Research Interests

My broad area of interest is human perception. The focus of my current research is intersensory integration between vision and proprioception (see below). Recently completed work conducted in collaboration with Ben Sachtler and Ian Curthoys was concerned with mechanisms underlying the visual illusion of motion described below and the aftereffect that occurs when vibration ceases (see abstracts of published papers and papers under revision). Ongoing research investigates adaptation processes within the proprioceptive-visual system in more detail.

I also investigate adaptation in the proprioceptive system in collaboration with researchers from the Prince of Wales Medical Research Institute. Other areas of interest are visual space perception, binocular vision, vision used in action and visual illusions.

PROPRIOCEPTIVE* manipulations and their VISUAL consequences
*Proprioception is the sense of position and movement of body parts

Senses work together but this is not obvious. Thus it may come as a surprise that manipulations or illusions affecting one sense may result in the illusory percept in another modality. This can be demonstrated using a simple mechanical stimulus - vibration. High-frequency (app. 100Hz) vibration can induce illusions of movements of body parts - proprioceptive illusions - as well as illusions of motion of visually perceived objects, as illustrated below

Vibration-induced SOMATIC (proprioceptive) illusions
	The picture illustrates the illusory effect induced by vibrations of the biceps (first described by Goodwin et al, Brain 95, 1972). The blindfolded subject is asked to track with her free arm the perceived movements of her vibrated arm. The vibrated arm is restrained by the experimenter and held in place. About 70-80% of people whose arm is vibrated in this way experience an illusory movement, which they indicate by moving their free forearm downwards. Paradoxically, the perceived movement is not necessarily accompanied by the perception of displacement of the arm.
Vibration-induced VISUAL illusions
	Vibration can be applied to any skeletal muscle. If the vibrated muscle determines the position of the eyes relative to the body and the earth, then vibration results in the illusory motion of visually perceived targets (Lackner & Levine, Aviat, Space and Environ Medicine 50, 1979). Figure on the right illustrates the effect of vibration of the right dorsal neck muscles: it results in leftward illusory motion of an isolated point seen in complete darkness (Biguer et al, Brain 111, 1988). The illusory motion is consistent with the following signals reaching the brain: a) retinal image of the target: stationary; b) the eyes: stationary relative to the head; c) the head: rotates to the left (a false signal; the head is stationary). A similar paradoxical dissociation as described for the somatic illusion also occurs here: ‘pure’ motion continues when dot displacement is no longer observed.