- Email: [email protected]
P36-10 A relationship between short-interval intracortical inhibition and the effectiveness of paired associative stimulation
29th International Congress of Clinical Neurophysiology interpreted as a rapid spread from the left to the right side and a left mesial frontal resection was performed. This lead to seizure freedom for six months. Thereafter, seizures reappeared and at present, he has 5 10 seizures daily in spite of being treated with four different AEDs. EEG and MR investigations point to a seizure start in the right hemisphere. fMRI cannot localise the left primary motor area. Since the seizure start is still believed to be in the left hemisphere, a navigated transcranial magnetic study (NBS) was performed in order to decide if another left sided resection is possible. Results: The hand and forearm muscles of the left side have normal somatotopic localisation in the right primary motor area (M1). The control of the right hand muscles is shifted to the corresponding area in the right hemisphere. The right forearm muscles are governed bilaterally from the respective M1s. The control of the right leg muscles is unaltered in the left M1. Conclusions: Using NBS, the localisation of the cortical control of different muscles can be investigated with high precision. In this case, a partial contralateral transfer of motor function of a forearm muscle could be demonstrated. P36-8 Insights from darkness: neural correlates of virtual route recognition in congenital blindness R. Kupers1 , D. Chebat2 , K. Madsen3 , O. Paulson3 , M. Ptito2,3 Institute of Neuroscience and Pharmacology, Panum Institute, Health Science Department, University of Copenhagen, Copenhagen, Denmark, 2 School of Optometry, University of Montreal, Montreal, Qc, Canada, 3 DRCMR, University of Copenhagen, Copenhagen, Denmark 1
The neural correlates of navigation in congenital blindness remain elusive, in part due to the difficulty in testing navigational skills of blind subjects using functional brain imaging. To circumvent this difficulty, we trained congenitally blind (CB) and matched blindfolded sighted control (SC) subjects in spatial navigation tasks, using the tongue display unit (TDU), a visual-to tactile sensory substitution device that converts visual information into electro-tactile pulses applied to the tongue. Ten CB and 10 SC participated in a route navigation and route recognition task. During route navigation, participants actively learned to navigate through either of two virtual routes that were presented via the TDU, using the arrow keys of a keyboard. In the passive route recognition task, the computer program guided the participants automatically through the routes. They then had to indicate which route had been presented. All participants learned both navigation tasks within 4 days of training. Following training, subjects participated in an fMRI study during which they repeated the route recognition task. CB showed increased BOLD responses in the right parahippocampus, posterior parietal cortex, precuneus, cuneus, inferior, middle and superior occipital gyri and fusiform gyrus during route recognition. Task-dependent BOLD signal changes were not seen in parahippocampus or any region of visual cortex of SC, despite equal task performance. However, when the route recognition task was performed under full vision in second group of 10 sighted subjects, the same areas were activated as in CB. These data suggests that in the absence of vision, cross-modal plasticity permits the recruitment of the same cortical network used for spatial navigation tasks in sighted subjects. P36-9 Toward the neural control of robotic hand: clinical and EEG changes after 4-weeks training in a human amputee M. Tombini1 , S. Micera2,3 , C. Porcaro4,5 , F. Zappasodi6 , J. Rigosa2 , G. Di Pino1,7 , G. Assenza1 , A. Benvenuto7 , L. Rossini7 , J. Carpaneto2 , M.C. Carrozza2 , E. Guglielmelli7 , P. Dario2 , P.M. Rossini1,8 1 Department of Neurology, Campus Biomedico University, Rome, Italy, 2 ARTS Lab, Scuola Superiore Sant’Anna, Pisa, Italy, 3 Institute for Automation, Swiss Federal Institute of Technology, Zurich, Switzerland, 4 ISTC-CNR, Ospedale Fatebenefratelli, Isola Tiberina, 00186 Rome, Italy, 5 School of Psychology and Birmingham University Imaging Centre (BUIC), University of Birmingham, Birmingham, UK, 6 Department of Clinical Sciences and Bioimaging, G. D’Annunzio University, Chieti, Italy, 7 Laboratory of Biomedical Robotics and Biomicrosystems, Campus Bio-Medico University, Rome, Italy, 8 Casa di Cura S. Raffaele, and IRCCS S. Raffaele-Pisana, Rome, Italy Objective: The feasibility of interfacing with amputee nerve stump to provide control of robotic hand has been investigated during a 4-weeks
S319 trial. Our aim was also to evaluate clinical and cortical changes following training with prosthesis and restoration of sensory feedback. Methods: Four thin-film longitudinal intra-fascicular electrodes (tf-LIFE4) were implanted in an amputee median and ulnar nerves for four weeks. Artificial intelligence classifiers were off-line implemented to analyse neural signals from LIFE recorded during different hand movements imagination; moreover, different types of current stimulation produced reproducible sensations. Changes in sensorimotor cortical organization and phantom limb syndrome were monitored via EEG and clinical scales. The event-related desynchronization/synchronization procedure and coherence analysis were applied to EEG data to improve LIFE signals identification and to monitor cortical rearrangements. Results: Sensations in different fingers were modulated by pulse frequency/width. Realtime control of neural output was achieved by the subject, and three actions of the robotic hand discriminated. An advanced and integrated analysis of movement-related nerve and brain signals allowed the extraction of motor information with good performance. EEG analysis clearly reflected learning phenomena. Three weeks after LIFE implant the subject regained a normal modulation of background rhythms preparing movement, consisting of a desynchronization pattern in alpha and beta band in the sensorimotor areas contralateral to the missing limb. Moreover coherence analysis evidenced a restored alpha band synchronization of rolandic area with frontal and parietal ipsilateral regions. In parallel, a phantom limb pain reduction was also observed. Conclusions: tf-LIFEs can work in human nerves for several weeks for output signal recordings. The information gathered from the EEG signals was shown to significantly improve the classification performance of different actions in a high percentage. EEG analysis of cortical rhythms clearly evidenced rearrangements of sensorimotor areas devoted to motor control along with significant phantom limb syndrome mitigation. P36-10 A relationship between short-interval intracortical inhibition and the effectiveness of paired associative stimulation N. Murase1,2 , B. Cengiz1 , M. van den Boss1 , J.C. Rothwell1 Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, United Kingdom, 2 Department of Neurology, Tokushima University School of Medicine, Tokushima, Japan 1
Objective: Paired associative stimulation (PAS) involves pairing sensory afferent input with transcranial magnetic stimulation (TMS) of motor cortex at an interval of 25 ms. Despite the fact that PAS is facilitatory, each pair of stimuli occurs at intervals appropriate for producing short afferent inhibition (SAI). To investigate this paradox further, we explored the changes in short-interval intracortical inhibition (SICI: interstimulus intervals (ISI) 1 5 ms)) using a threshold tracking (TT) method (Fisher RJ et al., 2002) following PAS. Methods and Results: Stimulation intensities were determined before PAS so as to optimize the value of SAI produced by each pair to within 0.5 0.8. PAS was then induced by applying at least 180 pairs of stimuli at 0.1 or 0.2 Hz. Using TT, cortical excitability was expressed as changes in the intensity of the test pulse required to evoke an MEP of 0.2 mV when a preceding conditioning shock had been applied. Conditioning shock (CS) intensity was set as 70% of test shock (TS) intensity. Twelve healthy volunteers (5 females, averaged age 33.6 years old) participated. The subjects were divided into 2 groups depending on whether they showed an excitatory (LTP-like) effect of PAS or not. Before PAS, in the group with a positive LTP-like effect (n = 8, MEP amplitude ratio of after/before PAS 1.78±0.80 (SD)), there was significantly more SICI at ISI = 2.5, 3 and 3.5 ms (p < 0.05) than in the group with an absent PAS effect (n = 6). The PAS-positive group also had a significant change of SICI after PAS, increase at ISI = 1 ms (p < 0.01) and decrease at ISI 3 ms (p < 0.01). In the group with an absent PAS effect, SICI was not changed. Conclusions: The effect of PAS varies between individual subjects. Individuals with a good PAS effect had more effective SICI than those with a poor response.
The neural correlates of navigation in congenital blindness remain elusive, in part due to the difficulty in testing navigational skills of blind subjects using functional brain imaging. To circumvent this difficulty, we trained congenitally blind (CB) and matched blindfolded sighted control (SC) subjects in spatial navigation tasks, using the tongue display unit (TDU), a visual-to tactile sensory substitution device that converts visual information into electro-tactile pulses applied to the tongue. Ten CB and 10 SC participated in a route navigation and route recognition task. During route navigation, participants actively learned to navigate through either of two virtual routes that were presented via the TDU, using the arrow keys of a keyboard. In the passive route recognition task, the computer program guided the participants automatically through the routes. They then had to indicate which route had been presented. All participants learned both navigation tasks within 4 days of training. Following training, subjects participated in an fMRI study during which they repeated the route recognition task. CB showed increased BOLD responses in the right parahippocampus, posterior parietal cortex, precuneus, cuneus, inferior, middle and superior occipital gyri and fusiform gyrus during route recognition. Task-dependent BOLD signal changes were not seen in parahippocampus or any region of visual cortex of SC, despite equal task performance. However, when the route recognition task was performed under full vision in second group of 10 sighted subjects, the same areas were activated as in CB. These data suggests that in the absence of vision, cross-modal plasticity permits the recruitment of the same cortical network used for spatial navigation tasks in sighted subjects. P36-9 Toward the neural control of robotic hand: clinical and EEG changes after 4-weeks training in a human amputee M. Tombini1 , S. Micera2,3 , C. Porcaro4,5 , F. Zappasodi6 , J. Rigosa2 , G. Di Pino1,7 , G. Assenza1 , A. Benvenuto7 , L. Rossini7 , J. Carpaneto2 , M.C. Carrozza2 , E. Guglielmelli7 , P. Dario2 , P.M. Rossini1,8 1 Department of Neurology, Campus Biomedico University, Rome, Italy, 2 ARTS Lab, Scuola Superiore Sant’Anna, Pisa, Italy, 3 Institute for Automation, Swiss Federal Institute of Technology, Zurich, Switzerland, 4 ISTC-CNR, Ospedale Fatebenefratelli, Isola Tiberina, 00186 Rome, Italy, 5 School of Psychology and Birmingham University Imaging Centre (BUIC), University of Birmingham, Birmingham, UK, 6 Department of Clinical Sciences and Bioimaging, G. D’Annunzio University, Chieti, Italy, 7 Laboratory of Biomedical Robotics and Biomicrosystems, Campus Bio-Medico University, Rome, Italy, 8 Casa di Cura S. Raffaele, and IRCCS S. Raffaele-Pisana, Rome, Italy Objective: The feasibility of interfacing with amputee nerve stump to provide control of robotic hand has been investigated during a 4-weeks
S319 trial. Our aim was also to evaluate clinical and cortical changes following training with prosthesis and restoration of sensory feedback. Methods: Four thin-film longitudinal intra-fascicular electrodes (tf-LIFE4) were implanted in an amputee median and ulnar nerves for four weeks. Artificial intelligence classifiers were off-line implemented to analyse neural signals from LIFE recorded during different hand movements imagination; moreover, different types of current stimulation produced reproducible sensations. Changes in sensorimotor cortical organization and phantom limb syndrome were monitored via EEG and clinical scales. The event-related desynchronization/synchronization procedure and coherence analysis were applied to EEG data to improve LIFE signals identification and to monitor cortical rearrangements. Results: Sensations in different fingers were modulated by pulse frequency/width. Realtime control of neural output was achieved by the subject, and three actions of the robotic hand discriminated. An advanced and integrated analysis of movement-related nerve and brain signals allowed the extraction of motor information with good performance. EEG analysis clearly reflected learning phenomena. Three weeks after LIFE implant the subject regained a normal modulation of background rhythms preparing movement, consisting of a desynchronization pattern in alpha and beta band in the sensorimotor areas contralateral to the missing limb. Moreover coherence analysis evidenced a restored alpha band synchronization of rolandic area with frontal and parietal ipsilateral regions. In parallel, a phantom limb pain reduction was also observed. Conclusions: tf-LIFEs can work in human nerves for several weeks for output signal recordings. The information gathered from the EEG signals was shown to significantly improve the classification performance of different actions in a high percentage. EEG analysis of cortical rhythms clearly evidenced rearrangements of sensorimotor areas devoted to motor control along with significant phantom limb syndrome mitigation. P36-10 A relationship between short-interval intracortical inhibition and the effectiveness of paired associative stimulation N. Murase1,2 , B. Cengiz1 , M. van den Boss1 , J.C. Rothwell1 Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, United Kingdom, 2 Department of Neurology, Tokushima University School of Medicine, Tokushima, Japan 1
Objective: Paired associative stimulation (PAS) involves pairing sensory afferent input with transcranial magnetic stimulation (TMS) of motor cortex at an interval of 25 ms. Despite the fact that PAS is facilitatory, each pair of stimuli occurs at intervals appropriate for producing short afferent inhibition (SAI). To investigate this paradox further, we explored the changes in short-interval intracortical inhibition (SICI: interstimulus intervals (ISI) 1 5 ms)) using a threshold tracking (TT) method (Fisher RJ et al., 2002) following PAS. Methods and Results: Stimulation intensities were determined before PAS so as to optimize the value of SAI produced by each pair to within 0.5 0.8. PAS was then induced by applying at least 180 pairs of stimuli at 0.1 or 0.2 Hz. Using TT, cortical excitability was expressed as changes in the intensity of the test pulse required to evoke an MEP of 0.2 mV when a preceding conditioning shock had been applied. Conditioning shock (CS) intensity was set as 70% of test shock (TS) intensity. Twelve healthy volunteers (5 females, averaged age 33.6 years old) participated. The subjects were divided into 2 groups depending on whether they showed an excitatory (LTP-like) effect of PAS or not. Before PAS, in the group with a positive LTP-like effect (n = 8, MEP amplitude ratio of after/before PAS 1.78±0.80 (SD)), there was significantly more SICI at ISI = 2.5, 3 and 3.5 ms (p < 0.05) than in the group with an absent PAS effect (n = 6). The PAS-positive group also had a significant change of SICI after PAS, increase at ISI = 1 ms (p < 0.01) and decrease at ISI 3 ms (p < 0.01). In the group with an absent PAS effect, SICI was not changed. Conclusions: The effect of PAS varies between individual subjects. Individuals with a good PAS effect had more effective SICI than those with a poor response.