Differences in prefrontal cortex activity based on difficulty in a working memory task using near-infrared...

Area of Science:

• Neuroscience
• Cognitive Psychology

Background:

• The prefrontal cortex (PFC) is crucial for executive functions, including working memory (WM).
• Understanding PFC activity during varying WM task loads is essential for cognitive neuroscience.

Purpose of the Study:

• To assess PFC activity using functional near-infrared spectroscopy (fNIRS) during the Sternberg WM task (ST) at three difficulty levels.
• To investigate hemodynamic responses in the PFC related to different WM task loads and phases (encoding, retention, retrieval).

Main Methods:

• 43 healthy, young, right-handed women performed the ST task with easy, medium, and hard difficulty levels.
• fNIRS was employed to measure changes in oxygenated hemoglobin (HbO), total hemoglobin (HbT), and oxygenation (Oxy) in the PFC.
• A controlled task design differentiated between encoding, retention, and retrieval phases.

Main Results:

• Participant performance decreased as task difficulty increased (easy > medium > hard).
• Increased PFC oxygenation (HbO, HbT, Oxy) was detected in the left lateral PFC and bilateral medial/lateral right PFC during medium and hard tasks compared to easy tasks.
• Significant differences in hemodynamic responses were observed across task difficulties.

Conclusions:

• The study demonstrates a relationship between WM task load and PFC activity, as indicated by hemodynamic changes.
• fNIRS can effectively detect differential PFC engagement across varying levels of WM difficulty.
• The controlled task design provides nuanced insights into PFC function during specific WM phases.