{"165731":{"#nid":"165731","#data":{"type":"news","title":"Primates\u2019 Brains Make Visual Maps Using Triangular Grids, Study Shows","body":[{"value":"\u003Cp\u003EPrimates\u2019 brains see the world through triangular grids, according to a new study published online October 28 in the journal \u003Cem\u003ENature\u003C\/em\u003E.\u003C\/p\u003E\u003Cp\u003EScientists 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.\u003C\/p\u003E\u003Cp\u003EThe finding has implications for understanding how humans form and remember mental maps of the world, as well as how neurodegenerative diseases such as Alzheimer\u2019s 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.\u003C\/p\u003E\u003Cp\u003EGrid cells\u2019 electrical activities were recorded by introducing electrodes into monkeys\u2019 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\u2019s eyes were focusing on. A single grid cell fires when the eyes focus on multiple discrete locations forming a grid pattern.\u003C\/p\u003E\u003Cp\u003E\u201cThe entorhinal cortex is one of the first brain regions to degenerate in Alzheimer\u2019s disease, so our results may help to explain why disorientation is one of the first behavioral signs of Alzheimer\u2019s,\u201d said senior author Elizabeth Buffalo, PhD, associate professor of neurology at Emory University School of Medicine and Yerkes National Primate Research Center. \u201cWe think these neurons help provide a context or structure for visual experiences to be stored in memory.\u201d\u003C\/p\u003E\u003Cp\u003E\u201cOur discovery of grid cells in primates is a big step toward understanding how our brains form memories of visual information,\u201d said first author Nathan Killian, a graduate student in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. \u201cThis is an exciting way of thinking about memory that may lead to novel treatments for neurodegenerative diseases.\u201d\u003C\/p\u003E\u003Cp\u003EIn the experiments in which rats\u2019 grid cells were identified, the cells fired whenever the rats crossed lines on an invisible triangular grid.\u003C\/p\u003E\u003Cp\u003E\u201cThe surprising thing was that we could identify cells that behaved in the same way when the monkeys were simply moving their eyes,\u201d Buffalo said. \u201cIt suggests that primates don\u2019t have to actually visit a place to construct the same kind of mental map.\u201d\u003C\/p\u003E\u003Cp\u003EAnother aspect of grid cells not previously seen with rodents is that the cells\u2019 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.\u003C\/p\u003E\u003Cp\u003E\u201cThese results demonstrate that grid cells are involved in memory, not just mapping the visual field,\u201d Killian said.\u003C\/p\u003E\u003Cp\u003EConsistent with previous reports on grid cells in rats, Killian and Buffalo observed \u201ctheta-band\u201d 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.\u003C\/p\u003E\u003Cp\u003EVision 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\u2019t mean grid cells necessarily have a different nature in primates.\u003C\/p\u003E\u003Cp\u003E\u201cWe are now training a monkey to move through a virtual 3-D space. My guess is that we\u2019ll find grid cells that fire in similar patterns as the monkey navigates through that space,\u201d she said.\u003C\/p\u003E\u003Cp\u003EBuffalo says future experiments could examine how monkeys navigate in real space, including changes in head or body orientation, to determine how grid cells respond.\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThe research was supported by the National Institute of Mental Health (R01MH093807, R01MH080007, MH082559) and the NIH Director\u2019s Office of Research Infrastructure Programs (P51OD11132).\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003EReference:N.J. Killian, M.J. Jutras, and E.A. Buffalo. A map of visual space in the primate entorhinal cortex. Nature (2012).\u003C\/p\u003E\u003Cp\u003EMedia contact: Lisa Newbern, \u003Ca href=\u0022mailto:lisa.newbern@emory.edu\u0022\u003Elisa.newbern@emory.edu\u003C\/a\u003E, 404-727-7709.\u003C\/p\u003E\u003Cp\u003EWriter: Quinn Eastman\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EPrimates\u2019 brains see the world through triangular grids, according to a new study published online October 28 in the journal \u003Cem\u003ENature\u003C\/em\u003E.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Primates\u0027 brains see the world through triangular grids, a new study shows."}],"uid":"27303","created_gmt":"2012-10-28 20:19:23","changed_gmt":"2016-10-08 03:13:02","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2012-10-28T00:00:00-04:00","iso_date":"2012-10-28T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"165721":{"id":"165721","type":"image","title":"Grid cell firing pattern","body":null,"created":"1449178936","gmt_created":"2015-12-03 21:42:16","changed":"1475894804","gmt_changed":"2016-10-08 02:46:44","alt":"Grid cell firing pattern","file":{"fid":"195554","name":"triangular-grids.jpg","image_path":"\/sites\/default\/files\/images\/triangular-grids_0.jpg","image_full_path":"http:\/\/tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/triangular-grids_0.jpg","mime":"image\/jpeg","size":109343,"path_740":"http:\/\/tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/triangular-grids_0.jpg?itok=9w5dZAnt"}}},"media_ids":["165721"],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"135","name":"Research"}],"keywords":[{"id":"1912","name":"brain"},{"id":"47971","name":"entorhinal cortex"},{"id":"47941","name":"grid cell"},{"id":"47951","name":"neurodegenerative"},{"id":"7276","name":"neuron"},{"id":"820","name":"vision"}],"core_research_areas":[{"id":"39441","name":"Bioengineering and Bioscience"}],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003ELisa Newbern\u003C\/p\u003E\u003Cp\u003EEmory University\u003C\/p\u003E\u003Cp\u003E(404) 727-7709\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022mailto:lisa.newbern@emory.edu\u0022\u003Elisa.newbern@emory.edu\u003C\/a\u003E\u003C\/p\u003E","format":"limited_html"}],"email":["lisa.newbern@emory.edu"],"slides":[],"orientation":[],"userdata":""}}}