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Biomedical subjects

R Takino

Publications and source records attributed to R Takino.

11 recordsLinked to original sources
PubMed1999

Functional magnetic resonance imaging of neural activity related to orthographic, phonological, and lexico-semantic judgments of visually presented characters and words.

Functional magnetic resonance imaging was used to investigate neural activity during the judgment of visual stimuli in two groups of experiments using seven and five normal subjects. The subjects were given tasks designed differentially to involve orthographic (more generally, visual form), phonological, and lexico-semantic processes. These tasks included the judgments of whether a line was horizontal, whether a pseudocharacter or pseudocharacter string included a horizontal line, whether a Japanese katakana (phonogram) character or character string included a certain vowel, or whether a character string was meaningful (noun or verb) or meaningless. Neural activity related to the visual form process was commonly observed during judgments of both single real-characters and single pseudocharacters in lateral extrastriate visual cortex, the posterior ventral or medial occipito-temporal area, and the posterior inferior temporal area of both hemispheres. In contrast, left-lateralized activation was observed in the latter two areas during judgments of real- and pseudo-character strings. These results show that there is no katakana "word form center" whose activity is specific to real words. Activation related to the phonological process was observed, in Broca's area, the insula, the supramarginal gyrus, and the posterior superior temporal area, with greater activation in the left hemisphere. These activation foci for visual form and phonological processes of katakana also were reported for the English alphabet in previous studies. The present activation showed no additional areas for contrasts of noun judgment with other conditions and was similar between noun and verb judgment tasks, suggesting two possibilities: no strong semantic activation was produced, or the semantic process shared activation foci with the phonological process.

Adult↗
PubMed1998

Separate cerebellar areas for motor control.

Cerebellar activation was measured using functional magnetic resonance imaging, while seven normal subjects tapped their fingers paced by tone sequences with or without tone omission. The cerebellar anterior lobe (Larsell's H IV-V) ipsilateral to the movement was activated to a similar degree irrespective of the presence or absence of the tone omission. In contrast, the lateral part of the bilateral posterior lobe (H VIIa) was significantly highly activated for the tone sequence with random omission, compared with either that without omission or that with regular omission. The result suggests that the H IV-V is involved in motor execution, while the lateral part of H VIIa is involved in on-line motor adjustment to unpredictable sensory stimuli.

Acoustic Stimulation↗
PubMed1998

Transition of brain activation from frontal to parietal areas in visuomotor sequence learning.

We studied the neural correlates of visuomotor sequence learning using functional magnetic resonance imaging (fMRI). In the test condition, subjects learned, by trial and error, the correct order of pressing two buttons consecutively for 10 pairs of buttons (2 x 10 task); in the control condition, they pressed buttons in any order. Comparison between the test condition and the control condition revealed four brain areas specifically related to learning: the dorsolateral prefrontal cortex (DLPFC), the presupplementary motor area (pre-SMA), the precuneus, and the intraparietal sulcus (IPS). We found that the time course of activation during learning was different between these areas. To normalize the individual differences in the speed of learning, we classified the performance of each subject into three learning stages: early, intermediate, and advanced stages. Both the relative increase of signal intensity and the number of activated pixels within the four areas showed significant changes across the learning stages, with different time courses. The two frontal areas, DLPFC and pre-SMA, were activated in the earlier stages of learning, whereas the two parietal areas, precuneus and IPS, were activated in the later stages. Specifically, DLPFC, pre-SMA, precuneus, and IPS were most highly activated in the early stage, in both the early and intermediate stages, in the intermediate stage, and in both the intermediate and advanced stages, respectively. The results suggest that the acquisition of visuomotor sequences requires frontal activation, whereas the retrieval of visuomotor sequences requires parietal activation, which might reflect the transition from the declarative stage to the procedural stage.

Adult↗
PubMed1998

Localizing the site of magnetic brain stimulation by functional MRI.

In order to locate the site of action of transcranial magnetic stimulation (TMS) within the human motor cortices, we investigated how the optimal positions for evoking motor responses over the scalp corresponded to the hand and leg primary-motor areas. TMS was delivered with a figure-8 shaped coil over each point of a grid system constructed on the skull surface, each separated by 1 cm, to find the optimal site for obtaining motor-evoked potentials (MEPs) in the contralateral first dorsal interosseous (FDI) and tibialis anterior (TA) muscles. Magnetic resonance imaging scans of the brain were taken for each subject with markers placed over these sites, the positions of which were projected onto the cortical region just beneath. On the other hand, cortical areas where blood flow increased during finger tapping or leg movements were identified on functional magnetic resonance images (fMRI), which should include the hand and leg primary-motor areas. The optimal location for eliciting MEPs in FDI, regardless of their latency, lay just above the bank of the precentral gyrus, which coincided with the activated region during finger tapping in fMRI studies. The direction of induced current preferentially eliciting MEPs with the shortest latency in each subject was nearly perpendicular to the course of the precentral gyrus at this position. The optimal site for evoking motor responses in TA was also located just above the activated area during leg movements identified within the anterior portion of the paracentral lobule. The results suggest that, for magnetic stimulation, activation occurs in the primary hand and leg motor area (Brodmann area 4), which is closest in distance to the optimal scalp position for evoking motor responses.

Brain Mapping↗
PubMed1998

Attention-regulated activity in human primary visual cortex.

Effects of attention to a local contour of a moving object on the activation of human primary visual cortex (area V1) were examined. Local cerebral oxygenation changes (an index of neuronal activity) in human area V1 were measured with functional magnetic resonance imaging (fMRI) in conditions including the following two: 1) when attention was selectively directed toward one side of a moving wedge (the attention condition) and 2) when the wedges were viewed passively (the passive condition). Activation in area V1 was found to be higher in the attention condition than in the passive condition. To our knowledge, this is the first finding that attention to motion activates as early as area V1. We suggest that attentional activation of area V1 is task dependent.

Attention↗
PubMed1996

Activation of human presupplementary motor area in learning of sequential procedures: a functional MRI study.

1. Using functional magnetic resonance imaging, we investigated the neural correlates of sequential procedural learning. During the test scans the subjects learned a new sequence (position or color) of button presses; during the control scans they pressed the buttons in any order. The comparison of the test and control scans was expected to reveal the neural activities related to learning, not sensory-motor processes. 2. We found that a localized area in what we regard to be the human homologue of the presupplementary motor area (pre-SMA) was particularly active for learning of new sequential procedures (either position or color sequences), not movements per se. 3. In contrast, the SMA proper (posterior to pre-SMA) was active for the performance of sequential movements, not learning. This was shown in another paradigm in which the subjects pressed the buttons in any order in the test scans and just watched the sequence in the control scans. 4. The learning-related pre-SMA region, which was consistent across different experiments in single subjects, was identified on only one side in each subject.

Humans↗
PubMed1990

Evoked potentials during REM sleep reflect dreaming.

Polygraphic recordings were collected for 11 normal subjects during sleep and wakefulness in order to investigate characteristics of the rapid eye movement (REM) associated potentials. EEGs were averaged using 5 different triggering points: (1) saccade onset under the normal ambient illumination, (2) saccade onset in the total darkness, (3) onset of REMs during REM sleep, (4) flash during REM sleep, and (5) flash during stage 2 sleep. In the central area, positive potentials appeared with waking saccades under the normal ambient illumination (P240L) and REMs (P185R). The latency of P185R associated with REMs was significantly shorter than that of P240L associated with waking saccades. These findings suggest that P185R is evoked by PGO waves occurring just before the REM. A small positive potential appeared in the occipital area with waking saccade under the normal ambient illumination (P260L) and REMs in the total darkness (P250R). Conspicuous absence of these waves for waking saccades in the total darkness suggests that P250R accompanied with REMs reflects activities involved with the cognitive processes occurring when a subject scans a dream image during REM sleep.

Adult↗
PubMed1987

Electrophysiological evidence for dreaming: human cerebral potentials associated with rapid eye movement during REM sleep.

In order to examine the relationship between rapid eye movement (REM) during REM sleep and dreaming, scalp EEGs (Fz, Cz, Pz and Oz) of 4 normal human subjects, time-locked to REM onset, to saccade onset toward fixation targets and to saccade onset in total darkness, were averaged. The results include the following: Three positive potentials were associated with REM: a sharp potential in the parieto-occipital area just before REM onset; a large, slow potential in the vertex area 140-180 msec after REM onset; and a potential in the occipital area 210-280 msec after REM onset. Three positive potentials, one being the so-called EM-antecedent potential and the others being the lambda response, were associated with the waking saccades toward targets: a sharp potential in the parieto-occipital area just before the saccade onset and two potentials in the occipital area with latencies of 140-150 and 260-310 msec from the saccade onset. Only the EM-antecedent potential appearing just before saccade onset was found in association with saccades in total darkness. The similarities between the 3 positive potentials during REM sleep and the lambda response during wakefulness, and the relationship between those potentials and dreaming, are discussed in terms of the neural processes occurring during REM sleep.

Action Potentials↗