Published online by Cambridge University Press: 25 August 2009
The thalamus functions as the principal relay station for sensory information destined for the cerebral cortex. It is made up of a number of nuclei, which can be grouped into relay nuclei and diffuse-projection nuclei (Table 9.1). Each relay nucleus is associated with a single sensory modality or motor system and projects to a specific region of the cerebral cortex with which it has reciprocal connections. The diffuse-projection group of nuclei have more widespread connections with the cortex and also interact with other thalamic nuclei. It is believed that this group of nuclei is involved with regulating the level of arousal of the brain. The limbic thalamus consists of a number of the thalamic nuclei that project to the limbic cortex and includes both relay and diffuse-projection nuclei.
Anatomy and behavioral considerations
The thalamus consists of a symmetrical pair of ovoid structures located above (dorsal to) the hypothalamus. The left thalamus and right thalamus are separated medially by the third ventricle and bounded laterally by the posterior limb of the internal capsule (Figures 9.1–9.3). The massa intermedia (interthalamic adhesion) is a bridge of cells that spans the third ventricle and joins the left with the right thalamus. The thalamus is bounded in front (anteriorly) by the head of the caudate nucleus and the genu of the internal capsule and behind (posteriorly) by the midbrain. The subthalamic nucleus (subthalamus) lies immediately below (ventral to) the thalamus and is sandwiched between the thalamus, internal capsule, and pretectal area (Figures 9.2 and 9.3).
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