Cortical activity and functional organisation during ocular pursuit is affected by concurrent upper limb movement.

Tracking a moving object with the eyes involves sensory-motor and cognitive processes, and is supported by a wide network of cortical areas. We investigated if cortical activity and network organisation in young adults are influenced by the availability of retinal input when pursuing a moving object, and whether this is modulated by extra-retinal input from concurrent upper limb movement. As expected, we found a decrease in average eye velocity, and increase in saccadic displacement, when the moving object was occluded, as well as a general facilitatory effect of oculo-manual tracking. We also found decreased activity in prefrontal and frontal cortex during oculo-manual compared to ocular tracking when the moving object was occluded. Following a short period of practice in the oculo-manual condition without occlusion, there was an increase in activity in prefrontal, parietal and visual cortex during ocular tracking. These findings could indicate how extra-retinal input during oculo-manual tracking reduces the need for attentional and predictive processes to extrapolate and pursue the occluded object. This is an important step in better understanding impaired oculo-manual coordination (e.g., age-related decline), potentially informing the development of more effective tasks for differential diagnosis and rehabilitation.