The neural basis of the hemodynamic response nonlinearity in human primary visual cortex: Implications for neurovascular coupling mechanism.

It has been well recognized that the nonlinear hemodynamic responses of the blood oxygenation level-dependent (BOLD) functional MRI (fMRI) are important and ubiquitous in a series of experimental paradigms, especially for the event-related fMRI. Although this phenomenon has been intensively studied and it has been found that the post-capillary venous expansion is an intrinsically nonlinear mechanical process, the existence of an additional neural basis for the nonlinearity has not been clearly shown. In this paper, we assessed the correlation between the electric and vascular indices by performing simultaneous electroencephalography (EEG) and fMRI recordings in humans during a series of visual stimulation (i.

A theoretical formulation of the electrophysiological inverse problem on the sphere.

The construction of three-dimensional images of the primary current density (PCD) produced by neuronal activity is a problem of great current interest in the neuroimaging community, though being initially formulated in the 1970s. There exist even now enthusiastic debates about the authenticity of most of the inverse solutions proposed in the literature, in which low resolution electrical tomography (LORETA) is a focus of attention. However, in our opinion, the capabilities and limitations of the electro and magneto encephalographic techniques to determine PCD configurations have not been extensively explored from a theoretical framework, even for simple volume conductor models of the head.

No genetic association between postsynaptic density-95 gene polymorphisms and schizophrenia.

Disturbed glutamatergic neurotransmission, especially disturbed N-methyl-D-aspartate (NMDA) receptor function, has been hypothesized to be involved in the pathophysiology of schizophrenia. It may also involve abnormalities in the intracellular signaling machineries that are linked to the NMDA receptor. Postsynaptic density-95 is known to bind NMDA receptor subunits and is involved in intracellular signal transduction and synaptic plasticity.

[A new intervention program for improvement of cognitive functions of senile dementia patients].

We proposed a new intervention program, the concept of which is derived from the knowledge of both brain science and clinical studies. We set up a hypothesis that activation of the association cortices by cognitive tasks may well improve the function of these cortices. To choose effective cognitive tasks for activation of the association cortices, we reviewed previous neuroimaging studies.

Cortical mechanisms of person representation: recognition of famous and personally familiar names.

Personally familiar people are likely to be represented more richly in episodic, emotional, and behavioral contexts than famous people, who are usually represented predominantly in semantic context. To reveal cortical mechanisms supporting this differential person representation, we compared cortical activation during name recognition tasks between personally familiar and famous names, using an event-related functional magnetic resonance imaging (fMRI). Normal subjects performed familiar- or unfamiliar-name detection tasks during visual presentation of personally familiar (Personal), famous (Famous), and unfamiliar (Unfamiliar) names.

Artifact reduction for simultaneous EEG/fMRI recording: adaptive FIR reduction of imaging artifacts.

Objective: We present a new method of effectively removing imaging artifacts of electroencephalography (EEG) and extensively conserving the time-frequency features of EEG signals during simultaneous functional magnetic resonance imaging (fMRI) scanning under conventional conditions.

Methods: Under the conventional conditions of a 5000 Hz EEG sampling rate, but in the absence of the MRI slice-timing signals, the imaging artifact during each slice scanning is theoretically inferred to be a linear combination of the average artifact waveform and its derivatives, deduced by band-limited Taylor's expansion. Technically, the imaging artifact reduction algorithm is equivalent to an adaptive finite impulse response (FIR) filter.

Artifact reduction for EEG/fMRI recording: nonlinear reduction of ballistocardiogram artifacts.

Objective: We present a new method of effectively removing the ballistocardiogram artifacts (BAs) of electroencephalography (EEG), recorded inside a 1.5 T static magnetic field scanner with no fMRI scanning, which conserves the time and frequency features of event-related EEG activity.

Methods: The BAs are approximated as deterministically chaotic dynamics.

[Cognitive rehabilitation for Alzheimer disease--the learning therapy].

We propose a new intervention program, the concept of which is derived from the knowledge of both brain science and clinical studies. We set up a hypothesis that activation of the association cortices by cognitive tasks may well improve the function of these cortices. To choose effective cognitive tasks for activation of the association cortices, we reviewed previous neuroimaging studies.

Cortical activation in the processing of passive sentences in L1 and L2: an fMRI study.

The question of whether the bilingual brain processes a first and second language (L1 and L2, respectively) differently is a central issue in many psycholinguistic and neurolinguistic studies. This study used functional magnetic resonance imaging (fMRI) to investigate whether late bilinguals process structurally complex sentences in L1 and L2 in different cortical networks. For this purpose, we directly compared brain activity during the processing of active and passive sentences in both L1 and L2.

Brain activation during the course of sentence comprehension.

The purpose of this study is to determine, by functional magnetic resonance imaging, how the activated regions of the brain change as a Japanese sentence is presented in a grammatically correct order. In this study, we presented constituents of a sentence to Japanese participants one by one at regular intervals. The results showed that the left lingual gyrus was significantly activated at the beginning of the sentence, then the left inferior frontal gyrus and left supplementary motor area, in the middle of the sentence, and the left inferior temporal gyrus, at the end of the sentence.

Male elderly subthreshold depression patients have smaller volume of medial part of prefrontal cortex and precentral gyrus compared with age-matched normal subjects: a voxel-based morphometry.

Background: The brain morphological changes in subthreshold depression (sD) have not been clarified. We examined the structural difference in regional gray matter volume between community-dwelling elderly subjects with sD and age-matched nondepressed normal subjects by voxel-based morphometry (VBM) based on magnetic resonance imaging (MRI).

Methods: Thirty-four community-dwelling elderly subjects with sD and 109 age-matched nondepressed normal subjects were studied by MRI.

Fusing EEG and fMRI based on a bottom-up model: inferring activation and effective connectivity in neural masses.

The elucidation of the complex machinery used by the human brain to segregate and integrate information while performing high cognitive functions is a subject of imminent future consequences. The most significant contributions to date in this field, known as cognitive neuroscience, have been achieved by using innovative neuroimaging techniques, such as electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI), which measure variations in both the time and the space of some interpretable physical magnitudes. Extraordinary maps of cerebral activation involving function-restricted brain areas, as well as graphs of the functional connectivity between them, have been obtained from EEG and fMRI data by solving some spatio-temporal inverse problems, which constitutes a top-down approach.

Introduction of Sd(a) carbohydrate antigen in gastrointestinal cancer cells eliminates selectin ligands and inhibits metastasis.

The Sd(a) blood group carbohydrate structure is expressed in the normal gastrointestinal mucosa. We reported previously that the expression of Sd(a) carbohydrate structures and beta1,4-N-acetylgalactosaminyltransferase (beta1,4GalNAcT) activity responsible for Sd(a) synthesis were remarkably decreased in cancer lesions of the gastrointestinal tract. In this study, we found that Sd(a) antigen was expressed mainly in chief cells of normal stomach but not in cancer tissue by immunohistologic staining.

Cortical activation during reading of ancient versus modern Japanese texts: fMRI study.

The purpose of this study was to investigate human brain activity during the reading of ancient Japanese texts using functional magnetic resonance imaging. Thirty right-handed normal Japanese subjects performed two reading tasks: covert reading of (1) ancient and (2) modern Japanese text. Common areas are activated during both tasks.

Reading aloud and arithmetic calculation improve frontal function of people with dementia.

Background: Recent findings of neuroimaging studies indicate that reading aloud and arithmetic calculation activate bilateral dorsolateral prefrontal cortex of humans. The purpose of this study was to measure the effect of reading aloud and arithmetic calculation, by elderly people who were clinically diagnosed with dementia Alzheimer type, on their brain functions and activities of daily living.

Methods: Sixteen experimental and 16 age- and Mini-Mental State Examination score-matched control subjects participated.

Therapeutic potential of follistatin for colonic inflammation in mice.

Background And Aims: Activins belong to the transforming growth factor-beta superfamily. Recent studies have shown that activin and its natural antagonist, follistatin, are involved in tissue repair and inflammatory processes. The aim of this study was to determine whether neutralization of activins with follistatin would have an in vivo anti-inflammatory effect in several murine models of colitis.

Cortical mechanisms of visual self-recognition.

Several lines of evidence have suggested that visual self-recognition is supported by a special brain mechanism; however, its functional anatomy is of great controversy. We performed an event-related functional magnetic resonance imaging (fMRI) study to identify brain regions selectively involved in recognition of one's own face. We presented pictures of each subject's own face (SELF) and a prelearned face of an unfamiliar person (CONT), as well as two personally familiar faces with high and low familiarity (HIGH and LOW, respectively) to test selectivity of activation to the SELF face.

fMRI activation maps based on the NN-ARx model.

The most significant progresses in the understanding of human brain functions have been possible due to the use of functional magnetic resonance imaging (fMRI), which when used in combination with other standard neuroimaging techniques (i.e., EEG) provides researchers with a potential tool to elucidate many biophysical principles, established previously by animal comparative studies.

Different roles of the frontal and parietal regions in memory-guided saccade: a PCA approach on time course of BOLD signal changes.

Although involvement of the frontoparietal regions in visually guided saccade and visuospatial attention has been established, functional difference of the frontal and parietal regions suggested in neuropsychological observations and lesion studies in animals has not been explicitly supported by functional imaging studies. Considering a possible disadvantage of cognitive subtraction in an interregional comparison, we directly compared the time course of BOLD signal changes across regions. Normal subjects performed a modified version of a memory-guided saccade task in which saccade was performed both during encoding and execution phases.

Role of the cerebellum in implicit motor skill learning: a PET study.

To depict neural substrates of implicit motor learning, regional cerebral blood flow was measured using positron emission tomography (PET) in 13 volunteers in the rest condition and during performance of a unimanual two-ball rotation task. Subjects rotated two balls in a single hand; a slow rotation (0.5 Hz) was followed by two sessions requiring as rapid rotation as possible.

One-step analysis of testis steroidogenesis from neonatal exposure to synthetic estrogen by normal-phase HPLC.

Neonatal exposure to synthetic estrogen endocrine disruptors or estrogen-receptor inhibitors induces developmental abnormalities in the male reproductive system. To investigate whether neonatal exposure affects spermatogenesis in juvenile and pubertal testis, Sprague-Dawley rat pups were given synthetic estrogen endocrine disruptors or estrogen-receptor inhibitors by a single injection on the day of birth at concentrations ranging between 2 to 40 mm, and sacrificed on day 21 (juvenile), 35 (prepuberty) or 50 (puberty). The testes were weighed and examined histologically at each stage.

Mental visual synthesis is originated in the fronto-temporal network of the left hemisphere.

Mental visual synthesis is the capacity for experiencing, constructing, or manipulating 'mental imagery'. To investigate brain networks involved in mental visual synthesis, brain activity was measured in right-handed healthy volunteers during mental imagery tasks, in which the subjects were instructed to imagine a novel object, that does not exist in the real world, by composing it from two visually presented words associated with a real object or two achromatic line drawings of a real object, using functional magnetic resonance imaging (fMRI). Both tasks activated the same areas in the inferior frontal and inferior temporal cortices of the left hemisphere.