More comprehensive proprioceptive stimulation of the hand amplifies its cortical processing

Area of Science:

• Neuroscience
• Somatosensory system research
• Brain mapping techniques

Background:

• Corticokinematic coherence (CKC) measures the relationship between limb movement and brain activity, reflecting proprioceptive feedback to the sensorimotor cortex.
• Understanding how the brain processes proprioceptive information from individual fingers is crucial for mapping the sensorimotor cortex.

Purpose of the Study:

• To investigate whether corticokinematic coherence (CKC) strength and cortical source location differ based on proprioceptive stimulation patterns of the right-hand digits.
• To determine optimal stimulation conditions for robust functional mapping of the human hand region in the sensorimotor cortex.

Main Methods:

• Magnetoencephalography (MEG) and three-axis accelerometers were used to record brain activity and finger kinematics in 21 volunteers.
• Three stimulation conditions were tested: simultaneous stimulation of all four fingers at the same frequency, individual finger stimulation at the same frequency, and simultaneous stimulation at finger-specific frequencies.

Main Results:

• CKC was significantly stronger during simultaneous stimulation of all four fingers at the same frequency (0.52 ± 0.02) compared to individual finger stimulation (0.45 ± 0.02).
• CKC was weaker during simultaneous stimulation at finger-specific frequencies (0.38 ± 0.02) compared to individual finger stimulation.
• CKC source locations were concentrated in the hand region of the sensorimotor cortex and did not show a distinct finger-specific somatotopic order, indicating overlapping neuronal circuits.

Conclusions:

• Proprioceptive afference from the fingers is processed in partly overlapping cortical neuronal circuits within the sensorimotor cortex.
• Simultaneous proprioceptive stimulation of the hand at the same frequency maximizes CKC strength, enabling efficient and reliable functional cortical mapping of the hand region.
• This optimized mapping approach using MEG is valuable for applications like pre-surgical planning.