2 Neuroscience2.7 Neural circuits

2.7.1 Neural circuits of function and their disturbance in psychiatric disorders

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Written by Resident Doctor Committee · Published

Circuit framework

Stage

Anatomy

Role

Input

Sensory pathways, vagal afferents, circumventricular organs

Reports bodily state

Integration

Hypothalamus, thalamus, amygdala, hippocampus, striatum

Adds context and memory

Cortex

Association, frontoparietal, medial prefrontal, cingulate

Allows deliberate control

Output

Brainstem, basal ganglia, cerebellum, spinal cord

Generates behaviour

Neuromodulation

Dopamine, noradrenaline, serotonin, acetylcholine

Sets gain, plasticity and value

Symptoms can arise from disturbed timing, connectivity, learning or modulation in intact anatomy.

Homeostatic circuits

  • Leptin, ghrelin and vagal signals reach the arcuate nucleus and the nucleus of the solitary tract.

  • Circumventricular organs sense osmolality.

  • In pain, the insula and cingulate add unpleasantness, and periaqueductal grey pathways modulate spinal transmission.

Action selection

  • Cortico-striato-pallido-thalamic loops select actions; the dorsal striatum handles motor choice and the ventral striatum adds value.

  • Dopamine bursts signal better-than-expected outcomes and pauses signal worse ones.

  • Devaluing the outcome reduces goal-directed action but may spare habits, which repetition strengthens.

Follow the arrows from cortex to striatum, through the globus pallidus to the thalamus and back to cortex: this is the cortico-striato-pallido-thalamic loop that selects actions, with dopamine from the substantia nigra acting on the striatum. Mikael Häggström , based on images by Andrew Gillies/User:Anaru and Patrick J. Lynch, CC BY-SA 3.0, via Wikimedia Commons

Cortical networks

Function

Network

Attention

Dorsal frontoparietal for goals; ventral salience system for the unexpected

Executive

Frontoparietal, holding goals and suppressing distraction

Social cognition

Temporoparietal junction, superior temporal sulcus, medial prefrontal

Feedback and symptoms

  • Top-down goals and predictions shape bottom-up evidence, and overweighted expectations distort perception.

  • Avoidance blocks corrective learning, and compulsions earn short-term relief.

Disturbance

Symptom

Impaired reward learning

Anhedonia

Aberrant salience

Delusional explanation

Poor inhibitory control

Impulsivity

Rigid habit

Compulsions

  • Mappings are many-to-many, and network differences between diagnoses may reflect cause, compensation or medication.

Revision material for the MRCPsych examinations. Not clinical guidance, and not for use in patient care.