# 08 - Thalamus

# Thalamus

© SPMM Course 
 They include striatum made of the caudate nucleus and putamen and pallidum made of globus 
pallidus. Putamen and globus pallidus are sometimes called lenticular/lentiform nucleus. 
 The subthalamic nuclei and the substantia nigra are both functionally related to the basal ganglia 
but are not considered to be a part of this structure. 
 Basal ganglia receive crucial inputs from glutamatergic corticostriatal projection. Alexander 
described five important circuits involving the basal ganglia. These are 
 
Motor circuit 
 
Oculomotor circuit 
 
Dorsolateral prefrontal circuit (executive) 
 
Anterior cingulate circuit (motivation) 
 
Lateral orbitofrontal circuit (social intelligence) 
 
Disorder 
Nature of basal ganglia dysfunction 
OCD 
Volumetric changes and higher blood flow to the caudate nuclei. Increased caudate 
metabolism in untreated subjects reduces after effective treatment. 
Tourette’s syndrome 
Striatal dopaminergic dysfunction 
Huntington chorea 
Degeneration of the striatum (mainly caudate nucleus) & selective loss of GABAergic 
neurons 
Wilson disease 
Copper deposits in the lenticular nuclei 
CO poisoning 
Acute bilateral anoxic damage to basal ganglia 
Hemiballismus 
Subthalamic nucleus damage (especially infarction) 
Parkinsonism 
Depigmentation of Substantia Nigra; Lewy bodies are seen. Striatal overactivity 
associated with bradykinesia 
Fahr's disease 
Progressive calcium deposition in the basal ganglia. (early onset cases present with 
schizophreniform psychoses and catatonia; later onset cases exhibit dementia and 
choreoathetosis) 
Thalamus 
 A large oval mass of grey matter nuclei in the subcortical region, relaying all types of sensory 
information onto cortex (except olfaction). 
 It also relays cerebellar and basal ganglia inputs to the cerebral cortex. 
 The thalamus is said to play a crucial role of filtering sensory information in preparation for 
cortical processing. 
 The anterior thalamus is a part of the limbic system. It receives the mamillothalamic tract and 
fornix and connects to the cingulate cortex. Thus, it relays information from hypothalamus and 
hippocampus onto the frontal cortex. 
 Pulvinar is associated with visual attention. Sleep spindles are generated in the reticular nucleus of 
the thalamus.