Ted Maddess (Ph.D.) 

        Visual Sciences Group
     Research School of Biological Sciences
     The Australian National University
        GPO Box 475
        Canberra A.C.T. 2601
        AUSTRALIA Contact details:-
 

• e-mail : ted.maddess@anu.edu.au (ted.maddess@anu.edu.au )
• phone : +61 2 6125 4099
• fax : +61 2 6125 3808
• office : Room O28, RSBS, ANU.
• Click here for a map of the ANU. RSBS is building 46, grid location E4.

Ted is a Senior Fellow (Assoc. Prof.) in the Visual Sciences Group of the Research School of Biological Sciences (RSBS, Annual reports ) at the Australian National University (ANU) in Canberra.  The Visual Sciences Group  and the closely allied  Developmental Neurobiology Group (also at RSBS) are part of an umbrella organisation at the ANU called  the Centre for Visual Sciences (CVS).  Ted is also Head of the Biotechnology Transfer Unit (BTU) at RSBS.

The ANU is an unusual university having two component parts consisting of: (1) The Faculties, which is an undergraduate teaching organisation; (2) a large research organisation called the Institute of Advanced Studies (IAS).  RSBS is one of a number the ANU/IAS Research Schools and Research Centres.  The research budget for the IAS is about $250M pa. Graduate students in the Visual Sciences group are normally enrolled in the Neuroscience Graduate Program, which is one of the many graduate programs in the ANU Graduate School. Scholarships are available for students doing their Ph.D.s and Honours years in the school, as well as Summer Research Scholarships for students in their earlier years who want to come and investigate what we can offer them.

In case you've just lobbed into my page and you want to know more about other things or people at the ANU, here are some useful links: ANU Directories,  ANU Staff E-mail List,  ANU Telephone Directory, List of ANU Web Sites. To get in touch with other interesting people in Australia see the Australasian Behavioural Neuroscience Registry. Otherwise, if you want to know more about my research read on.

SUMMARY OF TED'S RESEARCH

For the quick version see my Profile on the RSBS web site and my publication list.

My work on a new diagnostic method for detection of the eye disease glaucoma is perhaps most widely known. The commonest form of glaucoma affects of sight of abut 2% of persons over the age of 50 years in all countries. It is not to be confused with trachoma. The result of that work is the Frequency Doubling Technology Perimeter, a rapid and effective new eye test (e.g. AJO 2000 Editorial by Alward, and other papers in same AJO issue: 1, 2, 3, 4). The new test won myself and ANUTECH the Australian Technology Prize for 1999 and the 2002 Clunies Ross Science and Technology Prize. Click here for a history of the FDT perimeter.

My interests can be summarized under the heading of nonlinear and adaptive processes in vision.  My collaborators and I examine these topics employing a variety of methods ranging from single cell recording, through to evoked potential and eye movement recording, and psychophysical and behavioural methods. We work on humans, mammals and insects with an eye towards the comparative functional approach. We also engage in clinically relevant research on topics such as glaucoma, multiple sclerosis and myopia.

My original interest in vision was the optical design of invertebrate eyes.  I enjoyed the fact that you could see real physical constraints shaping eye structure and neural function. Invertebrates were particularly interesting because one could see how the physical constraints operated to produce similar solutions across a wide variety of invertebrate groups. The waveguide properties of photoreceptors were of particular interest to me.

Although my original interest in vision was the physical limitations imposed upon eyes by light, when I arrived at the ANU Prof. Adrian Horridge set me to work on motion-sensitive neurones in the optic lobes of insects.  Like most neurones these cells are very restricted in their information capacity, i.e. they literally have a low baud rate (about 90 bits/s). Working with Simon Laughlin it soon became apparent that, in order to encode the natural gamut of image velocities with any degree of fidelity, the motion-sensitive cells were required to employ sophisticated data compression strategies to regulate their response gain and temporal acuity (Maddess 1985;  Maddess & Laughlin 1985, see also Ibbotson et al. 1991;  Maddess, Dubois & Ibbotson 1991).  Other work arising from my thesis involved the mechanism of   production of afterimage-like effects in the motion sensing pathways (Maddess 1985, 1986).  Some of this work on insects is reviewed in an upcoming chapter (Maddess 2000) of a book on visual motion processing edited by two other members of the Visual Sciences Group (J.M. Zanker & J. Zeil).

Seeing that this real-time regulation or "adaptation" of temporal resolution and gain would also be   required in vertebrates, I obtained a Canadian Medical Research Council Fellowship and moved to the laboratory of Dr.Geoffrey Henry in the  Neuroscience Division of the ANU's John Curtin School of Medical Research (JCSMR) to do further studies of the visual cortex (Maddess, McCourt, Blakeslee, and Cunningham 1988; Maddess and Vidyasagar 1992). In the course of studying adaptation of the visual cortex a recurring theme was the involvement of another form of neural adaptation: the adaptive properties of gain control of the retinal ganglion cells.  This gain control is best expressed in the so called "Y" physiological type of retinal ganglion cell. I will also refer to these neurones as "My" cells because in primates they project to the "Magnocellular" layers of the LGN.

In addition to exhibiting a strong gain control mechanism the Y-cells express a strong second harmonic distortion.  I later came to understand that, for other reasons, these neurones could provide a sensitive litmus for damage caused by Primary Open Angle Glaucoma (POAG) (Maddess and Henry 1992; Maddess & Severt 1999, Maddess et al. 1998, 1999a,b, 2001).  I realized that one might be able to non-invasively access the My-cell pathway through visual stimuli designed to drive the My-cells exclusively by appealing to peculiarities of their gain control mechanism.  In particular if the My-cells were being driven exclusively one would expect to be able to find their characteristic second harmonic distortion in the visual percept, and one does: as the "spatial frequency doubling" (FD) illusion. Subsequent psychophysical experiments revealed that the granularity of the units producing the FD illusion was, everywhere on the retina, equal to the expected anatomical density of the My-cells (Maddess 1998).  Also the Pattern Electroretinogram becomes dominated by signals which look like "Y"-cell responses when subjects view FD stimuli (James et al. 1995; Maddess et al. 1997; Bedford et al. 1997). We also examined the diagnostic accuracy of a range of low spatial frequencies finding values around 0.5 cpd to be optimal (Maddess & Severt 1999). Human ability to gauge the scale of compound grating textures (Maddess and Kulikowski 1999) is another topic that has relevance to how we perceive FD patterns.

Several patents arose from that work (publication list) and the ANU's technology marketing company ANUTECH has licensed that intellectual property to  Welch Allyn Ltd (NY, USA) leading to the development of the Frequency Doubling Perimeter  (or).  The FDT perimeter is now marketed for Welch Allyn (for more information contact FDT@mail.welchallyn.com ) by Humphrey Instruments a division of Carl Zeiss. We also have several other potential diagnostic products under development, interested parties should contact Fiona Topfer at ANUTECH. Click here for a history of the FDT perimeter.

The work on glaucoma also lead to a collaboration with Dr. Ibbotson on more fundamental aspects of the control of eye movements (Maddess & Ibbotson 1992; Ibbotson & Maddess 1994), the first paper  was selected as a must read item amongst papers published in the last 5 years on oculomotor control by Current Opinion in Neurology. These papers describe the effects upon eye movements of neural adaptation to image motion. The most interesting result being that appropriate adapting stimuli, presented for as little as 1s, can cause one's subsequent following eye movements to proceed at half the normal velocity.

We have also begun to work on the Wallaby nucleus of the optic tract to obtain hard data on the brain areas controlling these eye movements (Ibbotson et al. 1994). We have also examined wallaby colour vision in behavioural and electrophysiological studies (Hemmi et al. 1999) revealing that like other mammals wallabies have blue/green colour vision .

We are also looking at novel Pattern Electroretinogram (PERG) and Visual Evoked Potential methods with Dr. A. James.  One idea is to perform more quantitative visual field testing for glaucoma, using multiple frequency doubling stimuli presented simultaneously to the eye (James et al. 1995, MFP1, MFP2).  A patent based on our results to date has been granted in the USA (publication list). Dr. James and I have also begun to look at methods for diagnosing Multiple Sclerosis. Most recently we have introduced multifocal methods using "Sparse Stimuli". These stimuli provide 15 time larger responses than conventional multifocal stimuli, providing a reduction in recording time of 3 to 4 fold. A patent application on the sparse method is at the PCT stage.

Other recent work includes the temporal dynamics of illusory brightness perception in humans (Davey, Maddess & Srinivasan 1998) and texture discrimination by bees (Yang and Maddess 1997; Maddess et al. 1999). Recent work examines our sensitivity to isotrigon textures (Maddess & Nagai 2001).
 

Last update 23.07.02
ted.maddess@anu.edu.au