NOBEL PRIZE IN PHYSIOLOGY OR
MEDICINE-2014
Thirty--four
years later May-Britt and Edvard Moser, of the Norwegian University of Science
and Technology in Trondheim, identified another type of nerve cell that
generates a coordinate system for precise path—finding, the assembly said.It said
that knowledge about the brain’s positioning system may “help us understand the
mechamism underpinning the devastating spatial memory loss” that affects people
with Alzheimer’s disease.The Nobel
awards in physics, chemistry, literature and peace will be announced later this
week. The economics prize will be announced next Monday.
John O´Keefe
and the other half jointly to
May-Britt Moser and
Edvard I. Moser
for their discoveries of
cells that constitute a positioning
system in the brain
system in the brain
How
do we know where we are? How can we find the way from one place to another? And
how can we store this information in such a way that we can immediately find
the way the next time we trace the same path? This year´s Nobel Laureates have
discovered a positioning system, an “inner GPS” in the brain that makes it
possible to orient ourselves in space, demonstrating a cellular basis for
higher cognitive function.
In
1971, John O´Keefe discovered the first component of this positioning system.
He found that a type of nerve cell in an area of the brain called the
hippocampus that was always activated when a rat was at a certain place in a
room. Other nerve cells were activated when the rat was at other places.
O´Keefe concluded that these “place cells” formed a map of the room.
More
than three decades later, in 2005, May-Britt and Edvard Moser discovered
another key component of the brain’s positioning system. They identified
another type of nerve cell, which they called “grid cells”, that generate a
coordinate system and allow for precise positioning and pathfinding. Their
subsequent research showed how place and grid cells make it possible to
determine position and to navigate.
The
discoveries of John O´Keefe, May-Britt Moser and Edvard Moser have solved a
problem that has occupied philosophers and scientists for centuries – how does
the brain create a map of the space surrounding us and how can we navigate our
way through a complex environment?
How
do we experience our environment?
The
sense of place and the ability to navigate are fundamental to our existence.
The sense of place gives a perception of position in the environment. During
navigation, it is interlinked with a sense of distance that is based on motion
and knowledge of previous positions.
Questions
about place and navigation have engaged philosophers and scientists for a long
time. More than 200 years ago, the German philosopher Immanuel Kant argued that
some mental abilities exist as a priori knowledge, independent of experience.
He considered the concept of space as an inbuilt principle of the mind, one
through which the world is and must be perceived. With the advent of
behavioural psychology in the mid-20th century, these questions could be
addressed experimentally. When Edward Tolman examined rats moving through
labyrinths, he found that they could learn how to navigate, and proposed that a
“cognitive map” formed in the brain allowed them to find their way. But
questions still lingered - how would such a map be represented in the brain?
John
O´Keefe and the place in space
John
O´Keefe was fascinated by the problem of how the brain controls behaviour and
decided, in the late 1960s, to attack this question with neurophysiological
methods. When recording signals from individual nerve cells in a part of the
brain called the hippocampus, in rats moving freely in a room, O’Keefe
discovered that certain nerve cells were activated when the animal assumed a
particular place in the environment (Figure 1). He could demonstrate that these
“place cells” were not merely registering visual input, but were building up an
inner map of the environment. O’Keefe concluded that the hippocampus generates
numerous maps, represented by the collective activity of place cells that are
activated in different environments. Therefore, the memory of an environment
can be stored as a specific combination of place cell activities in the
hippocampus.
May-Britt
and Edvard Moser find the coordinates
May-Britt
and Edvard Moser were mapping the connections to the hippocampus in rats moving
in a room when they discovered an astonishing pattern of activity in a nearby
part of the brain called the entorhinal cortex. Here, certain cells were
activated when the rat passed multiple locations arranged in a hexagonal grid
(Figure 2). Each of these cells was activated in a unique spatial pattern and
collectively these “grid cells” constitute a coordinate system that allows for
spatial navigation. Together with other cells of the entorhinal cortex that
recognize the direction of the head and the border of the room, they form
circuits with the place cells in the hippocampus. This circuitry constitutes a
comprehensive positioning system, an inner GPS, in the brain (Figure 3).
A
place for maps in the human brain
Recent
investigations with brain imaging techniques, as well as studies of patients
undergoing neurosurgery, have provided evidence that place and grid cells exist
also in humans. In patients with Alzheimer´s disease, the hippocampus and
entorhinal cortex are frequently affected at an early stage, and these
individuals often lose their way and cannot recognize the environment.
Knowledge about the brain´s positioning system may, therefore, help us
understand the mechanism underpinning the devastating spatial memory loss that
affects people with this disease.
The
discovery of the brain’s positioning system represents a paradigm shift in our
understanding of how ensembles of specialized cells work together to execute
higher cognitive functions. It has opened new avenues for understanding other
cognitive processes, such as memory, thinking and planning.
Key publications:
|
O'Keefe, J., and Dostrovsky, J. (1971). The hippocampus as a
spatial map. Preliminary evidence from unit activity in the freely‐moving rat. Brain Research 34, 171-175.
|
O´Keefe, J. (1976). Place units in the hippocampus of the
freely moving rat. Experimental Neurology 51, 78-109.
|
Fyhn, M., Molden, S., Witter, M.P., Moser, E.I., Moser, M.B.
(2004) Spatial representation in the entorhinal cortex. Science 305,
1258-1264.
|
Hafting, T., Fyhn, M., Molden, S., Moser, M.B., and Moser,
E.I. (2005). Microstructure of spatial map in the entorhinal cortex. Nature
436, 801-806.
|
Sargolini, F., Fyhn, M., Hafting, T., McNaughton, B.L.,
Witter, M.P., Moser, M.B., and Moser, E.I. (2006). Conjunctive representation
of position, direction, and velocity in the entorhinal cortex. Science 312,
758-762.
|
John O’Keefe was born in 1939 in New York City, USA, and holds both American
and British citizenships. He received his doctoral degree in physiological
psychology from McGill University, Canada in 1967. After that, he moved to
England for postdoctoral training at University College London. He has remained
at University College and was appointed Professor of Cognitive Neuroscience in
1987. John O´Keefe is currently Director of the Sainsbury Wellcome Centre in
Neural Circuits and Behaviour at University College London.
May-Britt Moser was born in Fosnavåg, Norway in 1963 and is a
Norwegian citizen. She studied psychology at the University of Oslo together
with her future husband and co-Laureate Edvard Moser. She received her Ph.D. in
neurophysiology in 1995. She was a postdoctoral fellow at the University of
Edinburgh and subsequently a visiting scientist at University College London
before moving to the Norwegian University of Science and Technology in
Trondheim in 1996. May-Britt Moser was appointed Professor of Neuroscience in
2000 and is currently Director of the Centre for Neural Computation in
Trondheim.
Edvard I. Moser was born in born 1962 in Ålesund, Norway and has
Norwegian citizenship. He obtained his Ph.D. in neurophysiology from the
University of Oslo in 1995. He was a postdoctoral fellow together with his wife
and co‐Laureate May‐Britt Moser, first at the University of
Edinburgh and later a visiting scientist in John O´Keefe´s laboratory in
London. In 1996 they moved to the Norwegian University of Science and Technology
in Trondheim, where Edvard Moser became Professor in 1998. He is currently
Director of the Kavli Institute for Systems Neuroscience in Trondheim.
Prof. John Kurakar
No comments:
Post a Comment