This prospective study aimed to examine the extent of DTi, identify the specific brain regions and neural networks involved, and determine the relationship between DTi and increased local brain activity and functional connectivity in younger adults.This prospective study aimed to examine the extent of DTi, identify the specific brain regions and neural networks involved, and determine the relationship between DTi and increased local brain activity and functional connectivity in younger adults.
The participants were 34 right-handed healthy individuals aged 18–30 years. The sample size was calculated using G Power 3.1 based on previous studies. Written informed consent was obtained from all participants. This study was approved by the Ethics Committee of the Faculty of Health Sciences at Hokkaido University. They performed the spiral-drawing task on the tablet in the sitting position as a motor task. They underwent a paced auditory serial addition test (PASAT) simultaneously or independently while their cortical activity was measured using functional near-infrared spectroscopy (fNIRS). Motor performance was measured by the balanced integration score, a balanced index of drawing speed and precision. The PASAT was administered with two difficulty levels defined by one (PASAT-1) and two (PASAT-2) second time intervals. fNIRS with 38 channels was used to measure brain activity in the bilateral frontoparietal regions during tasks. Multivariate Granger causality (GC) analysis was applied to examine causal connectivity across these regions. Repeated-measures ANOVA was performed on behavioral and fNIRS data, with Bonferroni and false discovery rate (FDR) corrections applied for multiple comparisons.
These motor and cognitive performances were significantly reduced in the DT condition compared to the corresponding single-task (ST) conditions. The DT conditions were also characterized by significantly increased activity in the right dorsal prefrontal cortex (DLPFC) compared to the ST conditions. The multivariate Granger causality (GC) analysis of the cortical activities in the selected frontoparietal regions further showed that a top-down causal connectivity from the right DLPFC to the right inferior parietal cortex selectively emerged in the DT conditions.
These findings suggest that DTi can occur even in cognitively proficient young adults, and the right DLPFC and the right frontoparietal connectivity may serve as biomarkers of neural inefficiency in DT processing.
These findings provide new insights into DTi and its underlying neural mechanisms and have implications for the clinical utility of cognitive-motor DTs applied to clinical populations with cognitive decline, such as those with psychiatric and brain disorders.
right DLPFC
Neural network
