Hz were tested in separate sessions, and for control the foot sole was stimulated at 25 Hz. Motor evoked potentials (MEPs) after single (recruitment curves) and paired-pulse transcranial magnetic stimulation (TMS) were recorded from FDI and APB muscles of the right hand. TMS assessments were carried out at baseline, immediately after, 30 min, 1 h and 2 h after end of MSTIM. Additionally the effect of MSTIM with 25 Hz was examined with fMRI at pre- and post-stimulation on 22 subjects. Results: After MSTIM with 25 Hz, MEP recruitment curves were increased at all post stimulation assessments in both muscles. The most significant effect was achieved after 1h. Intracortical inhibition was decreased within the first hour, while the intracortical facilitation was increased at all post stimulation assessments. No significant effects were found following MSTIM with 10 Hz and following foot-vibration. Cortical activation in the sensorimotor area was significantly increased in the post stimulation fMRI sessions. Conclusions: We conclude that 20 min MSTIM with a frequency of 25 Hz induces outlasting plastic changes in the primary motor cortex. These results could be of relevance for hemiplegic patients with motor deficits, to improve the rehabilitation outcome with vibration exercise in combination with motor training. 1
P22.8 The effect of preceding muscle activity on reaction time e3 J.M. Castellote1 , M. van den Berg2 , J. Valls Sol´ 1 National School of Occupational Medicine, Carlos III Institute of Health; Physical Medicine and Rehabilitation Dpt., Universidad Complutense de Madrid, Madrid, Spain, 2 National School of Occupational Medicine, Carlos III Institute of Health, Madrid, Spain, 3 Unidad de EMG y Control Motor, Servei de Neurologia, Hospital Clínico, Universidad de Barcelona, Barcelona, Spain Introduction: The speed in the execution of a ballistic movement involving joint displacement vary according to the motor set. We reasoned that premotor and movement times may be influenced by whether the muscle has been previously in a resting position or maintaining a tonic contraction. Objectives: To establish the effect of preceding muscle activation on reaction time. Methods: Subjects wearing surface EMG recording electrodes in the anterior deltoid and triceps brachii muscles and a sensor of arm movement were requested to react to the presentation of a visual stimulus by performing a ballistic upper limb abduction in one of the following conditions: resting quietly (control trials) and immediately after maintaining a tonic contraction of about 50% of the maximum force for a variable period of time (test trials). We measured onset of EMG activity to assess premotor time (PT), onset of joint displacement to assess movement time (MT) and the difference between both, to assess the electromechanical coupling time (emCT). Results: There were no differences in PT, MT or emCT between control and test trials during the first minute, but there was a significant