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Aston University researchers receive stimulus funds to study
fundamental processes of human vision

A team of researchers led by Professor Mark Georgeson and Dr
Timothy Meese at Aston University in Birmingham, UK have been
awarded over £1 million pounds worth of funding from the BBSRC
(Biotechnology and Biological Sciences Research Council) and the
EPSRC (Engineering and Physical Sciences Research Council) to
investigate some of the fundamental processes involved in human
vision.
The BBSRC project will see the Aston research team conduct
psychophysical experiments to study the binocular perception and
performance of human observers in order to develop a more complete
theory and understanding of binocular spatial vision through
successive refinements of a computational model.
Professor Georgeson explains: 'We have two eyes but see one
world. Although this may seem obvious (there is only one world),
there are conditions where we do see double. For example, if you
hold your index finger up a few inches in front of your nose, then
fix your gaze on a more distant object straight ahead; your finger
will be clearly seen as two, side by side. Then, as you switch your
gaze to the finger, the two will become one. This is binocular
fusion, or 'single vision' and it is achieved by the brain (the
visual cortex, containing millions of brain cells) piecing together
the information from both eyes. As a result, your ability to detect
very faint things, or to see fine details, is better with two eyes
than one. Our research aims to study single-vision and
double-vision in carefully controlled experiments, and to build a
general explanation in the form of a computer model that identifies
both the main mechanisms of binocular fusion and how they serve to
identify basic visual features such as lines and edges that may be
the building blocks of perception.'
Aston University specialises in rigorous research that makes an
impact on individuals, organisations and society, and this research
project could lead to potential healthcare applications in
optometry and vision correction.
Prof Georgeson continued: 'Presbyopia, which is the loss of
focussing adjustment by the eye at the age of 40 plus, is a
universal problem. One intriguing solution, known as 'monovision',
is to give each eye a different contact lens - one for far, the
other for near. After a period of adjustment, many users find this
works well, but it is not clear why. Optometrists often assume that
the brain is locally selecting the sharper image by suppressing the
more blurred one. By studying more precisely the conditions under
which blurred edges are combined (across the two eyes and within
one eye) our experiments - and the theoretical model that emerges -
should shed new light on the basis of 'monovision', perhaps leading
to improvements in diagnosis, treatment and prescription.
The second research grant is from the EPSRC. Dr Tim Meese
explains: 'When we open our eyes, we see, without effort. Our
visual experience begins with the mechanics of focussing the image
on the back of the eye; but to make sense of the image - to
perceive - our brains must identify the various parts of the image,
and understand their relations. Just like a silicon-based computer,
the brain performs millions of computations quickly and
effectively, more efficiently than we can ever sense. But what are
the computations that are needed to recognise, say, your mother; to
segment an object from its background; or even appreciate that one
part of an image belongs with another? The starting point for this
analysis is the distribution of light levels across the retinal
image, which we can think of as a set of pixels. Interesting parts
of the image (eg object boundaries) occur at regions of change:
where neighbouring pixels have very different values. These regions
are indentified by neurons in the primary visual cortex by
computing differences between adjacent pixel values to build a
neural image of local contrasts: the 'contrast image'. These
contrast -defined local image features are then combined across
retinal space at later stages of visual processing to represent
elongated contours (for example the branches of a tree) and
textured surfaces (for example a ploughed field) in what is
sometimes known as a 'feature map'.
'In this project we will utilise a new type of stimulus and
modelling framework that we have developed to investigate the
computational rules that control the point-by-point integration of
information in the 'contrast image.'
'The main users of this research will be vision scientists,
neurophysiologists and engineers working on spatial vision, the
neural of vision, visual cognition and image processing
algorithms.'
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