カスタムサイズのMEGと就学前のお子様でNeuromagnetic脳機能の計測

Hi, I'm Steven Crane. I'm co-director of the KIT Macquarie Brain Research Lab. The lab is part of the Macquarie Center for Cognitive Science at Macquarie University in Sydney, Australia.

Hello, I'm Illa Dessan and I work at the Macquarie Center for Cognitive Science at Macquarie University. Hi, I'm Melanie Reed and I work at the Macquarie Center for Cognitive Science. At Macquarie University, We use magnetoencephalography or MEG to study the brain mechanisms underlying the rapid acquisition of language in children from ages two to six years old.

MEG measures the magnetic fields produced by the brain cortex. Using MEG, we can observe which brain areas are active during language processing and how these different areas interact. There are two challenges in working with young children using any brain imaging system.

First, the typical laboratory environment is not child-friendly. Second, to participate in an MEG study, children must be instructed to keep movement to a minimum, and they're required to attend to a task for an extended period of time. So it was important for us to develop a protocol that enables us to use MEG while at the same time is enjoyable for children.

That said, the benefits of MEG far outweigh the challenges. MEG is a valuable tool for measuring brain function in children because of its extremely high temporal resolution and its good spatial resolution, and because it is completely non-invasive, it poses no conceivable risk to the neural tissue of children. In contrast to MEG, other neuro imaging techniques used strong magnetic fields and radioactive pharmaceuticals that may pose a risk for young children.

One of the key features of our child MEG system is that it was designed specifically to be used with young children. The custom size system was developed in collaboration with the Kanawa Institute of Technology and the Yokogawa Electric Corporation. In the following video, we will explain why it was necessary to develop a customized MEG system for children, and we will show you how we go about preparing children to be studied in the MEG system.

So join us for the next few minutes and we'll show you the lab. We'll explain the steps we have taken to make children enjoy participating in our studies. A laboratory has two MEG systems housed in the same magnetically shaped room.

The adult system consists of 160 sensors evenly spread out inside the MEG helmet, which offers a whole head coverage. The child MEG system has a similar layout, but it has 64 sensors making the helmet smaller and perfectly suited for preschoolers and infants. Magnetoencephalography or imaging is a neuroimaging technique that measures neuronal activity directly.

MEG can detect and amplified the faint magnetic fields generated by thousands of active neurons in the brain cortex. Detecting these weak magnetic fields is easily achieved by special sensors known as squids or superconductive quantum interference devices. Superconducting technology is needed to run the MEG systems.

The sensors require cooling with liquid helium at minus 270 degrees Celsius. The following sequence shows the systems being refilled with liquid helium, which needs to be done on a weekly basis. Liquid helium accounts for most of the operating costs of an MEG system.

Magnetic fields from the brain are extremely small in comparison to magnetic fields produced by all of the equipment in a modern lab. This means that MEG systems must be housed in a magnetically shielded room. The shielded room in our laboratory is constructed of three layers of perlo and one layer of copper.

The room weighs about 8.5 tons, and the floor of the laboratory had to be especially reinforced to bear its weight. The cost of the magnetically shielded room accounts for one third to a half of the capital cost of an MEG system. The room has a number of ports in the side so that visual stimuli can be projected into the room and other kinds of equipment can be operated through fiber optic cables.

MEG measures magnetic fields produced by active cells of the brain. A related technique electroencephalography measures the electrical component of these fields. EEG is a much simpler and less expensive technology, but does not have meg's ability to localize activity in the brain.

For studies with older children and adults, we often record both EEG and MEG at the same time. However, this is usually not practical with preschool children because of the longest setup Time required for EEG. Because MEG Uses sensors that are bathed in liquid helium, the sensors are in fixed positions within a vacuum sealed insulating helmet doer.

The helmet of a standard adult MEG system is designed to accommodate about 95%of adult heads. This means that the largest and smallest heads do not fit well in the adult helmet. This is a particular problem for preschool aged children because their heads are as much as two to three centimeters smaller in radius than adult heads.

Because MEG signals fall off very quickly with distance. This means that many of the senses in an adult helmet will not be effective for measuring signals from children's brains. Another problem is that children are more likely to move their heads in the large helmets during measurement sessions.

This causes a degradation of the MEG signals. This clip shows the MEG sensors in an adult system. With respect to a child's head, you can see that many of the sensors are quite far from the surface of the head.

This is why it is valuable to produce an MEG helmet doer that is custom sized to fit the heads of preschool aged children. In this clip, you can see that the sensors of our child MEG system are all very close to the surface of The head. Several steps need to Be completed before we can start the experiment.

Inside the MSR, we check if the child has anything made of Ferris material on them. Have you got anything in your pockets? No.And they've got second.

We fit the child with a cap that contains five marker coils. We then digitize the child's head shape or make a drawing of their heads as we call it. Then we get the child inside the MSR or the spaceship ready to play the game While we are getting the tie ready.

Inside the MSR, a movie of their choice is played on the screen above. Once they're lying down comfortably, we close the door and that acquisition starts. The experiment will typically last for about 20 minutes.

We invite the child to play a game inside the spaceship while they're watching a muted movie. In our case, children listen to a series of sentences attentively and repeat the word cheese as soon as they hear it. The cheese smell from the monkeys backpack.

Good job. The carrot cheese, excellent job Acoustic stimuli, such as speech as delivered to the child's ears through the plastic tubing that you see on the child's chest. We use child size foam ear pieces to fit the tubes inside their ears.

During the data acquisition, the child is monitored continuously through closed circuit video, and the experimenters can communicate with the child through a microphone. Prior to the MEG measurement, we fix five marker coils on a swimming cap, which is then placed on the child's head. During the MEG measurements, these are used to measure and Monitor head position and movement throughout data Acquisition.

The researcher and the parent, if they wish, stay with the child in the shielded room at all times. This is to ensure that the child is comfortable and the movement is minimized. At the end of the experiment, children are rewarded with a prize for performing the task correctly.

So which sticker would you like to choose? It's One On here On There. Those of you familiar with preschool aged children will know that their first choice would not be to lie still in a magnetically shielded room.

We use a number of techniques to make both the environment and the process child-friendly. The lab is filled with child-friendly stickers and soft toys. Testing is done over three to five visits to the laboratory.

The first meeting is usually used to introduce the child to the researchers and to the MEG environment. The child watches a toy, animal a bear, or Kermit the frog. Go through all of the steps they will be going through.

We introduce a theme for the testing sessions. The MEG system is a spaceship waiting to take the children on a space adventure. We have work booklets based on this theme that explain the steps we will be going through, and then with the crayon draw around it.

Just like we draw a picture of your head. It is vitally important that children are able to remain still both while digitization and testing take place. Okay, now we have to freeze.

Can you freeze like this? We communicate this by asking the children to show us how they freeze. Good job.

Pretty good.Freezing. The importance of being able to freeze is reinforced at Each visit at the lab. It is also important to ensure that Children have an understanding of each step of the experiment.

We explain the steps to children using language they can understand. For example, we refer to the cap containing the marker coils as an astronaut helmet. Do you feel like an astronaut yet?

And we describe digitizing as drawing a Picture of their head. If a child appears shy or Anxious, we will often use puppets to illustrate what the experiment is about. We also ask children their help so as to give them a better understanding of what we are going to be doing.

Children are usually happy to help a puppet go into the magnetically shielded room. If the child still doesn't want to go into the magnetically shielded room, we simply have periods of playtime until they feel more comfortable. When the tailies time familiar with all the steps in our protocol, we introduce the experimental task that is to be performed inside the MSR.

Mm.So do you remember, which is the magic word you had to repeat? Can I didn't hear that? Can I?

Can you say it again? Yes.Cheese.So, for instance, if I say something like, the other day I went to the park and I saw a piece of cheese. What do you do?

As you can see, conducting brain imaging studies with children requires specialized technology, and it requires procedures beyond those that are typically used in studies with adults. First, we developed a custom sized MEG helmet, which is designed to fit children's heads and to limit their head movement. Second, we made the laboratory child friendly using wall art and stuffed toys.

We employ methods that have been adapted to the needs and motivation of young children. Our laboratory is designed for measuring cognitive brain function in healthy and awake young children. Thus, the requirements are somewhat different than those that may be otherwise encountered in pediatric neuroimaging.

The advent of child MEG systems is an important advance for cognitive neuroscience. It will allow us to obtain measurements of brain function in an age range where fascinating and dramatic structuring of brain function is taking place. Currently, we know very little about these developmental processes.

We hope to fill this gap by studying children's brain function using MEG.