I now have enough information from textbooks and web sources to craft a comprehensive, well-referenced answer. Here are 9 neurology myths and facts:

FACT: We use virtually all of our brain, including during sleep.

The "10% myth" is perpetuated by movies like Limitless and Lucy, but neuroimaging and electrophysiology show that no region of the brain is entirely inactive. The brain consumes ~20% of the body's energy despite being only ~2% of its mass. Even during rest, the default mode network remains highly active — Northwestern Medicine. Neurons that go unused are pruned by the brain — there is no evolutionary benefit to carrying billions of dormant cells.

FACT: Both hemispheres work together as a deeply interconnected system.

While certain functions are lateralized (e.g., language is dominant in the left hemisphere for most right-handed individuals), large-scale neuroimaging studies show no evidence that individuals preferentially use one hemisphere over the other. Complex tasks — reasoning, creativity, language, emotion — engage distributed networks spanning both hemispheres simultaneously. The idea of a purely "creative right brain" vs. "logical left brain" is a pop-psychology oversimplification with no clinical support.

FACT: The brain retains neuroplasticity throughout life, and neurogenesis occurs in select adult brain regions.

As Kaplan & Sadock's Comprehensive Textbook of Psychiatry notes: "In the last decade, there has been a fundamental shift in paradigm regarding the limits of neurogenesis in the brain, with important implications for neural plasticity, mechanisms of disease etiology and therapy, and possibilities of repair." Neurogenesis continues in the hippocampal dentate gyrus and olfactory bulb in adults. Stroke rehabilitation, language learning, and motor skill training all demonstrate cortical map reorganization well into adulthood.

FACT: You cannot swallow your tongue, and inserting objects during a seizure is dangerous.

The tongue cannot be "swallowed" — it is anchored by the frenulum and floor of the mouth. Placing objects in the mouth during a seizure risks broken teeth, jaw injury, and harm to the rescuer. Correct first aid: protect the person from injury, turn them on their side (recovery position) to maintain airway patency, and time the seizure. Tongue-biting at the side of the tongue can occur, but this is not prevented by inserting anything into the mouth — Bradley and Daroff's Neurology in Clinical Practice.

FACT: More than 50% of people with epilepsy can identify seizure precipitants.

Bradley and Daroff's Neurology in Clinical Practice states: "More than 50% of subjects with epilepsy reported at least one precipitant." Common triggers include sleep deprivation, emotional stress, alcohol, photosensitive stimuli (flashing lights), and missed medications. Goldman-Cecil Medicine emphasizes identifying and correcting environmental and lifestyle triggers as a core part of epilepsy management. Seizure diaries and wearable technology are increasingly used to identify personal trigger patterns.

FACT: With modern disease-modifying therapy, many MS patients maintain normal or near-normal function for decades.

Neuroanatomy through Clinical Cases notes that while MS may evolve into a chronic progressive phase — especially if untreated — "severity of the disease varies greatly from patient to patient, and with good medical and neurological management, disability can be delayed." Modern high-efficacy DMTs (e.g., natalizumab, ocrelizumab, alemtuzumab) have dramatically changed the natural history of MS. Cognitive impairment, while common, does not inevitably progress to dementia, particularly in relapsing-remitting MS — confirmed at Brain Week 2024 (University of Bern).

FACT: Genetics is only one of many risk factors; lifestyle and environment play a major role.

Familial early-onset Alzheimer's (mutations in APP, PSEN1, PSEN2) accounts for less than 5% of all cases. The APOE ε4 allele increases risk but is neither necessary nor sufficient to cause the disease. The vast majority of Alzheimer's cases are sporadic and multifactorial. Cleveland Clinic neurologist Dr. Dylan Wint emphasizes that "lifestyle matters too — diet, exercise, and avoiding smoking and alcohol" are all modifiable risk factors. Cardiovascular risk factors (hypertension, diabetes, obesity) are strongly linked to dementia risk.

FACT: Brain death is irreversible cessation of all brain function, including the brainstem — it is legally and biologically equivalent to death.

Plum and Posner's Diagnosis and Treatment of Stupor and Coma carefully distinguishes these states: in a vegetative state, brainstem function is preserved (breathing, sleep-wake cycles); in coma, the patient is unresponsive but brainstem reflexes may persist; in brain death, there is complete and irreversible loss of all brain activity including the brainstem. Schwartz's Principles of Surgery notes that conditions mimicking brain death (severe hypothermia, drug overdose, hypoglycemia) must be rigorously excluded before a diagnosis can be made. Once confirmed by standardized testing, brain death is irreversible.

FACT: The brain is highly active during sleep, performing critical consolidation, repair, and clearance functions.

Kaplan & Sadock's Comprehensive Textbook of Psychiatry states: "Just as the old notion that the brain is silent during sleep has been disproved... Most subjects, if awakened, demonstrate active cognitive processing." During REM sleep, many brain regions are as active as wakefulness. Sleep serves essential neurological functions: memory consolidation (hippocampal replay), synaptic pruning, and — crucially — glymphatic clearance of metabolic waste products including amyloid-β and tau, the proteins implicated in Alzheimer's disease. Chronic sleep deprivation is now recognized as a significant risk factor for neurodegeneration.

Sources: Adams and Victor's Principles of Neurology (12th ed.) · Bradley and Daroff's Neurology in Clinical Practice · Plum and Posner's Diagnosis and Treatment of Stupor and Coma · Kaplan & Sadock's Comprehensive Textbook of Psychiatry · Goldman-Cecil Medicine · Neuroanatomy through Clinical Cases (3rd ed.) · MIT McGovern Institute · Cleveland Clinic · Northwestern Medicine

Here are 9 genuinely surprising, lesser-known neurology myths and facts:

FACT: Most concussions involve no loss of consciousness whatsoever.

Loss of consciousness occurs in fewer than 10% of concussions. The actual diagnostic hallmarks are post-traumatic amnesia (the classic "what happened?" loop), confusion, and altered mental status. Textbook of Family Medicine states plainly: "A concussion may or may not be associated with loss of consciousness." In fact, an athlete who briefly "sees stars" but never passes out may have a more significant concussion than one who was knocked out for 15 seconds. The LOC myth delays recognition of thousands of concussions each year. — Gray's Anatomy for Students; Goldman-Cecil Medicine

FACT: Phantom limb pain is a hard-wired consequence of cortical reorganization — it is entirely neurological.

After amputation, the brain's somatosensory cortex "map" for the missing limb doesn't just go dark — neighboring cortical regions invade that territory in a process called maladaptive plasticity. This abnormal rewiring generates genuine pain signals with no peripheral source. Eric Kandel's Principles of Neural Science notes: "Loss of a limb can lead to shrinking and even disappearance of the cortical representation of the limb. Abnormal reorganization likely contributes to phantom limb pain." This is why mirror therapy (tricking the brain with a reflection) can reduce pain — you're literally rewriting cortical maps. — Bradley and Daroff's Neurology; Ganong's Medical Physiology

FACT: The gut and brain are in constant two-way chemical conversation via the gut-brain axis.

The enteric nervous system (the gut's own neural network) contains over 500 million neurons — more than the spinal cord. It communicates with the brain via the vagus nerve, immune signals, and over 90% of the body's serotonin, which is produced in the gut, not the brain. Goodman & Gilman's references the gut-brain axis extensively in the context of psychiatric and neurological drug targets. Disrupted gut microbiota has been linked to Parkinson's disease (where gut pathology may actually precede brain lesions by years), anxiety, and depression.

FACT: Sleep is when the brain runs its waste disposal system — and skipping it literally lets toxic proteins build up.

The glymphatic system — a network of fluid channels alongside brain blood vessels — is nearly 10× more active during sleep, flushing out metabolic waste including β-amyloid and tau (the proteins that accumulate in Alzheimer's disease). Bradley and Daroff's Neurology confirms: "During sleep there is an increase in the interstitial space allowing for increased clearance of β-amyloid." Harrison's Principles (2025) adds that in mice engineered to develop Alzheimer's-like disease, sleep deprivation accelerated amyloid plaque formation. In other words, every night of poor sleep is a missed garbage collection for the brain.

FACT: The adult human brain generates approximately 700 new neurons in the hippocampus every single day.

For most of the 20th century, the dogma was "no new neurons after birth." This was overturned. Neuroscience: Exploring the Brain (5th ed.) states that radiocarbon dating studies of human hippocampal cells revealed "hippocampal neurons were continuously generated across the lifespan — in the adult human brain, 700 new neurons are added to the hippocampus every day." And in 2025, researchers directly observed newly formed neurons and their precursor cells in adult brains up to age 78, putting the debate largely to rest (Scientific American). These new neurons are involved in memory formation and emotional regulation. — Eric Kandel's Principles of Neural Science

FACT: Intelligence correlates with synaptic density and connectivity, not brain size.

Sperm whales have brains 5× heavier than humans, and elephants have more neurons in the cerebellum. What distinguishes human cognition is the density of synaptic connections — a grain-of-sand-sized piece of brain tissue contains 100,000 neurons and 1 billion synapses. Men on average have slightly larger brains than women, yet there is no demonstrated difference in cognitive capacity. As Penn LPS Online's neuroscience faculty note, "intelligence is determined by the number of synapses between brain cells, not brain girth." Einstein's brain was actually slightly smaller than average — but had unusually dense glial cells in key regions.

FACT: Several cognitive abilities actually improve with age, including emotional regulation, vocabulary, and conflict resolution.

While working memory and processing speed decline with age, the aging brain compensates via wisdom-related networks. Research cited at Penn LPS Online shows that comprehension, vocabulary, conflict resolution, and emotional regulation can improve into older age. Older adults also show reduced amygdala reactivity — they are genuinely less rattled by stress, not just better at hiding it. The brain also has five distinct developmental "eras" with turning points at ages 9, 23, 32, 66, and 83, each with reorganization and new capacities — identified in 2025 research.

FACT: Chronic pain is often a malfunction of the brain's own pain-processing circuits — even with no peripheral injury remaining.

The gate control theory of pain (Melzack & Wall) established that pain is not a passive signal from tissue to brain — it is actively modulated at every level of the nervous system. In conditions like fibromyalgia, complex regional pain syndrome, and central sensitization, the brain and spinal cord amplify pain signals even after peripheral healing is complete. Eric Kandel's Principles of Neural Science illustrates this with the gate-control model showing how inhibitory interneurons can suppress or amplify nociceptive input. This is why opioids often fail in chronic pain — they don't fix the central mis-wiring driving the pain.

FACT: In 2025, researchers discovered that healthy newborns have high tau levels — it appears to stabilize developing neurons.

Tau is widely known as a hallmark of Alzheimer's disease in adults, where it forms neurofibrillary tangles. But new research revealed that tau levels are naturally elevated in healthy neonatal brains, where it appears to serve a scaffolding function — stabilizing microtubules in developing neurons before naturally declining. As Healthcare Research Worldwide reports, "this challenges long-held assumptions about tau pathology" and opens the question of whether Alzheimer's pathology may partly reflect a misregulation of developmental programs. Understanding how the infant brain clears tau could point toward new preventive strategies.

Sources: Eric Kandel's Principles of Neural Science (6th ed.) · Neuroscience: Exploring the Brain (5th ed.) · Bradley and Daroff's Neurology in Clinical Practice · Harrison's Principles of Internal Medicine (2025) · Ganong's Review of Medical Physiology · Goldman-Cecil Medicine · Scientific American – 2025 Brain Discoveries