Nikos K. Logothetis &
Brian A. Wandell talk with ScienceWatch.com and
answer a few questions about this month's Fast Moving Front
in the field of Neuroscience &
Article: Interpreting the BOLD
Journal: ANNU REV PHYSIOL, 66: 735-769 2004
Addresses: Max Planck Inst Biol Cybernet, D-72076 Tubingen,
Max Planck Inst Biol Cybernet, D-72076 Tubingen,
Stanford Univ, Dept Psychol, Stanford, CA 94305 USA.
Why do you think your paper is highly
Functional magnetic resonance imaging (fMRI) and behavior are the principal
ways we learn about human brain activity. The vast majority of our
understanding about the brain, however, is derived from electrical
measurements of activity in animal brains. fMRI does not measure precisely
the same electrical responses—either action potentials or local field
potentials—that are measured in most animal experiments. Rather, fMRI
measures a blood oxygen level dependent (BOLD) signal.
Our understanding of the brain can be advanced greatly if we learn how to
combine the information acquired through these different methods. The
Annual Review paper we wrote was one of the first papers to
summarize our current understanding of the relationship between BOLD fMRI
and electrical measurements of neural activity. The review was written to
be a resource of references for advanced investigators; it also includes
sections that we hope are used by students to learn about the basic
principles of these different signal types.
Does it describe a new discovery, methodology, or
synthesis of knowledge?
Brian A. Wandell
The paper describes both a number of seminal studies that made fMRI
possible and the new physiological/MRI studies that address the nature of
the BOLD fMRI signal. We tried to describe various measurement methods and
synthesize our understanding of the similarities and differences between
Would you summarize the significance of your paper
in layman's terms?
fMRI is the mainstay of neuroimaging in cognitive neuroscience. The results
from fMRI are being applied to a variety of topics that span clinical
applications (pain management), legal applications (lie detection), and
education (how children learn to read).
Despite the rush to apply fMRI to important problems, scientists remain
unsure about the connection between the fMRI signal and the signals in the
fundamental computational elements of the brain (neurons). The review
describes what we do and do not know about the fMRI signal. The review aims
to show where the fMRI signal can be used to advantage, but also its
How did you become involved in this research and
were there any particular problems encountered along the way?
NL: I was trained as a neurophysiologist and spent years recording the
activity of single units in monkeys trained to perform a variety of
perceptual or cognitive tasks. Single-unit recordings also have
limitations, as they report the physiological properties of isolated
neurons rather than the properties of the networks that underlie any
Over the years it became clear to us that a global view of activity, in
particular a view that reports feedforward and feedback as well as
modulatory effects, would be utterly necessary to ensure correct
interpretation and evaluation of electrophysiological results. The
development of invasive MRI methods was definitely challenging but also
"Functional magnetic resonance
imaging (fMRI) and behavior are the principal
ways we learn about human brain
BW: Understanding how we see has always been an
inter-disciplinary field, spanning behavior, computation, and neuroscience.
I was trained to make behavioral measurements and work on computational
models. With the invention of fMRI, I was fortunate to be at an institution
with colleagues who could help me learn how to measure fMRI signals and
study the visual cortex of the human brain.
From the beginning, we recognized that data about the human brain function
and structure are precious; but we were always eager to connect human
measurements to the neural signals measured in macaque by
electrophysiologists. The opportunity to collaborate with Nikos, including
on this review, opened up a new range of possibilities for understanding
how to combine our work with other types of brain measurements.
Where do you see your research leading in the
To a better understanding of the important relationship between brain and
Do you foresee any social or political
implications for your research?
Work in fMRI has been used in many ways which are of broad interest. There
is a provocative claim that fMRI of the human brain can provide an
objective measure of a person's sensory experience and thoughts. Some
propose that fMRI be used to determine whether a person is telling the
truth, and this type of evidence has been admitted in courts in India.
Others use the method to measure "unconscious evaluation of Black and White
social groups," a code for evaluating racism.
Economists and marketing experts want to measure the brain to determine how
much a person values a product, while clinicians seek to use biofeedback to
help patients control their thoughts and feelings. There has been vigorous
criticism, both among scientists and the public, about some of these
applications. In our view, powerful applications that benefit society will
flow from a better theory of brain and mind. Many current proposals for
applications seem premature; but we have noted that historically
entrepreneurs are not shy.
Professor Dr. Nikos K. Logothetis
Max Planck Institute of Biological Cybernetics
Brian A. Wandell
Stein Family Professor and Chair
Stanford, CA, USA
Keywords: functional magnetic resonance imaging,
neuroimaging in cognitive neuroscience, electrical measurements of neural
activity, blood oxygen level dependent signal, pain management, lie