Measuring brain activity associated with visual recognition
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The Laboratory of Experimental Ophthalmology studies the human capacity to
visually perceive and comprehend the world around us. Combining behavioral
methods, fMRI, and computational techniques, we aim to unravel how the visual
information is processed and what are the critical brain structures involved.
The studies described below are relevant because they contribute to our
understanding of how humans perceive their environment, how our brains work,
and on the origin of human behaviour. Ultimately, these fundamental insights in
vision in health will also contribute to our understanding of vision in
disease, improving diagnostic options and rehabilitation.

Our overall aim is to gain knowledge about the process of visual recognition:
how do the eyes and the visual cortex extract and integrate local features from
the visual scene to create a stable percept? Often visual recognition requires
the visual system to fill-in partially missing information. In other cases, in
order to maximize the neuronal computational efficiency, visual features are
integrated. During the last decades several theories that attempt to explain
the way that the brain extracts and integrates visual information have been
formulated. However these theories are contradictory and still subject of
controversy. Based on our new experiments, we expect to be able to put various
existing theories to the test, and to develop and validate new ones. Moreover,
we now intend to focus on the role of learning and plasticity in the
recognition process.

In the long run, the conclusions gained from our proposed studies in healthy
observers will contribute to solving important clinical issues in
ophthalmologic pathologies such as glaucoma, amblyopia or macular degeneration,
in which visual recognition is impaired. Measuring the degree of this
impairment at a very early disease stage is an important diagnostic goal.
Nevertheless, symptoms may be masked by the integration or filling-in
processes, preventing such early diagnosis. Understanding the underlying
mechanisms in the healthy visual system will aid the development of more
accurate diagnostic and monitoring techniques. Moreover, various studies
suggest that perceptual learning * popularly referred to as *brain training* *
may aid in improving vision and thus serve as a rehabilitation tool. While this
notion is still controversial, it does warrant further studies on perceptual
learning and brain plasticity.

This serves three goals: i) to gain insight into the neural foundations of
vision, ii) to develop pointers towards better and more efficient ways to
diagnose ocular and neurological disease at an early stage, iii) to understand
perceptual learning and to gauge the role it may have for future rehabilitation
efforts.

The study consists of a series of observational studies. Each study will
contain two parts: 1) a psychophysical (behavioural) experiment and 2) an
(f)MRI experiment. During these experiments, observers will see visual stimuli
on a display, to which they will have to respond by making a decision and
indicating this decision by pressing a button or key. Meanwhile, the viewing
behavior of the observers is measured using a gaze-tracker.

There is no increase in risk associated with this study, nor do observers
benefit from participation. Observers will view images on a screen and respond
to these, undergo a number of basic and standard vision tests (visual acuity,
contrast sensitivity, visual fields) and be exposed to (f)MRI experiments with
a magnetic field of 3 Tesla and fast fluctuating magnetic gradients and
radio-frequency fields. These field strengths are commonly in use in fMRI and
MRI research. Until now no side effects have been reported or described in the
literature. In very rare cases, observers may experience a harmless, tickling
feeling, the result of an abdominal peripheral nerve being stimulated because
of the fluctuating magnetic fields.