A large ovoid mass of gray matter that forms the larger dorsal subdivision of the diencephalon and is located medial to the internal capsule and to the body and tail of the caudate nucleus. It functions in the relay of sensory impulses to the cerebral cortex.1
Did you get all that?
Thalamus, from the Greek thalámos — bedroom.
The brain's hub.
The two thalami are buried side by side at the center of the brain. They're about a centimeter across and together are shaped like an egg: ovoid. They're each bordered on top by half of the cerebrum, and are separated in the middle by the diencephalon emerging from the prosencephalon, a part of the mammalian brain. Below you'll find the third ventricle, home of the cerebellum and stem — our First Brain.
Axons from every sensory system except smell synapse at the thalamus, where they're relayed to corresponding regions of the cerebrum.
Thank thalamus for sunsets.
Currently, thalamic nuclei are classified as either "relay" or "association," depending on where the signals come from. Relays are driven by subcortical signals (like the optic tract); associates are driven by supercortical signals (from the cerebral cortex — more on this in a bit). Because the thalamus is the way point for sensory information, it's also responsible for discriminative sensory-motor functions. Movement based on perception.
New research shows that the thalamus is more than just a last pit stop for cortex-bound information; it passes information both to and from the cortex. Find a picture of a tree: you remember the oak in your backyard with the tire swing. Say the phrase "Steven Spielberg" — medical white sheets and a puckery-looking alien. By the give-and-take relationship with the cerebral cortex, the thalamus matches information gathered by the senses to knowledge contained in memory to form associations. This mechanism is in three "circuits" passing through the thalamus' center:
- The specific nuclei scans the cerebral cortex for active neurons, drawing up a "map" of active groups.
- The reticular formation makes informed guesses about the information gleaned from the cortical map based on a process of comparison and selection.
- The Intralaminar searches memory for possible associations, providing context to perception.
See hubcaps and the spokes make you think of snowflakes; think of snowflakes and remember lace; remember lace and remember paper doylies and grandmothers singing in the kitchen.
Thank thalamus for grandmothers singing in the kitchen.
1"Thalamus," Answers.com: http://www.answers.com/topic/thalamus
Sources
University of Idaho
http://www.sci.uidaho.edu/med532/thalamus.htm
Eberhard, John. "Architecture and the Mind."
http://www.architecture-mind.com/thalamus.htm
Wikipedia
http://en.wikipedia.org/wiki/Thalamus
University of Buffalo
http://serous.med.buffalo.edu/hearing/thalamus.html
About.com
http://biology.about.com/library/organs/brain/blthalamus.htm