ANNUAL SYMPOSIUM

Australia's science future 3-4 May 2000
Full listing of papers

Professor Mandyam Srinivasan holds a PhD in engineering and applied science from Yale University, and a DSc in neuroethology from the Australian National University. He is Professor of Visual Sciences at the Australian National University's Research School of Biological Sciences and the Director of the University’s Centre for Visual Science. Professor Srinivasan's research focuses on the principles of visual processing in simple natural systems and on the application of these principles to machine vision and robotics. He is the author of some 150 research papers in this field. In 1995 he was elected a Fellow of the Australian Academy of Science.

Symposium themes - Mind and brain
Small brains, smart minds
by Mandyam Srinivasan
M.V.Srinivasan@rsbs.anu.edu.au

Abstract
Anyone who has watched a fly make a flawless landing on the rim of a teacup, or marvelled at a honeybee speeding home after collecting nectar from a flower patch several kilometres away, would know that insects possess visual systems that are fast, reliable and accurate. Insects cope remarkably well with their world, despite possessing a brain that carries fewer than 0.01% as many neurons as ours does. Professor Srinivasan will explore the secrets of their success by describing research aimed at understanding the mechanisms underlying visual perception, navigation, learning, memory and 'cognition' in honeybees, and comparing these with human performance. He will also discuss the opportunities for incorporating insect-based principles into the design of novel, autonomous robots.

Anyone who has tried to swat a fly, or marvelled at a bee going home from a flower patch several kilometres away, will know that insects have a visual system that is fast, reliable and accurate. How do they do this with such small brains? If they use short cuts, could the methods be used in the design of machines and robots.

Because the two eyes of insects are close together, it is hard for them to use stereo vision to judge distance. Unlike humans, they can’t use triangulation, in which the large disparity between images from the left and right eyes can be used by the brain to estimate distance.

Instead, insects use motion cues to tell whether an object is close or distant. When bees fly through a narrow gap such as a hole in a window they fly through the centre of the hole. How do they do it?

We conducted an experiment with bees flying down a tunnel, changing the patterns on the walls. We found that bees balance the image velocities in the left and right visual fields. This strategy ensures that bees fly down the middle of the tunnel, without bumping into the side walls.

By putting the bees through a narrowing tunnel, we found how they control flight speed. The speed is regulated by holding constant the average velocity of the image of the environment. As the gap narrows, and the images come closer, the bees slow down. This ensures that the bees are flying at a safe speed when they go through a narrow gap.

We incorporated these ideas into a robot the size of a skateboard. A video camera on the robot captures two lateral views of its environment. The robot can then navigate down a curving passageway without any human control.

Corridor-following robot (from the website of the Australian National University's Biorobotic Vision Laboratory)

Another navigational problem for flying insects is landing. How does an insect make a smooth touchdown? We filmed the trajectories of landing bees. We found that the bees flew more slowly as they descended, that is, flight speed is proportional to height above the ground. Bees achieve this by holding the speed of the image of the ground constant as they approach it. This landing strategy automatically ensures a smooth touchdown.

When we combined these two rules, we created a simple model that encapsulates the bee’s landing strategy. We aim to put this model to use in a mechanical landing vehicle, a pilotless helicopter.

Ambiguous illustrations, with faces hidden in plants and trees, can take a while to fathom. But once we learn what to expect, perception is permanently changed. Does something similar happen in bees?

We did an experiment with camouflaged shapes. We trained bees with food on uncamouflaged objects. Then they could find the shape in the camouflage. Having learnt the rule, the bees could apply it to other shapes. So you can train bees to look at the world in new ways. That’s not bad for an insect.

Following Descartes, the bee’s philosophy of flight is: ‘I move, therefore I see.’

Bees are not automatons, but lessons learned from them can be applied to automatons. Robots are a good way to explore remote, inhospitable terrain, such as the surface of Mars, or areas containing land mines. With a large number of small robots (like an army of ants), the search will be more efficient and robust than it would be with one expensive robot. A distributed system is better than a centralised one.

Session discussion

Could you elaborate on how you have identified the causes of depression.

Ian Hickie. Thanks to the Australian Twin Registry, twin experiments and family experiments can model genetic variance underlying disease. The effects of changes over the life cycle as people get older and choose their own environments can also be studied.

To what extent is the surge in depression the result of a new diagnosis?

Ian Hickie. What is depression and what is stress over environment. We can look over 40 years using the same measures. Other indicators, such as drug and alcohol use, can show the rates of depression over centuries. The surge is not an artefact of recording; the statistics are more reliable. Changing diagnosis doesn’t explain the underlying trend.

How does an insect climbing high determine its altitude?

Mandyam Srinivasan. That hasn’t been explored yet. It could modulate speed. We should do an experiment. It is harder to estimate altitude when you are high above the ground. It would need large modulations.

Are there any differences between strains of bees in their responses to movement stimuli?

Mandyam Srinivasan. I haven’t explored that. Some mutants lack visual neurons and are motion-blind.

Does the collective intelligence of social insects, such as ants and bees, help them do anything that single insects can’t?

Mandyam Srinivasan. I don’t know if the individual skills I have been talking about would carry over. Collective behaviour is unique, there are lots of ways communicating.

Is the ability of a bee to find its way back to base over a long distance related to the near-distance navigation processes you have described?

Mandyam Srinivasan. Yes, the bee’s odometer is visually driven. Energy consumption is not the way they measure distance. Bees travelling a short distance in a narrow tunnel can be fooled into thinking they’ve gone a long way.

Does memory formation depend on the strength of emotion? Does marijuana have an effect?

Pankaj Sah. Yes, strength of emotion has a big effect. It is not known how but memories are put down more quickly.

Given that relationship between memory and emotion, reason could be natural selection favouring rational scientific thinking.

Pankaj Sah. I don’t agree. Scientists have strong emotional responses to their own ideas.

How much variance was there in the bees? Are some more stupid than others?

Mandyam Srinivasan. There was a variance of 20 per cent in performing the tasks. My wife called one bee Srini because when he was faced with a choice he took such a long time to make up his mind.

Is depression purely dysfunctional or does it have evolutionary purpose?

Ian Hickie. Anxiety and depression have evolutionary advantages. When an infant is separated from its mother it will start screaming. This is a response to attract the wanted person. It is intrinsic to behaviours that engage other people. Anxiety and depression are aberrant forms of signalling behaviours used to get people close to us.

What are the prospects for replacing damaged brain cells with animal cells?

Ian Hickie. The longer you stay active, the longer you can keep learning, even as you lose neurons. In disease, such as Parkinson’s disease, the ability to replace brain cells is an exciting development.

What do think of reports that imply the benefit of nutritional supplements, for example, Omega 3.

Ian Hickie. Studies in ageing people show that the possibility of benefit stands up to some scrutiny. For depression, less is indicated.

If a bee loses one eye, does it lose the capacity to navigate?

Mandyam Srinivasan. Such bees tend not to fly. Bees can transfer information from eye to the other, but I don’t know if a one-eyed bee could navigate.