Understanding human optokinesis: a behavioural and neuroimaging investigation

When the visual environment moves relative to us, retinal slip guides a compensatory reflexive eye movement to hold the image stationary on the retina, thus avoiding the unwanted consequences of motion blur. This type of eye movement is called optokinetic and is usually evoked when a large part of the visual image undergoes uniform motion and the observer's head is stationary. This eye movement is present in across many species with mobile eyes and serves to stabilise perception.
In the laboratory, optokinetic eye movements (nystagmus) can be readily observed by asking subjects to view a repeating, moving stimulus that fills a substantial proportion of the visual field. If the pattern - such as vertical lines - moves at appropriate speed (i.e. not too fast) the eyes will initially follow the motion (termed the slow phase) and once they have reached a certain distance from the primary position of gaze, an anti-compensatory flick will re-centre them (the fast phase). The time course of this sequence exhibits a characteristic sawtooth waveform and is called optokinetic nystagmus (OKN). Below 30 deg/s the velocity of the slow phase closely matches target speed.
The PhD project will use a combination of behavioural studies (eye tracking) and brain imaging to study the detailed mechanisms and neural circuitry underlying OKN.