Takenobu Murakami

Publications (14)42.89 Total impact

• Article: Homeostatic Metaplasticity of Corticospinal Excitatory and intracortical Inhibitory Neural Circuits in Human Motor Cortex.

  Takenobu Murakami, Florian Müller-Dahlhaus, Ming-Kuei Lu, Ulf Ziemann
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  ABSTRACT: Homeostatic metaplasticity, a fundamental principle for maintaining overall synaptic weight in the physiological range in neuronal networks, was demonstrated at the cellular and systems level predominantly for excitatory synaptic neurotransmission. Although inhibitory networks are crucial for regulating excitability, it is largely unknown to what extent homeostatic metaplasticity of inhibition also exists. Here, we employed intermittent and continuous transcranial magnetic theta burst stimulation (iTBS, cTBS) of primary motor cortex (M1) in healthy subjects for induction of long-term potentiation (LTP)-like and long-term depression (LTD)-like plasticity. We studied metaplasticity by testing the interactions of priming TBS with LTP/D-like plasticity induced by subsequent test TBS. Changes in excitatory neurotransmission were measured by the input-output curve of motor evoked potentials (IO-MEP), and changes in GABAAergic inhibitory neurotransmission by the input-output curve of short-interval intracortical inhibition (IO-SICI, 4 conditioning stimulus intensities of 70-100% active motor threshold, interstimulus interval 2.0 ms). Non-primed iTBS increased IO-MEP, while non-primed cTBS decreased IO-MEP. Pairing of identical protocols (iTBS→iTBS, cTBS→cTBS) resulted in suppression of the non-primed TBS effects on IO-MEP, and pairing of different protocols (cTBS→iTBS, iTBS→cTBS) enhanced the test TBS effects on IO-MEP. While non-primed TBS did not result in significant changes of IO-SICI, iTBS→iTBS resulted in IO-SICI decrease, and cTBS→cTBS in IO-SICI increase compared to the non-primed conditions. The changes in SICI induced by priming TBS correlated with the changes in MEP induced by subsequent test TBS. Findings demonstrate that plasticity in both excitatory and inhibitory circuits in human motor cortex are regulated by homeostatic metaplasticity, and that priming effects on inhibition contribute to the homeostatic regulation of metaplasticity in excitatory circuits.
  The Journal of Physiology 08/2012; · 4.72 Impact Factor
• Article: Facilitation of speech repetition accuracy by theta burst stimulation of the left posterior inferior frontal gyrus.

  Julia Restle, Takenobu Murakami, Ulf Ziemann
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  ABSTRACT: The posterior part of the inferior frontal gyrus (pIFG) in the left hemisphere is thought to form part of the putative human mirror neuron system and is assigned a key role in mapping sensory perception onto motor action. Accordingly, the pIFG is involved in motor imitation of the observed actions of others but it is not known to what extent speech repetition of auditory-presented sentences is also a function of the pIFG. Here we applied fMRI-guided facilitating intermittent theta burst transcranial magnetic stimulation (iTBS), or depressant continuous TBS (cTBS), or intermediate TBS (imTBS) over the left pIFG of healthy subjects and compared speech repetition accuracy of foreign Japanese sentences before and after TBS. We found that repetition accuracy improved after iTBS and, to a lesser extent, after imTBS, but remained unchanged after cTBS. In a control experiment, iTBS was applied over the left middle occipital gyrus (MOG), a region not involved in sensorimotor processing of auditory-presented speech. Repetition accuracy remained unchanged after iTBS of MOG. We argue that the stimulation type and stimulation site specific facilitating effect of iTBS over left pIFG on speech repetition accuracy indicates a causal role of the human left-hemispheric pIFG in the translation of phonological perception to motor articulatory output for repetition of speech. This effect may prove useful in rehabilitation strategies that combine repetitive speech training with iTBS of the left pIFG in speech disorders, such as aphasia after cerebral stroke.
  Neuropsychologia 05/2012; 50(8):2026-31. · 3.64 Impact Factor
• Article: State-dependent and timing-dependent bidirectional associative plasticity in the human SMA-M1 network.

  Noritoshi Arai, Florian Müller-Dahlhaus, Takenobu Murakami, Barbara Bliem, Ming-Kuei Lu, Yoshikazu Ugawa, Ulf Ziemann
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  ABSTRACT: The supplementary motor area (SMA-proper) plays a key role in the preparation and execution of voluntary movements. Anatomically, SMA-proper is densely reciprocally connected to primary motor cortex (M1), but neuronal coordination within the SMA-M1 network and its modification by external perturbation are not well understood. Here we modulated the SMA-M1 network using MR-navigated multicoil associative transcranial magnetic stimulation in healthy subjects. Changes in corticospinal excitability were assessed by recording motor evoked potential (MEP) amplitude bilaterally in a hand muscle. We found timing-dependent bidirectional Hebbian-like MEP changes during and for at least 30 min after paired associative SMA-M1 stimulation. MEP amplitude increased if SMA stimulation preceded M1 stimulation by 6 ms, but decreased if SMA stimulation lagged M1 stimulation by 15 ms. This associative plasticity in the SMA-M1 network was highly topographically specific because paired associative stimulation of pre-SMA and M1 did not result in any significant MEP change. Furthermore, associative plasticity in the SMA-M1 network was strongly state-dependent because it required priming by near-simultaneous M1 stimulation to occur. We conclude that timing-dependent bidirectional associative plasticity is demonstrated for the first time at the systems level of a human corticocortical neuronal network. The properties of this form of plasticity are fully compatible with spike-timing-dependent plasticity as defined at the cellular level. The necessity of priming may reflect the strong interhemispheric connectivity of the SMA-M1 network. Findings are relevant for better understanding reorganization and potentially therapeutic modification of neuronal coordination in the SMA-M1 network after cerebral lesions such as stroke.
  Journal of Neuroscience 10/2011; 31(43):15376-83. · 7.11 Impact Factor
• Article: Effective connectivity hierarchically links temporoparietal and frontal areas of the auditory dorsal stream with the motor cortex lip area during speech perception.

  Takenobu Murakami, Julia Restle, Ulf Ziemann
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  ABSTRACT: A left-hemispheric cortico-cortical network involving areas of the temporoparietal junction (Tpj) and the posterior inferior frontal gyrus (pIFG) is thought to support sensorimotor integration of speech perception into articulatory motor activation, but how this network links with the lip area of the primary motor cortex (M1) during speech perception is unclear. Using paired-coil focal transcranial magnetic stimulation (TMS) in healthy subjects, we demonstrate that Tpj→M1 and pIFG→M1 effective connectivity increased when listening to speech compared to white noise. A virtual lesion induced by continuous theta-burst TMS (cTBS) of the pIFG abolished the task-dependent increase in pIFG→M1 but not Tpj→M1 effective connectivity during speech perception, whereas cTBS of Tpj abolished the task-dependent increase of both effective connectivities. We conclude that speech perception enhances effective connectivity between areas of the auditory dorsal stream and M1. Tpj is situated at a hierarchically high level, integrating speech perception into motor activation through the pIFG.
  Brain and Language 10/2011; 122(3):135-41. · 3.12 Impact Factor
• Article: Observation-execution matching and action inhibition in human primary motor cortex during viewing of speech-related lip movements or listening to speech.

  Takenobu Murakami, Julia Restle, Ulf Ziemann
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  ABSTRACT: One influential theory posits that language has evolved from gestural communication through observation-execution matching processes in the mirror neuron system (MNS). This theory predicts that observation of speech-related lip movements or even listening to speech would result in effector and task specific increase of the excitability of the corresponding motor representations in the primary motor cortex (M1), since actual movement execution is known be effector and task specific. In addition, effector and task specific inhibitory control mechanisms should be important to prevent overt motor activation during observation of speech-related lip movements or listening to speech. We tested these predictions by applying focal transcranial magnetic stimulation to the left M1 of 12 healthy right-handed volunteers and measuring motor evoked potentials (MEPs) and short-interval intracortical inhibition (SICI) in a lip muscle, the right orbicularis oris (OO), vs. a hand muscle, the right first dorsal interosseus (FDI). We found that MEP and SICI increased only in the OO but not in the FDI during viewing of speech-related lip movements or listening to speech. These changes were highly task specific because they were absent when lip movements non-related to speech were viewed. Finally, the increase in MEP amplitude in the OO correlated inversely with accuracy of speech perception, i.e. the MEP increase was directly related to task difficulty. The MEP findings support the notion that observation-execution matching is an operating process in the putative human MNS that might have been fundamental for evolution of language. Furthermore, the SICI findings provide evidence that inhibitory mechanisms are recruited to prevent unwanted overt motor activation during action observation.
  Neuropsychologia 03/2011; 49(7):2045-54. · 3.64 Impact Factor
• Article: High-frequency transcutaneous electrical nerve stimulation (TENS) differentially modulates sensorimotor cortices: an MEG study.

  Takenobu Murakami, Ryosuke Takino, Isamu Ozaki, Tomoaki Kimura, Yoshinobu Iguchi, Isao Hashimoto
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  ABSTRACT: Transcutaneous electrical nerve stimulation (TENS) affects excitability of the central motor system as well as the somatosensory system. To determine whether TENS has influence on excitability in the sensorimotor cortices of TENS-treated finger muscle, we investigated magnetoencephalogram associated with voluntary, self-paced finger movement before and after TENS. High-frequency TENS was applied on the extensor digitorum muscle for 15 min. Subjects underwent alternate middle finger and thumb extension movements before and after the TENS. We recorded movement-related cortical magnetic field (MRCF) associated with TENS-treated middle finger movement and that from untreated thumb movement. The current source for motor field (MF) was located in the pre-central motor cortex and anteriorly-oriented, and that for motor evoked field one (MEF1) was found in the post-central somatosensory cortex and posteriorly-oriented. The amplitude of MF for TENS-treated middle finger movement decreased but unchanged for untreated thumb movement after TENS. The amplitude of MEF1 decreased for either finger movement after TENS. High-frequency TENS to the forearm muscle modulates excitability of the limited area of motor cortex but wider area of primary somatosensory cortex. High-frequency TENS to the forearm muscle modulates excitability of the primary somatosensory cortex and motor cortex in a different manner.
  Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 02/2010; 121(6):939-44. · 3.12 Impact Factor
• Article: Somatosensory evoked potentials and high-frequency oscillations in athletes.

  Takenobu Murakami, Kenji Sakuma, Kenji Nakashima
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  ABSTRACT: Athletes perform skilled movements during games and daily training. We hypothesized that the cortical representation in athletes differs from that in non-athletes. Somatosensory evoked potentials (SEPs) and high-frequency oscillations (HFOs) were recorded from seven healthy football players, seven healthy racquet players and seven healthy non-athletes. Electrical stimuli were delivered to the posterior tibial nerves and the median nerves, bilaterally. Cortical and spinal SEPs and sensory nerve action potentials (SNAPs) were recorded. SEPs were recorded by 0.3-3000Hz filter. HFOs were separated by 400-800Hz band-pass filtering. SNAPs were recorded by 20-2000Hz filter. The P37-N45 amplitude in football players and the N20-P25 amplitude in racquet players were significantly larger than those in non-athletes. The number of negative peaks of HFOs from the posterior tibial nerve in football players and the HFO amplitudes from the median nerve in racquet players were significantly larger than those in non-athletes. The earlier an individual started playing football, the larger the P37-N45 amplitude. Neither spinal SEPs nor SNAPs differed significantly among the three groups. Daily long-term training brings about plastic excitation in the somatosensory cortex representation of the trained limbs in athletes. Plastic changes in the somatosensory cortex are induced specifically by physical training.
  Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 11/2008; 119(12):2862-9. · 3.12 Impact Factor
• Article: High-frequency oscillations change in parallel with short-interval intracortical inhibition after theta burst magnetic stimulation.

  Takenobu Murakami, Kenji Sakuma, Takashi Nomura, Kenji Nakashima, Isao Hashimoto
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  ABSTRACT: Theta burst transcranial magnetic stimulation (TBS) causes changes in motor cortical excitability. In the present study, somatosensory-evoked potentials (SEPs) and high-frequency oscillations (HFOs) were recorded before and after TBS over the motor cortex to examine how TBS influenced the somatosensory cortex. SEPs following electric median nerve stimulation were recorded, and amplitudes for the P14, N20, P25, and N33 components were measured and analyzed. HFOs were separated by 400-800 Hz band-pass filtering, and root-mean-square amplitudes were calculated from onset to offset. SEPs and HFOs were measured before and after application of either intermittent or continuous TBS (iTBS/cTBS; 600 total pulses at 80% active motor threshold) over the motor cortex. Motor-evoked potentials (MEPs) and short-interval intracortical inhibition (SICI) of the first dorsal interosseous muscle were examined before and after TBS. MEPs, SICI, and HFO amplitudes were increased and decreased significantly after iTBS and cTBS, respectively. Wide-band SEPs did not change significantly after TBS. TBS changed the cortical excitability of the sensorimotor cortices. Changes in HFOs after TBS were parallel to those in SICI. The mechanisms of changes in HFOs after TBS may be the same as those in SICI.
  Clinical Neurophysiology 03/2008; 119(2):301-8. · 3.41 Impact Factor
• Article: Changes in somatosensory-evoked potentials and high-frequency oscillations after paired-associative stimulation.

  Takenobu Murakami, Kenji Sakuma, Takashi Nomura, Yusuke Uemura, Isao Hashimoto, Kenji Nakashima
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  ABSTRACT: Paired-associative stimulation (PAS), combining electrical median nerve stimulation with transcranial magnetic stimulation (TMS) with a variable delay, causes long-term potentiation or depression (LTP/LTD)-like cortical plasticity. In the present study, we examined how PAS over the motor cortex affected a distant site, the somatosensory cortex. Furthermore, the influences of PAS on high-frequency oscillations (HFOs) were investigated to clarify the origin of HFOs. Interstimulus intervals between median nerve stimulation and TMS were 25 ms (PAS(25)) and 10 ms (PAS(10)). PAS was performed over the motor and somatosensory cortices. SEPs following median nerve stimulation were recorded before and after PAS. HFOs were isolated by 400-800 Hz band-pass filtering. PAS(25) over the motor cortex increased the N20-P25 and P25-N33 amplitudes and the HFOs significantly. The enhancement of the P25-N33 amplitude and the late HFOs lasted more than 60 min. After PAS(10) over the motor cortex, the N20-P25 and P25-N33 amplitudes decreased for 40 min, and the HFOs decreased for 60 min. Frontal SEPs were not affected after PAS over the motor cortex. PAS(25/10) over the somatosensory cortex did not affect SEPs and HFOs. PAS(25/10) over the motor cortex caused the LTP/LTD-like phenomena in a distant site, the somatosensory cortex. The PAS paradigms over the motor cortex can modify both the neural generators of SEPs and HFOs. HFOs may reflect the activation of GABAergic inhibitory interneurons regulating pyramidal neurons in the somatosensory cortex.
  Experimental Brain Research 02/2008; 184(3):339-47. · 2.39 Impact Factor
• Article: Short latency afferent inhibition is not impaired in mild cognitive impairment.

  Kenji Sakuma, Takenobu Murakami, Kenji Nakashima
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  ABSTRACT: To determine whether cortical cholinergic circuit impairment exists in the mild cognitive impairment (MCI) brain. Fifteen healthy elderly controls (NC), 16 amnesic MCI subjects and 12 probable Alzheimer's disease (AD) subjects were recruited. Conditioning stimuli were delivered at the right wrist followed by test transcranial magnetic stimulation (TMS) of the left motor cortex. The center of the linear contiguous segment of the coil was placed over a point 5 cm lateral to the vertex on the interaural line. The interstimulus intervals (ISIs) between the conditioning stimuli and the test stimuli were set at 20, 40, 100, 200 and 600 ms. An inhibitory effect that occurred at ISIs as short as 20 ms was defined as short-latency afferent inhibition (SAI). SAI was significantly reduced in subjects with AD compared with NC, but it was not reduced in subjects with MCI. A difference in cortical excitability between subjects with AD and subjects with MCI could be captured by an in vivo neurophysiological method. The state of the neurotransmitter systems, including the cortical cholinergic system, is thought by some compensatory mechanisms to be kept at the normal level in subjects with MCI.
  Clinical Neurophysiology 08/2007; 118(7):1460-3. · 3.41 Impact Factor
• Article: Short-interval intracortical inhibition is modulated by high-frequency peripheral mixed nerve stimulation.

  Takenobu Murakami, Kenji Sakuma, Takashi Nomura, Kenji Nakashima
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  ABSTRACT: Cortical excitability can be modulated by manipulation of afferent input. We investigated the influence of peripheral mixed nerve stimulation on the excitability of the motor cortex. Motor evoked potentials (MEPs), short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) in the right abductor pollicis brevis (APB), extensor carpi radialis (ECR) and first dorsal interosseous (FDI) muscles were evaluated using paired-pulse transcranial magnetic stimulation (TMS) before and after high-frequency peripheral mixed nerve stimulation (150 Hz, 30 min) over the right median nerve at the wrist. The MEP amplitude and SICI of the APB muscle decreased transiently 0-10 min after the intervention, whereas the ICF did not change. High-frequency peripheral mixed nerve stimulation reduced the excitability of the motor cortex. The decrement in the SICI, which reflects the function of GABA(A)ergic inhibitory interneurons, might compensate for the reduced motor cortical excitability after high-frequency peripheral mixed nerve stimulation.
  Neuroscience Letters 07/2007; 420(1):72-5. · 2.11 Impact Factor
• Article: Gasperini syndrome, a report of two cases.

  Miwa Hayashi-Hayata, Hiroyuki Nakayasu, Mitsuru Doi, Yasuyo Fukada, Takenobu Murakami, Kenji Nakashima
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  ABSTRACT: We report 2 cases of Gasperini syndrome and consider them with the 11 previously reported cases to describe the clinical characteristics of this rare syndrome: Core neurological signs are peripheral facial nerve palsy and abducens nerve palsy of the affected side: Among all cases, imaging demonstrated a small lesion in the mediolateral tegmental pons (10/13 cases of microinfarction; 2/13 cases of microbleeding). We found that the responsible artery in ischemic Gasperini syndrome is mainly the long circumferential branch of the anterior inferior cerebellar artery; Case 1 is the first case thought to be caused by infarction of the basilar artery's paramedian branch.
  Internal Medicine 02/2007; 46(3):129-33. · 0.94 Impact Factor
• Article: Anterior and posterior inferior cerebellar artery infarction with sudden deafness and vertigo.

  Takenobu Murakami, Hiroyuki Nakayasu, Mitsuru Doi, Yasuyo Fukada, Miwa Hayashi, Takeo Suzuki, Yuichi Takeuchi, Kenji Nakashima
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  ABSTRACT: We report a patient with anterior and posterior inferior cerebellar artery infarction, which manifested as profound deafness, transient vertigo, and minimal cerebellar signs. We suspect that ischaemia of the left internal auditory artery, which originates from the anterior inferior cerebellar artery, caused the deafness and transient vertigo. A small lesion in the middle cerebellar peduncle in the anterior inferior cerebellar artery territory and no lesion in the dentate nucleus in the posterior inferior cerebellar artery territory are thought to explain the minimal cerebellar signs despite the relatively large size of the infarction. Thus a relatively large infarction of the vertebral-basilar territory can manifest as sudden deafness with vertigo. Neuroimaging, including magnetic resonance imaging, is strongly recommended for patients with sudden deafness and vertigo to exclude infarction of the vertebral-basilar artery territory.
  Journal of Clinical Neuroscience 01/2007; 13(10):1051-4. · 1.25 Impact Factor
• Article: Spontaneous haemophilus influenzae type B meningoventriculitis with intraventricular debris.

  Hiroyuki Nakayasu, Hiroaki Sawada, Mitsuru Doi, Miwa Hayashi, Takenobu Murakami, Kenji Nakashima
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  ABSTRACT: Here we report the first case of spontaneous occurrence of Haemophilus influenzae type B meningoventriculitis. A 47-year-old man suffered from fever and headache. He had neck stiffness, and his cerebrospinal fluid (CSF) was turbid and yellowish. Gram staining and latex agglutination test of his CSF indicated that Haemophilus influenzae type B was the causative organism. Cranial CT and MRI revealed right ventricular debris accumulation, periventricular hyperintense signal, and periventricular ependymal enhancement. He was treated with intravenous administration of antibiotics, and his clinical condition and MRI findings gradually improved. Six weeks after onset, he was discharged without sequelae.
  Internal Medicine 05/2005; 44(4):332-4. · 0.94 Impact Factor