Regional homogeneity approach to fMRI data analysis

Area of Science:

• Neuroscience
• Functional Magnetic Resonance Imaging (fMRI)
• Signal Processing

Background:

• Kendall's coefficient of concordance (KCC) is a statistical measure for time series similarity.
• KCC has been previously applied to cluster purification in fMRI data.
• Regional homogeneity (ReHo) is an fMRI analysis method assessing local functional connectivity.

Purpose of the Study:

• To introduce a novel fMRI analysis method combining ReHo and KCC.
• To investigate brain activity patterns in the primary motor cortex (M1) during finger movements.
• To compare KCC values between movement and rest conditions, and between ipsilateral and contralateral M1.

Main Methods:

• Developed a voxel-wise analysis using KCC to measure time series similarity with nearest neighbors, termed ReHo-KCC.
• Acquired fMRI data from six healthy subjects performing unilateral finger movements and a resting state.
• Compared ReHo-KCC values across left finger movement, right finger movement, and rest conditions.

Main Results:

• Bilateral primary motor cortex (M1) exhibited higher ReHo-KCC during finger movement tasks compared to the rest condition.
• Contrary to expectations, ipsilateral M1 showed significantly higher ReHo-KCC than contralateral M1 during unilateral finger movements.
• These findings align with electrophysiological evidence of increased ipsilateral M1 activity during unilateral movements.

Conclusions:

• The novel ReHo-KCC method provides a complementary approach to model-driven fMRI analysis.
• The results highlight increased ipsilateral M1 engagement during unilateral movements, challenging traditional contralateral dominance assumptions.
• Further research is needed to elucidate the neural mechanisms underlying ReHo and its implications for understanding brain function.