title: Now where was I? Cortical function during ocular and oculo-manual pursuit
Creators: name: Borot, L
Publisher: name: Liverpool John Moores University
Year: 2024

description: Coordinated eye and hand movements are often performed when carrying out daily activities. When executed concurrently with the goal of pursuing the same slow-moving moving object, the resulting smooth pursuit eye movement is facilitated by the available limb efference and afference. This is particularly evident when retinal input from the moving object is temporarily unavailable (e.g., during a transient occlusion), with concurrent limb movement providing extra-retinal input to the oculomotor system. Studies have shown that several cortical areas are involved in the control of smooth pursuit eye movement, and that their activity is mediated by factors that influence predictability of the object trajectory. However, the study of brain activity and functional connectivity between cortical areas has been limited to simple pursuit tasks, typically performed with eyes alone. The aim of the current thesis was to examine the impact of concurrent upper limb movement on cortical activity and network organisation in tasks of varying complexity and cognitive demand, which thus have greater fidelity with pursuit tasks performed when interacting with a complex and dynamic environment. In Chapter 2, a series of experiments was conducted using the Gorilla.sc online testing platform to examine the behavioural effects of performing a secondary change-detection task (colour or form stimulus array) concurrently (experiments 1-3) or consecutively (experiment 4) with a primary spatial prediction motion task. The primary task was performed with eyes alone (i.e., ocular pursuit) or with eyes and concurrent right upper limb movement (i.e., oculo-manual pursuit) in order to determine the impact of afferent and efferent signals. In Chapter 3, a lab-based version of the dual-task pursuit protocol was conducted that included a combination of eye tracking (i.e., video-oculography) and neuroimaging (Near InfraRed Spectroscopy - NIRS) of prefrontal cortical activity. In Chapter 4 a second lab-based experiment examined cortical activity within a wider network using a 24 by 24 NIRS optode array during ocular and oculo-manual pursuit of sinusoidal object motion (0.1Hz). This was done in a pre-test and post-test, which were separated by an adaptation phase in which participants pursued a continuously visible object in the oculo-manual condition. Across the two lab-based experiments, it was found that differences existed in cortical activity and network organisation between ocular and oculo-manual tracking, and that these were most evident in areas of prefrontal cortex. There was also evidence that smooth pursuit eye movement was facilitated by concurrent upper limb movement, although this was greater when the task involved pursuit of sine-wave object motion (Chapter 4) compared to step-ramp motion (Chapter 3). These results bring new insight to understanding the cortical basis of oculo-manual facilitation during smooth pursuit eye movement, and could provide a basis for future study of populations with acute and chronic neurological conditions, who exhibit changes in cognitive and/or oculomotor function.