Christian C. Ruff talks with
ScienceWatch.com and answers a few questions about
this month's Fast Moving Front in the field of Neuroscience
Article: Concurrent TMS-fMRI and psychophysics
reveal frontal influences on human retinotopic visual
CC;Blankenburg, F;Bjoertomt, O;Bestmann, S;Freeman,
E;Haynes, JD;Rees, G;Josephs, O;Deichmann, R;Driver,
Journal: CURR BIOL, 16 (15): 1479-1488 AUG 8 2006
Addresses: Univ Coll London, Inst Cognit Neurosci, 17 Queen
Sq, London WC1N 3AR, England.
Univ Coll London, Inst Cognit Neurosci, London WC1N 3AR,
Univ Coll London, Dept Psychol, London WC1H 0AP,
Univ Coll London, Wellcome Dept Imaging Neurosci, London
WC1N 3BG, England.
Univ Coll London, Sobell Dept Motor Neurosci & Movement
Disorders, London WC1N 3BG, England.
Max Planck Inst Human Cognit & Brain Sci, D-04103
Why do you think your paper is highly
I work in the field of human cognitive neuroscience, the discipline that
studies how brain processes give rise to what we see, think, feel, and do.
Many studies in this field have focused on the function of single brain
areas, by studying regionally specific brain activity changes while
participants engage in a cognitive task. Our paper extended this general
approach in two ways.
First, our study demonstrated that it is not just activation of one area,
but rather communication between different areas of the human brain that
can bring about a specific mental state—in our case, visual
perception. This general notion has always been discussed in the
literature, but had rarely been shown directly before.
Second, our study may have gathered interest because it brought causality
into human neuroimaging research. Many previous studies demonstrated that
particular forms of brain activity correlate with a mental function, but
could not show that such activity is indeed causally necessary.
"Our ultimate aim is to understand
how brain processes support thought and
In our study, we combined neuroimaging with a method to stimulate neurons
in the human brain. This strategy enabled us to show directly that
(stimulation-induced) neural activity in a region in the frontal part of
the human brain can change visual processing in interconnected posterior
visual brain regions, and influence the associated visual percept. I think
our study is highly cited as many readers recognize the explanatory power
of this causal approach to brain-behavior relationships.
Does it describe a new discovery, methodology, or
synthesis of knowledge?
It both describes a new discovery and illustrates a novel methodology.
Conceptually, our main question was whether visual cortex function can be
influenced by regions outside the parts of the brain traditionally thought
to be "visual." To show this, we had to devise a way to induce neural
activity in such regions while simultaneously measuring the impact of this
on neural activity in remote but interconnected visual cortex.
The appropriate technique turned out to be transcranial magnetic
stimulation (TMS, a non-invasive method to stimulate circumscribed brain
areas, which is often used therapeutically) combined concurrently with
functional magnetic resonance imaging (fMRI, which can measure neural
activity via oxygen consumption).
This methodical combination is quite complicated and had not been used
before for the same purpose, so our paper described and discussed both our
specific experimental findings as well as the necessary methodical
developments. I think our paper was thus received by the field not only as
a new finding on brain function, but also as a "proof-of-concept" for the
general experimental approach.
Would you summarize the significance of your paper
in layman’s terms?
Neuroscientists usually study human brain function by measuring neural
activity while participants perform experimental tasks. This approach has
identified many brain areas that seem to specifically activate during
different aspects of perception, thought, or behavior. However, what is
unclear from such findings is whether the observed neural activity is
causally responsible for the mental state, and to what degree the activated
brain regions interact.
In our study, we were interested in whether visual perception may involve
communication between a specific region in the frontal part of the
brain—called the frontal eye fields—and posterior brain regions
involved in processing visual input. We addressed this question by
stimulating the frontal eye fields while simultaneously measuring the
activity in the posterior visual brain regions.
We found that frontal stimulation indeed changed neural activity in visual
cortex and the associated perception. This finding is important, as it
demonstrates directly that functional interactions between different areas
of an interconnected brain network can cause a specific mental state. Our
study also generally outlines how the combination of brain stimulation and
brain imaging can allow neuroscientists to investigate functional
interactions in the human brain and their relation to cognition and
How did you become involved in this research and
were any particular problems encountered along the way?
"In our study, we combined
neuroimaging with a method to stimulate
neurons in the human
I started this research in London in 2003, when working in Jon Driver's
laboratory on the neural processes underlying the control of visual
attention—Jon Driver is Director of the Institute of Cognitive
Neuroscience at UCL.
At that time, many people proposed that attention involves influences of
frontal and parietal brain regions on visual cortex, but direct empirical
demonstrations for this were lacking for the human brain. So I decided to
work on this general topic with a combination of brain stimulation and
In the beginning, I sometimes cursed myself for having chosen this path, as
the technical complications of concurrent TMS-fMRI were tremendous, and
many datasets turned out to be unusable due to artifacts or other technical
problems. Fortunately Jon Driver was always very supportive and
encouraging, and I am very grateful to him for that.
Moreover, I was lucky that there were other people (the co-authors on my
studies) in the lab and at UCL's Functional Imaging Laboratory who were
also interested in setting up this technique, although for somewhat
different purposes. We could tackle many problems together; this made life
easier and more fun, for which I also want to thank them.
In the end, the risk and effort paid off, and based on our initial work, we
continue to acquire new datasets on causal functional interactions in the
Where do you see your research leading in the
Our ultimate aim is to understand how brain processes support thought and
behavior. The approach of combined brain stimulation and imaging allows
direct study of a new aspect of this relationship, namely the functional
contributions of communication between remote but interconnected brain
I hope we can use this approach to characterize the communication in brain
networks underlying many other aspects of human mental activity—such
as decision-making. It would also be interesting to see how these
functional brain interactions may account for individual differences, and
possibly for pathological disorders of thought and behavior—such as
Do you foresee any social or political implications
for your research?
Many people advocate that a better understanding of the neurobiological
basis of cognition and behavior will be essential for improving many
aspects of our society, including the legal system, education, the
structure of financial markets, and so forth. I would generally agree with
this position, but I do not think that we are already at a stage where we
can give specific recommendations that could be put into practice.
The one domain where I already see clear implications of our research is
for medical purposes. Brain stimulation methods are being increasingly used
for treating depression, stroke, and other brain disorders, and the
combination with neuroimaging, as implemented in our studies, can help
clinicians to devise effective treatment protocols for their patients.
Christian C. Ruff, Ph.D.
Laboratory for Social and Neural Systems Research
University of Zurich
Honorary Senior Lecturer
Institute of Neurology
University College London