Our work combines investigations in normal human beings and patients with many types of disorders such as ocular misalignment, abnormal eye movements, nystagmus, or vestibular dysfunction. A special focus has been on understanding mechanisms of abnormal eye movements, their deleterious effects on vision and spatial perception, and how these disabling consequences can be ameliorated. We use analytical control systems models for interpretation, and application to more accurate clinical diagnosis and better modes of treatment. This work is collaborative and translational, with an iterative process between the clinic and the laboratory, and computational modeling at the interface.
It has been known for decades that individuals working next to strong static magnetic fields can feel disoriented and vertiginous. The cause was unknown until we discovered its mechanism, which involves a Lorentz force resulting from the interaction of a strong static magnetic field with naturally-occurring ionic currents flowing through the inner ear endolymph into vestibular hair cells. We recently used magnetic vestibular stimulation (MVS) to study how the brain adapts to an unwanted inner ear imbalance. MVS is an easy and comfortable way to produce a sustained nystagmus, lasting minutes or hours in a normal individual, mimicking a pathological lesion. MVS is a useful tool for studying perceptual mechanisms that underlie the symptoms of patients with vestibular disorders. In addition, MVS has the potential to be used therapeutically, by producing a new bias to counteract a pathological one.
Our ability to maintain a stable perception of the world is a foundation of complex behavior. Such ‘orientation constancy’ is vital for us in order to maintain balance and make accurate movements. We study neural mechanisms of this key aspect of human spatial orientation, using a combination of psychophysical experiments, brain imaging, and transcranial magnetic stimulation (TMS).
A central question in vision research is how we perceive a stable world despite continuous retinal motion from eye movements. The brain may use an ‘efference copy’ of eye movement signal to determine if the object has actually moved or if the change in position is due to movement of the image on the retina. We study the mechanisms responsible for both perceptual and motor stability during eye movements in the horizontal, vertical and torsional (i.e., rotation around the line of sight) planes, using psychophysical experiments and eye movement recordings.
We employ various techniques for precise quantitative measures of eye movements, using dual magnetic scleral search coil recordings and video-oculography (VOG). We seek to innovate in development of eye movement recording and analysis, opening new vistas for research and clinical practice.