- Email: [email protected]
54. Electrophysiological findings in critical illness polyneuropathy and myopathy
Society Proceedings / Clinical Neurophysiology 121 (2010) e19–e34
a significant positive correlation in amplitude across subjects between on- and off-responses. These results suggested that 100 m for the on and off events has similar generating mechanisms as well as similar physiological significance relating to the automatic detection of somatosensory changes. doi:10.1016/j.clinph.2010.02.131
51. Dynamics of the visual change detection in the brain— Tomokazu Urakawa, Koji Inui, Koya Yamashiro, Ryusuke Kakigi (National Institute for Physiological Sciences, Okazaki, Japan) Here we investigated cortical dynamics of the sensory memory based visual change detection using color light emitting diodes. Diodes were arranged along the frame of a screen, and subjects watched a silent movie that was presented at the center of the screen. Two kinds of stimuli were delivered. One was a color change stimulus, in which the red color was followed by a blue one without an interval. The other was a standard stimulus, in which red was presented alone. The former was presented at a probability of 25% and the latter at 75%. The inter-stimulus interval (ISI) among these stimuli was manipulated from 250 to 2000 ms. We measured brain responses to the color change stimulus using magnetoencephalography, and compared them among the ISI conditions. Results of a multi-dipole analysis showed that the location of the dominant activity in the occipital area gradually shifted anteriorly with time. The late and anterior activity in response to the color change decreased in amplitude with an elongation of the ISI but the earlier and posterior activity did not, suggesting that the brain activity relating to the sensory memory based visual change detection appears at the anterior part of the visual area. doi:10.1016/j.clinph.2010.02.132
52. Transformation of MEG ERD/ERS signal between different head positions using Signal Space Separation method—Jun Matsubayashi, Masao Matsuhashi, Tatsuya Mima, Hidenao Fukuyama, Akira Mitani (Kyoto University, Kyoto, Japan) Transformation of magnetoencephalographic (MEG) signal between different head positions can be performed with Signal Space Separation (SSS) method. The objective of this study was to test the availability of SSS method for MEG event-related (de)synchronization (ERD/ERS) signal transformation in different head positions. Magnetic signals from a phantom head and a healthy volunteer were recorded using a whole-head 306-channel neuromagnetometer. An artificial dipole on the right parieto-temporal area of the phantom was activated with 10 nAm electric current (sinusoidal wave). Right median nerve of the volunteer was stimulated at the wrist with electric pulse of 0.3 ms, and recorded the rebound of beta oscillation over the left rolandic area. Each measurement was done in three different head positions, and head position transformation was performed with SSS method. Field distribution of raw MEG ERS signal was distinctly different from each other. In contrast, the channels which showed maximum intensity of SSS-corrected ERS signal were identical to each other. The intensity of the SSS-corrected signal, however, varied in a certain degree. doi:10.1016/j.clinph.2010.02.133
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53. Probabilistic and virtual registration for fNIRS data in action— Ippeita Dan, Daisuke Tsuzuki, Lkhamsuren Enkhtur (National Food Research Institute, Tsukuba, Japan) Functional near-infrared spectroscopy (fNIRS) measurement poses a technical drawback in that it measures cortical activities from the head surface without anatomical information of the object to be measured. Here we introduce two practical solutions. First, using the reference database, we established a probabilistic registration method that probabilistically estimates a set of MNI coordinates for a given head surface point described using international 10–20 positions. Second, we devised a virtual registration method, based on simulations in place of physical measurements for optode positioning. We registered virtual holders on synthetic heads and brains that represent size and shape variations among the population. The registered positions were normalized to MNI space. These methods allow the presentation of multi-subject fNIRS data in the MNI space with clear description of the associated positional variability. The standard deviation in probabilistic and virtual registrations thus performed for given head surface points were approximately within the range of several millimeters. Such data presentation on a common platform will not only strengthen the validity of the population analysis of fNIRS studies, but also facilitate both intra- and inter-modal data sharing among the neuroimaging community. doi:10.1016/j.clinph.2010.02.134
54. Electrophysiological findings in critical illness polyneuropathy and myopathy—Yumiko Kugio, Toshio Shimizu, Yumi Fujimaki, Yasuhiro Kagamihara (Tokyo Metropolitan Neurological Hospital, Tokyo, Japan) Critical illness polyneuropathy (CIP) and myopathy (CIM) are neuromuscular disorders that occur in critically ill patients. Five patients with CIP/CIM were studied retrospectively to investigate electrophysiological features from peripheral nerve conduction studies examined within 2–4 weeks after onset. All patients had motor abnormalities characterized by markedly reduced compound muscle action potential (CMAP) amplitude and prolonged duration of the CMAP without abnormal temporal dispersion or conduction block. Slowing of the motor conduction velocities was mild. In four patients, sensory nerve action potential amplitude was mildly decreased with mild slowing of sensory conduction velocities. The absence of abnormal temporal dispersion or conduction block in the motor nerves suggested the prolonged CMAP duration originated from conduction slowing or blocks in muscle-fiber contraction. The CIP and CIM frequently occurred simultaneously and could not be differentiated each other in patients with poor outcome. The prolongation of CMAP duration might be a characteristic feature of CIP/CIM, and might provide potential significance for differentiation from other acute motor axonal neuropathy like Guillain–Barre sydrome. doi:10.1016/j.clinph.2010.02.135
55. Relationship between pain and the stimulus duration in nerve conduction studies—Akiko Tamura, Masahiro Sonoo, Satoshi Hoshino, Tomoko Iwanami, Hiroyuki Shimada, Teruo Shimizu (Teikyo University, Tokyo, Japan) Shorter stimulus duration is generally considered to be less painful in nerve conduction studies. However, whether this holds true for
a significant positive correlation in amplitude across subjects between on- and off-responses. These results suggested that 100 m for the on and off events has similar generating mechanisms as well as similar physiological significance relating to the automatic detection of somatosensory changes. doi:10.1016/j.clinph.2010.02.131
51. Dynamics of the visual change detection in the brain— Tomokazu Urakawa, Koji Inui, Koya Yamashiro, Ryusuke Kakigi (National Institute for Physiological Sciences, Okazaki, Japan) Here we investigated cortical dynamics of the sensory memory based visual change detection using color light emitting diodes. Diodes were arranged along the frame of a screen, and subjects watched a silent movie that was presented at the center of the screen. Two kinds of stimuli were delivered. One was a color change stimulus, in which the red color was followed by a blue one without an interval. The other was a standard stimulus, in which red was presented alone. The former was presented at a probability of 25% and the latter at 75%. The inter-stimulus interval (ISI) among these stimuli was manipulated from 250 to 2000 ms. We measured brain responses to the color change stimulus using magnetoencephalography, and compared them among the ISI conditions. Results of a multi-dipole analysis showed that the location of the dominant activity in the occipital area gradually shifted anteriorly with time. The late and anterior activity in response to the color change decreased in amplitude with an elongation of the ISI but the earlier and posterior activity did not, suggesting that the brain activity relating to the sensory memory based visual change detection appears at the anterior part of the visual area. doi:10.1016/j.clinph.2010.02.132
52. Transformation of MEG ERD/ERS signal between different head positions using Signal Space Separation method—Jun Matsubayashi, Masao Matsuhashi, Tatsuya Mima, Hidenao Fukuyama, Akira Mitani (Kyoto University, Kyoto, Japan) Transformation of magnetoencephalographic (MEG) signal between different head positions can be performed with Signal Space Separation (SSS) method. The objective of this study was to test the availability of SSS method for MEG event-related (de)synchronization (ERD/ERS) signal transformation in different head positions. Magnetic signals from a phantom head and a healthy volunteer were recorded using a whole-head 306-channel neuromagnetometer. An artificial dipole on the right parieto-temporal area of the phantom was activated with 10 nAm electric current (sinusoidal wave). Right median nerve of the volunteer was stimulated at the wrist with electric pulse of 0.3 ms, and recorded the rebound of beta oscillation over the left rolandic area. Each measurement was done in three different head positions, and head position transformation was performed with SSS method. Field distribution of raw MEG ERS signal was distinctly different from each other. In contrast, the channels which showed maximum intensity of SSS-corrected ERS signal were identical to each other. The intensity of the SSS-corrected signal, however, varied in a certain degree. doi:10.1016/j.clinph.2010.02.133
e31
53. Probabilistic and virtual registration for fNIRS data in action— Ippeita Dan, Daisuke Tsuzuki, Lkhamsuren Enkhtur (National Food Research Institute, Tsukuba, Japan) Functional near-infrared spectroscopy (fNIRS) measurement poses a technical drawback in that it measures cortical activities from the head surface without anatomical information of the object to be measured. Here we introduce two practical solutions. First, using the reference database, we established a probabilistic registration method that probabilistically estimates a set of MNI coordinates for a given head surface point described using international 10–20 positions. Second, we devised a virtual registration method, based on simulations in place of physical measurements for optode positioning. We registered virtual holders on synthetic heads and brains that represent size and shape variations among the population. The registered positions were normalized to MNI space. These methods allow the presentation of multi-subject fNIRS data in the MNI space with clear description of the associated positional variability. The standard deviation in probabilistic and virtual registrations thus performed for given head surface points were approximately within the range of several millimeters. Such data presentation on a common platform will not only strengthen the validity of the population analysis of fNIRS studies, but also facilitate both intra- and inter-modal data sharing among the neuroimaging community. doi:10.1016/j.clinph.2010.02.134
54. Electrophysiological findings in critical illness polyneuropathy and myopathy—Yumiko Kugio, Toshio Shimizu, Yumi Fujimaki, Yasuhiro Kagamihara (Tokyo Metropolitan Neurological Hospital, Tokyo, Japan) Critical illness polyneuropathy (CIP) and myopathy (CIM) are neuromuscular disorders that occur in critically ill patients. Five patients with CIP/CIM were studied retrospectively to investigate electrophysiological features from peripheral nerve conduction studies examined within 2–4 weeks after onset. All patients had motor abnormalities characterized by markedly reduced compound muscle action potential (CMAP) amplitude and prolonged duration of the CMAP without abnormal temporal dispersion or conduction block. Slowing of the motor conduction velocities was mild. In four patients, sensory nerve action potential amplitude was mildly decreased with mild slowing of sensory conduction velocities. The absence of abnormal temporal dispersion or conduction block in the motor nerves suggested the prolonged CMAP duration originated from conduction slowing or blocks in muscle-fiber contraction. The CIP and CIM frequently occurred simultaneously and could not be differentiated each other in patients with poor outcome. The prolongation of CMAP duration might be a characteristic feature of CIP/CIM, and might provide potential significance for differentiation from other acute motor axonal neuropathy like Guillain–Barre sydrome. doi:10.1016/j.clinph.2010.02.135
55. Relationship between pain and the stimulus duration in nerve conduction studies—Akiko Tamura, Masahiro Sonoo, Satoshi Hoshino, Tomoko Iwanami, Hiroyuki Shimada, Teruo Shimizu (Teikyo University, Tokyo, Japan) Shorter stimulus duration is generally considered to be less painful in nerve conduction studies. However, whether this holds true for