Brain activation during vocal motor imagery: a pilot functional near-infrared spectroscopy (fNIRS) study
Narihiro Kodama1, Ryo Hatazoe2, Kohei Kotegawa2
1Department of Speech-Language Pathology and Audiology Faculty of Rehabilitation, Kawasaki University of Medical Welfare, 288 Matsushima, Kurashiki, 701-0193, Okayama, Japan. narihiro@mw.kawasaki-m.ac.jp.
Objective:
The purpose of this study was to clarify the differences in brain activation during actual vocalization and imagery, thereby deepening our understanding of the neural mechanisms underlying motor imagery.
Study Design:
Prospective study.
Methods:
A cross-sectional study was conducted on 23 healthy young adults (aged 21-22 years) who met strict voice and hearing criteria. Participants performed sustained phonation and vocal imagery tasks while listening to pre-recorded audio of the vowel /a:/ and humming /m:/. Brain activity in the right prefrontal cortex (rPFC), frontal pole (FP), and left prefrontal cortex (IPFC) was measured using a 16-channel functional near-infrared spectroscopy (fNIRS) system. A block design with baseline correction was applied to calculate changes in oxyhemoglobin concentration. Motor imagery ability was assessed using imagined Timed Up and Go Test (iTUG), and delta times between normal and maximum walking speeds were calculated.
Results:
No significant differences in activation values of the rPFC, FP, and IPFC were observed between the vocalization and imagery conditions. In addition, both conditions exhibited large variability across all regions, indicating substantial individual differences. Furthermore, while a significant correlation was found between the delta times of normal and maximum walking speeds, no significant correlations were observed between brain activation in the rPFC, FP, or IPFC and the delta times under the imagery condition.
Conclusions:
No significant differences were found in neural activation between vocalization and imagery, but high variability in both conditions suggests individual differences. This study highlights both the potential and limitations of using fNIRS to assess brain activity in these tasks.
