Primates' brains make visual maps using triangular grids
Primates' brains see the world through triangular grids, according to a new study published online Sunday in the journal Nature.
Scientists at Yerkes National Primate Research Center, Emory University, have identified grid cells, neurons that fire in repeating triangular patterns as the eyes explore visual scenes, in the brains of rhesus monkeys.
The finding has implications for understanding how humans form and remember mental maps of the world, as well as how neurodegenerative diseases such as Alzheimer's erode those abilities. This is the first time grid cells have been detected directly in primates. Grid cells were identified in rats in 2005, and their existence in humans has been indirectly inferred through magnetic resonance imaging.
Grid cells' electrical activities were recorded by introducing electrodes into monkeys' entorhinal cortex, a region of the brain in the medial temporal lobe. At the same time, the monkeys viewed a variety of images on a computer screen and explored those images with their eyes. Infrared eye-tracking allowed the scientists to follow which part of the image the monkey's eyes were focusing on. A single grid cell fires when the eyes focus on multiple discrete locations forming a grid pattern.
"The entorhinal cortex is one of the first brain regions to degenerate in Alzheimer's disease, so our results may help to explain why disorientation is one of the first behavioral signs of Alzheimer's," says senior author Elizabeth Buffalo, PhD, associate professor of neurology at Emory University School of Medicine and Yerkes National Primate Research Center. "We think these neurons help provide a context or structure for visual experiences to be stored in memory."
"Our discovery of grid cells in primates is a big step toward understanding how our brains form memories of visual information," says first author Nathan Killian, a graduate student in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. "This is an exciting way of thinking about memory that may lead to novel treatments for neurodegenerative diseases."
In the experiments in which rats' grid cells were identified, the cells fired whenever the rats crossed lines on an invisible triangular grid.
"The surprising thing was that we could identify cells that behaved in the same way when the monkeys were simply moving their eyes," Buffalo says. "It suggests that primates don't have to actually visit a place to construct the same kind of mental map."
Another aspect of grid cells not previously seen with rodents is that the cells' responses change when monkeys are seeing an image for the second time. Specifically, the grid cells reduce their firing rate when a repeat image is seen. Moving from the posterior (rear) toward the anterior (front) of the entorhinal cortex, more neurons show memory responses.
"These results demonstrate that grid cells are involved in memory, not just mapping the visual field," Killian says.
Consistent with previous reports on grid cells in rats, Killian and Buffalo observed "theta-band" oscillations, where grid cells fire in a rhythmic way, from 3 to 12 times per second. Some scientists have proposed that theta oscillations are important for grid cell networks to be generated in development, and also for the brain to put together information from the grid cells. In the monkeys, populations of neurons exhibited theta oscillations that occurred in intermittent bouts, but these bouts did not appear to be critical for formation of the spatial representation.
Vision is thought to be a more prominent sense for primates (monkeys and humans) compared with rodents, for whom touch and smell are more important. While grid cells in rodents and primates were detected in different types of experiments, Buffalo says that it doesn't mean grid cells necessarily have a different nature in primates.
"We are now training a monkey to move through a virtual 3-D space. My guess is that we'll find grid cells that fire in similar patterns as the monkey navigates through that space," she says.
Buffalo says future experiments could examine how monkeys navigate in real space, including changes in head or body orientation, to determine how grid cells respond.
Journal reference: Nature
Provided by Emory University
- The human brain uses a grid to represent space Jan 20, 2010 | not rated yet | 0
- Better understanding of mapmaking in the brain Aug 09, 2010 | not rated yet | 0
- Researchers probe link between theta rhythm, ability of animals to track location Apr 28, 2011 | not rated yet | 0
- Electrical oscillations critical for storing spatial memories in brain: study Apr 28, 2011 | not rated yet | 0
- Understanding how our brain perceives space May 28, 2012 | not rated yet | 0
- Motion perception revisited: High Phi effect challenges established motion perception assumptions Apr 23, 2013 | 3 / 5 (2) | 2
- Anything you can do I can do better: Neuromolecular foundations of the superiority illusion (Update) Apr 02, 2013 | 4.5 / 5 (11) | 5
- The visual system as economist: Neural resource allocation in visual adaptation Mar 30, 2013 | 5 / 5 (2) | 9
- Separate lives: Neuronal and organismal lifespans decoupled Mar 27, 2013 | 4.9 / 5 (8) | 0
- Sizing things up: The evolutionary neurobiology of scale invariance Feb 28, 2013 | 4.8 / 5 (10) | 14
Pressure-volume curve: Elastic Recoil Pressure don't make sense
May 18, 2013 From pressure-volume curve of the lung and chest wall (attached photo), I don't understand why would the elastic recoil pressure of the lung is...
If you became brain-dead, would you want them to pull the plug?
May 17, 2013 I'd want the rest of me to stay alive. Sure it's a lousy way to live but it beats being all-the-way dead. Maybe if I make it 20 years they'll...
MRI bill question
May 15, 2013 Dear PFers, The hospital gave us a $12k bill for one MRI (head with contrast). The people I talked to at the hospital tell me that they do not...
Ratio of Hydrogen of Oxygen in Dessicated Animal Protein
May 13, 2013 As an experiment, for the past few months I've been consuming at least one portion of Jell-O or unflavored Knox gelatin per day. I'm 64, in very...
Alcohol and acetaminophen
May 13, 2013 Edit: sorry for the typo in the title , can't edit I looked around on google quite a bit and it's very hard to find precise information on the...
Marie Curie's leukemia
May 13, 2013 Does anyone know what might be the cause of Marie Curie's cancer
- More from Physics Forums - Medical Sciences
More news stories
For combat veterans suffering from post-traumatic stress disorder, 'fear circuitry' in the brain never rests
Chronic trauma can inflict lasting damage to brain regions associated with fear and anxiety. Previous imaging studies of people with post-traumatic stress disorder, or PTSD, have shown that these brain regions can over-or ...
Neuroscience May 18, 2013 | 5 / 5 (1) | 0 |
The neural machinery underlying our olfactory sense continues to be an enigma for neuroscience. A recent review in Neuron seeks to expand traditional ideas about how neurons in the olfactory bulb might encode information about ...
Neuroscience May 17, 2013 | not rated yet | 0 |
(Medical Xpress)—What if the quality of your work depends more on your focus on the piano keys or canvas or laptop than your musical or painting or computing skills? If target users can be convinced, they ...
Neuroscience May 17, 2013 | 3.7 / 5 (3) | 0 |
Neurological disorders can have a devastating impact on the lives of sufferers and their families.
Neuroscience May 17, 2013 | 5 / 5 (1) | 0 |
If you're a left-brain thinker, chances are you use your right hand to hold your cell phone up to your right ear, according to a newly published study from Henry Ford Hospital in Detroit.
Neuroscience May 16, 2013 | 2 / 5 (2) | 0 |
Patients with treatment-resistant major depression saw dramatic improvement in their illness after treatment with ketamine, an anesthetic, according to the largest ketamine clinical trial to-date led by researchers from the ...
3 hours ago | 4.5 / 5 (2) | 0 |
Regular consumption of coffee is associated with a reduced risk of primary sclerosing cholangitis (PSC), an autoimmune liver disease, Mayo Clinic research shows. The findings were being presented at the Digestive Disease ...
3 hours ago | not rated yet | 0 |
Research presented at Digestive Disease Week (DDW) explores new methods for managing digestive health through diet and lifestyle.
3 hours ago | not rated yet | 0
The use of a smartphone application significantly improves patients' preparation for a colonoscopy, according to new research presented today at Digestive Disease Week (DDW). The preparation process, which begins days in ...
2 hours ago | not rated yet | 0
An increasing number of U.S. children are experiencing gastrointestinal issues that require interventions to resolve, according to research presented at Digestive Disease Week (DDW).
17 hours ago | not rated yet | 0 |
There are significant cost and risk factors associated with two procedures commonly used to diagnose or treat gastrointestinal problems, according to research presented at Digestive Disease Week (DDW).
2 hours ago | not rated yet | 0