2 Neuroscience2.11 Integrated neurobiology of syndromes and states

2.11 Integrated neurobiology of specific syndromes and states

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Written by Resident Doctor Committee · Published

Mechanisms behind symptoms

Mechanism

Proposed link

Aberrant salience

Delusions

Altered ventral striatal reward processing

Anhedonia

Impaired safety learning

Persistent fear and avoidance

Dorsal striatal habit control

Compulsive substance use

Cholinergic dysfunction

Inattention in delirium and dementia

  • Low cerebrospinal fluid 5-HIAA (5-hydroxyindoleacetic acid, the main serotonin metabolite) is linked to suicide. It is most marked after violent attempts and predicts death by suicide within a year.

  • Oxytocin release rises with mother-infant bonding through affectionate touch, shared gaze and infant-directed speech. Oxytocin also increases attention to faces and interpersonal trust.

  • Anterior insula activation tracks craving set off by drug cues, and smokers whose insula was damaged by stroke lost the urge to smoke.

  • In obsessive-compulsive disorder, resting glucose metabolism is raised in the orbitofrontal cortex and caudate nucleus. It falls in people who respond to a selective serotonin reuptake inhibitor or behaviour therapy.

Follow the arrows from orbitofrontal and anterior cingulate cortex to the head of the caudate, then through the globus pallidus and thalamus back to frontal cortex: resting metabolism in OCD is raised most consistently in the orbitofrontal cortex and caudate. Drawn for MRCPsychiatrist

Cause, consequence or compensation

Finding

Meaning

Example

Vulnerability

Precedes onset and predicts disorder

Small hippocampi in unexposed co-twins in post-traumatic stress disorder

State change

Present only during an episode

Subgenual cingulate hyperactivity in depression

Consequence

Caused by the illness or its treatment

Hippocampal loss tracking the number of depressive episodes

Compensation

Adaptive response to the abnormality

Prefrontal over-recruitment sustaining performance

Longitudinal, high-risk, early-episode and twin designs separate these four by their order in time.

Limits

  • Findings describe overlapping groups and cannot diagnose an individual.

  • A low prevalence of the outcome limits predictive value, especially for suicide.

  • One diagnosis contains varied biological profiles, and genetic liability overlaps across diagnoses.

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

2.11 Integrated neurobiology of specific syndromes and states | MRCPsychiatrist