During a seizure, large groups of brain cells fire electrical signals all at once in an uncontrolled burst, disrupting normal brain function for seconds to minutes. This surge of abnormal activity can affect movement, awareness, sensation, and emotions, and it also triggers changes in heart rate and breathing that most people never realize are part of a seizure. What a person experiences depends on where in the brain the electrical storm starts and how far it spreads.
What Happens Inside the Brain
Under normal conditions, neurons in your brain fire in organized patterns, passing signals to one another in a coordinated way. During a seizure, two things go wrong at the cellular level. First, individual neurons become hyperexcitable, meaning they fire rapid bursts of signals in response to far less stimulation than usual. Second, large numbers of neighboring neurons get recruited into this abnormal pattern, a phenomenon called hypersynchrony. The result is a wave of excessive electrical discharge that overwhelms the brain’s normal signaling.
This isn’t a malfunction in a single spot. A seizure is a network event that requires the participation of many neurons firing in lockstep, often involving both the outer brain (cortex) and deeper brain structures. Researchers using advanced EEG techniques have detected ultra-fast electrical bursts called “fast ripples,” oscillating at 250 to 600 Hz, in small patches of brain tissue. These localized bursts can synchronize and ignite a full seizure. Where those bursts originate determines which functions get disrupted: movement, vision, memory, emotion, or all of them at once.
The Four Phases of a Seizure
Not every seizure includes all four phases, and not everyone experiences them the same way. But the general pattern moves through a warning period, a main event, and a recovery period.
Prodrome
Hours or even a day or two before a seizure, some people notice subtle shifts: mood changes, unusual anxiety, difficulty sleeping or concentrating, or a vague sense that something is off. Not everyone gets a prodrome, but those who do often learn to recognize it as an early signal.
Aura
An aura is actually a small seizure in itself, a brief burst of electrical activity in one part of the brain. It may last only a few seconds and can feel deeply strange. Common aura experiences include déjà vu (the uncanny sense that a moment has happened before), jamais vu (seeing something familiar as though for the first time), a rising feeling in the stomach, numbness or tingling, sudden fear or panic, and sensory distortions like odd smells, tastes, or visual flickers. The specific sensation depends on which brain region is involved:
- Visual auras produce flashing lights, flickering colors, simple geometric patterns, or blind spots.
- Auditory auras cause buzzing, ringing, drumming, or single tones.
- Olfactory auras bring on a sudden smell, often unpleasant, with no source.
- Gustatory auras create acidic, bitter, salty, sweet, or metallic tastes.
- Somatosensory auras feel like tingling, electric-shock sensations, or a sense of movement in part of the body.
- Vestibular auras produce dizziness, spinning, or vertigo.
An aura sometimes stays isolated. Other times it’s the opening act before the seizure spreads further.
The Seizure Itself (Ictal Phase)
This is what most people think of when they picture a seizure. What happens during this phase varies enormously depending on the type. The person may lose awareness, stare blankly, twitch, convulse, smack their lips, pick at their clothing, or say strange words. Their heart races, breathing changes, and muscles may stiffen or jerk rhythmically. This phase typically lasts from a few seconds to a few minutes.
Recovery (Postictal Phase)
After the electrical storm subsides, the brain doesn’t snap back to normal immediately. The postictal state lasts five to 30 minutes on average but can stretch to hours or, after severe seizures, days. Confusion, exhaustion, headache, muscle soreness, memory gaps, and difficulty speaking are all common. Some people feel depressed, anxious, or emotionally raw. After severe seizures, a person may experience hallucinations, delirium, or temporary psychosis. Loss of bladder control, nausea, and elevated body temperature can also occur during this phase.
How Different Seizure Types Look and Feel
The two broadest categories are focal seizures, which start on one side of the brain, and generalized seizures, which involve both sides from the start.
Focal Seizures
In a focal aware seizure, the person stays conscious throughout. They might feel déjà vu, a strange stomach sensation, or have twitching on one side of the body. They can sometimes talk during the episode and remember it afterward. In a focal impaired awareness seizure, consciousness is disrupted. The person looks confused or dazed, may smack their lips or pick at their clothes, and typically can’t respond to questions for a few minutes. These are often mistaken for daydreaming or intoxication.
Generalized Seizures
Generalized motor seizures affect both sides of the body and almost always involve loss of consciousness. The most dramatic form is the tonic-clonic seizure: muscles stiffen (the tonic phase), the person may cry out and fall, and then rhythmic jerking follows (the clonic phase). These typically last a few minutes and leave the person confused and exhausted afterward.
Not all generalized seizures are convulsive. Absence seizures cause a brief, sudden lapse in consciousness, usually lasting under 15 seconds. The person may stare into space, blink rapidly, or make subtle chewing or hand movements. These are especially common in children and can happen dozens of times a day without being noticed.
Other generalized subtypes include myoclonic seizures (quick, lightning-fast jerks), atonic seizures (a sudden loss of muscle tone that causes the person to drop to the ground), and tonic seizures (muscles go rigid without the jerking phase).
What Happens to the Heart and Lungs
Seizures don’t just affect the brain. The autonomic nervous system, which controls heart rate and breathing, gets caught up in the electrical storm. During convulsive seizures, heart rate spikes to an average of about 139 beats per minute. Even nonconvulsive seizures raise the heart rate to around 105 beats per minute. Slow heart rate during a seizure is rare, occurring in less than half a percent of cases.
Breathing is affected even more dramatically. Temporary pauses in breathing (apnea) or shallow breathing occur in 43 to 59 percent of all seizures. During convulsive seizures, breathing can stop entirely for the duration of the event. After the seizure ends, the body often overcompensates with rapid breathing.
Perhaps the most surprising finding is how long these effects linger. After a convulsive seizure, the elevated heart rate takes a median of 60 minutes to return to baseline. The rapid breathing that follows takes about 25 minutes to normalize. After nonconvulsive seizures, these changes resolve in roughly a minute. This is one reason convulsive seizures leave people feeling so physically drained: their cardiovascular system has essentially been sprinting.
How to Help Someone Having a Seizure
If you see someone having a convulsive seizure, the most important things are simple: stay calm, stay with them, and keep the area safe. Move hard or sharp objects away. If they’re on the ground, gently roll them onto their side with their mouth pointing downward to keep the airway clear. Place something soft under their head, remove their glasses, and loosen anything tight around their neck.
Time the seizure. If it lasts longer than five minutes, call 911. Most seizures end on their own well before that point.
Three things to avoid, despite what you may have heard:
- Don’t hold the person down or try to restrain their movements. You could injure them or yourself.
- Don’t put anything in their mouth. People cannot swallow their tongue during a seizure. Forcing something between their teeth can break teeth or injure the jaw.
- Don’t give mouth-to-mouth. Breathing almost always resumes on its own once the seizure ends.
Once the seizure stops, help the person sit in a safe place and let them recover. Don’t offer food or water until they’re fully alert. Expect confusion and fatigue. Speaking calmly and telling them what happened can help, since many people have no memory of the event itself.