Enhanced cognitive interference during visuomotor tasks may cause eye-hand dyscoordination

Abstract

In complex visuomotor tasks, such as cooking, people make many saccades to continuously search for items before and during reaching movements. These tasks require use of short-term memory and task-switching (e.g., switching search between vegetables and spices). Cognitive load may affect visuomotor performance by increasing the demands on mental processes mediated by the prefrontal cortex, but mechanisms remain unclear. It is also unclear how patients with neurological injuries, e.g., stroke survivors, manage greater cognitive loads during visuomotor tasks. Using the Trail-Making Test, we have previously shown that stroke survivors make many more saccades, which are associated limb movements that are less smooth and slower. In this test, participants search for and make reaching movements towards twenty-five numbers and letters. It has a simple variant (Trails-A), and a cognitively challenging variant (Trails-B) that requires alphanumeric switching. The switching makes the task gradually harder as the Trails-B trial progresses (greater cognitive load). Here, we show that stroke survivors and healthy controls made many more saccades and had longer fixations as the Trails-B trial progressed. In addition, reaching speed slowed down for controls in Trails-B. We propose a mechanism where enhanced cognitive load may reduce inhibition from the prefrontal cortex and disinhibit the ocular motor system into making more saccades. These additional saccades may subsequently slow down motor function by disrupting the visual feedback loops used to control limb movements. These findings augment our understanding of the mechanisms that underpin cognitive interference dynamics when visual, ocular, and limb motor systems interact in visuocognitive motor tasks. NEW & Noteworthyo We used a neuropsychological test called the Trails-Making-test and analyze patterns of eye and reaching movements in controls and stroke survivors. We characterized how gaze and reaching movements change within a trial in the easier Trails-A and the more cognitively challenging Trails-B variant that requires alphanumeric switching. We found that as the Trails-B trial progressed participants made more saccadic eye movements and longer fixations, likely because of greater cognitive load.