Featured Research

from universities, journals, and other organizations

Link between theta rhythm and ability of animals to track location probed

Date:
April 29, 2011
Source:
Boston University
Summary:
New research supports the hypothesis that spatial coding by grid cells requires theta rhythm oscillations, and dissociates the mechanisms underlying the generation of entorhinal grid cell periodicity and head-direction selectivity.

In a paper published April 29 in the journal Science, a team of Boston University researchers under the direction of Michael Hasselmo, professor of psychology and director of Boston University's Computational Neurophysiology Laboratory, and Mark Brandon, a recent graduate of the Graduate Program for Neuroscience at Boston University, present findings that support the hypothesis that spatial coding by grid cells requires theta rhythm oscillations, and dissociates the mechanisms underlying the generation of entorhinal grid cell periodicity and head-direction selectivity.

Theta Rhythm -- The hippocampal theta rhythm is an oscillation that can be observed in EEG recordings from the hippocampus and other brain structures in numerous species of mammals including rodents, rabbits, dogs, cats, bats, and marsupials. In rats, the most frequently studied species, theta rhythmicity is easily observed in the hippocampus, but can also be detected in numerous other cortical and subcortical brain structures. Hippocampal theta, with a frequency range of 6-10 Hz, appears when a rat is engaged in active motor behavior such as walking or exploratory sniffing, and also during REM sleep. Models have proposed a role for theta rhythm in spatial navigation and episodic memory function.

Grid cells and Self-Localization -- Early studies on navigation revealed that most animals have an exceptional ability to keep track of their location, even in complete darkness. Research now suggests that this ability may involve computations in the entorhinal cortex. Single cell recordings from the entorhinal cortex during navigation have revealed a specific type of neuron that is able to track a rat's position. These cells have been termed 'grid cells' based on the fact that they fire when the rat is at regularly spaced locations in the environment, forming a hexagonal 'grid' in the environment. These cells might allow animals to keep track of their current location.

Computational neuroscientists, including Michael Hasselmo, have demonstrated how these grid cells could generate this regular spatial pattern based on theta oscillations in models. The models proposed that theta oscillations in the entorhinal cortex provide a baseline clocking mechanism. The model requires input from other cells that respond based on the current head direction of the animal or its current running speed. In the model, running speed and head direction inputs modulate the frequency of other oscillators, such that when these oscillations interact to influence the firing of a grid cell, they cause the grid cell to fire systematically dependent on the location of the animal.

Brandon et al., support this theoretical model by demonstrating that grid cells in the entorhinal cortex need the theta rhythm as a clock to help keep track of the animal's location. In the article, "Reduction of Theta Rhythm Dissociates Grid Cell Spatial Periodicity from Directional Tuning," Brandon et al., report that grid cells recorded in the medial entorhinal cortex of freely moving rats exhibit firing at regular spatial locations and temporal modulation with theta rhythm oscillations (4 to 11 hertz). The researchers analyzed grid cell spatial coding during reduction of network theta rhythm oscillations caused by inactivation of the medial septum (MS) with the drug muscimol. During MS inactivation, grid cells lost their spatial periodicity, whereas head-direction cells maintained their direction signal. Conjunctive grid-by-head-direction cells lost grid cell spatial periodicity but retained head-direction specificity. All cells showed reduced rhythmicity in autocorrelations and cross-correlations.

This finding provides experimental support for the role of oscillations in coding spatial location by neural circuits. Consistent with this data, other laboratories have shown that the same manipulation of MS that reduces theta rhythm can severely disrupt the behavioral ability of a rat to remember the location of prior events. The alteration of oscillatory dynamics in the entorhinal cortex could underlie impairments in the ability to remember the spatial location of events in an episode. For example, drugs that cause amnesia may do so through an influence on theta rhythm oscillations, and a change in oscillations could contribute to the influence of Alzheimer's disease on the formation of new memories.


Story Source:

The above story is based on materials provided by Boston University. Note: Materials may be edited for content and length.


Journal Reference:

  1. M. P. Brandon, A. R. Bogaard, C. P. Libby, M. A. Connerney, K. Gupta, M. E. Hasselmo. Reduction of Theta Rhythm Dissociates Grid Cell Spatial Periodicity from Directional Tuning. Science, 2011; 332 (6029): 595 DOI: 10.1126/science.1201652

Cite This Page:

Boston University. "Link between theta rhythm and ability of animals to track location probed." ScienceDaily. ScienceDaily, 29 April 2011. <www.sciencedaily.com/releases/2011/04/110428143153.htm>.
Boston University. (2011, April 29). Link between theta rhythm and ability of animals to track location probed. ScienceDaily. Retrieved October 21, 2014 from www.sciencedaily.com/releases/2011/04/110428143153.htm
Boston University. "Link between theta rhythm and ability of animals to track location probed." ScienceDaily. www.sciencedaily.com/releases/2011/04/110428143153.htm (accessed October 21, 2014).

Share This



More Plants & Animals News

Tuesday, October 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

'Cadaver Dog' Sniffs out Human Remains

'Cadaver Dog' Sniffs out Human Remains

AP (Oct. 21, 2014) Where's a body buried? Buster's nose can often tell you. He's a cadaver dog, specially trained to find human remains and increasingly being used by law enforcement and accepted in courts. These dogs are helping solve even decades-old mysteries. (Oct. 21) Video provided by AP
Powered by NewsLook.com
White Lion Cubs Born in Belgrade Zoo

White Lion Cubs Born in Belgrade Zoo

AFP (Oct. 20, 2014) Two white lion cubs, an extremely rare subspecies of the African lion, were recently born at Belgrade Zoo. They are being bottle fed by zoo keepers after they were rejected by their mother after birth. Duration: 00:42 Video provided by AFP
Powered by NewsLook.com
Traditional Farming Methods Gaining Ground in Mali

Traditional Farming Methods Gaining Ground in Mali

AFP (Oct. 20, 2014) He is leading a one man agricultural revolution in Mali - Oumar Diatabe uses traditional farming methods to get the most out of his land and is teaching others across the country how to do the same. Duration: 01:44 Video provided by AFP
Powered by NewsLook.com
Goliath Spider Will Give You Nightmares

Goliath Spider Will Give You Nightmares

Buzz60 (Oct. 20, 2014) An entomologist stumbled upon a South American Goliath Birdeater. With a name like that, you know it's a terrifying creepy crawler. Sean Dowling (@SeanDowlingTV) has the details. Video provided by Buzz60
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins