Masato Maeno

Analysis of brain activation by visual and auditory stimulation after visual and auditory simultaneous stimulation using F-MRI

It is said that the auditory spatial perception is strongly affected by visual cues, and when auditory and visual stimulation are given form different positions simultaneously, the source position of sound is mislead to the direction of visual stimulation. The purpose of this study is analyzing the brain response on f-MRI by simultaneous stimulation of auditory and visually sensors. f-MRI of some subjects were measured by using simultaneous stimulation, and the results of these experiments were analyzed and assessed. From these experiments, following characteristics became clear. 1) Simultaneous stimulation activate each cortex stronger than the results of single stimulation. 2) After giving auditory and visual stimulus as preliminary stimulation to subject, one type of stimulus was given to the subject. From this stimulation, both cortex were activated. This activation was weaker than the time of actually giving simultaneous stimulus. From investigation of these results, it seems that the relationship between auditory and visual cortex become clear.

The Analysis of a Simultaneous Measured Forearm’s EMG and f-MRI

Generally, voluntary muscles are able to be moved freely, if we want to move them consciously. In addition, EMG is generated in a muscle according to contraction of it. If we want control some equipment like an artificial hand by using EMG, a beginner cannot control it without concentration on the motion of equipment. However, if he/she is practiced in operation of the equipment as a result of training, he/she can control it without concentration. In other words, a skilled person has obtained some abilities from training, and these abilities will change brain functions. Making the change of brain function as a result of training clear by using f-MRI is our objective of this study. In our study, 6 channels EMG which are generated from right forearm are measured and basic hand motions are recognized by using them. In our experiment, a subject in a gantry of MRI moves his/her right hand, and generated 6 channels EMG are amplified, filtered and digitized. Digitized EMG data is analyzed and then a recognition result is indicated to a subject as an animation of the recognized hand motion by a LCD projector. A subject trains himself/herself in order to improve the recognition rate. F-MRI is measured while training continuously. In this paper, we will talk about our measurement system and the results of experiment.

The BOLD signal response for fluctuating stimulation images

In the measurement of brain function by using fMRI, increasing of blood flow and decreasing of deoxy-hemoglobin concentration as a cause of this increasing (BOLD: blood oxygenation level-dependent) are measured. And brain activity is evaluated as the function of BOLD signal. In the fMRI measurement, MRI data under stimulation and resting are measured periodically, and these data are compared and analyzed. This measuring method is usually used. However, periodic stimulation sometimes produces experience. And this experience may weaken the brain activity. Therefore, in order to suppress experience, fMRI was measured using fluctuated stimulation. And the results of this measurement were compared with the data that was measured using ordinary method.

Influence of moving sight by turning over frequency

In late years, f-MRI (functional magnetic resonance imaging) are used for analysis of a visual function. In case of the study for a visual function, the checker flag pattern consists of white square and black square is usually used for sight stimulation. In sight stimulation using this pattern, a color of square (black and white) changes alternately at constant frequency. It is usually called pattern reversal stimulation. When this pattern is used for stimulation, the subject sometimes feels movement for the shown stimulation pattern. We think that this sensation of movement relates to spatial frequency (that means the size of a square of a stimulation pattern) of a stimulation image and a turning over frequency of a stimulation pattern strongly. Our objectives of this study are the following. 1) Clarify a part of the brain that is a cause of this moving sensation. 2) Investigate the relationship among the magnitude of this sensation, spatial frequency and turning over frequency. Three normal adults were used for the subject. This time, turning over frequency was changed to 8 Hz by 1 Hz step under fixed spatial frequency. Under this condition, we examined the state of activation of a V1 area. In addition, we examined whether BOLD effect varied with a change of a stimulation color. In this experiment, we used blue and yellow color instead of black and white for stimulation, and the reaction was examined

Experiment result and the evaluation in block paradigm and single paradigm

Many researchers are investigating the brain function by using a block paradigm in fMRI measurement. However, there are some problems to pick up the activating area of brain for visual stimulation in analysis system which is equipped with MRI normally. It becomes a standard so that using the analysis software such as SPM may deal with such various problems. But, problems exist even if these software are used. Then, we advocate constructing a single paradigm which is a new measurement technique for considering BOLD effect, and specify a target part simply by using fMRI. We compared the ordinary block paradigm to the single paradigm through the aspect of the evaluation of the activating part in the MRI image and the change in the signal intensity (change of hemodynamics).

Experiment results and the evaluation in the block paradigm and the single paradigm

Many researchers are investigating the brain function by using a block paradigm in fMRI measurement. However, there are some problems to pick up the activating area of brain for visual stimulation in analysis system which is equipped with MRI normally. It becomes a standard so that using the analysis software such as SPM may deal with such various problems. But, problems exist even if these software are used. Then, we advocate constructing a single paradigm which is a new measurement technique for considering BOLD effect, and specify a target part simply by using fMRI. We compared the ordinary block paradigm to the single paradigm through the aspect of the evaluation of the activating part in the MRI image and the change in the signal intensity (change of hemodynamics).

f-MRI analysis under auditory and visual stimulations

It is said that the auditory spatial perception is strongly affected by visual cues, and when auditory and visual stimulation are given from different positions simultaneously, the source position of sound is mislead to the direction of visual stimulation. The purpose of this study is analyzing the brain response on f-MRI by simultaneous stimulation of auditory and visually sensors. f-MRI of some subjects were measured by using simultaneous stimulation, and the results of these experiments were analyzed and assessed. From these experiments, following characteristics became clear. 1) Simultaneous stimulation activate each cortex stronger than the results of single stimulation. 2) Simultaneous stimulation activate right cerebellum. From investigation of these results, it seems that the relationship between auditory and visual cortex become clear.