"Willed action": a functional MRI study of the human prefrontal cortex during a sensorimotor task

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Brain Imaging

Background:

• The concept of
• willed action
• has been investigated using neuroimaging techniques.
• Previous positron emission tomography (PET) studies suggested specific prefrontal cortex activity during tasks requiring response selection.

Purpose of the Study:

• To investigate human brain activity using functional MRI (fMRI) during a sensorimotor task.
• To compare fMRI findings with previous PET studies on
• willed action
• .
• To differentiate brain activation patterns between sensorimotor and verbal fluency tasks.

Main Methods:

• Used fMRI in a 2.1-T imaging spectrometer to study brain activity.
• Acquired echo-planar images from four coronal slices in the prefrontal cortex of nine healthy subjects.
• Employed a sensorimotor task involving finger movement selection after a stimulus.

Main Results:

• Observed bilateral activations in the dorsolateral prefrontal cortex, consistent with prior PET findings.
• Identified distinct activation foci in the left dorsolateral prefrontal cortex for sensorimotor (Brodmann area 46) and verbal fluency (Brodmann area 45) tasks.
• fMRI data revealed modality-specific activations, suggesting that
• willed action
• does not rely on a single, fixed brain region.

Conclusions:

• The concept of a singular brain region for
• willed action
• is not supported by the fMRI data.
• Different cognitive tasks, even those proposed to involve
• willed action
• , activate distinct neural pathways.
• fMRI's higher resolution clarifies modality-specific brain activations more definitively than PET.