Relation Between Cognitive Function and Baseline Concentrations of Hemoglobin in Prefrontal Cortex of Elderly People Measured by Time-Resolved Near-Infrared Spectroscopy.

We evaluated relationship between cognitive function and cerebral blood oxygenation (CBO) of the prefrontal cortex (PFC) at rest in 113 adults (age 72.3 ± 12.0 years). We employed a two channel time-resolved near-infrared spectroscopy (TRS), which allows non-invasive measurements of baseline concentrations of oxyhemoglobin (oxy-Hb), deoxyhemoglobin (deoxy-Hb), total-hemoglobin (t-Hb) (μM) and oxygen saturation (SO2, %) of the bilateral PFC without any tasks. We examined cognitive functions using the Mini-Mental State Examination (MMSE) (range from 0 to 30) and the Touch M which evaluates working memory function semi-automatically on a touchscreen (range from 0 to 100); the mean MMSE and Touch M scores of all subjects were 24.8 ± 4.6 (mean ± SD; range 11-30) and 41.3 ± 22.1 (range 1-100), respectively. Employing Pearson's correlation analysis, we evaluated correlation between the TRS parameters and cognitive function. We found a significant positive correlation between the MMSE scores and SO2 (r = 0.24, p < 0.02). In addition, we observed significant positive correlations between Touch M scores and baseline concentrations of oxy-Hb (r = 0.26, p < 0.02), total-Hb (r = 0.23, p < 0.05), and SO2 (r = 0.23, p < 0.05). TRS allowed us to evaluate the relation between CBO in the PFC at rest and cognitive function.