Comparison of motor cortex activation in response to individual finger movements from the right hand using functional near-infrared spectroscopy (fNIRS)

Abstract

This study investigates neural activations within the motor cortex during finger-tapping tasks using functional near-infrared spectroscopy (fNIRS). Focusing on individual fingers of the right hand, the research aims to describe and compare the different brain regions engaged during these specific motor activities. A group of six right-handed participants, aged 24 to 34 years, were recruited to perform finger-tapping tasks. Each task consisted of 10 seconds of finger-tapping followed by 10 seconds of rest, with 20 seconds of initial final rest. The functional connectivity analysis revealed that activation of motoric regions is common in all fingers while other brain regions involve different finger-tapping tasks. These findings reveal distinct neural activation patterns across the different fingers examined. The thumb finger shows a unique activation profile, suggesting it operates via independent neural circuits distinct from other fingers. In contrast, other fingers, such as the index and ring fingers, showed overlapping activation patterns, indicative of shared neural pathways. These findings gain further support from the integrated hemoglobin response analysis, which reveals distinct activation patterns for different fingers. Notably, the thumb exhibits the highest level of activation, whereas the other fingers activate specific but comparatively less extensive brain regions.

Through detailed statistical analysis, including Pearson correlation and t-tests, significant differences in activation levels were observed between specific finger pairs. The thumb showed a very low correlation with other fingers, the other finger pairs show both high positive and negative correlations. On the other hand, some finger pairs like thumb-little and ring-little show differences in the activation levels while other finger pairs the thumbs versus index, middle, and ring fingers, and other combinations such as index versus middle, ring, little, and middle versus ring, little have similar activation patterns. These variations in the activation levels highlight the complexity of motor control and suggest that different fingers are sometimes controlled by overlapping and sometimes by distinct neural pathways. From the integrated hemoglobin response analysis, different fingers show different activation patterns of which the thumb shows the highest level of activation.