Tablet Technology for Neuropsychological Testing and fMRI

Abnormal behaviour may be a warning sign of underlying brain disease. Neuropsychological (NP) tests - behavioural tasks that very commonly involve handwriting and drawing - are widely used in the clinic to detect abnormal brain function in a variety of brain diseases. Task-based functional magnetic resonance imaging (fMRI), a method for noninvasively mapping the brain activity that underlies specific behaviours, can possibly help to inform use of NP tests, and to improve their sensitivity and specificity. Task-based fMRI typically involves peripheral devices that are used to present sensory stimuli and record behavioural responses. Such devices (e.g. video projectors, key pads for detecting button presses) must be designed for compatibility with fMRI procedures, including operation at the very high magnetic field of the MRI system without introducing electromagnetic interference. The common fMRI-compatible devices are insufficient for evaluating many NP tests, however. Consequently, an fMRI-compatible tablet, including a touch-sensitive surface, was developed in the Graham laboratory to enable fMRI studies of NP tests that involve writing and drawing responses. In its original prototype, the tablet did not enable individuals to see their hand while performing writing and drawing actions. This missing feature, termed “visual feedback of hand position” (VFHP), may make it difficult for certain patient populations to interact easily with the tablet during task-based fMRI. The interactivity of the tablet thus should be improved before proceeding to map the brain activity of specific NP tests. This thesis focuses on developing a real-time system to integrate VFHP with the tablet in an augmented reality display, including simple computer graphics to present visual stimuli and tablet responses, and merged streaming video of the hand as it manipulates a stylus during writing and drawing behaviour. First, the new tablet prototype is developed and validated in the context of a writing task that involves copying sentences, showing that tablet interactivity is enhanced when VFHP is included. Second, the prototype is used to perform the first characterization of the brain activity in a control population of young healthy adults as they perform a novel NP test that was specially designed to detect and evaluate writing impairments in patients with Mild Cognitive Impairment and Alzheimer’s Disease. Third, the impact of adopting the tablet with and without VFHP is studied for a group of young healthy adults as they undergo fMRI while performing the trail making test (TMT), an NP test that is commonly used to assess the frontal lobes of the brain. Finally, future directions of this research are discussed, including use of this new tablet technology to assess patients with brain diseases in task-based fMRI trials.Ph.D

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

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

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

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