thalamus

Home > ... > Medicine > Anatomy and Physiology > Anatomy and Physiology > ...

thalamus

The Columbia Encyclopedia, Sixth Edition | 2008 | The Columbia Encyclopedia, Sixth Edition. Copyright 2008 Columbia University Press. (Hide copyright information) Copyright

thalamus , mass of nerve cells centrally located in the brain just below the cerebrum and resembling a large egg in size and shape. The thalamus is a routing station for all incoming sensory impulses except those of smell, transmitting them to higher (cerebral) nerve centers. In addition, it connects various brain centers with others. Thus the thalamus is a major integrative complex, enabling sensory stimuli to evoke appropriate physical reactions as well as to affect emotions. With the hypothalamus , the thalamus establishes levels of sleep and wakefulness. It is also vital to the neural feedback system controlling brain wave rhythms.

Hide all research tools
Print this article Print all entries for this topic Cite this article Link to this article
Link to this article

CloseClose

Create a link to this page

Copy and paste this link tag into your Web page or blog:

<a href="http://www.encyclopedia.com/topic/.aspx#1E1-thalamus" title="Facts and information about thalamus">thalamus</a>

Add this article to Del.icio.usBookmark this article on DiigoShare this article on FacebookSubmit this article to RedditGive this article a thumbs-up on StumbleUpon
Show all research tools

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"thalamus." The Columbia Encyclopedia, Sixth Edition. 2008. Encyclopedia.com. 28 Nov. 2009 <http://www.encyclopedia.com>.

"thalamus." The Columbia Encyclopedia, Sixth Edition. 2008. Encyclopedia.com. (November 28, 2009). http://www.encyclopedia.com/doc/1E1-thalamus.html

"thalamus." The Columbia Encyclopedia, Sixth Edition. 2008. Retrieved November 28, 2009 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-thalamus.html

Learn more about citation styles

thalamus

The Oxford Companion to the Body | 2001 | | © The Oxford Companion to the Body 2001, originally published by Oxford University Press 2001. (Hide copyright information) Copyright

thalamus The cerebral hemispheres of the brain consist of an outer layer of grey matter called cerebral cortex, with a core of white matter, surrounding masses of grey matter. The thalamus (of which there is one on each side) is a large and important mass of nerve cells or neurons. All sensory pathways (from eyes, ears, skin, etc.), except some of those concerned with the sense of smell, pass through the thalamus on their way to the cerebral cortex. The incoming fibres from each sensory system terminate on a dense clump of nerve cells called a nucleus, or on a set of such nuclei. In turn, the fibres of the cells in each thalamic nucleus run up to a particular area (or areas) of the cerebral cortex. Important pathways concerned with the control of movement, from the cerebellum and from motor nuclei called the basal ganglia, also pass through the thalamus. But the thalamus is more than merely a relay station.

Each thalamus is a large, bullet-shaped mass, consisting of a number of closely-packed nuclei. The two lie side by side, roughly in the middle of the entire brain, forming the walls of the central fluid-filled cerebral ventricle called the third ventricle. And above each thalamus is the lateral ventricle, within the cerebral hemisphere. In some individuals they are joined by a bridge of grey matter, the massa intermedia, stretching across the third ventricle. Below and in front of each thalamus is the hypothalamus, and to the side of each is the internal capsule – the important band of white matter containing the fibres of thalamic nerve cells, passing to the cerebral cortex above, together with fibres from the cortex running down. The thalamus is split into three major parts, lateral, medial and anterior, by a thin, Y-shaped fibrous sheet (see figure), containing so-called ‘non-specific’ nuclei (see below).

‘Specific’ thalamic nuclei

The lower part of the lateral thalamus contains large and very important nuclei, called specific nuclei, which relay sensory information to primary areas of the cerebral cortex. For instance, the ventral posterior nucleus (VP) is the main relay for information from the skin and deep tissues of the body, passing it up to the somatic sensory area of the cortex. The ventral anterior and ventral lateral nuclei receive fibres from, respectively, the corpus striatum (part of the basal ganglia) and the cerebellum, and they send fibres to parts of the frontal lobe of the cortex that are concerned with motor control. At the rear end of the thalamus are the smaller medial and lateral geniculate nuclei, relaying auditory and visual pathways, respectively, to the auditory and visual areas of the cortex.

In the major sensory nuclei of the thalamus, incoming fibres are generally distributed in strict topographic order and they therefore form ‘maps’ of the array of sensory receptors from which they derive. For instance, the opposite half of the body is represented within each VP. Fibres ascending from the spinal cord reach the lateral part, carrying signals from the main part of body, while the medial part receives input from the face and head via the fifth cranial nerve, the trigeminal nerve. This spatial arrangement is conserved as the fibres of cells in the VP run up, so that the input from the whole body is draped, upside down, over the somatic sensory cortex (which occupies a strip running vertically down the middle of the side of each hemisphere).

The nuclei of the upper part of the lateral thalamus send their fibres to regions of the cortex other than the primary sensory and motor areas. The lateral posterior nucleus and pulvinar are large structures, which send fibres to regions of the parietal and occipital lobes that are concerned with visual understanding and the integration of sensory information. The lateral dorsal nucleus receives fibres from the hippocampus and sends its axons to regions of limbic cortex on the inner surface of the hemisphere.

The medial thalamus consists essentially of the mediodorsal nucleus, which relays signals from hypothalamus and amygdala to the frontal lobe and also to the corpus striatum.

The anterior thalamus contains the anterior nucleus, which receives input from the mamillary body of the hypothalamus and sends fibres to a region called the cingulate cortex, on the midline surface of the hemisphere. All these structures are parts of the limbic system, which is concerned with the regulation of vital rhythms, emotions, appetites, and memory.

The cerebral cortex and the thalamus have evolved in parallel during mammalian evolution, and they constitute an intimately related functional system. Perhaps the most intriguing and least-understood feature of the thalamus is the fact that each specific nucleus receives at least as many fibres from its region of cerebral cortex as it sends fibres to that region. Thus thalamus and cortex are reciprocally interconnected, with some sort of recursive interplay occurring between them. Some argue that the thalamus acts not just to relay signals to the cerebral cortex, but as a dynamic conduit of information between one cortical area and another, regulating the flow of information according to attention and intention.

‘Non-specific’ thalamic nuclei

In between the specific sensory and motor relay nuclei of the thalamus is a system of smaller, more diffuse ‘non-specific’ nuclei, which are organized quite differently. They receive ascending fibres from the reticular formation, which stretches through the core of the brainstem and itself receives and integrates input from the sensory pathways. In turn, the non-specific nuclei of the thalamus send their fibres diffusely over the cerebral hemispheres, rather than to distinct areas. This pathway, from reticular formation to non-specific nuclei to the cortex, which is called the ascending reticular activating system, is thought to be involved in regulating the state of ‘arousal’ of the cortex during the cycle of sleeping and waking.

Laurence J. Garey, and Colin Blakemore


See also brain; cerebral cortex; hearing; somatic sensation; sleep; vision.
Hide all research tools
Print this article Print all entries for this topic Cite this article Link to this article
Link to this article

CloseClose

Create a link to this page

Copy and paste this link tag into your Web page or blog:

<a href="http://www.encyclopedia.com/topic/.aspx#1O128-thalamus" title="Facts and information about thalamus">thalamus</a>

Add this article to Del.icio.usBookmark this article on DiigoShare this article on FacebookSubmit this article to RedditGive this article a thumbs-up on StumbleUpon
Show all research tools

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

COLIN BLAKEMORE and SHELIA JENNETT. "thalamus." The Oxford Companion to the Body. Oxford University Press. 2001. Encyclopedia.com. 28 Nov. 2009 <http://www.encyclopedia.com>.

COLIN BLAKEMORE and SHELIA JENNETT. "thalamus." The Oxford Companion to the Body. Oxford University Press. 2001. Encyclopedia.com. (November 28, 2009). http://www.encyclopedia.com/doc/1O128-thalamus.html

COLIN BLAKEMORE and SHELIA JENNETT. "thalamus." The Oxford Companion to the Body. Oxford University Press. 2001. Retrieved November 28, 2009 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O128-thalamus.html

Learn more about citation styles

thalamus

World Encyclopedia | 2005 | © World Encyclopedia 2005, originally published by Oxford University Press 2005. (Hide copyright information) Copyright

thalamus One of two ovoid masses of grey matter located deep on each side of the forebrain. Sometimes called the sensory-motor receiving areas, they fulfil relay and integration functions in respect of sensory messages reaching the brain.

Hide all research tools
Print this article Print all entries for this topic Cite this article Link to this article
Link to this article

CloseClose

Create a link to this page

Copy and paste this link tag into your Web page or blog:

<a href="http://www.encyclopedia.com/topic/.aspx#1O142-thalamus" title="Facts and information about thalamus">thalamus</a>

Add this article to Del.icio.usBookmark this article on DiigoShare this article on FacebookSubmit this article to RedditGive this article a thumbs-up on StumbleUpon
Show all research tools

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"thalamus." World Encyclopedia. 2005. Encyclopedia.com. 28 Nov. 2009 <http://www.encyclopedia.com>.

"thalamus." World Encyclopedia. 2005. Encyclopedia.com. (November 28, 2009). http://www.encyclopedia.com/doc/1O142-thalamus.html

"thalamus." World Encyclopedia. 2005. Retrieved November 28, 2009 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-thalamus.html

Learn more about citation styles

Facts and information from other sites

Related topics

  Edit this list

Related articles from newspapers, magazines, and more

Thalamus segmentation from diffusion tensor magnetic resonance imaging.(Research Article)(Report)
Magazine article from: International Journal of Biomedical Imaging; 1/1/2007; ; 700+ words ; We propose a semi-automatic thalamus and thalamus nuclei segmentation algorithm from diffusion tensor magnetic...based on the mean-shift algorithm. Comparing with existing thalamus segmentation algorithms which are mainly based on K-means...
Thalamus Networks' Semi-annual Report January 1 - June 30, 2001.
Business Wire; 8/14/2001; 602 words ; ...Aug. 14, 2001 Net sales rose for Thalamus Networks (OMX:THALb.), from SEK...Power utility Bjare Kraft selected Thalamus as their supplier and operator, an agreement...offer interesting business opportunities Thalamus price strategy has always been to avoid...
Thalamus Releases New Broadband Services.
Business Wire; 9/18/2001; 587 words ; ...Sept. 18, 2001 During the fall, Thalamus Networks (OMX:THALb.) releases brand...and a variety of add-on services. Thalamus is the only company in Sweden that can...Thomas Rebermark, Marketing Manager of Thalamus Networks. "For example, a lot of users...
The Thalamus
Magazine article from: Clinical EEG and Neuroscience; 1/1/2008; ; 476 words ; The Thalamus Second Edition. Edited by: Edward G. Jones...set Hardcover, 1679 pages, $480.00 "The Thalamus" is a comprehensive compendium of known neurobiology of the thalamus. It is essential for any researcher with a focus...
Changes in regional cerebral blood flow in the thalamus after electroconvulsive therapy for patients with complex regional pain syndrome type 1 (preliminary case series)
Magazine article from: Regional Anesthesia and Pain Medicine; 9/1/2002; ; 700+ words ; ...electroconvulsive therapy (ECT) in the thalamus are related to the efficacy of ECT...significant changes in the rCBF of the thalamus using technetium-99m ethyl cysteinate...SPECT showed that the mean contralateral thalamus-tocerebellum ratio increased 11.5...
Swedish IT consultant Thalamus Networks AB makes bid for project management group HifabGruppen AB.
Newspaper article from: Nordic Business Report; 5/23/2008; 577 words ; ...23 May 2008-Swedish IT consultant Thalamus Networks AB makes bid for project management...www.m2.com Swedish IT consultant Thalamus Networks AB (OMX Stockholm: THAL B...management group HifabGruppen AB (Hifab). Thalamus Networks is prepared to pay SEK19.50...
Internet Services From Thalamus and Gothnet Released to Real Estate Company Alebyggen.
Business Wire; 11/14/2001; 527 words ; ...BUSINESS WIRE)--Nov. 14, 2001 Thalamus Networks' partnership with Gothnet has...Gothnet," says Jan Tidelius, CEO of Thalamus Networks. "It's a good example of...and the possibility to choose between Thalamus' variety of services and add-ons...
Imaging clues to schizophrenia. (MRI images of the thalamus show differences between schizophrenic and normal men) (Brief Article)
Magazine article from: Science News; 10/29/1994; 700+ words ; ...may spring from abnormalities in the thalamus and areas throughout the brain with anatomical...structure. Prior evidence suggests that the thalamus -- located deep within the brain...types of information. Troubles in the thalamus and its related structures, which extend...
Thalamus Networks AB signs letter of intent for broadband services with Swedish municipality.(Brief Article)
Newspaper article from: Nordic Business Report; 1/22/2003; 632 words ; ...NORDIC BUSINESS REPORT-22 January 2003-Thalamus Networks AB signs letter of intent for...The Swedish broadband services provider Thalamus Networks AB said today (22 January...Kumla Bostader AB. Under the agreement Thalamus Networks and the municipality would cooperate...
Thalamus Networks AB signs Internet access agreement with Eslovs bostad AB.(Brief Article)
Newspaper article from: Nordic Business Report; 5/2/2002; 535 words ; NORDIC BUSINESS REPORT-2 May 2002-Thalamus Networks AB signs Internet access agreement...The Swedish broadband services provider Thalamus Networks AB said today (2 May) that its unit Thalamus Operations had received a three-year contract...
Click to see an enlarged picture
thalamus. (Image by John A Beal, CC)

For students and teachers!

Encyclopedia.com provides students and teachers facts, information, and biographies from verified, citable sources, including:

Encyclopedia.com provides students and teachers facts, information, and biographies from verified, citable sources, including:

Current thalamus News: