What is the Goal of Your Research?

The brain has been considered the final frontier. One hundred billion neurons and their complex networks realize the sophisticated information processing for our sensation, movement, learning and thought. However, the neural mechanism of higher brain function is still unclear. The information processing in the neural networks is based on electric signals, and therefore if the electric signals are disturbed for any reason, various brain dysfunctions may occur and even obstruct or hinder daily life. In recent years, the brain-machine interface, which is a technology for connecting the brain and a device, has allowed paralyzed patients to be able to control a robot hand by only using his/her neural signals, or deaf patients to be able to hear sounds by directly stimulating neurons electrically in his/her inner ear. I am developing a microdevice for both recording the activity of many neurons and stimulating multiple sites electrically in various brain regions. My goal is to investigate the neural mechanism using this microdevice and develop new medical devices for restoring brain function.

 

What Kind of Devices Have You Developed and What Kind of Experiments do You Conduct?

For high-throughput recording of the electrical activity of neurons, multielectrode arrays are required. Traditional neuroscience uses a single electrode to record the electrical activity of neurons. By using recently advanced microfabrication techniques, multielectrode arrays have been made available which allow many recording and stimulation sites to be densely placed. Figure 1 shows a sixty four-channel (64-ch) three-dimensional (3D) electrode that we have developed recently. This electrode was designed for covering the whole brain area in a rat auditory cortex.

Figure 1  Multielectrode array made with microfabrication techniques and designed for covering whole brain area in a rat auditory cortex.

 We can’t record neural activities if we simply insert the electrode into brain tissue. We have to amplify the electrical signals because the electrical activities are at a range of several hundred microvolts (Figure 2). Commercially available multichannel amplifiers have their box size of around thirty centimeters, but I have developed a multichannel amplifier as an LSI chip that is a five millimeter square (Figure 2). Moreover, the chip not only amplifies signals but also stimulates using an instantaneous switching mechanism so that a recording point can be also used as an electrically stimulating site. As a result, an implantable microdevice which can record and stimulate multiple brain sites almost simultaneously has been developed (Figure 2).

Figure 2  A 64-ch LSI chip that can record and stimulate multiple brain sites, an implant board integrating the chip, and a recorded example in rats.

 

What Will be Your Next Goal?

In the future, we will investigate the neural mechanism of information processing in the brain using the developed microdevice, and we also hope to develop new medical devices to restore various brain functions utilizing this technology. Traditional neuroscience have analyzed the relationship between neural activities and various sensory stimulations and movement conditions, and then the information processing of the brain is estimated based on the obtained results. In contrast, the developed microdevice enables us to explain the causal relation of neural activities to the stimulations and movements by analyzing the perception or movement using a specific pattern of neural activity that is induced by the microdevice. In addition, I think there is a possibility to even restore and expand brain function by connecting the developed microdevice with a certain area of the brain (Figure 3). We have nearly reached a new horizon shown in the advanced technologies often presented in science fictions.

Figure 3  Restoring and expanding the brain function using microdevices. Recording (input) of a neural activity is processed and then output (as stimulation).