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Friday, September 27, 2013

The Thalamus as its ''Relay'' function

the thalamus is a part of diencephalon and has multiple functions. It translates information from all sensory pathways other than Olfaction and selectively distributes those impulses to appropriate parts of the cortex (''relay'' function). The following thalamic nuclei receive input from sensory pathways:

1.Ventral posterolateral (VPL) receives input from the spinothalamic tract (pain and temperature sensation) and medial lemniscus(position and proprioception). It transmits impulses to primary somatosensory cortex (Brodmann areas 3,1 & 2).
2.Ventral posteromedial nucleus (VPM) receives inputs from the trigeminal and gustatory pathways and transmits them to the primary sensory cortex (Brodmann's areas 3, 1 & 2).
3.Lateral geniculate body is a ''relay'' nucleus for the vision pathway. It receives impulses from the optic nerve and transmits them via the optic radiations to the visual cortex (calcarine sulcus)
4.Medial geniculate body is a part of the auditory pathway. It receives impulses from the superior olivary nucleus and the inferior colliculus of the pons, and projects them to the auditory cortex of the temporal lobe (Brodmann areas 41 & 42)

The olfactory tract is the only sensory pathway where input is not processed through thalamus.

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