Investigating the cortical oscillatory correlates of smooth pursuit eye movements: a magnetoencephalographic study

Models of motion perception propose that eye movement estimates are integrated into middle temporal cortex (MT+) as a mechanism that disambiguates world motion from retinal motion induced by ego movement. Little is known about the relationship between eye movement signals in this area and cortical oscillations, a phenomenon linked to perceptual and motor processing. Magnetoencephalography was used to examine the significance of oscillations in this area during pursuit. Results from Experiment 1 suggest low-frequency suppression in MT+ reflects eye position during sinusoidal tracking. A control study (Experiment 2) examining activity in response to retinal slip suggests this was not due to pursuit error when the stimulus changed direction. Experiment 3 examined oscillations during pursuit at various head-centred eye eccentricities. No difference was found in the magnitude of activity as a function of eye position during pursuit, suggesting modulations in these rhythms was related to another aspect of the eye movement. Experiment 4 found no specific effects of eye velocity on alpha or beta, but there was a consistent effect of eye speed on beta activity. Additionally, there was no such effect found between alpha and eye speed, suggesting some functional distinction in the role of these rhythms in pursuit behaviour. In Chapter 4, two experiments examined cortical changes during pursuit (Experiment 5) and retinal motion adaptation (Experiment 6), and the subsequent motion aftereffect. Beta suppression in MT+ during oculomotor adaptation was a significant predictor of the motion aftereffect duration, perhaps indicating that beta changes index the efficacy with which the visual motion system is able to recalibrate itself in the presence of a stationary stimulus following adaptation. Taken together, these results suggest a role for beta suppression in MT+ during pursuit, which seems to reflect the processing of extraretinal signals for oculomotor control and the estimation of head-centred motion