Revealing the link between eye movements and brain activity

Smooth pursuit and saccadic eye movements are both essential for vision, yet they serve distinct functions and are controlled by different neural systems. For example, while we can voluntarily make saccades—even with our eyes closed—it is nearly impossible to perform smooth pursuit without visual input. Patients with schizophrenia often show deficits in smooth pursuit, suggesting that these two types of eye movements rely on partly distinct neural networks. However, few studies have directly compared them under equivalent experimental conditions.

Using functional MRI, we examined whole-brain activity during both types of eye movements, carefully matching all parameters except for movement type. By applying the advanced preprocessing and analysis pipelines developed by the Human Connectome Project, we achieved highly precise mapping of brain activity.
Both movements, compared with fixation, activated a broad, overlapping network including early and higher visual areas in the occipital lobe, regions along the intraparietal sulcus in the parietal lobe, several oculomotor areas in the frontal lobe, the cerebellum, and subcortical regions. Interestingly, both also showed similar deactivation patterns in certain brain regions during eye movements. At the same time, distinct patterns emerged: smooth pursuit elicited stronger activity in visual and parietal regions, the posterior cingulate sulcus, and the superior parietal lobule, whereas saccades more strongly engaged frontal oculomotor areas and parietal regions along the intraparietal sulcus.

These findings provide new insight into the shared and distinct neural architectures supporting human eye movements. They may also enhance our understanding of psychiatric and neurological disorders such as schizophrenia and help identify early diagnostic markers. Beyond medicine, individual differences in pursuit ability could also relate to ball-sport performance, suggesting future applications in sports science. Our eye movements, through which we perceive the outside world, may serve as a unique window into the workings of the human mind and brain.