Background
A hallmark of Parkinson’s disease (PD) is a mismatch between the perceived effort and actual forces exerted during functional activities such as speech. Current evidence supports therapy to help reset this perception of effort, but the neurological underpinnings of such treatments are unclear. This study examined brain activity during tongue movements performed at varying levels of effort to determine (1) which brain areas are involved in each task, and (2) which areas, if any, scale in activation according to effort level. These results, considered with the neurological changes associated with PD, can be used to develop and refine treatment techniques for PD.
Methods
The structural and functional magnetic resonance (MR) data were previously collected from 20 healthy 40-60 year-old adults. Participants performed phoneme (speech sound) repetition and isometric tongue-to-palate presses while MR images were obtained. Ten datasets underwent whole brain analysis via SPM software to create a mask of shared activation. This mask was applied to the remaining 10 datasets to extract scaling data.
Results/Conclusion
Multiple areas including sensory, motor, and insular cortices were active during study tasks. The only area exhibiting statistically significant scaling was the left secondary sensorimotor cortex during the isometric tongue press. This area has been linked to processing of light touch, tactile attention, and somatosensory integration for voluntary skeletal movements. Additional activations were noted in the right insula, which is associated with motor control of speech and swallowing movements, as well as self-awareness
