Altered brain activation in schizophrenia during visually guided motor selection revealed by fMRI.
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Adult↗
Biomedical subjects
Y Yonekura
Publications and source records attributed to Y Yonekura.
Brain regions involved in verbal or non-verbal aspects of facial emotion recognition.
To depict the neural substrates for facial emotion recognition and to determine whether their activation is confounded by a verbal factor, we studied eight normal volunteers with functional magnetic resonance imaging (fMRI). Verbal and non-verbal sample stimuli were used in a facial emotion matching task and a gender matching task (control condition). Compared with the gender tasks, the emotion tasks significantly activated the right ventral prefrontal cortex, the right lingual cortex, and the left lateral fusiform cortex, irrespective of sample stimuli. The visual association cortices showed a significant interaction between the task and the material presented, as the activation for verbal materials was higher than for non-verbal materials during the emotion matching tasks. By contrast, no significant interaction was found in the right ventral prefrontal cortex. These results suggest that the verbal factor has a different effect on the neural networks for facial emotion, processing.
Brain Mapping↗
A milestone for normal development of the infantile brain detected by functional MRI.
OBJECTIVE: To investigate the relationship between cerebral cortical function and white matter myelination in the visual pathway in the evaluation of normal brain development. METHODS: The authors performed quantitative analysis of white matter myelination detected with conventional T1-weighted spin echo (SE) MRI and brain functional MRI (fMRI) using echoplanar imaging with photic stimulation in 27 neurologically normal infants (age range, 0 to 22 weeks). RESULTS: An age-dependent gradual increase in signal intensity was observed in optic radiation on the T1-weighted SE images, indicating progression of white matter myelination. A rapid age-dependent reverse in signal response was observed on fMRI. Infants older than 8 weeks showed a stimulus-induced signal decrease in the visual cortex, whereas infants younger than 7 weeks showed a signal increase. CONCLUSIONS: A rapid inversion of response revealed by fMRI with photic stimulation in infants suggests a change in oxygen consumption during neuronal activation, which is related to rapid synapse formation and accompanying increased metabolism. fMRI can detect dynamic metabolic changes during brain maturation, which is a different developmental process from white matter myelination. The metabolic changes detected by fMRI provide a milestone for the evaluation of normal brain development.
Brain↗
Neurotoxicity after hypoxia/during ischemia due to glutamate with/without free radicals as revealed by dynamic changes in glucose metabolism.
Fresh rat brain slices were incubated with [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG) in oxygenated Krebs-Ringer solution at 36 degrees C, and serial two-dimensional time-resolved images of [18F]FDG uptake in the slices were obtained on imaging plates. The fractional rate constant of [18F]FDG (proportional to the cerebral glucose metabolic rate) from pre-loading of ischemia (O(2) and glucose deprivation)/hypoxia (O(2) deprivation) to the reperfused/reoxygenated post-loading phase was quantitatively evaluated by applying the Gjedde-Patlak graphical method to the image data. Against ischemia an N-methyl-D-aspartate antagonist and hypothermia, but not a free radical scavenger, showed a protective effect when administered during ischemia, whereas no such effect was achieved with any of the above agents when administered after reperfusion. Against hypoxia, there was no protective effect with any of the above agents when administered during hypoxia, although an effect was noted with each when administered after reoxygenation. Excitatory amino acids during ischemia loading were found to be the main factor in the neuronal damage associated with ischemia, while in hypoxia, excitatory amino acids working in tandem with free radicals immediately after reoxygenation were implicated.
Animals↗
Posthypoxic reoxygenation-induced neurotoxicity prevented by free radical scavenger and NMDA/non-NMDA antagonist in tandem as revealed by dynamic changes in glucose metabolism with positron autoradiography.
Using a positron autoradiography technique, dynamic changes in the cerebral glucose metabolic rate (CMRglc) induced by hypoxia/reoxygenation were investigated in living brain slices. After incubating fresh rat brain slices (300 microm thick) with [(18)F]2-fluoro-2-deoxy-D-glucose ([(18)F]FDG) in oxygenated Krebs-Ringer solution at 36 degrees C, serial two-dimensional time-resolved images of [(18)F]FDG uptake in the slices were obtained on imaging plates. As compared to the unloaded control values, with hypoxia-loading [(18)F]FDG uptake increased markedly, suggesting enhanced glycolysis. The net influx constant (K) of [(18)F]FDG at pre-hypoxia-loading and after reoxygenation with loading hypoxia for various periods of time was quantitatively evaluated by applying the Patlak graphical method to the image data. Regardless of the brain region, with hypoxia of </=10-min duration, the K value returned to the preloading level, whereas with hypoxia of >/=20 min duration only partial or no recovery was seen, indicating irreversible neuronal damage. The 30-min administration of either N-methyl-D-aspartate (NMDA)/non-NMDA antagonist or a free radical scavenger at the same time as reoxygenation after 20 min hypoxia showed a neuroprotective effect inhibiting the decrease in the post-hypoxia-loading K value. In contrast, no such neuroprotective effect was evident with administration of either of these agents only during hypoxia loading, possibly indicating that immediately after reoxygenation neuronal damage was induced mediated by excitatory amino acids and free radicals in tandem. These results demonstrate that serial quantitative evaluation of CMRglc using this technique may be of use in investigating the brain tissue injury associated with hypoxia/reoxygenation as well as clarifying the underlying mechanisms and protective effect of various drugs against such injury.
6-Cyano-7-nitroquinoxaline-2,3-dione↗
Semi-quantitative approach to estimating GFR by magnetic resonance imaging.
OBJECTIVE: The purpose of this study was to compare a semi-quantitative approach to estimating glomerular filtration rate (GFR) by magnetic resonance imaging with radionuclide calculation of GFR, and to investigate whether spin echo or gradient echo is more suitable for estimating GFR. METHODS AND PATIENTS: Fourteen kidneys of seven patients (GFR ranging from 26 to 57 ml/min) were studied. Spin echo and gradient echo sequences interleaving each other at every excitation were used. After intravenous injection of gadopentetate dimeglumine, serial scans were performed. The signal intensities measured in the regions of interest were converted to time-transverse relaxation rate changes for both spin echo (DeltaR2) and gradient echo (DeltaR2*). The areas under the time-DeltaR2 and time-DeltaR2* curves were calculated as a semi-quantitative index of GFR for both spin echo and gradient echo images, and the results were compared by GFR measured by radionuclide imaging. RESULTS: The semi-quantitative index of the GFR calculated from spin echo images showed a significant correlation with the GFR measured by radionuclide imaging (r=0.85, P<0.001). On the other hand, the semi-quantitative index of the GFR calculated from gradient echo images showed no such correlation (r=0.46, P=0.10). CONCLUSION: Spin echo sequences may be more suitable than gradient echo sequences for the evaluation of GFR.
Adult↗
Difference in the metabolic response to photic stimulation of the lateral geniculate nucleus and the primary visual cortex of infants: a fMRI study.
The metabolic change that occurs during early development of the human brain was studied with functional magnetic resonance imaging (fMRI), in which the signal change reflects the balance between the supply and the demand of oxygen during stimulus-related neuronal activation. The subjects were 16 infants, aged < 1 year. They were sedated with pentobarbital, and 8-Hz flickering light was intermittently projected onto their eyelids. Two age groups were analyzed: infants < 60 days old and > 60 days old (corrected for gestational age at birth). The stimulus-related signal change was positive in the lateral geniculate nucleus regardless of the infants' age, but in the primary visual cortex reversed from positive in the younger group to negative in the older group. It is known that synaptogenesis in the lateral geniculate nucleus peaks before birth, and in the primary visual cortex accelerates in the second month after birth. Hence, the inversion of the stimulus-related signal change in the primary visual cortex may be due to an increased demand for oxygen owing to rapid synaptogenesis.
Aging↗
Functional asymmetry of human prefrontal cortex in verbal and non-verbal episodic memory as revealed by fMRI.
Functional neuroimaging studies have demonstrated preferential involvement of bilateral prefrontal cortex during episodic memory encoding and retrieval. The aim of the present study is to address the question whether left prefrontal model for encoding holds when highly non-verbal material is used, and which region of the brain is critically related to successful retrieval. To do this, seven normal subjects were investigated using functional magnetic resonance imaging (fMRI) during encoding and retrieval of word and checkerboard pattern. Our results revealed that word encoding activated the left prefrontal cortices and right cerebellum, whereas pattern encoding activated the bilateral middle frontal gyrus, superior parietal lobule, premotor area, and occipital visual cortex. Word-specific activation was found in the ventral prefrontal cortices, and pattern-specific activation located in the right dorsal prefrontal cortex. Conjunction analysis during encoding of word and pattern showed that activity in the left dorsal prefrontal cortex and the right cerebellum might relate to common neural network for encoding regardless of the type of material. Finally, the present study demonstrates strong association between the left ventral prefrontal cortex and retrieval success for word. The evidence, that both encoding and retrieval of words activated the left ventral prefrontal cortex, indicates that this area is involved in active and strategic operation of the mnemonic representation. A lack of the right prefrontal activation during retrieval was interpreted as that activity in this region might relate to retrieval effort rather than success.
Adult↗
Isolated heterotopic pancreas causing intussusception.
Pediatric intussusception is usually idiopathic in origin, and a pathological lesion at the leadpoint is identified in only a small proportion of cases. Meckel's diverticulum is the most common location when such a lesion is found. Heterotopic pancreas has been seen most frequently in the stomach or duodenum; however, ileal lesions are rare. In the ileum, heterotopic pancreas is usually associated with Meckel's diverticulum and may cause intestinal obstruction by intussusception. However, isolated heterotopic pancreas in the ileum is distinctly rare and usually discovered incidentally during surgery for other conditions. In a review of English language literature, there were only a few pediatric cases of isolated ileal heterotopic pancreas causing intussusception. We report three additional pediatric cases and discuss the clinical significance of this unexpected rare entity.
Choristoma↗
Hypoxic but not ischemic neurotoxicity of free radicals revealed by dynamic changes in glucose metabolism of fresh rat brain slices on positron autoradiography.
Dynamic changes in the regional cerebral glucose metabolic rate induced by hypoxia/reoxygenation or ischemia/reperfusion were investigated with a positron autoradiography technique. Fresh rat brain slices were incubated with [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG) in oxygenated Krebs-Ringer solution at 36 degrees C, and serial two-dimensional time-resolved images of [18F]FDG uptake in the slices were obtained. In the case of loading hypoxia (oxygen deprivation)/pseudoischemia (oxygen and glucose deprivation) for various periods of time, the net influx constant (K) of [18F]FDG at preloading and after reoxygenation/pseudoreperfusion (post-loading) was quantitatively evaluated by applying the Patlak graphical method to the image data. Regardless of the brain region, with hypoxia lasting > or =20 minutes, the postloading K value was decreased compared with the unloaded control, whereas with pseudoischemia of < or =40 minutes, approximately the same level as the unloaded control was maintained. Next, the neuroprotective effect against hypoxia/pseudoischemia loading induced by the addition of a free radical scavenger or an N-methyl-D-aspartate (NMDA) antagonist was assessed by determining whether a decrease in the postloading K value was prevented. Whereas with 20-minute hypoxia, both agents exhibited a neuroprotective effect, in the case of 50-minute pseudoischemia, only the NMDA antagonist did so, with the free radical scavenger being ineffective. These results demonstrate that hypoxia causes irreversible neuronal damage within a shorter period than ischemia, with both free radicals and glutamate suggested to be involved in tandem in the neurotoxicity induced by hypoxia, whereas glutamate alone is involved in ischemic neurotoxicity.
Animals↗
Vascular permeability: quantitative measurement with double-echo dynamic MR imaging--theory and clinical application.
Double-echo dynamic magnetic resonance (MR) imaging was used to evaluate both vascularity and permeability of tissues simultaneously. Vascularity was evaluated on the basis of the T2*-shortening effect due to the intravascular fraction of the contrast agent and permeability on the basis of the T1-shortening effect due to the extravascular fraction. Meningioma was characterized on the basis of higher vascularity and neurinoma on the basis of higher permeability. The proposed method enables better tissue characterization.
Adult↗
Inaudible high-frequency sounds affect brain activity: hypersonic effect.
Although it is generally accepted that humans cannot perceive sounds in the frequency range above 20 kHz, the question of whether the existence of such "inaudible" high-frequency components may affect the acoustic perception of audible sounds remains unanswered. In this study, we used noninvasive physiological measurements of brain responses to provide evidence that sounds containing high-frequency components (HFCs) above the audible range significantly affect the brain activity of listeners. We used the gamelan music of Bali, which is extremely rich in HFCs with a nonstationary structure, as a natural sound source, dividing it into two components: an audible low-frequency component (LFC) below 22 kHz and an HFC above 22 kHz. Brain electrical activity and regional cerebral blood flow (rCBF) were measured as markers of neuronal activity while subjects were exposed to sounds with various combinations of LFCs and HFCs. None of the subjects recognized the HFC as sound when it was presented alone. Nevertheless, the power spectra of the alpha frequency range of the spontaneous electroencephalogram (alpha-EEG) recorded from the occipital region increased with statistical significance when the subjects were exposed to sound containing both an HFC and an LFC, compared with an otherwise identical sound from which the HFC was removed (i.e., LFC alone). In contrast, compared with the baseline, no enhancement of alpha-EEG was evident when either an HFC or an LFC was presented separately. Positron emission tomography measurements revealed that, when an HFC and an LFC were presented together, the rCBF in the brain stem and the left thalamus increased significantly compared with a sound lacking the HFC above 22 kHz but that was otherwise identical. Simultaneous EEG measurements showed that the power of occipital alpha-EEGs correlated significantly with the rCBF in the left thalamus. Psychological evaluation indicated that the subjects felt the sound containing an HFC to be more pleasant than the same sound lacking an HFC. These results suggest the existence of a previously unrecognized response to complex sound containing particular types of high frequencies above the audible range. We term this phenomenon the "hypersonic effect."
Acoustic Stimulation↗
[Dopamine transporter SPECT in patients with Parkinson's disease].
The major neuropathological feature in Parkinson's disease (PD) is severe degeneration of the dopamine (DA) neurons in the substantia nigra. Dopamine transporter (DAT) is an important protein in the regulation of DA neurotransmission. It has been reported that PD patients show a loss of DAT in striatum. We report here the findings of single photon emission computed tomography (SPECT) of the DAT with 2 beta-carboxymethoxy-3 beta-(4[123I]iodophenyl)tropane ([123I] beta-CIT) to investigate striatal DAT in 10 patients with PD, one patient with vascular parkinsonism (VP), and one patient with dystonia syndrome. Patients were evaluated using the Webster rating scale. Specific/nondisplaceable striatal binding ratio (V3") was obtained in each case. In PD patients, the uptake of [123I] beta-CIT was reduced, especially in the tail of putamen compared with caudate nucleus. Even in the early stage of PD, the uptake of beta-CIT was reduced not only in the severely affected side, but also in the mildly disturbed side of the brain. Putamen caudate ratio was generally low in PD patients. In VP patient, the uptake was reduced, but putamen caudate ratio was not decreased. V3" values showed significant correlation with the severity of clinical symptoms such as self-care, facies, posture, gait, speech, and Hoehn-Yahr's stage. On the other hand, V3" values were not significantly correlated with the degree of tremor, seborrhea, and duration of the illness. In conclusion, we found that SPECT of the [123I] beta-CIT is a useful method for the diagnosis in the patients presenting parkinsonism, and for the clinico-physiological estimation of parkinsonian symptoms such as self-care, facies, posture, gait, and speech.
Adult↗
Evaluation of brain metabolism in steno-occlusive carotid artery disease by proton MR spectroscopy: a correlative study with oxygen metabolism by PET.
UNLABELLED: Carotid occlusive diseases may cause ischemic changes in both the gray matter and the white matter as a result of hemodynamic compromise. To validate the use of proton magnetic resonance spectroscopy (MRS) in evaluating the carotid occlusive diseases, we compared changes in peaks of choline, in the sum of creatine and phosphocreatine, and in N-acetyl-aspartate (NAA) of the white matter with cortical oxygen metabolism measured by PET. METHODS: Eleven patients with unilateral steno-occlusive carotid artery disease underwent PET and MRS. Ten age-matched healthy volunteers underwent MRS. No subjects had cortical infarction. MRS was performed bilaterally in the centrum semiovale. Regional blood flow, regional metabolic rate of oxygen (rCMRO2), and regional oxygen extraction fraction (rOEF) of the cerebral cortex were measured by the steady-state method with 15O gas. RESULTS: The asymmetry index of the ratio of NAA to the sum of creatine and phosphocreatine (NAA/Cr) correlated positively with the asymmetry index of rCMRO2 (r = 0.77; P < 0.01). Because rCMRO2 is a marker of tissue viability, the NAA/Cr of the centrum semiovale may reflect viable neuronal cells. The asymmetry index of the ratio of choline to the sum of creatine and phosphocreatine (Cho/Cr) showed a significant positive correlation with the asymmetry index of rOEF (r = 0.65; P < 0.05). All but 1 patient with an increased Cho/Cr (>1.03) showed an increase in rOEF of the ipsilateral cortex (>0.56). This finding may indicate membrane damage caused by ischemia, because the centrum semiovale is the deep watershed zone. CONCLUSION: The metabolic changes in the centrum semiovale detected by proton MRS reflect a hemodynamically compromised state and are useful in evaluating tissue viability.
Aged↗
Noninvasive estimation of FDG input function for quantification of cerebral metabolic rate of glucose: optimization and multicenter evaluation.
UNLABELLED: The aims of this study were to determine whether body weight or body surface area (BSA) should be used for noninvasive measurement of the cerebral metabolic rate of glucose (CMRGlc) by FDG PET with a standardized input function (SIF) and an autoradiographic method and to validate the procedure in a large population from different PET centers. METHODS: Plasma input functions measured by intermittent arterial blood sampling after intravenous injection of FDG, in 101 patients from 1 institution who were fasting for at least 4 h, were used to generate the SIF. The SIF was generated by averaging over 101 patients the input function normalized with the net injected dose and initial distribution volume (DV) of FDG estimated by the formula c x Ha x Wb, where H is body height and W is body weight. To evaluate the estimation of DV by BSA or body weight, the coefficient of variation (CV) of the ratio of Ha x Wb to the measured DV was calculated by changing a and b independently. Estimation of the CMRGlc with SIF based on the formula for DV was validated with an additional 192 subjects from 3 institutions who underwent FDG PET while fasting. The result of simulation was compared with the results of 4 previously published formulas for BSA and body weight. RESULTS: The optimal set of parameters, in which a was 0.80 and b was 0.35, minimized the CV. The averaged percentage error of the CMRGlc based on the optimal set of parameters for DV estimation and SIF was 8.9% for gray matter and 10.6% for white matter. Four BSA formulas brought about a similar error, which was significantly smaller than that based on body weight (P < 0.001, ANOVA). CONCLUSION: Noninvasive estimation of CMRGlc is made possible by careful measurement of the net injected dose and BSA.
Autoradiography↗
Analysis of music-brain interaction with simultaneous measurement of regional cerebral blood flow and electroencephalogram beta rhythm in human subjects.
To elucidate the neural substrates of the receptive aspect of music, we measured regional cerebral blood flow (rCBF) with positron emission tomography (PET) and simultaneously recorded the electroencephalogram (EEG) in eight normal volunteers. Compared with the rest condition, listening to music caused a significant increase in EEG beta power spectrum (13-30 Hz) averaged over the posterior two third of the scalp. The averaged beta power spectrum was positively correlated with rCBF in the premotor cortex and adjacent prefrontal cortices bilaterally, the anterior portion of the precuneus and the anterior cingulate cortex in both the rest and the music conditions. Listening to music newly recruited the posterior portion of the precuneus bilaterally. This may reflect the interaction of the music with the cognitive processes, such as music-evoked memory recall or visual imagery.
Adult↗
Potential usefulness of 18F-2-fluoro-deoxy-D-glucose positron emission tomography in cervical compressive myelopathy.
STUDY DESIGN: This case study describes the usefulness of high-resolution 18F-2-fluoro-deoxy-D-glucose (18FDG)-positron emission tomography (PET) for metabolic neuroimaging of the cervical spinal cord in patients with compressive myelopathy. OBJECTIVE: To examine whether 18FDG-PET imaging could visualize deterioration of cervical spinal cord function associated with a variable degree of compression and to determine its potential usefulness during assessment of myelopathy. SUMMARY OF BACKGROUND DATA: A few studies have described the use of 18FDG-PET imaging in cervical cord diseases, but visualization of the cervical spinal cord before and after surgical decompression for compressive myelopathy has not been reported. The potential usefulness of 18FDG-PET imaging for assessment of the function of compressed cervical cord has not been discussed previously. METHODS: An 18FDG-PET scan was performed before and after surgery in seven patients with cervical compressive myelopathy. The correlation between the metabolic rate of glucose of the cervical spinal cord and neurologic scores was evaluated. The metabolic rate of glucose in different vertebral levels was also measured. RESULTS: Preoperative metabolic rate of glucose was high in two patients but low in the other five. At the time of the second postoperative examination, metabolic rate of glucose was higher in six of the seven patients, and the increase was associated with neurologic improvement. Use of 18FDG was not related to changes in signal intensities on T2-weighted magnetic resonance images. The metabolic rate of glucose decreased at the affected vertebral level in four patients, increased in two, and did not change in one, relative to the unaffected levels. CONCLUSIONS: High-resolution 18FDG-PET neuroimaging may provide clinically useful qualitative and quantitative estimation of impaired metabolic activity of the compromised cervical spinal cord in compressive myelopathy. 18FDG-PET images may also offer additional information related to neuronal dysfunction induced by mechanical compression.
Adult↗
Dynamic changes in glucose metabolism induced by thiamine deficiency and its replenishment as revealed by a positron autoradiography technique using rat living brain slices.
Dynamic changes in the cerebral glucose metabolic rate (CMRglc) before and after thiamine replenishment were investigated in living brain slices obtained from pyrithiamine-treated (PT) and pair-fed control rats by use of a positron autoradiography technique. Fresh rat brain slices (300 microm thick) were incubated with [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG) in oxygenated Krebs-Ringer solution at 36 degrees C, during which serial two-dimensional images of [18F]FDG uptake in the slices were constructed on the imaging plates. The net influx constant (=K) of [18F]FDG was determined by a Patlak graphical method of the image data. Prior to thiamine pyrophosphate (TPP)-loading, the K value in the neurologically symptomatic PT was higher in all brain regions except the thalamus and mammillary body than the control, suggesting compensatory enhanced glycolysis. The rapid decrease in this heightened net influx constant immediately after TPP-loading was surmised to be due to activation of pyruvate oxidation with lactate as the substrate, with this inhibiting the glycolysis. From > or = 150 min after TPP-loading, the K value continued to show low values in the thalamus and mammillary body, which are regarded as the responsible sites for Korsakoff syndrome, whereas in all other sites recovery to control values was observed. These findings suggest that using this technique the quantitative evaluation of serial local changes in CMRglc from thiamine deficiency to after its replenishment may be useful in elucidating the pathophysiology and prognosis of Wernicke's encephalopathy.
Animals↗