On the Application of Near Infrared Optical Imaging in Developmental Psychology Research

February 08, 2024

Abstract: This article introduces a new type of brain imaging technology that can be used to explore infant brain development-near infrared optical imaging. The system introduces the development history of this technology, the principles and methods used, and its research and application in infant development

It has been more than ten years since the first NIR optical imaging was applied to infant brain functional imaging research. The continuous improvement and application of NIRS in the next 10 years will make a significant contribution to our understanding of the developing brain. We believe that fNIRS will build an important bridge between our current understanding of cortical activity in the developing brain and adult brain function. At the same time, the vast majority of pre-speech stage infant behavior research now uses the gaze time paradigm, and a large part of the development of cognitive neuroscience research is relatively low. fNIRS allows us to explain the relationship between cortical activity localization and behavioral responses in early human development. In addition, the NIRS system is not expensive, it is also relatively portable, it can allow the baby to sit on the parents' knees to a certain degree of activity, and more importantly, the spatial positioning results of hemodynamics can be compared with adult brain function fMRI data. fNIRS is an ideal tool for studying babies.

Nerve activity results from the electrical conduction activity of neuronal cells. In the metabolism of neuronal activity, neuronal cells will undergo some changes, oxygen consumption will increase significantly, and the attached cerebral blood flow and oxygen supply will also increase. A typical hemodynamic response to neuronal activity in the adult cortex is an increase in oxyhemoglobin in the bloodstream and a less significant decrease in deoxyhemoglobin, which results in an increase in total hemoglobin in the bloodstream. Neuroimaging methods are divided into two types: one is the observation of direct activation of brain activity (EEG, MEG); the other is the subsequent hemodynamic response (PET, fMRI, fNIRS).

These techniques are all built on adult subjects. They must be applied to infant subjects with strict restrictions or they cannot be used at all. Some articles using these techniques to study infants have been published, but these studies It is generally restricted to the subjects of sleeping and sleepy young infants. For many years, the primary choice for studying brain functional imaging in sober infants is EEG, which is a non-invasive technique with a high temporal resolution, but a very low spatial resolution. The emergence of fNIRS provides a new option for studying functional imaging of infant brain.

Using NIRS to study infants' brain functional activities is a rapidly growing field. Since 1998, the number of papers has increased at a rate five times that of the previous year. However, the early fNIRS research focused on the activation area of the cerebral cortex for basic stimulation, such as the auditory area of speech perception, or the high-frequency flash visual area. Until recently, researchers have begun to pay attention to many complex stimuli. Activation of various brain regions. In addition, more and more researchers have begun to pay attention to the coding problems of sober babies, such as object processing, social interaction, biological motion processing, motion observation, and face processing. In these studies, fNIRS was used to locate hemodynamic responses of special cortexes, such as the superior temporal groove (gaze, biomotor processing), orbitofrontal cortex (mother's face, emotion perception), sensorimotor area (action observation), Prefrontal cortex (object eternity), occipitotemporal cortex (dynamic object). Locating the activated cortical area and allowing the subject to exercise slightly, this is the most significant feature of using fNIRS to study the early development of the human brain.

1 Near infrared optical imaging: basic principles and methods

In this optical technology, light is emitted from the transmitter, reflected back to the receiver through the skin, skull, and underlying brain tissue. ② The attenuation of light (wavelength between 650nm-1000nm) depends not only on the absorption of light by tissues, but also on the scattering effect of light. In addition, oxyhemoglobin and deoxyhemoglobin have different characteristics for the absorption of near infrared light, so that the blood oxygen level can be measured. Assuming that the scattering is constant, the measured changes in near infrared light attenuation can be used to calculate the values of oxyhemoglobin (HbO2), deoxyhemoglobin (HHb), and total hemoglobin (HbT = HbO2 + HHb). After understanding the optical path in the tissue, HbO2, HHb, and HbT can be expressed in units of molar. This change in blood oxygen protein can be used to mark changes in cerebral blood flow, so it can provide a new method for studying brain function. ③

Previous studies have pointed out that the hemodynamic parameters obtained by NIRS are similar to the BOLD (blood oxygen dependent level) obtained by fMRI. It is worth noting that, unlike the BOLD data of fMRI, fNIRS can measure the concentration data of HbO2 and HHb separately.

2 Development and application of infant fNIRS research

Infant fNIRS studies have a higher rejection rate than studies that use adults as subjects. About 40% of this part of the excluded data is non-compliant. A large part of this can be attributed to the difficulty of designing such a method, which requires a composite transmitter-receiver probe to be worn on the baby's head and be effective and comfortable. Therefore, a lot of time and energy are

Used to improve NIRS in order to make it an effective tool for infant research. The requirement of a NIRS headgear that can be used for infant research is that it must be comfortable, lightweight, able to be placed in a short time, and must provide stable optical measurement data in each channel. Unlike the adult experiment, it is impossible to stop the experiment on the baby's head and adjust the headgear before starting the experiment. The headgear must be able to be firmly fixed on the head, and any movement of the baby will not change the position of the transmitter-receiver strap, which can eliminate the motion artifacts in the optical signal. A series of channels on the headgear must be surrounded by a semi-rigid structure, and must have some flexibility to fit the head, while maintaining a fixed separation distance between each transmitter and receiver. When the fragile fiber comes out of the hood, keep it away from the baby's face and the distance he can reach with his hand. In the process of wearing the headgear, the babies should not be disturbed excessively (this will cause them to not want to start the experiment). In the process of recording the data, the headgear cannot be conspicuous to avoid the baby being distracted during the experiment.

In the future, a possible research area of fNIRS is to investigate the differences between individuals. For example, it may help to diagnose some typical and atypical symptoms in infants and see if he may be suffering from the developmental abnormality of autism. Disease, and thus provide some contribution to diagnosis and treatment. The sample size of such clinical research is usually very small, so the optimal design of the headgear is particularly important, so that complete optical data can be obtained, and the data to be eliminated is made as small as possible.

references

[1] Imada, T., Zhang, Y., Cheour, M., Taulu, S., Ahonen, A., Kuhl, PK, 2006. Infant speech perception activates Broca's area: a developmental magnetoencephalography study. Neuroreport 17: 957 –962.

[2] Elwell, CE, 1995. A Practical Users Guide to Near Infrared Spectroscopy. Hamma-matsu Photonics, UK.

[3] Delpy, DT, Cope, M., 1997. Quanti? Cation in tissue near-infrared spectroscopy.Philos. Trans. R. Soc. Lond. B: Biol. Sci. 352,649–659.

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