Functional MRI of Handwriting Tasks: A Study of Healthy Young Adults Interacting with a Novel Touch-Sensitive Tablet

Abstract

Handwriting is a complex human activity that engages a blend of cognitive and visual motor skills. Current understanding of the neural correlates of handwriting has largely come from lesion studies of patients with impaired handwriting. Task-based fMRI studies would be useful to supplement this work. To address concerns over ecological validity, previously we developed a fMRI-compatible, computerized tablet system for writing and drawing including visual feedback of hand position and an augmented reality display. The purpose of the present work is to use the tablet system in proof-of-concept to characterize brain activity associated with clinically relevant handwriting tasks, originally developed to characterize handwriting impairments in Alzheimer's disease patients. As a prelude to undertaking fMRI studies of patients, imaging was performed of twelve young healthy subjects who copied sentences, phone numbers, and grocery lists using the fMRI-compatible tablet. Activation maps for all handwriting tasks consisted of a distributed network of regions in reasonable agreement with previous studies of handwriting performance. In addition, differences in brain activity were observed between the test subcomponents consistent with different demands of neural processing for successful task performance, as identified by investigating three quantitative behavioral metrics (writing speed, stylus contact force and stylus in air time). This study provides baseline behavioral and brain activity results for fMRI studies that adopt this handwriting test to characterize patients with brain impairments.

Keywords: ecological validity; fMRI; handwriting; neuropsychological tests; pen-and-paper test; visual feedback of hand position.

FIGURE 1

Handwriting tasks for fMRI and representative behavioral responses: (A) copying a grocery list; (B) copying phone numbers; (C) copying a sentence.

FIGURE 2

Box and whisker plots of behavioral performance metrics (A) handwriting speed s, (B) stylus in air time, IAT, and (C) stylus contact force, F for three handwriting tasks during fMRI, involving copying a grocery list, phone numbers, and a sentence. For each box, the interior horizontal line shows the median value, and edges of the box are estimates of the first and third quartile. The whiskers extend to the most extreme data points not considered outliers (2.7 times the sample standard deviation assuming a normal distribution). Outlier points are shown as crosses. Statistically significant differences between tasks (p < 0.05) are indicated by an asterisk.

FIGURE 3

Activation maps of the first principal component (PC1) for (a) all handwriting tasks vs. baseline; (b) copying a sentence vs. copying phone numbers; and (c) copying a sentence vs. copying a grocery list. All activations are thresholded at the false discovery rate of q = 0.01. Activation maps were not statistically significant for any other principal components. IFG, inferior frontal gyrus; MiFG, middle frontal gyrus; STG, superior temporal gyrus; ITG, inferior temporal gyrus; MiOG, middle occipital gyrus; IPL, inferior parietal lobule; SPL, superior parietal lobule; SMA, supplementary motor area; PostCB, posterior cerebellum; VWFA, visual word form area; aPCU, anterior precuneus; GMFA, graphomotor frontal area; SuMG, supramarginal gyrus.