Brain Regions & Functions — INBDE Review
Cortical lobes, basal ganglia, limbic system, brainstem, cerebellum, and vascular territories — with the lesion patterns that show up most often on the INBDE. 11 board-style MCQs.
Concept summary & clinical relevance.
Quick-reference structure first, then nerve-by-nerve detail. Mnemonics in amber, clinical pearls in blue.
Brain regions are best learned by what they do — and what shows up clinically when they're damaged. Lesion-based reasoning is what the INBDE tests: aphasia patterns, hemineglect, hemianopia, Parkinson's, and the vascular territories of MCA/ACA/PCA strokes.
| Lobe | Key functions | Classic lesion |
|---|---|---|
| Frontal | Voluntary movement (precentral gyrus); executive (prefrontal); motor speech (Broca's, dominant) | Broca's aphasia: effortful, “broken” speech with intact comprehension |
| Parietal | Somatosensation (postcentral gyrus); calculation/praxis (dominant); spatial attention (non-dominant) | Hemineglect (non-dominant lesion); 2-point discrimination loss |
| Temporal | Auditory cortex; language comprehension (Wernicke's, dominant); memory (hippocampus); emotion (amygdala) | Wernicke's aphasia: fluent nonsense, poor comprehension; hippocampal lesion → no new memories |
| Occipital | Primary visual cortex | Contralateral homonymous hemianopia (often with macular sparing) |
| Brainstem level | CN nuclei | Clinical correlation |
|---|---|---|
| Midbrain | CN III, IV | Pupillary reflexes; eye movements |
| Pons | CN V (motor for mastication), VI, VII, VIII | Trigeminal motor + facial expression + balance |
| Medulla | CN IX, X, XI, XII; respiratory & cardiac centers | Loss of respiratory drive = medullary lesion |
| Artery | Territory | Classic deficit |
|---|---|---|
| MCA (dominant) | Lateral cortex: face & arm motor/sensory + language | Aphasia + face/arm hemiparesis |
| MCA (non-dominant) | Same region, opposite hemisphere | Hemineglect + face/arm hemiparesis |
| ACA | Medial cortex (leg motor/sensory area) | Contralateral leg weakness; abulia |
| PCA | Occipital lobe; thalamus | Contralateral homonymous hemianopia |
Cerebral lobes
- Frontal: precentral gyrus = primary motor cortex (voluntary movement, contralateral). Prefrontal cortex = executive function (planning, judgment, impulse control). Broca's area (dominant) = motor speech.
- Parietal: postcentral gyrus = primary somatosensory cortex (touch, pain, temperature, proprioception). Non-dominant parietal = spatial attention; lesion → hemineglect.
- Temporal: primary auditory cortex; Wernicke's area (dominant) = language comprehension; hippocampus = memory consolidation; amygdala = fear/emotion.
- Occipital: primary visual cortex; lesion → contralateral homonymous hemianopia.
Deep gray systems
- Basal ganglia (caudate, putamen, globus pallidus, subthalamic nucleus, substantia nigra): smooth voluntary movement.
- Parkinson's = substantia nigra dopaminergic loss → bradykinesia, rigidity, resting tremor.
- Huntington's = caudate atrophy → chorea.
- Hemiballismus = subthalamic nucleus lesion → flinging movements.
Diencephalon
- Thalamus: relay station for all sensory information except smell.
- Hypothalamus: homeostasis (temperature, hunger, thirst, sleep, autonomics) and endocrine control via the pituitary.
Cerebellum
- Compares motor plan to actual movement → coordination and balance.
- Vermis lesion: wide-based, “drunk” gait.
- Hemisphere lesion: ipsilateral intention tremor and dysmetria.
- Flocculonodular lobe: balance and eye movements.
CSF & ventricles
- Produced by the choroid plexus in the ventricles.
- Flow: lateral ventricles → foramen of Monro → 3rd → aqueduct of Sylvius → 4th → foramina of Luschka/Magendie → subarachnoid space → arachnoid granulations → venous sinuses.
- Obstructive hydrocephalus: blocked flow (e.g., aqueduct stenosis).
- Communicating hydrocephalus: impaired absorption at arachnoid villi.
11 board-style MCQs.
Active recall is the highest-yield study method for the INBDE. Pick an answer, check it, and read why every distractor is wrong — that's where the learning compounds.
The MCQs above are Core Recall — testing what you've memorized. The book adds a full Clinical Integration set: board-style patient scenarios where you apply this anatomy to real clinical reasoning. That's the section the INBDE actually weights heaviest.
- Question 1EasyThe precentral gyrus corresponds to which functional area of the brain?
- Question 2EasyLesion to Broca's area produces which deficit?
- Question 3EasyWhich lesion causes fluent but meaningless speech with poor comprehension?
- Question 4EasyWhich structure consolidates short-term memory into long-term memory?
- Question 5ModerateParkinson's disease results from degeneration of which basal ganglia component?
- Question 6EasyWhich sensory modality bypasses the thalamus?
- Question 7ModerateWhich brainstem structure contains nuclei for cranial nerves III and IV?
- Question 8EasyFailure of respiratory drive localizes to which structure?
- Question 9EasyWhich structure produces cerebrospinal fluid?
- Question 10ModerateA stroke in the left middle cerebral artery (MCA) of a right-handed patient is most likely to cause:
- Question 11ModerateWhich artery supplies most of the motor and sensory cortex for the legs?
900 INBDE-style MCQs with full explanations across 18 chapters — Core Recall plus board-style Clinical Integration scenarios — alongside Learning Summaries, Integration Bridges, and Review Boxes. Built by Dr. Isaac Sun for dental students who want to think like a clinician, not just memorize.
Founder, KYT Dental Services · Author, KYT INBDE series. These MCQs and Learning Summaries are part of a structural-thinking framework Dr. Sun uses with patients in the chair.