Mapping functional hemodynamic and metabolic responses to dementia: a broadband spectroscopy pilot study

Significance Broadband near-infrared spectroscopy (bNIRS) can simultaneously monitor several chromophores including the oxidative state of cytochrome c-oxidase (oxCCO), an oxygen metabolism biomarker whose activity is altered in Alzheimer’s disease. Being a portable and non-invasive neuromonitoring technique, bNIRS could thus provide accessibility to brain-specific biomarkers and aid in the dementia diagnostic pathway. Aim We use bNIRS recorded functional haemodynamic and oxCCO changes to assess their relevance in Alzheimer’s disease dementia as potential biomarkers. Approach Using a visual-stimulus paradigm, we recorded functional changes in oxy-, deoxy-haemoglobin and oxCCO in three similarly aged cohorts: healthy controls (n=5), individuals with mild cognitive impairment (n=7) and individuals with Alzheimer’s dementia (n=7). We then selected features from these functional responses to find the best correlation with clinical cognitive markers (cognitive and behavioural test scores and clinical diagnosis) using canonical correlation analysis.

We found individual variations in peak amplitude and time-to-peak for all the stimulus-evoked bNIRS signals across the three cohorts. Canonical correlation analysis showed a strong correlation between bNIRS features and the clinical cognitive markers (r=0.902). However, repeating the same analysis by excluding the bNIRS oxCCO features leads to a significantly lower correlation (r=0.687) with the clinical markers.

oxCCO could be a crucial biomarker, partly explaining cognitive differences with dementia. bNIRS uniquely provides a portable and non-invasive technique to monitor several chromophores simultaneously including oxCCO with potential future applications in tracking dementia progression. Competing Interest Statement Author John OBrien has indicated COI in the manuscript