Exploring the composition of the recurrent neural activity accompanied with g rhythm by injecting simulated complex conductance
s Neuroscience Research 68S (2010) e4 e52 e45 their fingers at their will, which could facilitate the use of their paretic hand in their daily activities. In HANDS therapy, the patients wore a wrist hand splint and carried a portable IVES in a waist bag for 8 h during the daytime. The system was active for 8 h, patients were instructed to use their paretic hand as much as possible while wearing the HANDS system. Their non paretic upper extremity was not restrained. HANDS therapy was conducted for 3 weeks. The patients were also instructed to practice bi manual activities in their daily lives. To examine the effects of the HANDS system, Nonrandomized controlled, cohort before after, single blinded trial conducted with 36 chronic stroke patients with hemiparesis. Furthermore, we studied changes in selected markers of brain and spinal plasticity induced by the training program using EMG and transcranial magnetic stimulation (TMS) The paretic upper extremity motor function improved after 3 weeks HANDS therapy. Neurophysiologically, the intervention induced restoration of presynaptic and long loop inhibitory connections as well as disynaptic reciprocal inhibition. Paired pulse TMS study indicated plastic change in the affected hemisphere. The HANDS therapy may offer a promising option for the management of the paretic UE in patients with stroke. doi:10.1016/j.neures.2010.07.442 S3 7 1 4 Probing and restoring sensorimotor function with robotic interfaces Roger Gassert Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland The rapid evolution of computerand virtual reality technology over the past decades has provided researchers with novel tools allowing to explore human auditory and visual perception as well as cognitive function. Realtime computer graphics and audio hardware can be used to create virtual environments with which humans can interact under well controlled and repeatable conditions, thereby allowing to investigate how subjects react and adapt to these conditions in behavioral and neuroscience studies. These conditions can further be manipulated to explore how humans integrate information from different sensory modalities and how they react to perceptual conflicts. More recently, robotic devices, in the form of haptic interfaces, have been added to such environments, extending them to also incorporate physical interaction, resulting in a powerful tool for the investigation of sensorimotor control and interactions. Recent studies in such multi modal environments combined with functional neuroimaging have demonstrated the potential of this technology in exploring the neural mechanisms underlying sensorimotor control and related dysfunctions. Such systems are also being increasingly applied in robot assisted rehabilitation, providing multimodal feedback with the aim of positively supporting the neuroplastic process. The precise and objective measuring abilities of robotic devices also motivate their use in the diagnosis and assessment of sensorimotor function and impairment, making them truly powerful tools to probe and restore sensorimotor function. This talk will show examples of ongoing research in these fields, and provide an outlook on future developments, which will bring a closer link between brain, body and robotic systems in order to assist humans and augment their abilities in an intuitive and optimal way. doi:10.1016/j.neures.2010.07.443 S3 7 1 5 Neurorehabilitation with brain machine interface Keiichiro Shindo 1,3 Junichi Ushiba 2, Meigen Liu 3 1 Department of Rehabilitation Medicine, Tokyo Metropolitan Rehabilitation Hospital, Tokyo 2 Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, Kanagawa 3 Department of Rehabilitation Medicine, Keio University School of Medicine, Tokyo Brain machine interface (BMI) has been originally proposed for controlling robotic arms or computer cursors, and recently, neurorehabilitation using a BMI has been proposed in patients with severe paresis after stroke. Such BMI estimates the patient,s motor intentions from the amplitude of the arc shaped waveform in the electroencephalogram (EEG) over the primary sensory motor cortex (called sensory motor rhythm, SMR) and reflects it for visual guidance, electrical stimulation to muscles, or motor driven orthosis. This leads to afferent feedback or movement observation for the patients and could help in guiding cortical reorganization. Indeed, upon prolonged use, such a solution induces plastic changes in the SMR of stroke patients. But it remains unclear how BMI system gives clinical and physiological effects in patients with stroke. This presentation highlights our newly developed BMI system using an EEG driven hand orthosis in response to the motor intention of the paralyzed hand. Chronic stroke patients with moderate to severe hand paresis received the BMI training for 1 h once or twice a week over a period of 4 7 months. After this BMI training, the suppression of SMR in EEG with motor intention was significantly enhanced on bilateral sensorimotor cortices. The voluntary electromyographic activities of the affected finger extensors newly appeared in patients with severe paresis. Transcranial magnetic stimulation study showed decreased resting motor threshold in the affected hemisphere, suggesting that this BMI training facilitated corticospinal excitability and contributed to improvements in the neuromuscular system. Neurorehabilitation using a BMI is expected as a therapeutic approach for severe upper extremity paresis in patients with stroke. doi:10.1016/j.neures.2010.07.444 S3 7 2 1 Exploring the composition of the recurrent neural activity accompanied with rhythm by injecting simulated complex conductance Kenji Morita Dept Cogn Neurosci, Univ of Tokyo, Tokyo It has been shown in vivo (Pesaran et al. 2002, Nat Neurosci) and in vitro (Hasenstaub et al. 2005, Neuron) that neuronal sustained activity in the neocortex can be accompanied by an oscillation in the local field potential (LFP) in the range (30 80 Hz) to which individual neuronal spikes are phaselocked. Such an LFP oscillation was shown to have information usable for task execution (Pesaran, 2002) and can thus be functionally relevant. As for the mechanism, chemical and electrical interactions between the fastspiking (FS) inhibitory cells and/or reciprocal interactions between the FS cells and the excitatory pyramidal cells are suggested to be responsible. It remained unclear, however, how recurrent excitation between the pyramidal cells is related to the oscillation, while recurrent excitation is suggested to play a central role in the generation of the sustained activity itself. In order to address this issue, we used the conductance injection dynamic clamp technique to stimulate a pyramidal cell in vitro by virtual recurrent inputs (Morita et al. 2008, J Neurosci) which were simulated based on the in vivo observed distributions of pyramidal and FS firing phases with regard to the cycle (Hasenstaub, 2005) By varying parameters such as the degree of modulation and the latency in the simulated recurrent inputs, we have explored a condition that is recursively consistent with the spike phase distributions used for simulating these inputs. We found that in order for the consistency to hold, recurrent excitation should be considerably demodulated, which can be achieved at least partially through the conduction delay in the axonal collaterals (Izhikevich et al. 2004, Cereb Cortex) and the dendrites. I will discuss the implications of this result in terms of the mechanism and the function, and also a strategy to apply a similar approach to the FS cell so as to get a whole picture of the modulated sustained activity and its functional role. doi:10.1016/j.neures.2010.07.445 S3 7 2 2 Minimum conditional entropy principle for irregular firing of cortical neurons Yasuhiro Tsubo Tomoki Fukai NCT, RIKEN BSI, Wako Spike sequences recorded from cortical neurons in an awake animal are highly irregular. It is crucial for elucidating the cognitive function in the brain to understand how the irregular spike sequences recorded from in vivo cortical neurons are caused by intrinsic properties of the neurons and/or input properties from surrounding neurons. Previously, we found that the ISIs recorded from in vivo neurons in rat motor cortex during a selfpaced forelimb movement task obeyed long tailed power law distributions. To explain this observation, we proposed a hypothesis that the instantaneous firing rate of in vivo cortical neurons varies largely over time obeying gamma distribution and the distribution is designed in a way to minimizing averaged neuronal noise (minimum conditional entropy principle) It remains, however, unclear how the neuronal systems will dynamically generate the irregular spike sequence with the power law distributed ISIs. We analyzed the effect of the input signal and intrinsic membrane properties to the properties of the output spike sequences. We showed that neurons can generate the irregular spike sequences obeying the power law ISIs when the instantaneous amplitude of balanced input obeys Gaussian distribution (e.g. Ornstein Uhlenbech process) Because Gaussian distributed amplitude of balanced input is correspond to a gamma distributed instantaneous variance of balanced input, instantaneous firing rate obeys a gamma distribution
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