Cortico-Basal Ganglia thalamo cortical loop

Question 1

CBGTC Loop Definition

Answer 1

A closed-loop neural circuit involving the cerebral cortex, basal ganglia, thalamus, and back to the cortex

Question 2

CBGTC Loop Function

Answer 2

o Movement initiation and regulation
o Cognitive flexibility
o Emotional regulation

Question 3

• CBGTC* Clinical Relevance

Answer 3

Implicated in Parkinson’s, Huntington’s, OCD, ADHD, Tourette’s, schizophrenia, and addiction.

Question 4

key components (3):

Answer 4

(1) cerebral cortex
(2) Basal Ganglia
(3)Thalamus

Question 5

cerebral cortex role:

Answer 5

initiates signals processed through loop

Question 6

cerebral cortex functional divisions (4):

Answer 6

o Motor Cortex: M1, premotor, SMA

o Oculomotor: Frontal eye fields (FEF), SEF

o Prefrontal (Associative): DLPFC, lateral OFC

o Limbic: ACC, medial OFC

Question 7

o Motor Cortex:

Answer 7

: M1, premotor, SMA

Question 8

o Oculomotor

Answer 8

Frontal eye fields (FEF), SEF

Question 9

o Prefrontal (Associative):

Answer 9

DLPFC, lateral OFC

Question 10

Limbic:

Answer 10

ACC, medial OFC

Question 11

Cerebral Cortex: species comparison:

Answer 11

o Rodents lack DLPFC; their mPFC combines ACC and DLPFC-like functions

Question 12

basal ganglia subcompartments (4)

Answer 12

striatum
globus pallidus
substantia nigra
subthalamic nucleus (STN)

Question 13

striatum (component basal ganglia) can be further divided into (4:2 dorsal 2 ventral):

Answer 13

 Dorsal: Caudate + Putamen
 Ventral: Nucleus accumbens + Olfactory tubercle

Question 14

globus pallidus (component basal ganglia) can be further divided:

Answer 14

Internal (GPi) and External (GPe)

Question 15

substantia nigra (component basal ganglia) can be further divided:

Answer 15

Pars compacta (SNpc) & Pars reticulata (SNr)

Question 16

thalamus function:

Answer 16

Relays processed input from the basal ganglia back to the cortex.

Question 17

thalamus connections:

Answer 17

: Receives from BG; projects to specific cortical targets.

Question 18

Striatal Microanatomy: compartments (2):

Answer 18

• Patch/Striosome: Substance P, μ-opioid receptor
• Matrix: ChAT, AChE, somatostatin

Question 19

Striatal Microanatomy: Neuron Types: projection neurons:

Answer 19

: Medium spiny neurons (MSNs; GABAergic)
o Striatonigral projecting (direct)
o Striatopallidal projecting (indirect)

Question 20

Striatal Microanatomy: Neuron Types: interneurons:

Answer 20

o FS (fast-spiking interneurons, GABA)
o LTS (low-threshold spiking interneurons, GABA)
o LA (large aspiny neurons, ACh)

Question 21

Broader Cortico-Subcortical Loops

Answer 21

• CTC: Cortex ↔ Thalamus
• CBGTC: Cortical-basal ganglia-thalamo-cortical
• CCTC: Cerebello-cortico-thalamo-cortical

Question 22

Clinical Disorders Involving CBGTC Loops:
Movement Disorders

Answer 22

• Parkinson’s Disease: Loss of SNpc dopamine → hypokinesia
• Huntington’s Disease: Early loss of indirect MSNs → hyperkinesia
• Tourette’s Syndrome: Dysregulated basal ganglia inhibition

Question 23

Clinical Disorders Involving CBGTC Loops:Neuropsychiatric Disorders

Answer 23

• ADHD:
  o ↓ tonic dopamine in basal ganglia → impulsivity, inattention
• OCD:
  o ↑ direct / ↓ indirect pathway activity → repetitive behaviors
• Addiction:
  o Ventral striatum (NAc) dopamine surge
  o Striatonigrostriatal spirals → habitual drug seeking

Question 24

• The CBGTC loop integrates

Answer 24

motor, cognitive, and emotional processes

Question 25

* Dysfunction in specific nodes or pathways results in

Answer 25

characteristic neurological or psychiatric symptoms.

Question 26

* The basal ganglia act as an

Answer 26

action selector, mediating competition between behavioral options.