Associate Professor, Dept. of Ophthalmology & Visual Sciences

Research Description

Currently my research is directed at developing simple behavioural, non-invasive tests of visual function in small laboratory animals. This is of widespread interest in the research community as most medical research on the causes and treatment of visual diseases go through a stage where there is extensive testing in small laboratory animals. In the past, researchers have had to rely on anatomical or electrophysiological measures to gauge the state of the eye, and these techniques have their own strengths and weaknesses. They also do not measure what we really care about in a patient: does the treatment improve vision in a patient?

Together with Dr. Glen Prusky, now at the Weill Medical College of Cornell University, we have developed two visual tests for small rodents:

  1. Visual Water Task (VWT): The animal chooses between two sides using the visual patterns on computer monitors as a guide [watch movie #1]. It takes several weeks to train and test the animals, but it is the most sensitive and detects losses in the eyes and in the visual cortex.
  2. Virtual Optokinetic System (VOS): This uses a simple visual reflex, the tendency to rotate when the whole visual world around you is moving in one direction [watch movie #2]. As no training is needed and a threshold measurement can be obtained in minutes, this task has proved useful for studying development, retinal degeneration and experimental treatments.

Our experimental investigations using these two tasks have 3 themes:

  1. Description of the visual capabilities of rats and mice. These prototypical mammals have visual systems that are simpler but still rather similar to what humans have. Besides describing simple visual capabilities like visual acuity, contrast sensitivity and motion coherence, we have also conducted experiments on visual memory [watch movie #3].
  2. Development and Plasticity: The visual system develops using genetic and environmental information. We have confirmed in rodents that early deprivation can cause the same sort of visual deficits seen in primates and cats, permitting these species of rodents to become better choices for studying the mechanisms that underlie visual plasticity. Recently we have discovered two novel forms of visual plasticity in which the experience causes an enhancement of function.
  3. Retinal Diseases: Some retinal diseases are caused by or influenced by genetic mutations and our behavioral tests have allowed us to study the time course of retinal degeneration in several mutants and to evaluate the efficacy of possible therapies. This movie simulates what the effects are of a gradual loss of retinal function in rats with the RCS mutation.

Past Research

My early research in Graham Goddard’s lab was on long-term potentiation in the hippocampus. Together with fellow students Carol Barnes and Bruce McNaughton we established that LTP had all the characteristics necessary for it to be the basic mechanism of memory. I then spent an intellectually stimulating but professionally unproductive period at McGill University studying plasticity in visual-vestibular interactions and the role of the superior colliculus saccadic eye movements. I have always been interested in vision and since the mid 1970s I’ve collaborated with Max Cynader and his students in electrophysiological studies of processing in visual cortex.