The thalamus fuctions as the way station for information passing throughout the brain. It also is an important site of decisional information regarding what information should continue for further processing.
Specific inputs enter the various thalamic nuclei. Regulatory inputs arise from innervated cortical areas, as well as diffuse cholinergic, noradrenergic, and serotonergic signals from the reticular formation. These regulatory inputs outnumber the specific inputs in most cases.
Virtually all sensory information passes through the thalamus (except olfaction) en route to the sensory cortex. The thalamus and acortex are connected by fibres running both ways within the internal capsule, which spans the striatum of the basal ganglia.
The ventral posterior and geniculate bodies are termed sensory nuclei.
The thalamus is thought to be especially important for perception of pain.
Motor information, including from the cerebellum, the subthalamus, and the basal ganglia, is referred to the thalamus before sending it to the motor cortex.
The thalamus conveys information from the cerebellum and globus pallidus to the motor cortex.
The ventral anterior and ventral lateral nuclei are termed motor nuclei.
Information pertaining to mood and cognitive function also passes through the thalamus.
Along with the subthalamus, it receives projections from the basal ganglia important for motor function.
The pontocerebellum also provides thalamic input to regulate motor control.
The thalamus is a big, oval collection of nuclei separated into two. The halves are separated by the narrow third ventricle.
Thalamic nuclei can be grouped into three regions - anterior, medial, and lateral nuclear groups. The internal medullary lamina subdivides the three regions.
The lateral group composes most of the thalamus and can be further divided into the dorsal and ventral tiers.
intralaminar thalamic nucleus
Thalamic neurons can be in two physiologic states, detemined by regulatory state.
Tonic mode exists when neurons are slightly depolarized, with slight additional depolarization causing a trian of aciton potentials.
Burst mode occurs when neurons are hyperpolarized. SLight depolarization opens voltage-gated Calcium channels, resulting in a few action potentials.
tends to calcify with age; normally midline; deviation is useful during imaging
The thalamus is supplied by small branches from the posterior cerebral artery, and infarcts can be far-reaching. Effects include: