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Journal of neurosurgery 2009 Sep; 111(4)
A novel composite targeting method using high-field magnetic resonance imaging for subthalamic nucleus deep brain stimulation.
OBJECT: Accurate localization of the subthalamic nucleus (STN) is important for proper placement of the electrodes in deep brain stimulation (DBS) surgery for patients with advanced Parkinson disease. The authors evaluated the accuracy of our modifie... expand abstractd composite targeting method and the value of using high-field MR imaging for targeting the STN. METHODS: Thirteen patients with advanced Parkinson disease underwent bilateral STN DBS based on 3-T MR imaging, and 13 patients underwent surgery based on 1.5-T MR imaging. By sequentially referring to the postmammillary commissure, the red nucleus, the mammillothalamic tract, and the STN, the modified composite targeting method determined the stereotactic coordinates for targeting the STN. The accuracy and efficacy of the composite targeting method and 3-T MR imaging were evaluated by using the intraoperative microelectrode recording, the postoperative imaging study, and the postoperative clinical improvement. RESULTS: The landmark structures for targeting the STN were visualized clearly with 3-T MR imaging. The mean (+/- SD) path length through the STN of the central track was 4.9 +/- 1.1 mm in the 3-T group and 3.1 +/- 2.0 mm in the 1.5-T group (p < 0.001). Twenty-one (81%) of 26 electrodes were placed in the central track in the 3-T group, whereas 8 (31%) of 26 electrodes were placed in the central track in the 1.5-T group (p = 0.006). The rest of the electrodes were placed in the noncentral optimum track for alleviating parkinsonian motor symptoms. The mean Unified Parkinson's Disease Rating Scale motor part score during off period was reduced by 53% in the 3-T group and by 41% in the 1.5-T group (p = 0.14). The mean reductions of levodopa equivalent daily doses were 48.6% in the 3-T group and 43.7% in the 1.5-T group (p = 0.61). CONCLUSIONS: The use of the modified composite targeting method referring to the multiple landmarks with 3-T MR imaging offers reliable and clinically effective target for STN DBS surgery. collapse abstract
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NeuroImage 2010 Jan; 49(2)
Gait disturbance associated with white matter changes: a gait analysis and blood flow study.
To clarify the mechanisms underlying gait disturbance secondary to age-related white matter changes (ARWMC), cerebral perfusion was investigated during treadmill walking. Twenty subjects with extensive hyperintensities in the periventricular and deep... expand abstract white matter on T(2)-weighted magnetic resonance images (MRI) were recruited. The ARWMC subjects were classified into gait-disturbed (GD) and non-GD groups according to clinical criteria. All the subjects underwent gait analyses and cerebral perfusion measurements during both gait and rest by using single photon emission computed tomography. The GD group showed greater double support time/phase and stride width, and slower walking velocity, than the non-GD group. In an analysis of pooled data from all the subjects, gait-induced increases in cerebral perfusion were observed in the supplementary motor areas (SMA), lateral premotor cortex (PMC), primary motor and somatosensory areas, visual areas, basal ganglia and cerebellum. A between-group comparison of gait-induced perfusion changes showed relative underactivation of the SMA, thalamus and basal ganglia, together with relative overactivation of the PMC, in the GD group compared with the non-GD group. In a separate correlation analysis including all the subjects, as the double support phase was longer (that was, gait disturbance was more severe), the gait-induced perfusion changes were proportionally reduced in the SMA, visual cortex, and thalamus. The present study suggests that abnormalities in the basal ganglia-thalamo-cortical loops partly explain gait disturbance observed in a subset of subjects with ARWMC. collapse abstract
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NeuroImage 2009 Dec; 49(1)
Differential effect of double-pulse TMS applied to dorsal premotor cortex and precuneus during internal operation of visuospatial information.
Human neuro-imaging studies have often reported co-activation of the dorsal premotor cortex (PMd) and the posterior parietal cortex (PPC) during internal operation of visuospatial information, referred to here as "visuospatial mental operation". Howe... expand abstractver, the functions assigned to the PMd and PPC during these tasks are still unclear. Here, we examined the significance of these two areas for a visuospatial mental operation using the transcranial magnetic stimulation (TMS) technique. Subjects performed a task in which a visuospatial mental operation was required. A localization study conducted prior to the TMS experiment using functional magnetic resonance imaging (fMRI) revealed that the PMd and the medial part of the PPC, precuneus (PCu), were specifically activated during the visuospatial mental operation. Then, we impeded the activities of the PMd and the PCu in the right hemisphere during the same task using double-pulse TMS to determine whether these activities were necessary for the task. The TMS was applied at different times in relation to the visuospatial mental operation cue. Consequently, only the TMS applied at 300 ms after the cue affected the task performance. Furthermore, we found that the TMS at this time to each area differentially affected the performance: TMS to the PMd hindered the performance of the task whereas TMS to the PCu facilitated it without a speed/accuracy trade-off. These effects were not found in the control condition that lacked a visuospatial mental operation. These findings suggest that the PMd and the PCu are involved in differential aspects of visuospatial mental operations. collapse abstract
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Epileptic disorders : international epilepsy journal with videotape 2009 May; 11(2)
Impairment of the cortical GABAergic inhibitory system in catatonic stupor: a case report with neuroimaging.
We report the case of a 32-year-old patient who presented with catatonic stupor during the course of acute aseptic encephalitis involving the right frontotemporal area. Flumazenil-PET performed during the stupor indicated decreased benzodiazepine rec... expand abstracteptor binding in the right frontotemporal area where glucose metabolism was preserved as revealed by FDG-PET. An injection of diazepam immediately ameliorated catatonic symptoms and reduced widespread high amplitude slow EEG activities with right frontotemporal predominance. Compared with a SPECT study performed a week earlier, there was no abnormal right-sided anteriorly predominant cerebral hyperperfusion after injection of diazepam. While neither flumazenil- nor FDG-PET could be repeated, and with the caveat that generalized convulsions occurred initially and epilepsia partialis continua was present for two weeks starting on the 23rd day after illness onset, these findings suggest that in our case the presentation with catatonic stupor may be related to impairment of the cortical GABAergic inhibitory system. collapse abstract
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Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale 2009 Jun; 196(3)
Enhancement of pinch force in the lower leg by anodal transcranial direct current stimulation.
Transcranial direct current stimulation (tDCS) is a procedure to polarize human brain. It has been reported that tDCS over the hand motor cortex transiently improves the performance of hand motor tasks. Here, we investigated whether tDCS could also i... expand abstractmprove leg motor functions. Ten healthy subjects performed pinch force (PF) and reaction time (RT) tasks using the left leg before, during and after anodal, cathodal or sham tDCS over the leg motor cortex. The anodal tDCS transiently enhanced the maximal leg PF but not RT during its application. Neither cathodal nor sham stimulation changed the performance. None of the interventions affected hand PF or RT, showing the spatial specificity of the effect of tDCS. These results indicate that motor performance of not only the hands but also the legs can be enhanced by anodal tDCS. tDCS may be applicable to the neuro-rehabilitation of patients with leg motor disability. collapse abstract
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Cerebral cortex (New York, N.Y. : 1991) 2009 Oct; 19(11)
Stimulus-response profile during single-pulse transcranial magnetic stimulation to the primary motor cortex.
We examined the stimulus-response profile during single-pulse transcranial magnetic stimulation (TMS) by measuring motor-evoked potentials (MEPs) with electromyographic monitoring and hemodynamic responses with functional magnetic resonance imaging (... expand abstractfMRI) at 3 Tesla. In 16 healthy subjects, single TMS pulses were irregularly delivered to the left primary motor cortex at a mean frequency of 0.15 Hz with a wide range of stimulus intensities. The measurement of MEP proved a typical relationship between stimulus intensity and MEP amplitude in the concurrent TMS-fMRI environment. In the population-level analysis of the suprathreshold stimulation conditions, significant increases in hemodynamic responses were detected in the motor/somatosensory network, reflecting both direct and remote effects of TMS, and also the auditory/cognitive areas, perhaps related to detection of clicks. The stimulus-response profile showed both linear and nonlinear components in the direct and remote motor/somatosensory network. A detailed analysis suggested that the nonlinear components of the motor/somatosensory network activity might be induced by nonlinear recruitment of neurons in addition to sensory afferents resulting from movement. These findings expand our basic knowledge of the quantitative relationship between TMS-induced neural activations and hemodynamic signals measured by neuroimaging techniques. collapse abstract
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Neurocase : case studies in neuropsychology, neuropsychiatry, and behavioural neurology 14(6)
Small orbitofrontal traumatic lesions detected by high resolution MRI in a patient with major behavioural changes.
We report a case of a male patient who showed personality changes and marked social problems after a traumatic brain injury. Although suspected to have lesions in the orbitofrontal cortex because of the typical characteristics of his behavioural chan... expand abstractge, lesions were not apparent using conventional imaging techniques. However, investigation using high-resolution MRI revealed lesions in the orbitofrontal cortex. Our case suggests that standard MRI scanning techniques may have only limited power. Hence, we stress the important role played by qualitative assessments of emotion, personality, and social behaviour in evaluating sequelae of traumatic orbitofrontal injuries. collapse abstract
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Journal of vision 8(10)
Neural correlates of the stereokinetic effect revealed by functional magnetic resonance imaging.
The stereokinetic effect (SKE) refers to a visual phenomenon in which a two-dimensional figure rotating in the fronto-parallel plane about the visual axis can create the impression of a three-dimensional (3-D) object. Although several characteristics... expand abstract of SKE suggest that the perceptual mechanisms involved in SKE may differ from those of the kinetic depth effect (KDE), the differences between SKE and KDE in neural mechanisms have not yet been investigated. In order to determine the cortical areas involved in SKE, we presented a variety of SKE stimuli in a series of functional magnetic resonance imaging experiments, controlling for motion and contrast energies as well as stimulus presentation paradigm. Cortical activation associated with SKE was observed in the middle temporal complex (hMT+), lateral occipital area (LO), V3B, inferior temporal gyrus (ITG), fusiform gyrus (FG), and dorsal intraparietal sulcus anterior (DIPSA). On the other hand, ITG, FG, and DIPSA were also activated by the static versions of SKE stimuli. hMT+, LO, and V3B are also known to be activated in KDE. These findings suggest that general motion-dependent 3-D object processing may be performed in these areas. collapse abstract
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NeuroImage 2009 Mar; 45(2)
Connectivity and signal intensity in the parieto-occipital cortex predicts top-down attentional effect in visual masking: an fMRI study based on individual differences.
Top-down attention affects even the early stages of visual processing. For example, several studies have reported that instructions prior to the presentation of visual stimuli can both enhance and reduce visual masking. The finding that top-down proc... expand abstractessing influences perceptual processing is called the attentional effect. However, the magnitude of the attentional effect differs between individuals, and how these differences relate to brain activation remains to be explained. One possibility would be that activation intensity predicts the magnitude of the attentional effect. Another possible explanation would be that effective connectivity among activated areas determines the attentional effect. In the present study, we used structural equation modeling to analyze individual differences in the attentional effect on visual masking, in relation to the signal and connectivity strength of activated brain regions prior to presentation of the visual stimuli. The results showed that signal intensity was positively correlated with attentional effect in the occipital areas, but not in fronto-parietal areas, and the effect was also positively correlated with connective efficiency from the right intraparietal sulcus (IPS) to the bilateral fusiform gyrus (GF). Furthermore, a higher degree of effective connections from the right IPS to the GF led to greater neural activity in the GF. We therefore propose that the effective modulator in the parietal areas and strong activation in the visual areas together and in cooperation predict higher attentional effects in visual processing. collapse abstract
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Behavioural brain research 2009 Mar; 198(1)
Functional coupling underlying motor and cognitive functions of the dorsal premotor cortex.
This review article discusses mechanisms of how distinct behavioral operations are organized by different modules distributed in the frontal cortex. Cognitive manipulation often requires a flow of multiple elementary sub-operations processed in speci... expand abstractalized brain regions. The dorsolateral prefrontal cortex (dlPFC) is likely responsible for attentional selection, which orients organisms' mental resources to behaviorally relevant information. The dorsal premotor cortex (PMd) is implicated to possess a functional gradient along the rostral-caudal axis. The rostral sector of the PMd (pre-PMd) is involved in various cognitive/premovement processes while its caudal sector (PMd proper) primarily controls actual movement. Neurophysiology studies in monkeys have shown that the pre-PMd, when functionally coupled with the dlPFC, may transform independent working memory items into a single sequence (sequence generation). A neuroimaging study has shown that the pre-PMd is indeed involved in sequence generation under the influence of the dlPFC in humans. It has been also indicated that the dlPFC and the pre-PMd are functionally coupled when attentional selection and sequence generation are to be unified for serial information processing. Functional interplay through the prefrontal-premotor connections may mediate the integration of specific sub-operations for multi-step cognitive manipulation. Furthermore, evidence from a meta-analysis of the imaging literature is argued for an idea that the coupling pattern with other frontal cortical areas may characterize of the function of the pre-PMd and PMd proper in various motor and cognitive tasks. collapse abstract
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Journal of neurology 2008 Oct; 255(11)
Hemispheric asymmetry of the arcuate fasciculus: a preliminary diffusion tensor tractography study in patients with unilateral language dominance defined by Wada test.
OBJECTIVE: Lateralization of language function is a prominent feature of human brain function, and its underlying structural asymmetry has been recently reported in normal right-handed subjects. By means of diffusion tensor tractography (DTT), we inv... expand abstractestigated the asymmetry of the language network, namely, the arcuate fasciculus in patients in whom the unilateral language dominance was defined by Wada test. METHODS: DTT was performed in 24 patients with a focal lesion or an epileptic focus outside the C-shaped segment of the arcuate fasciculus. The arcuate fasciculus was reconstructed by placing two regions-of-interest in the deep white matter lateral to the corona radiata. The pathway was then divided into one terminating in the temporal lobe (FT tract) and the other in the parietal lobe (FP tract). The relative number and volume of the FT and FP tracts in each hemisphere were submitted to repeated measure ANOVA separately, with the hemisphere as a within-subject factor and with the side of pathology as a between subject factor. RESULTS: The FT tract showed a significantly larger number and volume in the language dominant hemisphere than in the non-dominant hemisphere, while, for the FP tract, no significant hemispheric difference was observed in the relative number or volume. There was a tendency that the FT tract was less lateralized when the pathology was located in the dominant hemisphere than in the non-dominant hemisphere. CONCLUSION: Dominance of the FT tract in the language dominant hemisphere was demonstrated for the first time in a patient population and implicated a clinical utility of DTT for non-invasive evaluation of language lateralization. Our preliminary study might indicate reorganization of the language network in conjunction with pathology. collapse abstract
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Cerebral cortex (New York, N.Y. : 1991) 2008 Dec; 19(1)
Involvement of insula and cingulate cortices in control and suppression of natural urges.
The physiology of control and suppression of natural urges is not well understood. We used [(15)O]H(2)O positron-emission tomography imaging to identify neural circuits involved in suppression of spontaneous blinking as a model of normal urges. Suppr... expand abstractession of blinking was associated with prominent activation of bilateral insular-claustrum regions, right more than left; activation was also found in bilateral anterior cingulate cortex (ACC), supplementary motor areas, and the face area of the primary motor cortex bilaterally. These results suggest a central role for the insula possibly together with ACC in suppression of blinking. collapse abstract
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Cerebral cortex (New York, N.Y. : 1991) 2008 Nov; 18(12)
Motor planning, imagery, and execution in the distributed motor network: a time-course study with functional MRI.
Activation of motor-related areas has consistently been found during various motor imagery tasks and is regarded as the central mechanism generating motor imagery. However, the extent to which motor execution and imagery share neural substrates remai... expand abstractns controversial. We examined brain activity during preparation for and execution of physical or mental finger tapping. During a functional magnetic resonance imaging at 3 T, 13 healthy volunteers performed an instructed delay finger-tapping task either in a physical mode or mental mode. Number stimuli instructed subjects about a finger-tapping sequence. After an instructed delay period, cue stimuli prompted them either to execute the tapping movement or to imagine it. Two types of planning/preparatory activity common for movement and imagery were found: instruction stimulus-related activity represented widely in multiple motor-related areas and delay period activity in the medial frontal areas. Although brain activity during movement execution and imagery was largely shared in the distributed motor network, imagery-related activity was in general more closely related to instruction-related activity than to the motor execution-related activity. Specifically, activity in the medial superior frontal gyrus, anterior cingulate cortex, precentral sulcus, supramarginal gyrus, fusiform gyrus, and posterolateral cerebellum likely reflects willed generation of virtual motor commands and analysis of virtual sensory signals. collapse abstract
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NeuroImage 2008 Jun; 41(3)
Neural mechanisms involved in mental imagery and observation of gait.
Brain activity during observation and imagery of gait was investigated. Sixteen subjects were scanned with a 3-Tesla MRI scanner while viewing six types of video clips: observation of gait movement (GO) from the third-person perspective, observation ... expand abstractof stepping movement, observation of standing posture, "virtual walking" (VW) that was observation of visual scenes mimicking the visual afferent during walking, and the scrambled version of the GO and VW stimuli. In the VW condition, moving scenes provided a virtual visual environment in which subjects easily imagined as if they were actually walking from the first-person perspective. A behavioral experiment revealed a correlation of cadence during actual walking with that during imaginary walking under the influence of the VW stimuli, indicating that a gait planning mechanism was shared by actual walking and gait imagery. The VW condition activated the dorsal premotor cortex (PMd), supplementary motor area/cingulate motor area (SMA/CMA), parahippocampal gyrus, and subcortical nuclei. The GO stimuli yielded activation of the SMA, PMd, inferior frontal gyrus, and inferior parietal lobule. Moreover, the conjunction null test of GO and VW revealed common activity in the SMA/CMA and PMd, which were reportedly active during actual gait movement, in addition to visual areas. Detailed analyses of activity during stepping or standing observation supported the specificity of the SMA and PMd to GO. These findings suggest that motor planning centers of gait, including the SMA and PMd, are activated during both imagination (first-person perspective) and observation (third-person perspective) of gait behaviors. collapse abstract
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Brain and nerve = Shinkei kenkyū no shinpo 2008 Feb; 60(3)
Neural substrates underlying cognitive expertise
Recent behavioral and neuro-anatomical studies of cognitive expertise have suggested that that superior performance in memory experts is neither due to extraordinary general intelligence nor anatomical brain difference. Furthermore, functional neuro-... expand abstractimaging studies have revealed that expert performance in mental abacus and memory experts is not attributable to increased brain activities of the process that exists in non-experts or to hyper-activity in the prefrontal cortex. On the contrary, cognitive experts utilize brain areas that are not used by non-experts. These brain regions are directly related to exceptional knowledge and unique strategies that are acquired by experts through extensive practice. These neuro-imaging findings support psychological theories that cognitive expertise is achieved by developing extensive knowledge and novel cognitive strategies not used by non-experts. These lines of evidence suggest that ordinary people could become experts through appropriate practice. collapse abstract
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NMR in biomedicine 2007 Nov; 20(8)
Fractional anisotropy and mean diffusivity: comparison between 3.0-T and 1.5-T diffusion tensor imaging with parallel imaging using histogram and region of interest analysis.
We performed a comparison study focusing on differences in fractional anisotropy (FA) and mean diffusivity (MD) between 3-T and 1.5-T diffusion tensor imaging (DTI) with parallel imaging. Thirty healthy volunteers underwent DTI with an eight-channel ... expand abstractphased-array coil at both 3 T and 1.5 T. Histogram and region of interest (ROI) analyses were performed. Paired t tests were applied for statistical analysis. Signal-to-noise ratios of these regions were also measured. For histogram analysis, peak location of FA was significantly lower at 3 T than at 1.5 T (P = 0.04). Mean FA was significantly higher at 3 T than at 1.5 T (P = 0.002). Peak location of MD was significantly lower at 3 T than at 1.5 T (P < 0.001). Mean MD was significantly lower at 3 T than at 1.5 T (P < 0.001). In ROI analysis, FA was significantly larger at 3 T than at 1.5 T in the centrum semiovale (P < 0.001), middle cerebellar peduncle (P < 0.001), cerebral peduncle (P = 0.006), posterior limb of the internal capsule (P = 0.007), genu (P < 0.001) and splenium (P < 0.001). FA was significantly lower at 3 T than at 1.5 T in the globus pallidus (P < 0.001). MD was significantly smaller at 3 T than at 1.5 T in the globus pallidus (P = 0.007), thalamus (P < 0.001), centrum semiovale (P < 0.001), middle cerebellar peduncle (P < 0.001), cerebral peduncle (P = 0.01), posterior limb of the internal capsule (P < 0.001), genu (P = 0.01) and splenium (P < 0.001). Significant differences in FA and MD exist between 3 T and 1.5 T for whole-brain histogram analysis and ROI analysis. collapse abstract
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Psychiatry research 2007 Oct; 156(1)
Impaired facial emotion recognition and reduced amygdalar volume in schizophrenia.
Structural abnormalities of the amygdala and impaired facial emotion recognition have been reported in schizophrenia. Most studies demonstrated reduced amygdalar volumes in schizophrenia patients, and difficulty in recognizing negative facial emotion... expand abstracts has also been reported. However, findings on the deficit in facial emotion recognition have been inconsistent, and the relationships between this impairment and amygdalar volume reduction remain unclear. In this study, we investigated these relationships by performing volumetric analysis of the amygdala and evaluation of facial emotion recognition performance in the same subjects with schizophrenia. The sample group comprised 20 schizophrenia patients and 20 matched healthy controls. We measured the volumes of the amygdalae with high-resolution magnetic resonance imaging (MRI) at 3.0 Tesla. Additionally, we included a task that evaluated the subjects' ability to recognize the intensity of basic facial emotions. We found that impaired facial emotion recognition in schizophrenia patients is emotion-specific (sadness, surprise, disgust, and anger). Moreover, the volume of each amygdala on either side of the brain was reduced. Finally, we found a correlation between left amygdalar volume and the recognition of sadness in facial expressions. This study demonstrated that amygdala dysfunction may contribute to impaired facial emotion recognition in schizophrenia. collapse abstract
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Cerebral cortex (New York, N.Y. : 1991) 2008 Mar; 18(4)
The representation of blinking movement in cingulate motor areas: a functional magnetic resonance imaging study.
Recent anatomical evidence from nonhuman primates indicates that cingulate motor areas (CMAs) play a substantial role in the cortical control of upper facial movement. Using event-related functional magnetic resonance imaging in 10 healthy subjects, ... expand abstractwe examined brain activity associated with volitional eye closure involving primarily the bilateral orbicularis oculi. The findings were compared with those from bimanual tapping, which should identify medial frontal areas nonsomatotopically or somatotopically related to bilateral movements. In a group-level analysis, the blinking task was associated with rostral cingulate activity more strongly than the bimanual tapping task. By contrast, the bimanual task activated the caudal cingulate zone plus supplementary motor areas. An individual-level analysis indicated that 2 foci of blinking-specific activity were situated in the cingulate or paracingulate sulcus: one close to the genu of the corpus callosum (anterior part of rostral cingulate zone) and the posterior part of rostral cingulate zone. The present data support the notion that direct cortical innervation of the facial subnuclei from the CMAs might control upper face movement in humans, as previously implied in nonhuman primates. The CMAs may contribute to the sparing of upper facial muscles after a stroke involving the lateral precentral motor regions. collapse abstract
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European radiology 2007 Oct; 17(11)
Gray matter-white matter contrast on spin-echo T1-weighted images at 3 T and 1.5 T: a quantitative comparison study.
Discrepancies exist in the literature regarding contrast between gray and white matter on spin-echo (SE) T1-weighted MR imaging at 3 T. The present study quantitatively assessed differences in gray matter-white matter contrast on both single- and mul... expand abstractti-slice SE T1-weighted imaging between 3 and 1.5 T. SE T1-weighted sequences with the same parameters at both 3 and 1.5 T were used. Contrast-to-noise ratio (CNR) between gray and white matter (CNR(GM-WM)) was evaluated for both frontal lobes. To assess the effects of interslice gap, multi-slice images were obtained with both 0 and 25% interslice gap. Single-slice CNR(GM-WM) was higher at 3 T (17.66 +/- 2.68) than at 1.5 T (13.09 +/- 2.35; P < 0.001). No significant difference in CNR(GM-WM) of multi-slice images with 0% gap was noted between 3 and 1.5 T (3T, 8.61 +/- 2.55; 1.5T, 7.43 +/- 1.20; P > 0.05). Multi-slice CNR(GM-WM) with 25% gap was higher at 3T (12.47 +/- 3.31) than at 1.5 T (9.73 +/- 1.37; P < 0.001). CNR(GM-WM) reduction rate of multi-slice images with 0% gap compared with single-slice images was higher at 3T (0.47 +/- 0.13) than at 1.5 T (0.38 +/- 0.09; P = 0.02). CNR(GM-WM) on single-slice SE T1-weighted imaging and CNR(GM-WM) on multi-slice images with 25% interslice gap were better at 3 T than at 1.5 T. The influence of multi-slice imaging on CNR(GM-WM) was significantly larger at 3T than at 1.5 T. collapse abstract
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Neuroreport 2007 Jul; 18(10)
Heterospecific and conspecific social cognition in the anterior cingulate cortex.
The development of human social cognition has allowed interactions with other species and the formation of a cooperative multi-species society. This feature posited keen attention on the following question: is heterospecific social cognition represen... expand abstractted in the same brain areas as conspecific social cognition? Here we investigated brain activity accompanying the facial recognition of familiar humans and of companion dogs, both of whom had real social interactions with participants. The rostroventral anterior cingulate cortex responded to both species whereas the caudal anterior cingulate cortex was sensitive only to familiar humans. Social cognition processes may be dual-layered: the rostroventral anterior cingulate cortex is associated with fundamental and intuitive aspects, whereas the caudal anterior cingulate cortex is concerned with the analysis of complex social interactions. collapse abstract
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Neurology 2007 Jun; 68(23)
Neuroimaging of neuronal circuits involved in tic generation in patients with Tourette syndrome.
OBJECTIVE: To identify brain regions generating tics in patients with Tourette syndrome using sleep as a baseline. METHODS: We used [15O]H2O PET to study nine patients with Tourette syndrome and nine matched control subjects. For patients, conditions... expand abstract included tic release states and sleep stage 2; and for control subjects, rest states and sleep stage 2. RESULTS: Our study showed robust activation of cerebellum, insula, thalamus, and putamen during tic release. CONCLUSION: The network of structures involved in tics includes the activated regions and motor cortex. The prominent involvement of cerebellum and insula suggest their involvement in tic initiation and execution. collapse abstract
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Journal of neurosurgery 2007 Mar; 106(4)
Clinical impact of integrated functional neuronavigation and subcortical electrical stimulation to preserve motor function during resection of brain tumors.
OBJECT: The authors evaluated the clinical impact of combining functional neuronavigation with subcortical electrical stimulation to preserve motor function following the removal of brain tumors. METHODS: Forty patients underwent surgery for treatmen... expand abstractt of brain tumors located near pyramidal tracts that had been identified by fiber tracking. The distances between the electrically stimulated white matter and the pyramidal tracts were measured intraoperatively with tractography-integrated functional neuronavigation, and correlated with subcortical motor evoked potentials (MEPs) and clinical symptoms during and after resection of the tumors. Motor function was preserved after appropriate tumor resection in all cases. In 18 of 20 patients, MEPs were elicited from the subcortex within 1 cm of the pyramidal tracts as measured using intraoperative neuronavigation. During resection, improvement of motor weakness was observed in two patients, whereas transient mild motor weakness occurred in two other patients. In 20 patients, the distances between the stimulated subcortex and the estimated pyramidal tracts were more than I cm, and MEPs were detected in only three of these patients following stimulation. CONCLUSIONS: Intraoperative functional neuronavigation and subcortical electrical stimulation are complementary techniques that may facilitate the preservation of pyramidal tracts around 1 cm of resected tumors. collapse abstract
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The Journal of neuroscience : the official journal of the Society for Neuroscience 2007 Mar; 27(13)
Functional coupling of human prefrontal and premotor areas during cognitive manipulation.
Evidence indicates the involvement of the rostral part of the dorsal premotor cortex (pre-PMd) in executive processes during working memory tasks. However, it remains unclear what the executive function of pre-PMd is in relation to that of the dorsol... expand abstractateral prefrontal cortex (DLPFC) and how these two areas interact. Using functional magnetic resonance imaging (fMRI), brain activity was examined during a delayed-encoding recognition task. Fifteen subjects had prelearned several four-code standard sequences and super sequences (SUPs) consisting of a train of two standard sequences to form "chunks" in long-term memory. During fMRI, subjects remembered eight-code encoding stimuli presented as an SUP or two unlinked standard sequences (2STs). A memory probe prompted the subjects to recognize codes across two chunks (ACROSS) or within a single chunk. A 2 x 2 factorial design was used to test two types of working memory manipulation: (1) a reductive operation selecting codes from chunks ("segmenting") and (2) a synthetic operation converting unlinked codes into a sequence ("binding"). Response time data supported the behavioral effects of each operation. Event-related fMRI showed that the "segmenting operation" activated the DLPFC bilaterally, whereas the "binding operation" enhanced the left pre-PMd activity. Activity in the ventrolateral prefrontal cortex suggested its involvement in the retrieval of task-relevant information from long-term memory. Furthermore, effective connectivity analysis indicated that the left pre-PMd and ipsilateral DLPFC interacted specifically during the ACROSS recognition of 2STs, the condition that involved both operations. We propose specific neural substrates for working memory manipulation: the DLPFC for segmenting/attentional selection and the pre-PMd for binding/sequencing. The functional coupling between the DLPFC and pre-PMd appears to play a role in combining these distinct operations. collapse abstract
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Neurology 2007 Mar; 68(13)
Cognitive slowing in Parkinson disease is accompanied by hypofunctioning of the striatum.
OBJECTIVE: To investigate whether cognitive slowing in Parkinson disease (PD) reflects disruption of the basal ganglia or dysfunction of the frontal lobe by excluding an influence of abnormal brain activity due to motor deficits. METHODS: We measured... expand abstract neuronal activity during a verbal mental-operation task with H(2)(15)O PET. This task enabled us to evaluate brain activity change associated with an increase in the cognitive speed without an influence on motor deficits. RESULTS: As the speed of the verbal mental-operation task increased, healthy controls exhibited proportional increase in activities in the anterior striatum and medial premotor cortex, suggesting the involvement of the corticobasal ganglia circuit in normal performance of the task. By contrast, patients with PD lacked an increase in the striatal activity, whereas the medial premotor cortex showed a proportional increase. CONCLUSIONS: Although the present study chose a liberal threshold and needs subsequent confirmation, the findings suggest that striatal disruption resulting in abnormal processing in the corticobasal ganglia circuit may contribute to cognitive slowing in Parkinson disease, as is the case in motor slowing. collapse abstract
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Neuroscience letters 2007 Mar; 415(3)
Subregions of human parietal cortex selectively encoding object orientation.
Computation of object orientation could be an independent process from those of other object features, but currently neither the location of human brain areas selectively coding orientation information nor an optimum experimental paradigm have yet be... expand abstracten established. In this study, functional magnetic resonance imaging was used to investigate brain activation in the parietal cortices related to object orientation. Using an Arabic digit whose spatial attributes were carefully manipulated, we found parietal areas exclusively sensitive to object orientation, but not to general spatial attention. It seems that, by excluding confounds such as mental manipulation or working memory as well as inherent spatial information within the stimuli, functional segregation within the parietal lobe can be effectively probed. collapse abstract
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