Single trial hemodynamic response estimation in a block anagram solution study using fNIR spectroscopy

Near infrared spectroscopy (NIRs) has shown great potential in examining functional brain activity during cognitive tasks by enabling the measurement of changes in the concentration of deoxygenated and oxygenated hemoglobin. It has attracted great interest due to its portability, low cost, safety and non-invasiveness. We present a novel single trial hemodynamic response estimation algorithm in an anagram solution study using functional NIRs (fNIRs). The temporal profile of the hemodynamic response to each single trial stimulus is estimated by minimizing the error between the oxygenation data measured by fNIRs and a linear model. No prior assumption on the amplitude, latency, or variance of the hemodynamic response is required other than its shape to be a γ function. Once the estimates of single trial hemodynamic responses gathered from the dorsolateral prefrontal cortex are obtained, features, such as maximum amplitude, rise time, etc., are extracted and compared for different difficulty levels of the test.