Design Of Near-Infrared Brain Function Imager And Its Application In The Research Of Dyslexia

Near-Infrared Spectroscopy (NIRS) is one of the main contents of biomedical photonics. Its purpose is to quantify the concentration of some chromophores in tissue. When cortex's area is active, its local blood volume increases. The increasing extent represents the intensity of activity. Therefore the changes of blood volume can be the index of brain function activity. Because NIRS can measure the changes of blood volume and oxygenation of cortex, it is applied widely in the research of brain function activity. In this thesis, the basic principle of NIRS is introduced and a brain function imager of 24 channels based on continuous wave (CW) NIRS is presented, which has advantages of high temporal resolution(20 ms) and big imaging area (6×12 cm). The software of the system has the functions of sampling the data of light's intensity; calculating and displaying the changes of blood volume and oxygenation; presenting the visual stimulates used by cognitive psychology research to subjects; recording the responses and response time of subjects during task. The software can accurately synchronize the presenting of stimulates and the sampling of data. It is important to analyzing experimentation's results The results of blood model test indicated that this system can measure the changes of blood volume and oxygenation with a high responsivity. Developmental dyslexia is a kind of prevalent psychologic disease. It can be defined as an unexpectedly low reading ability relative to IQ. The deference of brain function activation between Chinese dyslexia children and no-impaired children during Chinese phonetic and semantic processing was investigated using Near-Infrared Spectroscopy. This experimental results presented a new evidence to indicate that there is abnormity of neural systems for dyslexic children during Chinese word reading.