Anatomic and functional variability: the effects of filter size in group fMRI data analysis

Area of Science:

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

Background:

• Optimal spatial filtering in group fMRI is essential for accurate analysis.
• Filters must balance blending homologous regions with preserving distinct functional areas.
• Previous studies have not definitively established optimal filter parameters for sensorimotor cortex analysis.

Purpose of the Study:

• To determine the optimal spatial filter size for group fMRI analysis.
• To evaluate the impact of varying Hanning filter sizes on sensorimotor cortex activation.
• To assess test-retest reliability and anatomical precision in relation to filter size.

Main Methods:

• Hanning filters ranging from 0.0 to 18.0 mm were applied to group fMRI data.
• Six healthy controls performed a finger-tapping task across two time points.
• Talairach-based measurements and test-retest reliability were used to evaluate filter performance.

Main Results:

• Two distinct functional activation regions were identified in the sensorimotor cortex.
• These regions merged when the spatial filter size exceeded approximately 6.0 mm.
• The initial hypothesis of distinct motor and sensory activations was not supported due to variability.

Conclusions:

• Spatial filter size significantly impacts the delineation of functional regions in group fMRI.
• A filter size of approximately 6.0 mm appears optimal for resolving sensorimotor cortex activity in this cohort.
• Choosing an appropriate spatial filter size presents inherent challenges in fMRI data analysis.