Definitions from


Most textbooks will tell you that the thalamus is a "relay" that simply relays signals from auditory, somatic, visceral and visual regions of the peripheral nervous system to the cerebral cortex. The real picture is more complicated, and the commonly accepted function of the thalamus nowadays is that it modulates, in addition to relaying, sensory signals to and from cortex.

It is common to classify thalamic nuclei as either "relay nuclei" or "association nuclei" on the basis of the source of their driving inputs, whether they are subcortical or cortical. Relay nuclei receive their driving inputs from subcortical sources including ascending afferents (medial lemniscus for somatosensory information, optic tract for visual information, etc...) and project predominantly to primary sensory cortical areas. On the other hand, association nuclei receive their driving inputs from other cortical areas. (See Sherman and Guillery's "Exploring the Thalamus", 2002)

All text on this page only - is available under the terms of the GNU Free Documentation License (see Copyrights for details). Disclaimers.".

Learn more about indoor environmental quality.