Neurosciences is the largest single section in Paper A at approximately 27% (40 of 150 marks). It is also the section that candidates consistently perform worst on. This is partly because medical school neuroscience teaching is variable and partly because the MRCPsych demands a depth that goes beyond undergraduate level.
This crash guide covers the essential neuroscience for Paper A, structured by question frequency.
Neuroanatomy: The Structures That Matter
The Limbic System
The limbic system is the most examined neuroanatomical topic. Know its components and their functions:
- Hippocampus: Memory consolidation (declarative/episodic), spatial navigation. Bilateral lesion = anterograde amnesia (Korsakoff syndrome, hippocampal sclerosis in temporal lobe epilepsy). Vulnerable to glucocorticoid excess and hypoxia.
- Amygdala: Emotional processing (particularly fear and threat detection), emotional memory. Bilateral lesion = Kluver-Bucy syndrome (hyperorality, hypersexuality, emotional blunting, visual agnosia). Overactive in anxiety disorders and PTSD.
- Cingulate gyrus: Anterior cingulate = conflict monitoring, error detection, emotional regulation. Posterior cingulate = visuospatial orientation, memory retrieval.
- Hypothalamus: Autonomic control, endocrine regulation, circadian rhythms, appetite, thirst, temperature, emotional responses. Lesion = endocrine disturbance, autonomic dysregulation.
- Thalamus: Sensory relay station. Mediodorsal nucleus = memory and emotion (lesion in Korsakoff syndrome). Anterior nucleus = part of Papez circuit.
- Septal area: Pleasure and reward (intracranial self-stimulation in animal models).
The Basal Ganglia
Know the two main circuits:
Direct pathway: Cortex → Striatum → Globus pallidus interna (GPi)/Substantia nigra pars reticulata (SNr) → Thalamus → Cortex. Net effect: facilitates movement. Dopamine (D1 receptor) activates this pathway.
Indirect pathway: Cortex → Striatum → Globus pallidus externa (GPe) → Subthalamic nucleus (STN) → GPi/SNr → Thalamus → Cortex. Net effect: inhibits movement. Dopamine (D2 receptor) suppresses this pathway.
Clinical correlates: Parkinson’s disease = dopamine depletion → increased indirect pathway activity → bradykinesia/rigidity. Huntington’s disease = loss of indirect pathway (GPe/STN) → chorea. Antipsychotics (D2 blockade) → increased indirect pathway → EPS.
Prefrontal Cortex
Divided into three functional regions:
- Dorsolateral PFC: Executive function (planning, working memory, cognitive flexibility). Dysfunction = dysexecutive syndrome.
- Orbitofrontal PFC: Social cognition, impulse control, reward processing. Dysfunction = disinhibition, poor judgement, emotional lability.
- Ventromedial PFC: Emotional regulation, decision-making, empathy. Dysfunction = affective dysregulation, impaired decision-making.
Neurochemistry: Neurotransmitter Systems
Dopamine Pathways
Four major pathways, each with distinct functions and clinical relevance:
- Mesolimbic: VTA → Nucleus accumbens. Reward, motivation, salience. Hyperactivity = positive symptoms of schizophrenia.
- Mesocortical: VTA → Prefrontal cortex. Executive function, cognition. Hypoactivity = negative and cognitive symptoms of schizophrenia.
- Nigrostriatal: Substantia nigra pars compacta → Striatum. Motor control. Degeneration = Parkinson’s disease. Blockade = EPS (antipsychotics).
- Tuberoinfundibular: Hypothalamus → Anterior pituitary. Prolactin inhibition. Blockade (antipsychotics) = hyperprolactinaemia.
Serotonin (5-HT) Pathways
Raphe nuclei → widespread cortical and subcortical projections. Multiple receptor subtypes (at least 14). Key ones for Paper A:
- 5-HT1A: Autoreceptor (somatodendritic). Agonist action (buspirone, partial SSRI effect) = anxiolytic.
- 5-HT2A: Postsynaptic. Blockade contributes to atypical antipsychotic effect. Agonism (LSD, psilocybin) = hallucinogenic.
- 5-HT3: Ion channel. Involved in nausea and vomiting (ondansetron blocks this).
- 5-HT7: Involved in circadian rhythm regulation and mood.
GABA and Glutamate
GABA: The main inhibitory neurotransmitter. GABA-A receptor = ion channel (benzodiazepines, barbiturates, alcohol, z-drugs all potentiate GABA-A). GABA-B receptor = metabotropic (baclofen).
Glutamate: The main excitatory neurotransmitter. NMDA receptor (ketamine, phencyclidine, memantine) is the most exam-relevant. NMDA receptor hypofunction is a leading neurochemical hypothesis for schizophrenia (explains why PCP/ketamine produce schizophrenia-like symptoms).
Neuroimaging: Which Modality for Which Question
| Modality | Measures | When to use |
|---|---|---|
| CT | Structural (bone, blood, calcification, gross atrophy) | Emergency: acute intracranial pathology (bleed, mass, fracture) |
| MRI | Structural (soft tissue, grey/white matter, hippocampal volume) | Research in schizophrenia (reduced grey matter), Alzheimer’s (hippocampal atrophy), multiple sclerosis |
| fMRI | Blood-oxygen-level-dependent (BOLD) signal → regional brain activity | Research: localising cognitive functions, functional connectivity in psychiatric disorders |
| PET | Metabolic activity (glucose metabolism via FDG) or receptor density/occupancy | Research: D2 receptor occupancy by antipsychotics, amyloid imaging in Alzheimer’s |
| SPECT | Regional cerebral blood flow (rCBF) as proxy for activity | Clinical: distinguishing Alzheimer’s from frontotemporal dementia (temporoparietal hypoperfusion in Alzheimer’s, frontal in FTD) |
| DTI | White matter tract integrity (diffusion of water molecules) | Research: white matter connectivity in schizophrenia, autism, TBI |
| MRS | Metabolite concentrations (NAA, choline, creatine, glutamate) | Research: neurotransmitter levels in vivo |
Neuropsychology: Lobar Syndromes and Cognitive Domains
Frontal lobe syndrome: Three subtypes you must know:
- Dorsolateral: Dysexecutive (poor planning, reduced cognitive flexibility, impaired working memory, perseveration)
- Orbitofrontal: Disinhibited (impulsivity, inappropriate social behaviour, emotional lability, poor judgement)
- Medial frontal: Apathetic (reduced initiation, abulia, mutism, urinary incontinence)
Temporal lobe: Dominant (left): language deficits (Wernicke’s aphasia, sensory dysphasia), verbal memory impairment. Non-dominant (right): prosopagnosia (face recognition), visuospatial deficits, emotional recognition deficits. Hippocampal: anterograde amnesia. Amygdala: emotional processing deficits.
Parietal lobe: Dominant: Gerstmann syndrome (acalculia, agraphia, finger agnosia, left-right disorientation). Non-dominant: hemispatial neglect (left), constructional apraxia, anosognosia.
Occipital lobe: Cortical blindness, Anton syndrome (denial of blindness with confabulation), visual agnosia, prosopagnosia (fusiform gyrus).
High-Yield Facts for Quick Revision
- Papez circuit: Hippocampus → Fornix → Mammillary bodies → Mammillothalamic tract → Anterior thalamus → Cingulate gyrus → Entorhinal cortex → Hippocampus
- Blood supply: Anterior cerebral artery = medial frontal/parietal. Middle cerebral artery = lateral hemisphere (most strokes). Posterior cerebral artery = occipital lobe, medial temporal.
- Circle of Willis: Anterior communicating, posterior communicating, anterior cerebral, internal carotid, posterior cerebral arteries. Complete circle in ~50% of people.
- Ventricular system: Lateral (I, II) → Foramen of Monro → Third ventricle → Aqueduct of Sylvius → Fourth ventricle → Foramina of Luschka/Magendie → Subarachnoid space.
- EEG rhythms: Alpha (8–12 Hz, relaxed/eyes closed), Beta (>12 Hz, alert/active), Theta (4–8 Hz, drowsy), Delta (<4 Hz, deep sleep). Epilepsy: spike-wave discharges (generalised), sharp waves (focal).
PsychStar’s Paper A bank covers all neuroscience topics with exam-style questions and full teaching cascades. Start with 5 free questions at psychstar.io/try.