The microstructural border between the motor and the cognitive domain in the human cerebral cortex

Area of Science:

• Neuroscience
• Neuroanatomy
• Motor Control

Background:

• The agranular frontal cortex, specifically Brodmann's areas 4 and 6, is vital for voluntary motor control.
• Area 6, encompassing supplementary motor areas and premotor cortex, guides movements using internal or external cues.
• The precise location of area 6's rostral border is critical for interpreting functional neuroimaging data in humans.

Purpose of the Study:

• To investigate if the gyral pattern of the frontal lobe can indicate the topography of the rostral border of area 6.
• To create a population map of area 6 in the human frontal lobe.

Main Methods:

• Ten postmortem human brains were scanned using T1-weighted MRI.
• Brains were serially sectioned, and area 6 was identified through cytoarchitectonic analysis.
• Histological volumes were reconstructed in 3D, spatially normalized, and superimposed to generate a population map.

Main Results:

• On the mesial surface, the rostral border of area 6 is located rostral to the anterior commissure, with variable distances.
• On the lateral convexity, the border shifts caudally, situated on the precentral gyrus near the sylvian fissure, also with individual variation.
• No distinct macroanatomical landmark reliably demarcates the boundary between area 6 and the prefrontal cortex.

Conclusions:

• The precise border between the motor and cognitive domains of the frontal cortex cannot be determined by external anatomical landmarks alone.
• Accurate interpretation of functional neuroimaging requires overlaying activation maps with detailed microstructural maps, like the generated population map of area 6.