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Norihiro Sadato

Publications and source records attributed to Norihiro Sadato.

At least 55 records · Page 3Linked to original sources
PubMed2004

Phonemic manipulation in Japanese: an fMRI study.

Phonological awareness is the ability to manipulate abstract phonological representations of language and is crucial to the process of learning to read. The neural substrates underlying this appear to be modality-independent at least in alphabetic languages. Japanese language has different orthographic "kana" system, in which each "kana" character strictly corresponds to a syllable. To investigate the neural substrates underlying phonological manipulation of the Japanese language, functional magnetic resonance imaging (fMRI) was used. Neuroimaging data were obtained from adult healthy volunteers during auditory and visual vowel exchange tasks, identical except for the modality of stimuli presentation: a voice and Japanese "kana" characters. Cerebellar vermis was activated by vowel exchange tasks of both modalities. The posterior parts of the superior temporal sulcus (STS) were active during the auditory tasks, suggesting that phonological representations of auditory stimuli are manipulated in this area. These findings are consistent with the previous studies with alphabetic languages. In contrast, the intraparietal sulci, which has been implicated for visuospatial tasks, was active during the visual tasks. This modality-dependent activation may indicate that the simple orthographic rule of the Japanese allows an alternate visual strategy to conduct the phonological awareness task, bypassing manipulation of phonological representation.

Adult↗
PubMed2004

Learned audio-visual cross-modal associations in observed piano playing activate the left planum temporale. An fMRI study.

Lip reading is known to activate the planum temporale (PT), a brain region which may integrate visual and auditory information. To find out whether other types of learned audio-visual integration occur in the PT, we investigated "key-touch reading" using functional magnetic resonance imaging (fMRI). As well-trained pianists are able to identify pieces of music by watching the key-touching movements of the hands, we hypothesised that the visual information of observed sequential finger movements is transformed into the auditory modality during "key-touch reading" as is the case during lip reading. We therefore predicted activation of the PT during key-touch reading. Twenty-six healthy right-handed volunteers were recruited for fMRI. Of these, 7 subjects had never experienced piano training (naïve group), 10 had a little experience of piano playing (less trained group), and the remaining 9 had been trained for more than 8 years (well trained group). During task periods, subjects were required to view the bimanual hand movements of a piano player making key presses. During control periods, subjects viewed the same hands sliding from side to side without tapping movements of the fingers. No sound was provided. Sequences of key presses during task periods consisted of pieces of familiar music, unfamiliar music, or random sequences. Well-trained subjects were able to identify the familiar music, whereas less-trained subjects were not. The left PT of the well-trained subjects was equally activated by observation of familiar music, unfamiliar music, and random sequences. The naïve and less trained groups did not show activation of the left PT during any of the tasks. These results suggest that PT activation reflects a learned process. As the activation was elicited by viewing key pressing actions regardless of whether they constituted a piece of music, the PT may be involved in processes that occur prior to the identification of a piece of music, that is, mapping the complex sequence structure of hand movements onto the sequence of sounds.

Adolescent↗
PubMed2004

Functional association of the amygdala and ventral prefrontal cortex during cognitive evaluation of facial expressions primed by masked angry faces: an event-related fMRI study.

The present study examined the functional association of the amygdala and right ventral prefrontal cortex (PFC) during cognitive evaluation of facial expressions. A situation was created where emotional valence of the stimuli was unconsciously manipulated by using subliminal affective priming. Twelve healthy volunteers were asked to evaluate the facial expressions of a target face (500-ms duration) such as "anger", "neutral", or "happy". All target faces expressed relatively weak anger. Just before the presentation of the target face, a prime of three conditions of 35-ms duration, angry face, neutral face, and white blank was presented. The subjects could not consciously identify the primes in this procedure. Activity in the right amygdala was greater with subliminal presentation of the angry prime compared with subliminal presentation of a neutral face or white-blank stimuli. Most importantly, the degree of activation of the right amygdala was negatively correlated with that of the right ventral PFC only with the anger prime. Furthermore, activation of the amygdala was positively correlated with rate of judgment when the subjects recognized anger in the target faces. These results are discussed in terms of the functional association between the right PFC and the amygdala and its influence on cognitive processing.

Adult↗
PubMed2004

The neural substrates of conscious color perception demonstrated using fMRI.

It is well established that seeing color activates the ventral occipital cortex, including the fusiform and lingual gyri, but less is known about whether the region directly relates to conscious color perception. We investigated the neural correlates of conscious color perception in the ventral occipital cortex. To vary conscious color perception with the stimuli-remaining constant, we took advantage of the McCollough effect, an illusory color effect that is contingent on the orientation of grating stimuli. Subjects were exposed to a specific combination of chromatic grating patterns for 10 min to induce the McCollough effect. We compared brain activities measured while the subjects viewed achromatic grating stimuli before (PRE) and after the induction of the McCollough effect (POST) using functional magnetic resonance imaging (fMRI). There were two groups: one group was informed that they would perceive illusory color during the session (INFORMED group), whereas the other group was not informed (UNINFORMED group). The successful induction of the McCollough effect was confirmed in all subjects after the fMRI experiment; nevertheless, only approximately half of the UNINFORMED subjects had been aware of the color during the POST session, while the other half had not. The left anterior portion of the color-selective area in the ventral occipital cortex, presumably V4alpha, was significantly active in subjects who had consciously perceived the color during MR scan. This study demonstrates the activity in a subregion of the color-selective area in the ventral occipital cortex directly related to conscious color perception.

Adult↗
PubMed2004

Functional imaging of gustatory perception and imagery: "top-down" processing of gustatory signals.

By recalling gustatory memories, it is possible to generate vivid gustatory perceptions in the absence of gustatory inputs. This gustatory image influences our gustatory processing. However, the mechanism of the "top-down" modulation of gustatory perception in the human is still unclear. Our findings propose a new perspective on the neural basis of gustatory processing. Although gustatory imagery and gustatory perception shared common parts of neural substrates, there was an asymmetrical topography of activation in the insula: the left insula was predominantly activated by gustatory imagery tasks. In addition, the middle and superior frontal gyri were not activated by gustatory perception but they participated in the generation of gustatory hallucinations. These regions in the frontal cortex may mediate the "top-down" control of retrieving gustatory information from the storage of long-term memories.

Adult↗
PubMed2004

Metabolic neuroimaging of the cervical spinal cord in patients with compressive myelopathy: a high-resolution positron emission tomography study.

OBJECT: The authors conducted a study to examine whether high-resolution [18F]fluorodeoxyglucose (FDG)-positron emission tomography (PET) could be used to visualize deterioration of cervical spinal cord function associated with various degrees of compression and to determine its potential usefulness during assessment of compressive myelopathy. METHODS: In 23 patients requiring decompressive surgery for myelopathy FDG-PET was performed. The preoperative findings of high-resolution FDG-PET were compared with the neurological scores and magnetic resonance (MR) imaging findings. The preoperative standardized uptake value (SUV) of FDG utilization rate of the cervical cord correlated with the pre- (r = 0.497, p = 0.016) and postoperative neurological scores (r = 0.595, p = 0.003), as well as with the rate of neurological improvement postoperatively (r = 0.538, p = 0.008). The FDG utilization rate did not correlate with the high signal intensity on T2-weighted MR images. CONCLUSIONS: Analysis of these results indicates that high-resolution FDG-PET imaging provides useful qualitative and quantitative estimates of impaired metabolic activity of the compromised cervical cord that correlate closely with the severity of neurological dysfunction.

Adult↗
PubMed2003

The neural substrates of driving at a safe distance: a functional MRI study.

An important driving skill is the ability to maintain a safe distance from a preceding car. To determine the neural substrates of this skill we performed functional magnetic resonance imaging of simulated driving in 21 subjects. Subjects used a joystick to adjust their own driving speed in order to maintain a constant distance from a preceding car traveling at varying speeds. The task activated multiple brain regions. Activation of the cerebellum may reflect visual feedback during smooth tracking of the preceding car. Co-activation of the basal ganglia, thalamus and premotor cortex is related to movement selection. Activation of a premotor-parietal network is related to visuo-motor co-ordination. Task performance was negatively correlated with anterior cingulate activity, consistent with the role of this region in error detection and response selection.

Adult↗
PubMed2003

Facial recognition reactivates the primary visual cortex: an functional magnetic resonance imaging study in humans.

In order to investigate how the brain represents sensory-specific information during memory retrieval, we examined functional magnetic resonance imaging's during a face-recognition task. When compared with activation associated with viewing of novel faces, recognition of faces presented 5 min before scanning activated the primary visual cortex, consistent with the hypothesis that retrieved facial information is coded by the reactivation of the brain regions engaged during sensory perception. This reactivation was not observed 14 weeks following initial presentation of the faces despite no significant difference in recognition rate between the two intervals. This suggests that accessing of visual information during memory retrieval is associated with the primary visual cortex, and that its activation is time-dependent--probably related to the memory transformation or consolidation.

Adult↗
PubMed2003

Dissociable neural responses in the hippocampus to the retrieval of facial identity and emotion: an event-related fMRI study.

In studies with brain-damaged patients and experimental animals, the medial temporal lobe, including the hippocampus and parahippocampal gyrus, has been found to play a critical role in establishing declarative or episodic memory. We measured the neural response in these structures, using event-related functional magnetic resonance imaging, while six healthy subjects performed the retrieval task for facial identity and emotion, respectively. Under the identity condition, the subjects participated in a yes/no recognition test for neutral faces learned before the scanning. Under the emotion condition, the subjects learned the faces with positive or negative expression and retrieved their expressions from neutral cue faces. The results showed that the left hippocampus is primarily involved in the identification of learned faces, and that the adjacent parahippocampal gyrus responds more to target than to distracter events. These results indicate a specific engagement of the left hippocampal regions in conscious recollection and identification of physiognomic facial features. The activity in the right hippocampus increased under both the identity and emotion conditions. The present results may relate with the functional model of face recognition in which the left hemisphere contributes to the processing of detailed features and the right hemisphere is efficient in the processing of global features.

Adult↗
PubMed2003

Tactile-visual cross-modal shape matching: a functional MRI study.

The process and location of integration of information from different sensory modalities remains controversial. We used functional MRI to investigate the neural representation of cross-modal matching between tactile and visual shape information in eleven normal volunteers. During the scan, patterns of 2D shapes were presented both tactually and visually, simultaneously. Four different matching tasks were performed: tactile-tactile with eyes closed (TT), tactile-tactile with visual input (TTv), visual-visual with tactile input (VVt), and tactile-visual (TV). The TT task activated the contralateral primary sensorimotor area, and the postcentral gyrus, superior parietal lobules, anterior portion of the intraparietal sulcus, secondary somatosensory cortex, thalamus, dorsal premotor area, cerebellum, and supplementary motor area bilaterally, without occipital involvement. Visual matching activated the primary visual cortex and the lingual and fusiform gyri bilaterally. A cross-modal area was identified by subtracting TTv images from TV images, subtracting VVt images from TV images, and then determining common active areas. There was one discrete area that was active bilaterally; the posterior intraparietal sulcus close to the parieto-occipital sulcus. These data suggest that shape information from different sensory modalities may be integrated in the posterior intraparietal sulcus during tactile-visual matching tasks.

Adult↗
PubMed2003

Internal simulation of expected sensory experiences before movements get started.

The functions of the cortical and subcortical motor areas have been regarded as the execution and control of limb movements. We introduce recent neuroimaging evidence in humans that somatic sensation elicited by afferent inputs that signal limb movement also engage the motor areas. It is generally understood that somatic sensation can only be experienced once movement has been executed. Here we provide evidence that somatic sensation of limb movement can be internally simulated before the movement gets started by recruiting the motor areas. It is suggested that the sensory experiences that are expected when movements are actually executed can be internally simulated in the network of the motor areas during motor imagery.

Animals↗
PubMed2003

Prospective comparison of 18F-FDG PET with conventional imaging modalities (MRI, CT, and 67Ga scintigraphy) in assessment of combined intraarterial chemotherapy and radiotherapy for head and neck carcinoma.

UNLABELLED: To preserve the oral organs and functions in patients with head and neck carcinoma, accurate determination of the appropriate treatment after neoadjuvant chemotherapy and radiotherapy is of critical importance. We evaluated the diagnostic accuracy of (18)F-FDG PET relative to that of other conventional imaging modalities in the assessment of therapeutic response after combined intraarterial chemotherapy and radiotherapy as an organ preservation protocol. METHODS: The study was prospectively performed on 23 consecutive patients with head and neck squamous cell carcinoma who completed the treatment regimen and underwent 2 (18)F-FDG PET studies before and after neoadjuvant chemoradiotherapy. (67)Ga scintigraphy (only before therapy) as well as MRI and CT (both before and after therapy) were also performed. All images were blindly and independently interpreted without knowledge of histologic findings. The level of confidence in image interpretation was graded by means of a 5-point rating system (0 = definitely no tumor to 4 = definite tumor). RESULTS: Before treatment, (18)F-FDG PET detected primary tumors in all 23 patients and was more sensitive (100%) than MRI (18/23; 78.3%), CT (15/22; 68.2%), and (67)Ga scintigraphy (8/20; 40%), with a confidence level of 3 or 4 as a positive tumor finding. After chemoradiotherapy, residual tumors were histologically confirmed in 4 patients (pathologic complete response rate, 19/23; 82.6%). Although posttreatment (18)F-FDG PET showed almost equal sensitivity (4/4; 100%) compared with MRI (3/3; 100%) or CT (3/4; 75%), its specificity (17/19; 89.5%) was superior to MRI (7/17, 41.2%) and to CT (10/17; 58.8%) for primary lesions. Regarding metastases to neck lymph nodes, only specificity for posttreatment images was calculated because no metastasis was confirmed in any patients after treatment. Six subjects had (18)F-FDG PET-positive lymph nodes, which had pathologically no tumor cells and suggested an inflammatory reactive change after therapy. Therefore, the specificity of posttreatment (18)F-FDG PET (17/23; 73.9%) was almost identical to that of MRI (17/20; 85%) and CT (16/21; 76.2%) for neck metastasis. With combined chemoradiotherapy monitored with (18)F-FDG PET, 8 patients avoided surgery and the remaining 15 patients underwent a reduced form of surgery. CONCLUSION: (18)F-FDG PET facilitates differentiation of residual tumors from treatment-related changes after chemoradiotherapy, which may be occasionally difficult to characterize by anatomic images. (18)F-FDG PET has a clinical impact for the management of patients with head and neck cancers after neoadjuvant chemoradiotherapy by optimizing surgical treatment for each patient and contributes to the improvement of the patient's quality of life.

Aged↗
PubMed2002

Superior digit memory of abacus experts: an event-related functional MRI study.

Abacus experts exhibit superior short-term memory for digits, but the underlying neurophysiological mechanism remains unknown. Using event-related fMRI, we examined the brain activity of abacus experts and non-experts during the memory retention period of a delayed match-to-sample task using digits as stimuli. In controls, activity was greater in cortical areas related to verbal working memory, including Broca's area. In contrast, in experts, activity was greater in cortical areas related to visuo-spatial working memory, including the bilateral superior frontal sulcus and superior parietal lobule. This provides neurophysiological evidence that abacus experts utilize a visuo-spatial representation for digit memory.

Adolescent↗
PubMed2002

FDG-PET for prediction of tumour aggressiveness and response to intra-arterial chemotherapy and radiotherapy in head and neck cancer.

The aim of this study was to evaluate the possible usefulness of fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) for predicting tumour aggressiveness and response to intra-arterial chemotherapy (THP-ADM + 5-FU + carboplatin) and radiotherapy in head and neck carcinomas. Twenty patients with squamous cell carcinoma (SCC) of the head and neck were included in the study. All patients completed the treatment regimen, and each patient underwent two FDG-PET studies, one prior to and one at 4 weeks after the chemoradiotherapy. For the quantitative evaluation of regional FDG uptake in the tumour, standardised uptake values (SUVs) with an uptake period of 50 min were used. The pre-treatment SUV (pre-SUV) and post-treatment SUV (post-SUV) were compared with immunohistologically evaluated tumour proliferative potential (MIB-1 and PCNA), tumour cellularity and other parameters including histological grade, tumour size and stage, clinical response and histological evaluation after therapy. All neoplastic lesions showed high SUVs (mean, 9.75 mg/ml) prior to the treatment, which decreased significantly after the therapy (3.41 mg/ml, P<0.01). Pre-SUV did not show any correlation with MIB-1, PCNA, cellularity or other parameters. However, lower post-SUV was significantly correlated with good histological results after therapy (no viable tumour cells, n=16). In comparison with moderately differentiated SCCs, well-differentiated SCCs exhibited significantly lower post-SUV and a larger difference between pre- and post-SUVs. Lesions with a high pre-SUV (>7 mg/ml) showed residual tumour cells after treatment in 4 out of 15 patients, whereas patients whose lesions showed a low pre-SUV (<7 mg/ml, five patients) were successfully treated. Four out of six tumours with a post-SUV higher than 4 mg/ml had viable tumour cells, whereas all tumours (14/14) with a post-SUV lower than 4 mg/ml showed no viable tumour cells. Computational multivariate analysis using multiple regression revealed four factors (MIB-1 labelling index, cellularity, the number of MIB-1 labelled tumour cells and tumour size grade) contributing to pre-SUV and pre-post SUV (difference between pre-treatment SUV and post-treatment SUV in each patient) with statistical significance. FDG uptake in the tumour might reflect tumour aggressiveness, which is closely related to the proliferative activity and cellularity. Pre-treatment FDG-PET is useful in predicting the response to treatment, and post-treatment FDG-PET is of value in predicting residual viable tumours. FDG-PET has a profound impact on the treatment strategy for head and neck carcinomas.

Aged↗
PubMed2002

Brain activation during whole body cooling in humans studied with functional magnetic resonance imaging.

Regional activation of the brain was studied in humans using functional magnetic resonance imaging during whole body cooling that produced thermal comfort/discomfort. Eight normal male subjects lay in a sleeping bag through which air was blown, exposing subjects to cold air (8 degrees C) for 22 min. Each subject scored their degree of thermal comfort and discomfort every min. As the subjects reported more discomfort the blood oxygen level dependent response in the bilateral amygdala increased. There was no activation in the thalamus, somatosensory, cingulate, or insula cortices. This result suggests that the amygdala plays a role in the genesis of thermal discomfort due to cold.

Adult↗
PubMed2002

Internally simulated movement sensations during motor imagery activate cortical motor areas and the cerebellum.

It has been proposed that motor imagery contains an element of sensory experiences (kinesthetic sensations), which is a substitute for the sensory feedback that would normally arise from the overt action. No evidence has been provided about whether kinesthetic sensation is centrally simulated during motor imagery. We psychophysically tested whether motor imagery of palmar flexion or dorsiflexion of the right wrist would influence the sensation of illusory palmar flexion elicited by tendon vibration. We also tested whether motor imagery of wrist movement shared the same neural substrates involving the illusory sensation elicited by the peripheral stimuli. Regional cerebral blood flow was measured with H215O and positron emission tomography in 10 right-handed subjects. The right tendon of the wrist extensor was vibrated at 83 Hz ("illusion") or at 12.5 Hz with no illusion ("vibration"). Subjects imagined doing wrist movements of alternating palmar and dorsiflexion at the same speed with the experienced illusory movements ("imagery"). A "rest" condition with eyes closed was included. We identified common active fields between the contrasts of imagery versus rest and illusion versus vibration. Motor imagery of palmar flexion psychophysically enhanced the experienced illusory angles of plamar flexion, whereas dorsiflexion imagery reduced it in the absence of overt movement. Motor imagery and the illusory sensation commonly activated the contralateral cingulate motor areas, supplementary motor area, dorsal premotor cortex, and ipsilateral cerebellum. We conclude that kinesthetic sensation associated with imagined movement is internally simulated during motor imagery by recruiting multiple motor areas.

Adolescent↗
PubMed2002

Visual detection of motion speed in humans: spatiotemporal analysis by fMRI and MEG.

Humans take a long time to respond to the slow visual motion of an object. It is not known what neural mechanism causes this delay. We measured magnetoencephalographic neural responses to light spot motion onset within a wide speed range (0.4-500 degrees /sec) and compared these with human reaction times (RTs). The mean response latency was inversely related to the speed of motion up to 100 degrees /sec, whereas the amplitude increased with the speed. The response property at the speed of 500 degrees /sec was different from that at the other speeds. The speed-related latency change was observed when the motion duration was 10 msec or longer in the speed range between 5 and 500 degrees /sec, indicating that the response is directly related to the speed itself. The source of the response was estimated to be around the human MT+ and was validated by functional magnetic imaging study using the same stimuli. The results indicate that the speed of motion is encoded in the neural activity of MT+ and that it can be detected within 10 msec of motion observation. RT to the same motion onset was also inversely related to the speed of motion but the delay could not be explained by the magnetic response latency change. Instead, the reciprocal of RT was linearly related to the reciprocal of the magnetic response latency, suggesting that the visual process interacts with other neural processes for decision and motor preparation.

Adult↗