Understanding effector selectivity in human posterior parietal cortex by combining information patterns and...

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Motor Control

Background:

• The posterior parietal cortex (PPC) was traditionally thought to have separate regions for planning eye and limb movements.
• Recent evidence suggests limited effector specificity, proposing a more efficient, less modular organization with shared and distinct activations.
• The specific factors differentiating these shared and distinct representations remain unclear.

Purpose of the Study:

• To investigate the cortical representations for planning eye, hand, and foot movements within the PPC.
• To elucidate the nature of effector-specific and effector-common representations in the PPC.
• To understand how the PPC differentiates and integrates representations for different effectors.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was employed in human participants.
• A combination of multivariate and univariate fMRI measures assessed effector-related representational content.
• Multivariate measures identified distinct versus common representations across effectors.
• Univariate measures identified actively involved representations during movement preparation.

Main Results:

• Distinct, effector-specific representations were found: eye movements in posterior IPS, hand movements in anterior IPS, and foot movements in the anterior precuneus.
• Crucially, regions responsive to one effector also contained active representations common to the other two effectors.
• Rostral PPC areas appear to code for dichotomies of effectors, not single effectors.

Conclusions:

• The PPC exhibits a sophisticated organization with both distinct and common effector representations.
• This organization supports efficient effector selection by coding both the chosen effector and its alternatives.
• The findings challenge strictly modular views of PPC function, favoring a more integrated and efficient model.