Tablet-Based Functional MRI of the Trail Making Test: Effect of Tablet Interaction Mode

Abstract

The Trail Making Test (TMT) is widely used for assessing executive function, frontal lobe abilities, and visual motor skills. Part A of this pen-and-paper test (TMT-A) involves linking numbers randomly distributed in space, in ascending order. Part B (TMT-B) alternates between linking numbers and letters. TMT-B is more demanding than TMT-A, but the mental processing that supports the performance of this test remains incompletely understood. Functional MRI (fMRI) may help to clarify the relationship between TMT performance and brain activity, but providing an environment that supports real-world pen-and-paper interactions during fMRI is challenging. Previously, an fMRI-compatible tablet system was developed for writing and drawing with two modes of interaction: the original cursor-based, proprioceptive approach, and a new mode involving augmented reality to provide visual feedback of hand position (VFHP) for enhanced user interaction. This study characterizes the use of the tablet during fMRI of young healthy adults (n = 22), with half of the subjects performing TMT with VFHP and the other half performing TMT without VFHP. Activation maps for both TMT-A and TMT-B performance showed considerable overlap between the two tablet modes, and no statistically differences in brain activity were detected when contrasting TMT-B vs. TMT-A for the two tablet modes. Behavioral results also showed no statistically different interaction effects for TMT-B vs. TMT-A for the two tablet modes. Tablet-based TMT scores showed reasonable convergent validity with those obtained by administering the standard pen-and-paper TMT to the same subjects. Overall, the results suggest that despite the slightly different mechanisms involved for the two modes of tablet interaction, both are suitable for use in fMRI studies involving TMT performance. This study provides information for using tablet-based TMT methods appropriately in future fMRI studies involving patients and healthy individuals.

Keywords: executive function; fMRI; neuropsychological tests; pen-and-paper test; trail making test; visual feedback of hand position.

Figure 1

Trail making test (TMT) task design for fMRI experiments: (A) TMT-A for 60 s; (B) Baseline visual fixation for 10 s; (C) TMT-B for 60 s.

Figure 2

The two modes of interacting with the fMRI-compatible tablet system. Subject performing TMT-A (A) with VFHP; (B) without VFHP. VFHP, Visual feedback of hand position; LEDs, Light emitting diodes.

Figure 3

Box and whisker plots of behavioral performance parameters for subjects who performed all TMT tasks either with VFHP or without VFHP: (A) seconds per link (Spl); (B) dwell time (DT); (C) linkage length (L); (D) contact force (F). For each box, the center horizontal line shows the median parameter value, and the 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 data points are shown as crosses.

Figure 4

The first principal component (PC1) depicting brain activity for commonly activated brain regions in TMT-A vs. baseline and TMT-B vs. baseline for the two tablet interaction modes. Activation maps are thresholded at a false discovery rate of q = 0.05.

Figure 5

Principal components (PCs) depicting brain activity for TMT-B vs. TMT-A. (A) PC1 activation map for performance with VFHP. (B) PC1 activation map for performance without VFHP. (C) PC2 activation map for performance without VFHP. Activation maps are thresholded at a false discovery rate of q = 0.05. The PC2 activation maps for performance with VFHP are not statistically significant.