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Takashi Hanakawa

Publications and source records attributed to Takashi Hanakawa.

At least 19 recordsLinked to original sources
PubMed2006

Fibers from the dorsal premotor cortex elicit motor-evoked potential in a cortical dysplasia.

OBJECTIVE: To identify the fibers originating from the dorsal premotor cortex (dorsal PMC) that contribute to motor-evoked potentials (MEP), we have applied integrated functional neuronavigation and awake surgery during removal of an epileptic cortical dysplasia located in the right premotor cortex. METHODS: Chronic subdural electrodes were employed for functional mapping during a routine invasive evaluation for intractable epilepsy. After the fibers originating from the dorsal PMC were plotted into the tractography-integrated functional neuronavigation, subcortical MEPs and clinical symptoms were examined during resection of the epileptogenic dorsal PMC. RESULTS: During removal of the epileptogenic area, MEPs were elicited by electrical stimulation of the fibers originating from the dorsal PMC, which were separated from the pyramidal tracts from the precentral gyrus. Resection of the dorsal PMC and its fibers caused a transient dysmetric movement of the left toe without motor weakness. CONCLUSION: Functional corticospinal tract fibers originating from the dorsal PMC can be defined and removed safely under local anesthesia with the aid of integration of functional neuronavigation and subcortical electrical stimulation.

Adolescent↗
PubMed2006

Corticospinal tract localization: integration of diffusion-tensor tractography at 3-T MR imaging with intraoperative white matter stimulation mapping--preliminary results.

Institutional review board approval and written informed consent were obtained. The purpose of this study was to prospectively validate usefulness of diffusion-tensor (DT) fiber tractography of the corticospinal tract at 3-T magnetic resonance imaging, in combination with the subcortical motor-evoked potential (MEP) technique, as a tool for tractography-guided neurosurgery. DT imaging and corticospinal tractography were performed at 3 T in eight patients (four men, four women; mean age, 41 years; age range, 23-58 years) with intracranial space-occupying lesions. Tractography data were transferred to a neuronavigation system, and tractography-guided neurosurgery was performed. During lesion resection, subcortical MEPs were recorded. Positive MEP response was observed in four patients. No patients developed new motor weakness postoperatively. Complementary use of tractography and MEP may be useful for intraoperative depiction of corticospinal tracts.

Adult↗
PubMed2006

Direct and fast detection of neuronal activation in the human brain with diffusion MRI.

Using MRI, we found that a slowly diffusing water pool was expanding (1.7 +/- 0.3%) upon activation on the human visual cortex at the detriment of a faster diffusing pool. The time course of this water phase transition preceded the activation-triggered vascular response detected by usual functional MRI by several seconds. The observed changes in water diffusion likely reflect early biophysical events that take place in the activated cells, such as cell swelling and membrane expansion. Although the exact mechanisms remain to clarify, access to such an early and direct physiological marker of cortical activation with MRI will provide opportunities for functional neuroimaging of the human brain.

Adult↗
PubMed2006

The neural basis of social tactics: An fMRI study.

One of the most powerful ways of succeeding in complex social interactions is to read the minds of companions and stay a step ahead of them. In order to assess neural responses to reciprocal mind reading in socially strained human relationships, we used a 3-T scanner to perform an event-related functional magnetic resonance imaging study in 16 healthy subjects who participated in the game of Chicken. Statistical parametric mapping showed that the counterpart effect (human minus computer) exclusively activated the medial frontal area corresponding to the anterior paracingulate cortex (PCC) and the supramarginal gyrus neighboring the posterior superior temporal sulcus (STS). Furthermore, when we analyzed the data to evaluate whether the subjects made risky/aggressive or safe/reconciliatory choices, the posterior STS showed that the counterpart had a reliable effect regardless of risky or safe decisions. In contrast, a significant opponent x selection interaction was revealed in the anterior PCC. Based on our findings, it could be inferred that the posterior STS and the anterior PCC play differential roles in mentalizing; the former serves as a general mechanism for mentalizing, while the latter is exclusively involved in socially risky decisions.

Adult↗
PubMed2006

Song and speech: brain regions involved with perception and covert production.

This 3-T fMRI study investigates brain regions similarly and differentially involved with listening and covert production of singing relative to speech. Given the greater use of auditory-motor self-monitoring and imagery with respect to consonance in singing, brain regions involved with these processes are predicted to be differentially active for singing more than for speech. The stimuli consisted of six Japanese songs. A block design was employed in which the tasks for the subject were to listen passively to singing of the song lyrics, passively listen to speaking of the song lyrics, covertly sing the song lyrics visually presented, covertly speak the song lyrics visually presented, and to rest. The conjunction of passive listening and covert production tasks used in this study allow for general neural processes underlying both perception and production to be discerned that are not exclusively a result of stimulus induced auditory processing nor to low level articulatory motor control. Brain regions involved with both perception and production for singing as well as speech were found to include the left planum temporale/superior temporal parietal region, as well as left and right premotor cortex, lateral aspect of the VI lobule of posterior cerebellum, anterior superior temporal gyrus, and planum polare. Greater activity for the singing over the speech condition for both the listening and covert production tasks was found in the right planum temporale. Greater activity in brain regions involved with consonance, orbitofrontal cortex (listening task), subcallosal cingulate (covert production task) were also present for singing over speech. The results are consistent with the PT mediating representational transformation across auditory and motor domains in response to consonance for singing over that of speech. Hemispheric laterality was assessed by paired t tests between active voxels in the contrast of interest relative to the left-right flipped contrast of interest calculated from images normalized to the left-right reflected template. Consistent with some hypotheses regarding hemispheric specialization, a pattern of differential laterality for speech over singing (both covert production and listening tasks) occurs in the left temporal lobe, whereas, singing over speech (listening task only) occurs in right temporal lobe.

Adult↗
PubMed2006

Comparison of 3.0- and 1.5-T three-dimensional time-of-flight MR angiography in moyamoya disease: preliminary experience.

PURPOSE: To prospectively compare 3.0- and 1.5-T three-dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiography in patients with moyamoya disease, with special emphasis on the visualization of abnormal netlike vessels (moyamoya vessels). MATERIALS AND METHODS: Study protocols were approved by the local ethics committee; written informed consent was obtained from all patients. The study included 24 consecutive patients with moyamoya disease (four male and 20 female patients). Patients ranged in age from 17 to 66 years (mean age, 41 years). Moyamoya disease had been diagnosed in all patients before they were entered into the study. All patients underwent 3D TOF MR angiography at both 3.0 and 1.5 T; imaging examinations were performed within 14 days of each other. Maximum intensity projections (MIPs) obtained with MR angiography performed at both 3.0 and 1.5 T were evaluated by two neuroradiologists; the visualization of moyamoya vessels was graded according to a 4-point scale. For both 3.0- and 1.5-T imaging, the number of high-signal-intensity areas and the summation of cross-sectional areas of high signal intensity on source images obtained at the same level of MR angiography were compared quantitatively by using the Wilcoxon matched-pair signed-rank test. RESULTS: Moyamoya vessels were better visualized on MIPs obtained with 3.0-T imaging than on MIPs obtained with 1.5-T imaging (P < .001). At the identical level of the source image, 3.0-T imaging depicted more high-signal-intensity areas than did 1.5-T imaging. Wider cross-sectional areas of moyamoya vessels were visualized with 3.0-T imaging than with 1.5-T imaging (P < .001). CONCLUSION: Moyamoya vessels are better depicted with MR angiography at 3.0 T than at 1.5 T.

Adolescent↗
PubMed2006

Brain activity during visuomotor behavior triggered by arbitrary and spatially constrained cues: an fMRI study in humans.

Rule-based behavior associating nonspatial visual stimuli with learned responses is called arbitrary visuomotor mapping, an ability that enriches behavioral repertoire. To better understand the underlying neural correlates, the present functional magnetic resonance imaging (fMRI) study explored brain activity during visually informed movement involving two different types of cues and two different effectors. After being trained on the tasks, six healthy subjects performed right or left finger tapping tasks according to either arbitrary cues or spatially constrained cues. An event-related fMRI experiment was conducted on a 3-T MRI. The image data were analyzed with statistical parametric mapping. With the aid of the probabilistic architectonic map in the stereotaxic space, we identified three types of task-related brain activity: cue-selective, effector-selective, and nonselective. The left ventrolateral prefrontal cortex and the rostral part of the right dorsal premotor cortex (PMd) exhibited cue-selective activity, which was greater during the arbitrary condition than the spatially constrained condition. The left ventral prefrontal activity may reflect retrieval of visuomotor association from memory in arbitrary context. The rostral part of the left PMd showed nonselective activity while the caudal part of the PMd on each side showed conspicuous effector-selective activity to the contralateral movement. These findings suggest functional demarcation of the PMd between its rostral and dorsal parts during visuomotor mapping.

Adult↗
PubMed2006

Diffusion-tensor fiber tractography: intraindividual comparison of 3.0-T and 1.5-T MR imaging.

PURPOSE: To prospectively evaluate the depiction of brain fiber tracts at 3.0- versus 1.5-T diffusion-tensor (DT) fiber tractography performed with parallel imaging. MATERIALS AND METHODS: Institutional review board approval was obtained, and each subject provided written informed consent. Subjects were 30 healthy volunteers (15 men, 15 women; mean age, 28 years; age range, 21-46 years). Single-shot spin-echo echo-planar magnetic resonance (MR) sequences with parallel imaging were applied. Four fiber tracts were reconstructed: corticospinal tract (CST), superior longitudinal fasciculus (SLF), corpus callosum (CC), and fornix. Two neuroradiologists compared 3.0- and 1.5-T tractography in terms of fiber tract depiction by using five depiction scores (scores 0-4) and numbers of reconstructed tract fibers and in terms of lateral asymmetry in the CST by using numbers of reconstructed fibers. The Wilcoxon signed rank test was applied for statistical analysis. RESULTS: Visual scores for both CST hemispheres (P < .001), the right SLF (P = .005), the CC (P = .01), and the right fornix (P = .04) were higher at 3.0-T DT tractography. Larger numbers of CST (right, P = .008; left, P < .001), SLF (right, P = .001; left, P = .02), and fornix (bilaterally, P = .02) tract fibers were depicted at 3.0 T. The asymmetry index for the CST was lower (P < .001) at 3.0 T. Visual scores for the left SLF and the left fornix and numbers of CC tract fibers were not significantly different. CONCLUSION: Depiction of most fiber tracts was improved at 3.0-T DT tractography compared with depiction at 1.5-T tractography.

Adult↗
PubMed2006

Increased midbrain gray matter in Tourette's syndrome.

OBJECTIVE: To investigate cerebral structure in Tourette's syndrome (TS). METHODS: Voxel-based morphometry study of high-resolution MRIs in 31 TS patients compared with 31 controls. RESULTS: Increased gray matter mainly in the left mesencephalon in 31 TS patients. INTERPRETATION: This result constitutes strong and direct evidence supporting Devinsky's hypothesis (Devinsky O. Neuroanatomy of Gilles de la Tourette's syndrome. Possible midbrain involvement. Arch Neurol 1983;40:508-514) according to which midbrain disturbances play an important pathogenic role in TS.

Adolescent↗
PubMed2006

MR imaging of Liliequist's membrane.

Liliequist's membrane is an arachnoid structure well-known to neurosurgeons. However, the importance of this membrane had been lost until the development of endoscopic third ventriculostomy (ETV). ETV is superior in its minimal invasiveness, but in some subgroups of hydrocephalus, the effectiveness of ETV may be reduced. Liliequist's membrane may block the cerebrospinal fluid (CSF) flow from the defect of the third ventricle floor, which may cause failure of ETV. Liliequist's membrane can be visualized on magnetic resonance (MR) imaging in normal healthy individuals, however, its visibility is different among individuals. CSF artifacts exist to varying degrees, but do not impede visualization of Liliequist's membrane in most subjects. Since Liliequist's membrane is a cisternal structure, the three-dimensional (3D) constructive interference in steady state (CISS) sequence is useful. The outcome of ETV could be predicted with MR imaging findings of Liliequist's membrane in a patient with obstructive hydrocephalus. High-field (> or =3 Tesla) MR imaging of Liliequist's membrane also offers superior resolution and is expected to provide additional information about Liliequist's membrane.

Arachnoid↗
PubMed2006

Early experience with 3-T magnetic resonance tractography in the surgery of cerebral arteriovenous malformations in and around the visual pathway.

OBJECTIVE: To evaluate of the role of magnetic resonance (MR) tractography on the optic radiation with a 3-T MR unit in the surgery of cerebral arteriovenous malformation (AVM) in and around the visual pathway. METHODS: Of the 322 patients with cerebral AVMs admitted to our clinic between 1978 and 2005, a study of MR tractography was made on 29 patients. Ten of those patients had AVMs in and around the visual pathway and were included in this study. There were two men and eight women ranging in age from 15 to 64 years (mean age, 34.5 +/- 14.8 yr). All of the patients underwent 3-T tractography of optic radiation (OR) and neuro-ophthalmologic evaluation. Four of the 10 patients underwent surgical resection of the AVM. A postoperative 3-T MR study and a neuro-ophthalmologic evaluation was performed 1 month after surgery in most patients. RESULTS: The preoperative patients for whom tractography demonstrated a continuous bundle of OR from the medial temporal region to the primary visual cortex had minimal or no visual field loss, whereas the patients for whom the tractography did not show a continuous bundle of OR had significant visual loss. The patients for whom tractography in the postoperative study demonstrated a bundle of OR experienced no postoperative deterioration of the visual field loss, whereas the patients for whom tractography did not demonstrate a bundle of OR exhibited significant visual field loss. CONCLUSION: This technique is thought to be useful in confirming the integrity of and localizing deviated tract and in evaluating the surgical risk, especially for nonhemorrhagic AVMs in and around the visual pathways, taking some limitations of this method into consideration.

Adolescent↗
PubMed2006

"Target bypass": a method for preoperative targeting of a recipient artery in superficial temporal artery-to-middle cerebral artery anastomoses.

OBJECTIVE: To introduce a method for preoperative targeting of a proper recipient artery in superficial temporal artery-to-middle cerebral artery anastomosis. METHODS: Six operations for superficial temporal artery-to-middle cerebral artery anastomosis in four patients with moyamoya disease or moyamoya-like disease and two operations in two patients with atherosclerotic cerebrovascular occlusive disease accompanied by coronary artery stenosis were performed using our method. Before surgery, a 3-Tesla magnetic resonance imaging study was performed with axial T1-weighted three-dimensional magnetization-prepared rapid acquisition gradient-echo sequences and three-dimensional time-of-flight magnetic resonance angiography. Data on quantitative regional cerebral blood flow were obtained by iodine-123-labeled N-isopropyl-iodoamphetamine single-photon emission computed tomography or positron emission computed tomography. The magnetic resonance angiography and regional cerebral blood flow data sets were registered with the magnetization-prepared rapid acquisition gradient-echo data set by means of the coregistration function of the SPM2 software. We examined the arteries located on or near the cortex where the regional cerebral blood flow had significantly decreased and used the coregistered data set and MRIcro software to select the cortical artery with the largest diameter as the target recipient artery. At the surgery, the data sets were applied to the neuronavigation system and the actual site of the target was confirmed in the operation before scalp incision. The superficial temporal artery was anastomosed with the target through a small craniotomy. RESULTS: Successful bypass surgery to the target was confirmed in all cases. CONCLUSION: The "target bypass" method might be effective for cases with moyamoya disease or for cases requiring surgery through a small craniotomy.

Adult↗
PubMed2006

[Focal cortical dysplasia at the primary somatosensory cortex could manifest both intractable partial epilepsy and cortical reflex myoclonus].

We report a 31-year-old patient who suffered from the left foot motor seizure since 6 years of age. In addition to spontaneous seizures, the seizures tended to be triggered by somatosensory stimulus to the left foot. Recently, he developed irregular myoclonic jerks of the left foot. Neurologically, he had mild impairment of fine movements of the left foot, but otherwise no weakness or sensory disturbance was noted. Interictal spikes were frequently recorded at the vertex region, where ictal discharges also started during the video-EEG monitoring. Electrical stimulation of the left tibial nerve evoked giant cortical components of somatosensory evoked potentials and C-reflex. Magnetoencephalographic study of both interictal and jerk-locked averaged spikes located the equivalent current dipole of both activities at the left foot primary somatosensory cortex (SI), where 3 tesla MRI revealed a focal abnormality consistent with focal cortical dysplasia. The present non-invasive investigation suggests that focal cortical dysplasia at SI could manifest intrinsic, autonomous, epileptogenicity as well as extrinsic, stimulus-sensitive, hyperexcitability, which are clinically manifested as spontaneous seizures and cortical reflex myoclonus, respectively.

Adult↗
PubMed2005

Enduring representational plasticity after somatosensory stimulation.

Somatosensory stimulation (SS), leading to increases in motor cortical excitability, influences motor performance in patients with brain lesions like stroke. The mechanisms by which SS modulates motor function are incompletely understood. Here, we used functional magnetic resonance imaging (fMRI, blood-oxygenation-level-dependent (BOLD), and perfusion imagings simultaneously acquired in a 3 T magnet) to assess the effects of SS on thumb-movement-related activation in three regions of interest (ROI) in the motor network: primary motor cortex (M1), primary somatosensory cortex (S1), and dorsal premotor cortex (PMd) in healthy volunteers. Scans were obtained in different sessions before and after 2-h electrical stimulation applied to the median nerve at the wrist (MNS), to the skin overlying the shoulder deltoid muscle (DMS), and in the absence of stimulation (NOSTIM) in a counterbalanced design. We found that baseline perfusion intensity was comparable within and across sessions. MNS but not DMS nor NOSTIM led to an increase in signal intensity and number of voxels activated by performance of median nerve-innervated thumb movements in M1, S1, and PMd for up to 60 min. Task-related fMRI activation changes were most prominent in M1 followed by S1 and to a lesser extent in PMd. MNS elicited a displacement of the center of gravity for the thumb movement representation towards the other finger representations within S1. These results indicate that MNS leads to an expansion of the thumb representation towards other finger representations within S1, a form of plasticity that may underlie the influence of SS on motor cortical function, possibly supporting beneficial effects on motor control.

Adult↗
PubMed2005

Surgical resection of an epileptogenic cortical dysplasia in the deep foot sensorimotor area.

Epileptogenic foci in the foot/leg motor area of cortex are rarely resected, due to the risks of the surgical procedures. A 31-year-old right-handed man with cortical dysplasia deep in the central sulcus suffered from disturbances in walking due to frequent daily seizures. Following subdural electrode implantation to define the epileptogenic area and assess cortical function, limited regions of cortex were removed from the foot/leg primary motor and sensory areas under local anesthesia until the epileptiform discharges disappeared. Postoperative motor weakness and sensory disturbances completely resolved within 2 weeks and 2 months, respectively; the patient has been free from seizures for more than a year and a half postsurgery. Intraoperative examination demonstrated that small and moderate cortical dysplasia in the depths of the central sulcus exhibits both intrinsic epileptogenicity and function. Focused resection of the lower extremity of the sensorimotor area may be a surgical strategy for intractable epilepsy if resolution of clinical symptoms with minimal dysfunction due to the limited size of the resection is expected to follow surgery.

Adult↗
PubMed2005

The role of the dorsal stream for gesture production.

Skilled gestures require the integrity of the neural networks involved in storage, retrieval, and execution of motor programs. Premotor cortex and/or parietal cortex lesions frequently produce deficits during performance of gestures, transitive more than intransitive. The dorsal stream links object information with object action, suggesting that mechanical knowledge of tool use is stored focally in the brain. Using event-related fMRI, we explored activity during instructed-delay transitive and intransitive hand gestures. The comparison between planning-preparation and execution of gestures demonstrated a temporal rostral to caudal gradient of activation in the ventral premotor cortex (PMv) and inferior to superior gradient of activation in the posterior parietal cortex (PPc). Comparison between transitive and intransitive gestures established a functional specificity within the dorsal stream for mechanical knowledge. Results demonstrate that not only PPc but also the PMv acts in the processing of sensorimotor information during gestures. This might be the substrate underlying selective deficits in ideomotor apraxia patients.

Adult↗
PubMed2005

Functional activity related to risk anticipation during performance of the Iowa Gambling Task.

Risk anticipation is an important cognitive/emotional component of decision making. The Iowa Gambling Task [Bechara, A., Damasio, A.R., Damasio, H., Anderson, S.W., 1994. Insensitivity to future consequences following damage to human prefrontal cortex. Cognition 50, 7-15], which is the most widely used "risk-anticipation task" in clinical studies, has been demonstrated to be sensitive to lesions involving the ventromedial prefrontal cortex or amygdala. However, the critical neural circuitry involved in this complex task has not yet been fully clarified even in healthy subjects. Using a 3-T scanner, we performed an event-related functional magnetic resonance imaging study in 14 healthy subjects performing the task. The statistical parametric mapping showed that the risk anticipation component (risky decisions minus safe decisions) exclusively activated the medial frontal gyrus. Furthermore, we found a significant interindividual correlation between the task performance and the magnitude of brain activity during risky decisions. These results indicate that the Iowa Gambling Task does recruit the neural circuitry that is critical in decision making under uncertainty, particularly when subjects perceive the risk of their decision.

Adult↗