Using a Japanese super-computer,
a team of scientists have carried out the largest ever imitation of the
way a brain's cells connect with each other. This will pave the way for
a better understanding of the extremely complex human brain, they say.
Researchers from the RIKEN, a Japanese research body, the Okinawa Institute of Science & Technology (OIST) in Japan and the Forschungszentrum Julich, a research institute in Germany, used the K-computer in Julich to carry out the neuronal network simulation.
The brain consists of some 200 billion nerve cells, also called neurons. These are linked to each other by trillions of connections called synapses. Small electrical impulses are fired across the neurons through synapses, each of which contains an estimated 1000 switches for routing the message. The total network runs into hundreds of trillions of pathways. Just the topmost layer of the brain, the cerebral cortex has an estimated 125 trillion synapses, according to research by Stephen Smith, a professor at Stanford University.
The latest simulation managed to create a virtual or electronic neuronal network of 1.73 billion nerve cells connected by 10.4 trillion synapses. For this feat, it used a open-source software called NEST and 82,944 processors of the K computer. The process took 40 minutes, to complete the simulation of 1 second of neuronal network activity in real, biological, time.
Although the simulated network is huge, it only represents 1% of the neuronal network in the brain. The nerve cells were randomly connected and the simulation itself was not supposed to provide new insight into the brain - the purpose of the endeavor was to test the limits of the simulation technology developed in the project and the capabilities of K. In the process, the researchers gathered invaluable experience that will guide them in the construction of novel simulation software.
The team was led by Markus Diesmann in collaboration with Abigail Morrison both now with the Institute of Neuroscience and Medicine at Julich.
Simulating a large neuronal network and a process like learning requires large amounts of computing memory. Synapses, the structures at the interface between two neurons, are constantly modified by neuronal interaction and simulators need to allow for these modifications.
More important than the number of neurons in the simulated network is the fact that during the simulation each synapse between excitatory neurons was supplied with 24 bytes of memory. This enabled an accurate mathematical description of the network. In total, the simulator coordinated the use of about 1 petabyte of main memory, which corresponds to the aggregated memory of 250,000 PCs.
"If peta-scale computers like the K Computer are capable of representing 1% of the network of a human brain today, then we know that simulating the whole brain at the level of the individual nerve cell and its synapses will be possible with exa-scale computers hopefully available within the next decade," explains Diesmann. One 'peta' is a thousand trillion and one 'exa' is a thousand 'peta'.
The achievement on K computer is encouraging news for the Human Brain Project (HBP) of the European Union, scheduled to start this October. The central supercomputer for this project will be based at the Forschungszentrum Julich.
Researchers from the RIKEN, a Japanese research body, the Okinawa Institute of Science & Technology (OIST) in Japan and the Forschungszentrum Julich, a research institute in Germany, used the K-computer in Julich to carry out the neuronal network simulation.
The brain consists of some 200 billion nerve cells, also called neurons. These are linked to each other by trillions of connections called synapses. Small electrical impulses are fired across the neurons through synapses, each of which contains an estimated 1000 switches for routing the message. The total network runs into hundreds of trillions of pathways. Just the topmost layer of the brain, the cerebral cortex has an estimated 125 trillion synapses, according to research by Stephen Smith, a professor at Stanford University.
The latest simulation managed to create a virtual or electronic neuronal network of 1.73 billion nerve cells connected by 10.4 trillion synapses. For this feat, it used a open-source software called NEST and 82,944 processors of the K computer. The process took 40 minutes, to complete the simulation of 1 second of neuronal network activity in real, biological, time.
Although the simulated network is huge, it only represents 1% of the neuronal network in the brain. The nerve cells were randomly connected and the simulation itself was not supposed to provide new insight into the brain - the purpose of the endeavor was to test the limits of the simulation technology developed in the project and the capabilities of K. In the process, the researchers gathered invaluable experience that will guide them in the construction of novel simulation software.
The team was led by Markus Diesmann in collaboration with Abigail Morrison both now with the Institute of Neuroscience and Medicine at Julich.
Simulating a large neuronal network and a process like learning requires large amounts of computing memory. Synapses, the structures at the interface between two neurons, are constantly modified by neuronal interaction and simulators need to allow for these modifications.
More important than the number of neurons in the simulated network is the fact that during the simulation each synapse between excitatory neurons was supplied with 24 bytes of memory. This enabled an accurate mathematical description of the network. In total, the simulator coordinated the use of about 1 petabyte of main memory, which corresponds to the aggregated memory of 250,000 PCs.
"If peta-scale computers like the K Computer are capable of representing 1% of the network of a human brain today, then we know that simulating the whole brain at the level of the individual nerve cell and its synapses will be possible with exa-scale computers hopefully available within the next decade," explains Diesmann. One 'peta' is a thousand trillion and one 'exa' is a thousand 'peta'.
The achievement on K computer is encouraging news for the Human Brain Project (HBP) of the European Union, scheduled to start this October. The central supercomputer for this project will be based at the Forschungszentrum Julich.
New 'grid cells' in brain keep track of location
A
research team from Drexel University, the University of Pennsylvania,
UCLA and Thomas Jefferson University identified the grid cells using
direct human brain recordings.
RELATED
NEW DELHI: A team of scientists in the US has discovered a new type of
cell in the brain that helps people to keep track of their relative
location while going through an unfamiliar area. These cells have been
dubbed "grid cells" because they get activated in a triangular grid
pattern.
A research team from Drexel University, the University of Pennsylvania, UCLA and Thomas Jefferson University identified the grid cells using direct human brain recordings. Their findings are being published in the latest issue of the scientific journal Nature Neuroscience.
The "grid cell" is distinct among brain cells because its activation represents multiple spatial locations. This behavior is how grid cells allow the brain to keep track of navigational cues such as how far you are from a starting point or your last turn. This type of navigation is called path integration.
"Each grid cell responds at multiple spatial locations that are arranged in the shape of a grid," said Joshua Jacobs of Drexel who led the research. "This triangular grid pattern thus appears to be a brain pattern that plays a fundamental role in navigation. Without grid cells, it is likely that humans would frequently get lost or have to navigate based only on landmarks. Grid cells are thus critical for maintaining a sense of location in an environment."
The researchers were able to discern these cells because they had the rare opportunity to study brain recordings of epilepsy patients with electrodes implanted deep inside their brains as part of their treatment. The team studied the relation between how the participants navigated in the video game and the activity of individual neurons.
During brain recording, the 14 study participants played a video game that challenged them to navigate from one point to another to retrieve objects and then recall how to get back to the places where each object was located. The participants used a joystick to ride a virtual bicycle across a wide-open terrain displayed on a laptop by their hospital beds. After participants made trial runs where each of the objects was visible in the distance, they were put back at the center of the map and the objects were made invisible until the bicycle was right in front of them. The researchers then asked the participants to travel to particular objects in different sequences.
While these cells are not unique among animals — they have been discovered previously in rats — and a prior study in 2010, that used noninvasive brain imaging, suggested the existence of the cells in humans, this is the first positive identification of the human version of these cells.
"The present finding of grid cells in the human brain, together with the earlier discovery of human hippocampal 'place cells,' which fire at single locations, provide compelling evidence for a common mapping and navigational system preserved across humans and lower animals," said Michael Kahana, a co-author and professor of psychology at the University of Pennsylvania.
The team's findings also suggest that these grid patterns may in fact be more prevalent in humans than rats, because the study found grid cells not only in the entorhinal cortex — where they are observed in rats — but also, in a very different brain area — the cingulate cortex.
"Grid cells are found in a critical location in the human memory system called the entorhinal cortex," said Itzhak Fried, who is a professor of neurosurgery at the David Geffen School of Medicine at UCLA. "This discovery sheds new light on a region of the brain that is the first to be affected in Alzheimer's Disease with devastating effects on memory"
The entorhinal cortex is part of the brain that has been studied in Alzheimer's disease research and according to Jacobs, understanding grid cells could help researchers understand why people with the disease often become disoriented. It could also help them show how to improve brain function in people suffering from Alzheimer's.
A research team from Drexel University, the University of Pennsylvania, UCLA and Thomas Jefferson University identified the grid cells using direct human brain recordings. Their findings are being published in the latest issue of the scientific journal Nature Neuroscience.
The "grid cell" is distinct among brain cells because its activation represents multiple spatial locations. This behavior is how grid cells allow the brain to keep track of navigational cues such as how far you are from a starting point or your last turn. This type of navigation is called path integration.
"Each grid cell responds at multiple spatial locations that are arranged in the shape of a grid," said Joshua Jacobs of Drexel who led the research. "This triangular grid pattern thus appears to be a brain pattern that plays a fundamental role in navigation. Without grid cells, it is likely that humans would frequently get lost or have to navigate based only on landmarks. Grid cells are thus critical for maintaining a sense of location in an environment."
The researchers were able to discern these cells because they had the rare opportunity to study brain recordings of epilepsy patients with electrodes implanted deep inside their brains as part of their treatment. The team studied the relation between how the participants navigated in the video game and the activity of individual neurons.
During brain recording, the 14 study participants played a video game that challenged them to navigate from one point to another to retrieve objects and then recall how to get back to the places where each object was located. The participants used a joystick to ride a virtual bicycle across a wide-open terrain displayed on a laptop by their hospital beds. After participants made trial runs where each of the objects was visible in the distance, they were put back at the center of the map and the objects were made invisible until the bicycle was right in front of them. The researchers then asked the participants to travel to particular objects in different sequences.
While these cells are not unique among animals — they have been discovered previously in rats — and a prior study in 2010, that used noninvasive brain imaging, suggested the existence of the cells in humans, this is the first positive identification of the human version of these cells.
"The present finding of grid cells in the human brain, together with the earlier discovery of human hippocampal 'place cells,' which fire at single locations, provide compelling evidence for a common mapping and navigational system preserved across humans and lower animals," said Michael Kahana, a co-author and professor of psychology at the University of Pennsylvania.
The team's findings also suggest that these grid patterns may in fact be more prevalent in humans than rats, because the study found grid cells not only in the entorhinal cortex — where they are observed in rats — but also, in a very different brain area — the cingulate cortex.
"Grid cells are found in a critical location in the human memory system called the entorhinal cortex," said Itzhak Fried, who is a professor of neurosurgery at the David Geffen School of Medicine at UCLA. "This discovery sheds new light on a region of the brain that is the first to be affected in Alzheimer's Disease with devastating effects on memory"
The entorhinal cortex is part of the brain that has been studied in Alzheimer's disease research and according to Jacobs, understanding grid cells could help researchers understand why people with the disease often become disoriented. It could also help them show how to improve brain function in people suffering from Alzheimer's.
Congratulation for the great post. Those who come to read your article will find lots of helpful and informative tips.
ReplyDeleteSamsung - 14" Laptop - 4GB Memory - 500GB Hard Drive - Titan Silver