Changes in prefrontal cortex near infrared spectroscopy activity as a function of difficulty in a visual P300 paradigm

The P300 event-related potential is an index of attentional resources related to target detection. Source localization and functional magnetic resonance imaging (fMRI) research has indicated that, among other regions, the prefrontal cortex contributes to the generation of the P300. Similar to fMRI, near infrared (NIR) spectroscopy measures change in blood oxygen levels, but offers several advantages including portability, low expense, and superior temporal resolution. No studies to date have examined the extent to which prefrontal cortex NIR spectroscopy measures are active during the P300 paradigm. To address this knowledge gap, participants completed a two-difficulty visual oddball task in which NIR spectroscopy and P300 data were collected in a counterbalanced order. Confirmatory results indicate that the P300 event-related potential is attenuated as a function of task difficulty. Similarly, NIR spectroscopy measures of oxygenated hemoglobin in the right medial prefrontal cortex are attenuated as a function of task difficulty. The results suggest that prefrontal cortex NIR spectroscopy measures are sensitive to task difficulty in a visual P300 oddball task.