Evoked effective connectivity of the human neocortex

Area of Science:

• Neuroscience
• Electrophysiology
• Brain Connectivity

Background:

• Cortical connectivity is crucial for brain function and pathology.
• In vivo imaging methods offer insights but lack electrophysiological detail and causality.
• Effective connectivity, the causal influence between neural populations, requires direct measurement.

Purpose of the Study:

• To map human cortico-cortical connectivity using direct electrophysiological recordings.
• To investigate the directional nature of effective connectivity between cortical regions.
• To compare direct electrophysiological findings with noninvasive functional connectome studies.

Main Methods:

• Cortico-cortical evoked potential (CCEP) mapping via single pulse electrical stimulation.
• Subdural electrode arrays used in 25 epilepsy patients undergoing monitoring.
• Stimulation of adjacent electrode pairs and recording from remaining electrodes; coregistration to Brodmann areas (BA).

Main Results:

• CCEPs reliably identified functional networks with an inverse distance relationship.
• Directional connections were prevalent: 43% early and 50% late responses showed dominance.
• Motor cortex, BA6-9, somatosensory cortex, anterior cingulate, and Broca's area showed consistent outgoing connections; BA20/39 showed highest outdegree.

Conclusions:

• Direct electrophysiological mapping reveals detailed, directional human cortical networks.
• Motor, sensory, premotor, and language areas function as key network hubs.
• This study provides a foundation for interpreting noninvasive functional connectome data.