The document discusses neuroimaging techniques such as functional near-infrared spectroscopy (fNIRS). fNIRS uses near-infrared light to monitor changes in oxygenated and deoxygenated hemoglobin in the brain in response to neural activity. It provides a portable, low-cost way to monitor brain activity and oxygenation levels during cognitive tasks. The document discusses how fNIRS works, its applications in detecting brain activity and lie detection by measuring hemodynamic responses in the prefrontal cortex. It also compares fNIRS to other neuroimaging techniques such as fMRI and discusses its potential for use in brain-computer interfaces.