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31 practice questions across all five Brain Bee rounds. Every one comes with a full explanation — not just which option is correct, but why the most tempting wrong answer is wrong, and how the same idea tends to be asked at a practical station or in the live oral. Answer keys are easy to find; the reasoning is the part that actually moves your score.
By Dr. Shekhar C Singh, AIIMS New Delhi — reviewed August 3, 2026.
Decide on an answer and say why out loud before opening the explanation. Retrieval under commitment is what builds durable memory — reading the answer first feels productive and teaches you almost nothing.
Most items you lose in competition are ones where you knew the topic but picked the near-miss. Each explanation names the tempting wrong answer and gives you the discriminator that separates them.
The heaviest rounds are spoken and timed. Give yourself 20–30 seconds per question and answer aloud in a full sentence — it is a different, harder skill than recognizing the right option in silence.
Content recall from the free Brain Facts book — the neuron, signaling, neurotransmitters, development and the senses. In the published championship format this is the single largest block of points (50 of 100) — and everything else is built on it.
1.During the rising (depolarizing) phase of an action potential, which ion movement is primarily responsible?
Answer: B — Na⁺ flowing into the neuron
Voltage-gated Na⁺ channels open once the membrane reaches threshold, and Na⁺ rushes inward down both its concentration and electrical gradients — driving the membrane sharply positive. The tempting wrong answer is K⁺ efflux: that is real, but it belongs to the *falling* phase (repolarization), because K⁺ channels open more slowly and stay open longer, which also produces the after-hyperpolarization. Ca²⁺ matters at the axon terminal for neurotransmitter release, not for the rising phase of the axonal spike.
Competition tip: Written rounds love the sequence. Fix the order in your head as: threshold → Na⁺ in (rise) → Na⁺ channels inactivate and K⁺ out (fall) → brief hyperpolarization → Na⁺/K⁺ pump restores the gradients.
2.Saltatory conduction increases the speed of an action potential because the impulse:
Answer: B — Jumps between the nodes of Ranvier
Myelin insulates the axon, so voltage-gated Na⁺ channels are concentrated at the gaps between myelin segments — the nodes of Ranvier. The depolarization effectively leaps from node to node instead of regenerating at every point along the membrane, which is far faster and more metabolically efficient. "Travels along the myelin" is the trap: current spreads passively *under* the myelin, but the action potential is only regenerated at the nodes.
Competition tip: This links straight to the patient-diagnosis round: demyelination in multiple sclerosis destroys saltatory conduction, which is why MS produces slowed or failed conduction rather than a cut nerve.
3.Which neurotransmitter is released at the neuromuscular junction of skeletal muscle?
Answer: C — Acetylcholine
Motor neurons release acetylcholine onto nicotinic receptors on the muscle fiber, opening cation channels and triggering the muscle action potential. Dopamine, GABA and serotonin are all central neurotransmitters and are not used at the skeletal neuromuscular junction. GABA is the distractor worth understanding: it is the main *inhibitory* transmitter in the adult CNS, so it could never drive muscle contraction.
Competition tip: Worth knowing the clinical hook: myasthenia gravis is caused by antibodies against these nicotinic acetylcholine receptors, producing fatigable weakness that worsens through the day.
4.What is the principal excitatory neurotransmitter in the adult human CNS?
Answer: A — Glutamate
Glutamate drives the great majority of fast excitatory transmission in the brain, acting on AMPA and NMDA receptors, and NMDA receptor activity is central to long-term potentiation and therefore to learning and memory. GABA and glycine are the main inhibitory transmitters (GABA predominantly in the brain, glycine in the spinal cord and brainstem). Norepinephrine is a modulatory transmitter with wide projections from the locus coeruleus, not the workhorse excitatory transmitter.
5.Which sensory modality does NOT relay through the thalamus on its way to the cortex?
Answer: C — Olfaction
Olfaction is the classic exception: olfactory receptor neurons project to the olfactory bulb and from there to the olfactory cortex directly, bypassing the thalamic relay that every other major sensory modality uses. Vision relays through the lateral geniculate nucleus, hearing through the medial geniculate nucleus, and touch through the ventral posterolateral nucleus. This anatomical shortcut is often linked to how directly smell can evoke memory and emotion.
Competition tip: This is one of the most reliably asked facts across every level of the competition — know it as a rule with exactly one exception.
6.Long-term potentiation (LTP), the cellular model of learning, is most closely associated with which structure?
Answer: B — Hippocampus
LTP was first characterized in the hippocampus, where repeated high-frequency stimulation strengthens synaptic transmission for hours or longer — the leading cellular model of how memories are encoded. The hippocampus is required for consolidating new declarative memories, which is why bilateral hippocampal damage produces dense anterograde amnesia. The cerebellum does have its own plasticity and is essential for motor learning, but it is not where LTP is classically studied.
7.Which glial cell myelinates axons in the central nervous system?
Answer: B — Oligodendrocyte
Oligodendrocytes myelinate CNS axons, and a single oligodendrocyte can wrap segments of many different axons. Schwann cells do the same job in the peripheral nervous system, but each Schwann cell myelinates exactly one segment of one axon — that one-to-many versus one-to-one distinction is the most commonly tested part of this. Astrocytes support the blood-brain barrier and regulate the extracellular environment; microglia are the resident immune cells.
Competition tip: CNS versus PNS myelination explains why multiple sclerosis (CNS, oligodendrocytes) and Guillain-Barré syndrome (PNS, Schwann cells) present so differently.
8.Which brain region is the master regulator of circadian rhythm, receiving direct input from the retina?
Answer: A — Suprachiasmatic nucleus of the hypothalamus
The suprachiasmatic nucleus (SCN) sits in the hypothalamus just above the optic chiasm and receives direct retinal input, which is how light entrains the body clock. The pineal gland is the tempting answer because it secretes melatonin — but it does so *under instruction from* the SCN, making it the effector rather than the pacemaker. The superior colliculus handles visual orienting reflexes, and the nucleus accumbens is part of the reward circuit.
Identify structures by sight on real brains, atlases and 3D models, usually against a clock. Part of the structure round (25 of 100 points, alongside histology and MRI) and the hardest thing to self-study.
1.You are handed a brain and asked to identify the primary motor cortex. Which gyrus do you point to?
Answer: B — Precentral gyrus
The primary motor cortex occupies the precentral gyrus, immediately *anterior* to the central sulcus, in the frontal lobe. The postcentral gyrus — directly behind the same sulcus, in the parietal lobe — is the primary somatosensory cortex, and swapping these two is the single most common error on this station. The mnemonic that survives pressure: motor is in front, sensation is behind, and the central sulcus divides them.
Competition tip: On a real specimen, find the central sulcus first by tracing it down from the superior margin, then decide which side you are on. Identify the landmark, then the structure — never guess the structure directly.
2.Which structure connects the two cerebral hemispheres and is most clearly seen on a midsagittal section?
Answer: A — Corpus callosum
The corpus callosum is the large arched commissure carrying the bulk of interhemispheric fibers, and its four named parts — rostrum, genu, body and splenium — are visible in a single sweep on a midsagittal cut. The fornix is the distractor to rule out carefully: it also arches on midsagittal section and sits just below the corpus callosum, but it is the main *output tract of the hippocampus*, not a commissure between hemispheres. The internal capsule and corona radiata are projection fibers running vertically to and from the cortex.
Competition tip: If a midsagittal station shows two arched white-matter structures stacked one above the other, the upper and much thicker one is the corpus callosum and the thinner one beneath it is the fornix.
3.The striatum consists of which two structures?
Answer: B — Caudate nucleus and putamen
The striatum is the caudate nucleus plus the putamen. The trap is the *lentiform* nucleus, which is the putamen plus the globus pallidus — the putamen belongs to both groupings, which is exactly why examiners like this pair. Keep them separate by remembering that the striatum is defined by shared input (it is the main input station of the basal ganglia) while the lentiform nucleus is defined purely by its lens-like shape on a coronal section.
4.Which cranial nerve innervates the lateral rectus muscle, and what happens when it is damaged?
Answer: C — CN VI (abducens) — the eye cannot abduct, causing horizontal double vision
The abducens nerve (CN VI) supplies the lateral rectus, the muscle that turns the eye outward — so a palsy leaves the affected eye unable to abduct, producing horizontal diplopia that worsens on looking toward the affected side. The classic summary is LR6 SO4, remainder 3: lateral rectus is CN VI, superior oblique is CN IV, and all the other extraocular muscles are CN III. Each of the wrong options here is a genuine deficit, just of a different nerve.
Competition tip: Cranial nerve stations frequently pair a structure with a functional consequence. Learn each nerve as a triplet — number, name, and what visibly breaks — because that is the form the live oral asks it in.
5.Which arteries join to complete the posterior part of the Circle of Willis?
Answer: B — Posterior communicating arteries
The paired posterior communicating arteries link each internal carotid to the posterior cerebral artery on the same side, closing the ring posteriorly; the single anterior communicating artery closes it anteriorly by joining the two anterior cerebral arteries. The middle cerebral arteries are the major distractor — they are large and prominent, but they run laterally into the Sylvian fissure and are not part of the ring itself.
Competition tip: The reason this matters clinically is collateral flow: an intact circle lets blood cross to a territory whose supplying vessel is blocked, which is why identical occlusions can produce very different strokes in different people.
6.Trace the flow of cerebrospinal fluid. Which sequence is correct?
Answer: A — Lateral ventricles → third ventricle → cerebral aqueduct → fourth ventricle → subarachnoid space
CSF is produced mainly by the choroid plexus in the lateral ventricles, passes through the interventricular foramina (of Monro) into the third ventricle, then down the cerebral aqueduct into the fourth ventricle, and exits through the median and lateral apertures into the subarachnoid space, where it is reabsorbed at the arachnoid granulations. Option 3 simply reverses the true direction, which is why it looks plausible at a glance.
Competition tip: Because the cerebral aqueduct is the narrowest point in the whole pathway, it is the commonest site of obstruction — which is the anatomical basis of obstructive hydrocephalus.
7.A structure on the brainstem is identified as the site where the corticospinal tract crosses the midline. Where are you?
Answer: C — The medulla, at the pyramidal decussation
The corticospinal (pyramidal) tract crosses in the lower medulla at the pyramidal decussation, which is precisely why a lesion above it produces weakness on the *opposite* side of the body while a lesion below it produces weakness on the same side. The cerebral peduncles and internal capsule both carry these fibers, but carry them before they have crossed.
Competition tip: Almost every "which side is the lesion on?" question in the clinical round resolves to knowing where the relevant tract crosses. Learn the decussation points and the laterality follows automatically.
Cell types and tissue patterns down the microscope or on photomicrographs — glia, neuron classes, and the landmark slides that recur year after year.
1.A photomicrograph shows a cortex with three layers, one of which is a single row of very large flask-shaped neurons. Which tissue is this?
Answer: B — Cerebellar cortex
The cerebellar cortex has exactly three layers — molecular, Purkinje and granular — and the single row of large flask-shaped Purkinje cells between the outer molecular layer and the densely packed granular layer is unmistakable once seen. Cerebral cortex is the main distractor but is six-layered and has no comparable single-file row of giant cells. This is one of the highest-yield slides in the entire competition.
Competition tip: Count layers first, then look for a signature cell. Three layers plus a row of giant neurons is cerebellum; six layers with pyramidal cells is cerebral cortex.
2.Which glial cell forms the end-feet that contribute to the blood-brain barrier?
Answer: B — Astrocyte
Astrocytes extend perivascular end-feet that wrap cerebral capillaries and induce and maintain the tight junctions between endothelial cells that constitute the blood-brain barrier. They also buffer extracellular potassium, recycle neurotransmitters such as glutamate, and support synapses. Microglia are the immune cells, oligodendrocytes myelinate, and ependymal cells line the ventricles and help move CSF.
3.On a peripheral nerve cross-section, which cell would you expect to see forming myelin?
Answer: B — Schwann cell
Schwann cells myelinate peripheral axons, each one wrapping a single internodal segment of a single axon — so a peripheral nerve section shows one Schwann cell nucleus per myelinated segment. Oligodendrocytes are the CNS equivalent and are not found in peripheral nerve. Satellite cells are real peripheral glia, but they surround neuronal cell bodies in ganglia rather than forming myelin.
Competition tip: If a slide is labelled as peripheral nerve and an option says oligodendrocyte, you can eliminate it on location alone — a fast way to save time under station pressure.
4.Which of the following would appear as white matter on a freshly cut brain section, and why?
Answer: B — Regions dense in myelinated axons
White matter looks white because myelin is lipid-rich and reflects light — so white matter is where myelinated axon tracts run. Grey matter, by contrast, is dominated by neuronal cell bodies, dendrites and synapses, which is where processing happens. That is the underlying logic of cortical anatomy: gray on the outside as a processing sheet, white beneath it as the wiring connecting regions.
Competition tip: This flips on MRI, where the appearance depends on the sequence rather than on light reflection — a distinction worth holding separately in your head for the imaging round.
The same anatomy you know from the whole brain, now on a 2D slice. Orientation and sequence recognition matter as much as the structures themselves.
1.On a T2-weighted MRI, how does cerebrospinal fluid appear?
Answer: A — Bright (high signal)
On T2-weighted images, fluid is bright — CSF in the ventricles and subarachnoid space appears white. On T1-weighted images the reverse is true and CSF appears dark, while fat is bright. The single most useful habit is to identify the sequence before identifying anything else, because the entire interpretation depends on it. Many edema and demyelination lesions are also bright on T2, which is why T2 and FLAIR are used to hunt for pathology.
Competition tip: A quick check that works under pressure: glance at the ventricles. Bright ventricles means T2; dark ventricles means T1.
2.Which imaging plane best displays the full anterior-to-posterior extent of the corpus callosum?
Answer: C — Midsagittal
The midsagittal plane cuts down the midline between the hemispheres and shows the corpus callosum along its whole arc, with the rostrum, genu, body and splenium all in one image — along with the brainstem, cerebellum and fourth ventricle. Coronal sections cross it, showing only a slice at one anterior-posterior level, and axial sections show it in fragments.
Competition tip: Orient yourself on every scan before naming structures: identify the plane, then find one certain landmark, then work outward from it.
3.On an axial MRI at the level of the basal ganglia, which structure lies between the caudate nucleus and the lentiform nucleus?
Answer: B — Internal capsule
The internal capsule runs between the caudate nucleus medially and the lentiform nucleus laterally, forming the distinctive V-shape (opening laterally) that makes this the most recognizable axial slice in the brain. Its anterior limb, genu and posterior limb carry the projection fibers to and from the cortex — including the corticospinal fibers, which is why a small capsular stroke can cause a dense hemiparesis out of all proportion to its size.
Clinical reasoning from a presentation back to a diagnosis, across roughly 20 neurological and psychiatric disorders. This is where reasoning beats memorization.
1.A 68-year-old has a tremor in the right hand that is worst at rest and lessens when reaching for a cup. He has slowed movement, stiffness, reduced arm swing and a quiet voice. What is the most likely diagnosis?
Answer: B — Parkinson's disease
The combination of a resting tremor, bradykinesia and rigidity is the classic triad of Parkinson's disease, caused by degeneration of dopaminergic neurons in the substantia nigra pars compacta. Essential tremor is the distractor that matters most, and the discriminator is when the tremor appears: essential tremor is an *action* tremor that worsens on reaching for something and is typically bilateral, whereas the Parkinsonian tremor is present at rest and improves with movement — exactly as described here. A cerebellar lesion would produce an intention tremor with ataxia, and Huntington disease causes chorea rather than rigidity.
Competition tip: For every movement disorder, ask one question first: when does the abnormal movement appear — at rest, on action, or on approaching a target? That single axis separates most of the differential.
2.A 27-year-old woman had painful loss of vision in one eye two years ago that recovered. She now has numbness and weakness in both legs over several days. MRI shows several periventricular white-matter lesions. What is the most likely diagnosis?
Answer: A — Multiple sclerosis
Multiple sclerosis is defined clinically by lesions disseminated in **time and space** — here an episode of optic neuritis two years ago (one site, one time) and a separate spinal presentation now (a different site, a different time), supported by periventricular white-matter lesions on MRI. It is an autoimmune demyelinating disease of the CNS targeting oligodendrocyte-derived myelin. Guillain-Barré is the closest distractor but is a *peripheral* demyelinating illness with rapidly ascending weakness and lost reflexes over days, and it does not produce prior optic neuritis or CNS white-matter plaques.
Competition tip: Whenever a vignette gives you two neurological events separated by a long interval and in different parts of the nervous system, think demyelination first — that "time and space" pattern is doing deliberate work in the question.
3.A 71-year-old suddenly cannot speak fluently. His words are effortful and telegraphic, but he follows complex commands correctly and knows what he wants to say. His right arm is weak. Where is the lesion?
Answer: A — Left frontal lobe (Broca's area) and adjacent motor cortex
Effortful, non-fluent speech with *preserved comprehension* is Broca's (expressive) aphasia, localizing to the left inferior frontal gyrus — and because the adjacent precentral gyrus serves the face and arm, an accompanying right-sided weakness fits a left middle cerebral artery territory stroke. The critical discriminator against Wernicke's aphasia is comprehension: Wernicke's patients speak fluently but with little meaning and *cannot* follow commands, which is the opposite of what is described. Language is left-hemisphere dominant in the overwhelming majority of people, and the weakness is right-sided because the corticospinal tract has already crossed.
Competition tip: Two questions resolve almost every aphasia vignette: is speech fluent, and is comprehension intact? Non-fluent with intact comprehension is Broca; fluent with impaired comprehension is Wernicke.
4.A 55-year-old has progressive weakness. Examination shows muscle wasting and fasciculations in the hands together with brisk reflexes and spasticity in the legs. Sensation is entirely normal. What is the most likely diagnosis?
Answer: B — Amyotrophic lateral sclerosis (ALS)
ALS is the one disorder that characteristically produces **upper and lower motor neuron signs together while completely sparing sensation**. The wasting and fasciculations are lower motor neuron features; the spasticity and brisk reflexes are upper motor neuron features; and the preserved sensation is what excludes most alternatives. A peripheral neuropathy would give lower motor neuron signs *with* sensory loss, and multiple sclerosis characteristically involves sensory pathways too.
Competition tip: Train yourself to sort every weakness vignette into upper motor neuron, lower motor neuron, or both, and then ask separately whether sensation is involved. "Both, with normal sensation" points strongly to ALS.
5.A 42-year-old develops irregular, jerky, dance-like involuntary movements, along with irritability and declining memory. His father developed similar symptoms at a similar age. Which structure is most affected?
Answer: B — Caudate nucleus
This is Huntington disease — an autosomal dominant CAG trinucleotide repeat disorder producing the triad of chorea, cognitive decline and psychiatric change, with the strong family history the vignette supplies. The pathology falls hardest on the striatum, and caudate atrophy is prominent enough to be visible on imaging as enlarged frontal horns of the lateral ventricles. Substantia nigra is the distractor for Parkinson disease, which causes poverty of movement rather than excess movement.
Competition tip: Basal ganglia disorders split neatly into too little movement (Parkinson, substantia nigra) and too much movement (Huntington, striatum). Sorting on that axis first makes the rest straightforward.
6.A 76-year-old has had slowly progressive memory loss over three years, worst for recent events, with word-finding difficulty and getting lost in familiar places. There is no weakness and no sudden deterioration. Which is most likely?
Answer: A — Alzheimer's disease
A gradual, continuously progressive decline that begins with recent (episodic) memory and spreads to language and spatial orientation is the typical course of Alzheimer's disease, whose pathology — amyloid plaques and neurofibrillary tangles — appears earliest in the hippocampus and entorhinal cortex. Vascular dementia is the key distractor and classically progresses in *sudden steps* tied to vascular events, often with focal signs, rather than the smooth decline described. Normal pressure hydrocephalus presents with the distinct triad of gait disturbance, urinary incontinence and dementia, and Creutzfeldt-Jakob disease progresses over months rather than years.
Competition tip: The tempo of a dementia is diagnostic information in its own right: years and smooth suggests Alzheimer; step-wise suggests vascular; weeks to months suggests prion disease.
7.A 60-year-old develops sudden weakness of the right face and arm with slurred speech. Symptoms began abruptly 40 minutes ago. Which vascular territory is most likely involved?
Answer: A — Left middle cerebral artery
Abrupt onset points to a vascular event, and the face-and-arm predominant pattern reflects the lateral convexity of the motor and sensory cortex — the middle cerebral artery territory, where the face and hand occupy the largest share of the homunculus. Because the corticospinal tract crosses in the medulla, right-sided weakness localizes to the **left** hemisphere, and the accompanying speech disturbance fits left-hemisphere language dominance. Posterior cerebral artery strokes chiefly affect vision, and basilar occlusion produces brainstem signs with reduced consciousness.
Competition tip: Face and arm worse than leg suggests middle cerebral artery; leg worse than arm suggests anterior cerebral artery, because the leg area sits on the medial surface.
8.A 19-year-old has episodes in which she stops mid-sentence, stares blankly for about ten seconds with slight eyelid fluttering, then resumes with no memory of the pause and no confusion afterwards. What is the most likely diagnosis?
Answer: A — Absence seizures
Brief staring spells with abrupt onset and offset, no warning, and — critically — **no post-episode confusion** are typical absence seizures, which are generalized from the outset and classically show a 3 Hz spike-and-wave pattern on EEG. The distractor to rule out is a focal seizure with impaired awareness, which usually lasts longer, often includes automatisms such as lip-smacking, and is characteristically followed by a period of post-ictal confusion. Syncope involves loss of postural tone with a fall, which is absent here.
Competition tip: The presence or absence of a post-ictal state is one of the highest-yield discriminators in seizure vignettes, and it is easy to overlook because it describes what happens *after* the event.
9.A 24-year-old has had six months of hearing voices, fixed false beliefs of being watched, disorganized speech, and marked social withdrawal, with no drug use and a clear sensorium. Which neurotransmitter system is most implicated?
Answer: A — Excess dopaminergic transmission in mesolimbic pathways
This presentation fits schizophrenia, and the long-standing dopamine hypothesis holds that positive symptoms such as hallucinations and delusions relate to excess dopaminergic transmission in the mesolimbic pathway — consistent with the fact that most antipsychotics are D2 receptor antagonists. Deficient nigrostriatal dopamine is the deliberate near-miss: that is Parkinson disease, and it is also why blocking dopamine to treat psychosis can produce Parkinsonian side effects. Basal forebrain acetylcholine loss is associated with Alzheimer disease.
Competition tip: When a vignette gives a psychiatric diagnosis, expect the follow-up to be pharmacological. Knowing which transmitter and which pathway — not just the disease name — is what the oral round is really testing.
These are original practice items, written by our faculty to match the published round structure of the competition. They are not reproduced past papers, and no past paper is reproduced anywhere on this site. The neuroscience in them is standard and checkable against the free Brain Facts book from the Society for Neuroscience and any standard neuroanatomy or neurology text.
Round names and their relative weighting have varied between years and between the national and international levels, so treat the round groupings here as a way to organize your practice rather than a guarantee of any particular year’s format. Check your own chapter’s published rules for what you will actually face.
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A chapter-by-chapter Brain Facts plan and how to prepare each round, with a study timeline.
Every structure the practical round expects you to identify, and how each one is tested.
Where the US chapters are, how to enter, and what is announced so far for the 2026–27 season.
Written questions you can drill alone. The neuroanatomy practical, the patient-diagnosis round and the live two-strike oral need someone to quiz you on unlabeled images and push back on your reasoning out loud. That is what our coaching adds — on top of the free material, not instead of it.
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