Quiz of the Day
The Human Brain
Saturday, 10 October 2026
Anchored to World Mental Health Day (Oct 10), exploring neuroscience, psychology, memory, and how the mind works
1. Approximately how many neurons does the adult human brain contain?
- 1 million
- 86 billion
- 500 thousand
- 10 trillion
The adult human brain contains roughly 86 billion neurons, a figure established by neuroscientist Suzana Herculano-Houzel using a technique that dissolves brain tissue into a uniform 'soup' to count cell nuclei. This revised the long-repeated estimate of 100 billion. Each neuron can form thousands of connections, creating a network of staggering complexity.
2. Which part of the brain is primarily responsible for balance and coordinating movement?
- Cerebellum
- Hippocampus
- Medulla
- Amygdala
The cerebellum, whose name means 'little brain' in Latin, sits at the back of the skull and fine-tunes balance, posture, and coordinated movement. Although it makes up only about 10% of the brain's volume, it contains more than half of all the brain's neurons. Damage to it can cause a wobbly, uncoordinated gait known as ataxia.
3. Which brain structure is most strongly associated with forming new long-term memories?
- Cerebellum
- Thalamus
- Hippocampus
- Pons
The seahorse-shaped hippocampus is essential for converting short-term experiences into durable long-term memories. Its name comes from the Greek words for 'horse' and 'sea monster' because of its curved shape. London taxi drivers, who memorize the city's vast street network, have been shown to develop a larger posterior hippocampus.
4. The amygdala is best known for processing which of the following?
- Vision
- Digestion
- Hearing
- Fear and emotion
The amygdala is an almond-shaped cluster of nuclei deep in the temporal lobes that plays a central role in processing fear and other strong emotions. It helps trigger the body's rapid 'fight-or-flight' response before the conscious mind has fully assessed a threat. People with rare damage to the amygdala can lose the normal ability to feel fear.
5. What is the wrinkled outer layer of the cerebrum called?
- Brain stem
- Cerebral cortex
- Corpus callosum
- Meninges
The cerebral cortex is the brain's deeply folded outer layer, responsible for higher functions like thought, language, and voluntary movement. Its folds and grooves dramatically increase surface area; if flattened out, the cortex would cover roughly the area of a large dinner napkin. Despite its importance, it is only about 2 to 4 millimeters thick.
6. What are the chemical messengers that carry signals across the gaps between neurons?
- Hormones
- Neurotransmitters
- Antibodies
- Electrolytes
Neurotransmitters are chemicals released at synapses to pass signals from one neuron to the next across a tiny gap called the synaptic cleft. Well-known examples include dopamine, serotonin, and acetylcholine. Many psychiatric medications work by adjusting how these molecules are released, received, or recycled in the brain.
7. World Mental Health Day is observed each year on which date?
- October 10
- April 7
- October 1
- September 10
World Mental Health Day has been observed on October 10 since 1992, when it was launched by the World Federation for Mental Health. It aims to raise awareness of mental health issues and mobilize support around the world. The World Federation for Mental Health announces a different theme for the day each year.
8. The corpus callosum is a thick bundle of nerve fibers that connects what?
- The cerebellum and the cortex
- The two cerebral hemispheres
- The eyes and the brain
- The brain and the spinal cord
The corpus callosum is the brain's largest white-matter structure, made of roughly 200 million nerve fibers linking the left and right cerebral hemispheres. It lets the two sides of the brain share information and coordinate. In rare cases it is surgically cut to treat severe epilepsy, producing fascinating 'split-brain' effects studied by Roger Sperry.
9. Which neurotransmitter is most commonly linked to reward, motivation, and pleasure?
- Keratin
- Dopamine
- Collagen
- Insulin
Dopamine is a neurotransmitter central to the brain's reward and motivation systems, spiking in anticipation of rewards to reinforce behaviors. It also plays a key role in movement, which is why the loss of dopamine-producing cells causes the tremors of Parkinson's disease. Many addictive drugs work by flooding the brain with dopamine.
10. Which lobe of the brain is primarily responsible for processing visual information?
- Temporal lobe
- Frontal lobe
- Occipital lobe
- Parietal lobe
The occipital lobe sits at the very back of the brain and is dedicated mainly to processing what we see. Because vision is handled so far from the eyes, a blow to the back of the head can cause people to 'see stars' or flashes of light. The primary visual cortex here maps the visual field in remarkable detail.
11. What does the term 'neuroplasticity' refer to?
- The hardening of brain tissue with age
- The brain's ability to reorganize and form new connections
- A type of brain-imaging scan
- A surgical procedure on the brain
Neuroplasticity is the brain's lifelong capacity to rewire itself by forming, strengthening, or pruning connections between neurons. It underlies learning, memory, and recovery after injury, as healthy regions can sometimes take over lost functions. Once thought to stop after childhood, plasticity is now known to continue throughout adult life.
12. The brain is about 2% of body weight, but roughly what share of the body's energy does it consume?
- About 2%
- About 20%
- About 75%
- About 50%
Although it accounts for only about 2% of body weight, the brain uses roughly 20% of the body's energy and oxygen. This makes it one of the most metabolically demanding organs, running almost continuously even during sleep. Its hunger for glucose is why mental fatigue can feel so draining.
13. The famous patient known as 'H.M.' lost which ability after brain surgery in 1953?
- The ability to feel physical pain
- The ability to speak
- The ability to form new long-term memories
- The ability to recognize faces
Henry Molaison, known for decades only as 'H.M.', had large portions of his medial temporal lobes, including much of the hippocampus, removed in 1953 to treat severe epilepsy. The surgery left him unable to form new long-term memories, a condition called anterograde amnesia. His case transformed scientists' understanding of how memory is organized in the brain.
14. Which is the brain's main inhibitory neurotransmitter, calming neural activity?
- GABA
- Dopamine
- Glutamate
- Serotonin
GABA (gamma-aminobutyric acid) is the brain's principal inhibitory neurotransmitter, reducing the excitability of neurons and helping to keep activity in balance. It works in opposition to glutamate, the main excitatory neurotransmitter. Many anti-anxiety drugs, such as benzodiazepines, enhance GABA's calming effects.
15. What is the fatty insulating sheath around nerve fibers that speeds up signal transmission?
- Glia
- Dendrite
- Synapse
- Myelin
Myelin is a fatty substance that wraps around the axons of many neurons, acting like insulation on an electrical wire. It allows nerve signals to jump between gaps called nodes of Ranvier, dramatically speeding transmission. In multiple sclerosis, the immune system attacks myelin, disrupting communication between the brain and body.