Brain Activity during the Observation, Imagery, and Execution of Tool Use: An fNIRS/EEG Study

Abstract

This study used a functional near-infrared spectroscopy (fNIRS)/electroencephalogram (EEG) system to investigate brain activity during a daily living situation where subjects are engaged in the observation, imagery, and execution of tool use. The subjects were 24 healthy adults who signed an agreement to participate in the present study. All subjects were right-handed according to the Edinburgh Handedness Inventory. The subjects sat on a chair and participated in the observation, imagery, and execution of chopstick and hammer movements. Each trial consisted of observation, imagery, and execution and the trials were performed in triplicate. The timing protocol was 15.0, 15.0, 15.0, 15.0, and 15.0 s for rest, task, rest, task, and rest, respectively, and brain activity was measured during these periods. fNIRS and EEG were used to measure brain activity. Optical fibers of fNIRS were positioned over the frontoparietal area. Oxyhemoglobin served as a parameter, and NIRS-statistical parametric mapping (SPM) was used for data analysis. EEG measurements were made using 32 electrodes with an international 10–20 system. The event-related desynchronization of the Mu frequency band (8-12 Hz) was calculated by power spectrum analysis. The brain regions activated during the imagery and execution of the chopsticks movement were the dorsolateral prefrontal cortex, inferior frontal gyrus, premotor cortex, and primary somatosensory cortex, while the mu ERD values were obtained under both conditions. The brain regions that were mainly activated under all three conditions of the hammer movement, i.e., observation, imagery, and execution, were the dorsolateral prefrontal cortex, inferior frontal gyrus, and premotor cortex, while the mu ERD values were obtained under all three conditions. These results suggest that brain activity during the observation, imagery, and execution of tool use differed according to the sensory modality linked to a tool.