Shining the light on dark adaptation

If their early careers are anything to go by, Trevor Lamb and Ed Pugh could be considered an odd couple to be researching dark adaptation and the photoreceptor's response to light. Lamb initially studied electrical engineering at the University of Melbourne before moving into physiology, while Pugh's first degree was in mathematics before moving into psychology and later neuroscience.

Lamb became interested in nerves and the brain in his final year of his engineering degree, and did a transfer course into physiology leading to a master's. He then moved to Cambridge University to pursue a PhD with Alan Hodgkin, who had discovered the action-potential impulse of the nerve axon. When Lamb arrived, however, Hodgkin had switched to photoreceptors, and Lamb followed that line.

At Cambridge, where he expected to stay for three years but ended up lasting 31, Lamb became interested in the phenomenon of dark adaptation - the recovery of the visual system after exposure to very intense light. Looking through the literature, he says, it turned out that the best data available was published by one EN Pugh of the University of Philadelphia: Pugh had been working on colour vision and human psychophysical dark adaptation. Lamb wrote to Pugh requesting any further data and was sent a spare copy of Pugh's PhD thesis. They have been collaborating ever since, on and off for 25 years, and were jointly awarded the 2006 Proctor Medal by the US-based Association for Research in Vision and Ophthalmology.

Lamb, who helped develop the suction pipette technique for recording electrically from photoreceptors with King-Wai Yau and Denis Baylor, returned to Australia in 2003 as a Federation Fellow. He runs the Visual Neuroscience Laboratory at the John Curtin School of Medicine at ANU, and is research director of the ARC Centre of Excellence in Vision Science. Here, he is looking at a number of aspects of photoreceptors and early events in the retina.

"We are interested in how it is that the photoreceptor's response to light turns off - the shut-off of the light response - and the molecular mechanisms underlying that," he says. "We are also interested in how this shut-off contributes to recovery after exposure to bright light.

"We are interested in this recovery in two realms: one is the short term, the very rapid shut-off that occurs within a second or so, and then secondly the very slow tail of the shut-off that occurs over many minutes, because that turns out to be involved in dark adaptation recovery. We are going from the level of single cells - using the suction pipette technique on single cells of mice and zebrafish - and on up to humans.

"We record from our own eyes using the electroretinogram to measure signals from the retina to work out what is going on, both in the photoreceptors and also the next layer of cells, the rod bipolar cells. Basically, we are looking at how activity in those cells influences the performance of the overall visual system."