Dynamic synchronization of cortical rhythmic gamma-band activity: a neural code of dexterity in human somatosensory cortex

To investigate neural coding characteristics in the human primary somatosensory cortices, the cortical representation of two fingers with different levels of functional skill has been focused (the thumb –high dexterous– and the little finger –low dexterous–). The finger dexterity was scored by the Fingertip writing test. In the two hemispheres, dynamic neural synchronization was analysed in the three characteristic alpha ([7, 13]Hz), beta ([14, 32]Hz) and gamma ([33, 44]Hz) frequency bands of oscillatory activity of neurons connected with the investigated fingers in primary sensory cortex. The stimulation of the thumb recruited in the dominant hemisphere a neural network more phase locked selectively in gamma band than the stimulation of the little finger. The dynamic gamma band intraregional phase locking correlated with the contra-lateral finger dexterity, suggestings to be a coding mechanism for functional prevalence, in addition to the somatotopic central map differentiation.