Functional near-infrared spectroscopy: looking at the brain and language mystery from a different angle

Assessing Multilingual Speakers' Language Processing through functional near-infrared spectroscopy (fNIRS)

Multilinguals' navigation through three or more language systems utilizing one cognitive system is a phenomenon of recent interest. Few functional near-infrared spectroscopy (fNIRS) studies have focused on brain activations concerning multilinguals. The present study uses picture-naming and fNIRS technique to explore the prefrontal brain activations amongst neurotypical multilinguals belonging to four major provinces of Pakistan. The 26 right-handed participants utilize their native language (Punjabi, Pushto, Sindhi or Balochi), first language (Urdu) and second language (English) distinctively in the experiment. Brain imaging results demonstrate a significant activation of the right prefrontal cortex among the multilingual adults along with left laterality. Moreover, results indicate significant activation of channels demonstrating heavier cognitive load with English in comparison to first or native language(s). The paper suggests that right dorsolateral prefrontal cortex and right medial prefrontal cortex play a significant role in language processing alongside the left prefrontal cortex, exemplifying that peripheral activation during word retrieval, processing and production is a possibility.

APPLICATION OF FUNCTIONAL NEAR-INFRARED SPECTROSCOPY IN NEUROLOGICAL DISEASES: EPILEPSY, STROKE AND PARKINSON

The functional near-infrared spectroscopy (fNIRS) technology is an optical imaging technology that applies near-infrared light to measure the oxygenated and deoxygenated hemoglobin concentration alteration in cortical brain structures. It has the ability to directly measure changes in the blood oxygen level of the high temporal resolution associated with neural activation. Thus, it has been utilized in different neurological diseases, such as epilepsy, stroke, and Parkinson. The work of this paper will focus on the application of the fNIRS in the three neurological diseases and the principle of fNIRS. Moreover, the difficulties and challenges that the technology is currently experiencing have been discussed.

An Exploration of the Effect of Hemodynamic Changes Due to Normal Aging on the fNIRS Response to Semantic Processing of Words

Like other neuroimaging techniques assessing cerebral blood oxygenation, near-infrared spectroscopy (NIRS) has been applied in many neurocognitive studies. With NIRS, neural activation can be explored indirectly via hemodynamic changes in the imaged region. In studies of aging, changes in baseline physiology and brain anatomy confound NIRS measures seeking to investigate age-related changes in neuronal activity. The field is thus hampered by the complexity of the aging process itself, and statistical inferences from functional data acquired by optical imaging techniques must be interpreted with care. Multimodal integration of NIRS with both structural and baseline physiological assessments is crucial to avoid misinterpreting neuroimaging signals. In this study, a combination of two different optical techniques, anatomical MRI and Arterial Spin Labeling (ASL), was used to investigate age-related changes in activation during a lexical-semantic processing task. Quantitative analysis revealed decreased baseline oxyhemoglobin and cerebral blood flow in the older adults. Using baseline physiology measures as regressors in the investigation of functional concentration changes when doing analyses of variance, we found significant changes in task-induced areas of activity. In the right hemisphere, more significant age-related activity was observed around the junction of the inferior frontal gyrus and inferior precentral sulcus, along with engagement of Wernicke's area. In the left hemisphere, the degree and extent of frontal activation, including the dorsolateral prefrontal cortex and inferior frontal gyrus, differed between age groups. Measuring background physiological differences and using their values as regressors in statistical analyses allowed a more appropriate, age-corrected understanding of the functional differentiations between age groups. Age-corrected baselines are thus essential to investigate which components of the NIRS signal are altered by aging.