Early Detection of Alzheimer’s Disease Using Non-invasive Near-Infrared Spectroscopy

Abstract

Mild cognitive impairment (MCI) is a cognitive disorder characterized by memory impairment, wherein patients have an increased likelihood of developing Alzheimer’s disease (AD). The classification of MCI and different AD stages is therefore fundamental for understanding and treating the disease. This study aimed to comprehensively investigate the hemodynamic response patterns among various subject groups. Functional near-infrared spectroscopy (fNIRS) was employed to measure signals from the frontal and bilateral parietal cortices of healthy controls (n = 8), patients with MCI (n = 9), mild (n = 6), and moderate/severe AD (n = 7) during a digit verbal span task (DVST). The concentration changes of oxygenated hemoglobin (HbO) in various subject groups were thoroughly explored and tested. Result revealed that abnormal patterns of hemodynamic response were observed across all subject groups. Greater and steeper reductions in HbO concentration were consistently observed across all regions of interest (ROIs) as disease severity developed from MCI to moderate/severe AD. Furthermore, all the fNIRS-derived indexes were found to be significantly and positively correlated to the clinical scores in all ROIs (R ≥ 0.4, P < 0.05). These findings demonstrate the feasibility of utilizing fNIRS for the early detection of AD, suggesting that fNIRS-based approaches hold great promise for exploring the mechanisms underlying the progression of AD.

A Systematic Review of Cerebral Functional Near-Infrared Spectroscopy in Chronic Neurological Diseases—Actual Applications and Future Perspectives

“…In most of the reviewed applications, fNIRS probes were placed over the PFC, as this cortical area is mainly associated with high-level processing functions [64]. We identified 40 studies performed with a total of 977 AD and 477 MCI patients (208 amnestic MCI), as well as with 792 age-matched HC subjects (Table 2) Most studies were addressed to the monitoring of tissue oxygenation [65][66][67][68][69][70], the investigation of functional resting-state activity and connectivity [64,[71][72][73], the assessment of specific cognitive functions [74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90][91][92][93] such as visuospatial deficits [94,95] and additional ecological applications [96,97]. Though most studies reported cross-sectional reports, we also retrieved six longitudinal ones [98][99][100][101][102][103], thus strongly supporting the idea that fNIRS can represent a viable tool for long-term monitoring of cerebral activity from the early phases of the disease or during r...…”

“…However, the WM task performance and the averaged response were lower and delayed in the AD group compared to HCs, suggesting that the α4β2 nicotinic acetylcholine receptor system supports PFC activity associated with cognitive tasks. Recently, Li et al [91] investigated the hemodynamic response patterns of MCI and AD patients of different severity during a verbal digit span task. Lower HbO2 concentrations across frontal and bilateral parietal cortices were associated with the severity of the disease, while MMSE scores were significantly correlated with all fNIRS-derived hemodynamic indices.…”

Application of functional near-infrared spectroscopy in the healthcare industry: A review

“…The mean and slope of the HbO responses were correlated with the clinical scores, and the scores of the MCI patients stayed below those of the mild and moderate-to-severe AD patients. 236…”

“…244 A time-series analysis revealed that the reduction or decline in HbO levels becomes steeper when the intensity of AD progresses. 236…”

“…98,286 Therefore, studying multiple brain areas is important to understand the underlying changes occurring in patients' brains. [30][31][32][33][34]79,121,236,266,272 Functional and e®ective connectivity analyses are useful to understand the processing that takes place in the human brain, and covering more brain areas will allow for better understanding based on the experimental conditions. 4,271,[295][296][297]352 The bundled optode approach that creates hundreds of channels at di®erent brain depths with high spatial resolution can assuredly assist in the creation of 3D images via fNIRS, which can be compared with those created via fMRI.…”