Medial Dorsal Nucleus
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The medial dorsal nucleus (or mediodorsal nucleus of thalamus, dorsomedial nucleus, dorsal medial nucleus, or medial nucleus group) is a large nucleus in the
thalamus The thalamus (: thalami; from Greek language, Greek Wikt:θάλαμος, θάλαμος, "chamber") is a large mass of gray matter on the lateral wall of the third ventricle forming the wikt:dorsal, dorsal part of the diencephalon (a division of ...
. It is separated from the other thalamic nuclei by the internal medullary lamina. The medial dorsal nucleus is interconnected with the
prefrontal cortex In mammalian brain anatomy, the prefrontal cortex (PFC) covers the front part of the frontal lobe of the cerebral cortex. It is the association cortex in the frontal lobe. The PFC contains the Brodmann areas BA8, BA9, BA10, BA11, BA12, ...
, therefore involved in prefrontal functions. Damage to the interconnected tract or the nucleus itself will result in similar damage to the prefrontal cortex. It is also believed to play a role in
memory Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembe ...
.


Structure

The medial dorsal nucleus relays inputs from the
amygdala The amygdala (; : amygdalae or amygdalas; also '; Latin from Greek language, Greek, , ', 'almond', 'tonsil') is a paired nucleus (neuroanatomy), nuclear complex present in the Cerebral hemisphere, cerebral hemispheres of vertebrates. It is c ...
and olfactory cortex and projects to the prefrontal cortex and the limbic system, and in turn relays them to the prefrontal association cortex. As a result, it plays a crucial role in attention, planning, organization, abstract thinking, multi-tasking, and active memory. The connections of the medial dorsal nucleus have even been used to delineate the prefrontal cortex of the Göttingen minipig brain. By stereology the number of brain cells in the region has been estimated at around 6.43 million
neuron A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...
s in the adult human brain and 36.3 million glial cells, with the newborn having quite different numbers: around 11.2 million neurons and 10.6 million glial cells.


Parts of nucleus

The medial dorsal nucleus has four parts. # paralaminar part of the medial dorsal nucleus # magnocellular part of the medial dorsal nucleus # parvicellular/parvocellular part of the medial dorsal nucleus # densocellular part of the medial dorsal nucleus


Function


Pain processing

While both the ventral and medial dorsal nuclei process pain, the medial dorsal nucleus bypasses primary cortices, sending their axons directly to secondary and association cortices. The cells also send axons directly to many parts of the brain, including nuclei of the limbic system such as the lateral nucleus of the amygdala, the anterior cingulate, and the hippocampus. This part of the sensory system, known as the non-classical or extralemniscal system is less accurate, and less detailed in regards to sensory signal analysis. This processing is known colloquially as "fast and dirty" rather than the "slow and accurate" processing of the classical or lemniscal system. This pathway activates parts of the brain that evoke emotional responses.


Saccadic efference copy

The medial dorsal nucleus is also presumed to play a role in monitoring internal movements of the eye. Specifically, its function is to relay the information about how the eyes will be moved (efference copy, also known as corollary discharge) from the superior colliculus to the frontal eye fields (FEF) in order to aid the neurons in FEF to change their receptive fields to where the visual stimuli will appear after the saccade.


Clinical significance

Damage to the medial dorsal nucleus has been associated with Korsakoff's syndrome.


Additional images

File:Constudthal.gif, Thalamus File:Territoriostalamo.svg, Thalamus File:Thalamus3en1b.png, Human left thalamus (left upper rear view)


References

* Aage R. Moller "Pain: Its anatomy, physiology and treatment" 2012


External links

* {{DEFAULTSORT:Medial Dorsal Nucleus Thalamic nuclei