Working memory (WM) refers to the temporary maintenance of information that is no longer accessible in the environment, and the manipulation of this information for subsequent use. PET and functional MRI studies suggest that prefrontal cortex (PFC) is involved in WM. Here, we report a functional near-infrared spectroscopy (NIRS) study on the PFC activation caused by a WM task, a verbal n-back task. During performance of the task, concentration changes of oxy-Hb (HbO<sub>2</sub>), deoxy-Hb (Hb), and total-Hb (HbT) in subjects’ prefrontal cortex were monitored by a 24-channel functional NIRS imager. The behavioral performances (accuracy and response time) were recorded simultaneously. Results revealed that as memory load increased, subjects showed poorer behavioral performance as well as monotonously increasing magnitudes of the activations in the left ventrolateral PFC (VLPFC) and bilateral dorsolateral PFC (DLPFC). In addition, the analysis of comparison between subjects showed that certain relations likely exist between the cerebral activation and the performance parameters for an individual subject: lower accuracy is accompanied by longer response time and further activation. Such means that the subject with difficulty in solving a problem will demonstrate more significant hemodynamic changes compared with the subject without difficulty in solving the same problem.
Human prefrontal cortex (PFC) helps mediate working memory (WM), a system that is used for temporary storage and manipulation of information and is involved with many higher-level cognitive functions. Here, we report a functional near-infrared spectroscopy (NIRS) study on the PFC activation caused by verbal WM task. For investigating the effect of memory load on brain activation, we adopted the “n-back” task in which subjects must decide for each present letter whether it matches the letter presented n items back in sequence. 27 subjects (ages 18-24, 13 females) participated in the work. Concentration changes in oxy-Hb (HbO<sub>2</sub>), deoxy-Hb (Hb), and total-Hb (HbT) in the subjects’ prefrontal cortex were monitored by a 24-channel functional NIRS imager. The cortical activations and deactivations were found in left ventrolateral PFC and bilateral dorsolateral PFC. As memory load increased, subjects showed poorer behavioral performance as well as monotonically increasing magnitudes of the activations and deactivations in PFC.
For studying prefrontal cortical function in short-term memory two tasks were designed. In task one, a plus expression appears on screen for 300 milliseconds every other 2 seconds and the subject is required to give it’s answer but not to remember it. In task two, an Arabic numeral presents on screen as the same frequency as in task one. While a number is present, the subject need adding it to the sum he got last time. As subjects, 26 children participated in the work. Blood volume changes(BVCs) of right prefrontal cortex(PC) under two cognitive tasks were examined using functional near infrared imaging(fNIRI), a noninvasive technique for localizing regional BVCs which correlate with neural activities. The BVCs caused by short-term memory for numbers were retrieved from BVCs by task one and task two. Results revealed that short-term memory is related to PC and the near-infrared spectroscopy(NIRS) can be used to study prefrontal cortical function in short-term memory.
Developmental dyslexia is a kind of prevalent psychologic disease. Some functional imaging technologies, such as FMRI and PET, have been used to study the brain activities of dyslexics. NIRS is a kind of novel technology which is more and more widely being used for study of the cognitive psychology. However, there aren’t reports about the dyslexic research using NIRS to be found until now. This paper introduces a NIRS system of four measuring channels. Brain activities of dyslexic subjects and normal subjects during reading task were studied with the NIRS system. Two groups of subjects, the group of dyslexia and the group of normal, were appointed to perform two reading tasks. At the same time, their cortical activities were measured with the NIRS system. This experimental result indicates that the brain activities of the dyslexic group were significantly higher than the control group in BA 48 and that NIRS can be used for the study of human brain activity.
The continuous light coming from the Argon Gas Ion Laser can be converted to pulse light when an optical chopper is equipped. The sample is excited by the pulse light in the confocal microscopy system. The light intensity of the excitation light and the phosphorescence is simultaneously recorded in terms of gray value by the confocal microscopy system. The phosphorescence lifetime measurement can be realized with time-resolved analysis for the phosphorescence intensity decay. The different decay lifetimes of the Oxy- Phor R2 sample under different oxygen concentration are measured with the reconstructed confocal microscopy system.