We study brain functional imaging on the basis of instrumentation, signal processing, electronics, and information and communication technologies while putting emphasis on methodologies.
Brain functional imaging
We are particularly interested in language processing in the brain. Language communication is one of the most important features of humanity and so language processing studies cannot be done with the animal studies. We study differences in brain processing depending on the context, for instance priming, by using brain functional imaging. In the future, we seek to apply this study to development of brain-computer interfaces (BCIs) to send not only commands generated with keyboards and mice but also contextual and emotional information to computers.
Application of instrumentation
We use a unique development EEG recording system which consists of a point-grounded Faraday shielded room, a multi-channel very-low-noise analog voltage amplifier, a multi-channel high-resolution simultaneous analog-to-digital convertor, audio and visual stimulation devices without any sample and frame drops, and a PC to control the overall experiment. Know-how accumulated in electronics studies allows us to record EEG without power line noise. The clock of stimulators and that of the A/D converter are perfectly locked. Thus, the EEG recoding is vertically as well as horizontally precise. Also, real-time access of EEG samples during recording, which is essential to develop BCIs.
Application of signal processing
We analyze EEGs recorded with the above-mentioned system with unique development signal processing tools. Event-related EEG data is usually a function in terms of time, channel, and epoch (sometimes called trial). Temporal and spatial filters play intrinsic roles with respect to each other. There is, however, no filter along the epoch axis. This is because epoch has no own order. If an order is given to epochs, epoch filters may play a specific role different from both temporal and spatial filters. For instance, we use instantaneous phases to give the epochs an order. This allows us to reveal directional phase synchronization relationship between brain areas and to separately extract evoked, amplitude-modulated, and phase-modulated components from averaged EEG.
Application of electronics
We use a unique development electronics working with the brain in real-time to facilitate and inhibit brain functions. This electronics is just invasively attached on the scalp and communicates with the brain in an electric way. The electronics is primarily a negative resistance and so positively and negatively amplifies the current from active EEG sources in the brain. In contrast to the current stimulation techniques to the brain, the electronics does not give forced stimulation but changes the brain dynamics.
Application of information and communication technologies
We apply spectrum spreading to coding stimulations to the brain in behavioral experiments and decoding recorded EEGs. Used codes have characteristics which do not used for the multiple communication and these characteristics are useful to identify the brain system.