Comparing verbal working memory load in auditory and visual modalities using functional near-infrared spectroscopy.

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Psychology

Background:

• The n-back task is a standard measure of verbal working memory (VWM) capacity.
• Previous studies on auditory versus visual VWM activation have yielded conflicting results.
• Functional magnetic resonance imaging (fMRI) studies suggest auditory VWM may require more cognitive effort than visual VWM.

Purpose of the Study:

• To investigate whether dorsolateral prefrontal cortex (DL-PFC) activation, an indicator of cognitive effort, differs between auditory and visual VWM tasks.
• To determine if DL-PFC activation is influenced by VWM load and stimulus modality.

Main Methods:

• 16 young adults performed auditory and visual n-back tasks at four VWM load levels.
• Functional near-infrared spectroscopy (fNIRS) was used to measure prefrontal cortex (PFC) activation.
• fNIRS was chosen as a silent neuroimaging method to avoid scanner noise artifacts.

Main Results:

• DL-PFC activation significantly increased with higher VWM load.
• No significant differences in DL-PFC activation were found between auditory and visual VWM modalities.
• DL-PFC activation positively correlated with reaction time across all conditions.

Conclusions:

• Both auditory and visual VWM modalities appear to demand similar levels of cognitive effort.
• Previous fMRI findings of modality differences may be attributed to scanner noise.
• fNIRS is a viable method for measuring cognitive effort, indexed by DL-PFC activation, in VWM tasks.