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What Happens to Your Neurons During a Concussion? The Cellular Science of Brain Injury · Understanding the Brain

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  Speaker 1: Ah, yes, we've seen it many times in the movies
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  Speaker 1: where a blunt object can cause amnesia with a blow
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  Speaker 1: to the head. But does it really? Can a second
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  Speaker 1: blow to the head really restore your memory as well? Well,
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  Speaker 1: it's falling out. On Ginnikon's Island, getting hit on the
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  Speaker 1: head could produce a medical condition. The characters might suddenly
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  Speaker 1: forget who they were, where they lived, or even recognize
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  Speaker 1: their friends. Fortunately, TV had a convenient cure. Hit the
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  Speaker 1: person again on the head. Somehow, the second impact would
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  Speaker 1: restore the memories the first head erased. Hollywood has used
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  Speaker 1: variations of this storyline for decades, from soap operas to
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  Speaker 1: The Bourne Identity. But there's a fascinating neurological question. Can
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  Speaker 1: a physical blow actually erase someone's memories, and could another
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  Speaker 1: one bring them back? To answer that, we need to
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  Speaker 1: understand what happens on the side of the brain during
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  Speaker 1: a TBI, traumatic brain injury. When someone's head experiences a
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  Speaker 1: sudden impact, the brain can accelerate, decelerate, or rotate within
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  Speaker 1: the skull. These movements create mechanical forces that stretch and
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  Speaker 1: deform brain tissue. Even without a skull fracture, neurons and
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  Speaker 1: their connecting fibers, called axons, can experience significant stress. At
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  Speaker 1: the cellular level, the consequences are complicated. Mechanical deformation can
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  Speaker 1: disrupt neuronal membranes, causing potassium to move out of cells
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  Speaker 1: and calcium to enter. This triggers increased neurotransmitter release, including glutamate.
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  Speaker 1: Glutamate is essential for normal learning and memory, but excessive
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  Speaker 1: activity can contribute to excitotoxic injury. Meanwhile, neurons require additional
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  Speaker 1: energy to restore their normal electrical balance. The problem is
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  Speaker 1: that concussions can also disrupt cerebral blood flow and mitochondrial
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  Speaker 1: energy production. Scientists will call this mismatch between increased energy
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  Speaker 1: demand and impaired energy availability. Now consider memory. One particularly
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  Speaker 1: important brain structure is the hippocampus, the memory place. It
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  Speaker 1: helps encode and consolidate new memories. Damage or disruption involving
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  Speaker 1: the hippocampus and its connective networks can interfere with memory formation.
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  Speaker 1: But not all amnesia is the same. There's retrograde amnesia,
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  Speaker 1: which involves losing access to memories formed before an injury.
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  Speaker 1: Someone might forget the hours or days leading up to
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  Speaker 1: an accident. Enterograde amnesia involves difficulty forming new memories after
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  Speaker 1: the injury. A patient may repeatedly ask what happened because
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  Speaker 1: they can't retain the explanation. Then there's disassociative amnesia, sometimes
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  Speaker 1: associated with disassociative fugue, Will you leave the house? Do
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  Speaker 1: you have unexpected travel or wandering associated with identity confusion?
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  Speaker 1: Disassociative amnesia involves autobiographical memory disruption that cannot be explained
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  Speaker 1: by a neurological injury or substances. Let's return to Gilligan's Island.
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  Speaker 1: Could a second blow restore someone's memory? There is no
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  Speaker 1: credible neurological evidence supporting that treatment. In fact, another impact
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  Speaker 1: could produce additional injury. Repeated concussions can prolong recovery and
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  Speaker 1: increase the risk of persistent neurological problems. A rare but
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  Speaker 1: catastrophic condition called second impact syndrome has been described when
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  Speaker 1: another head injury occurs before recovery from an earlier concussion.
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  Speaker 1: Repeated head impacts are also associated with what they call
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  Speaker 1: chronic traumatic encephalopathy, or CTE, a neurodegenerative pathology identified after death,
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  Speaker 1: although individual risk and the relationship between exposure and disease
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  Speaker 1: remain under investigation. Here's another misconception. Memories are not stored
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  Speaker 1: in one isolated compartment that can be switched on or
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  Speaker 1: off or restarted. They depend on distributed neural networks involving
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  Speaker 1: the hippocampus, cortex, and other brain regions. So the next
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  Speaker 1: time Gilligan loses his memory after being struck by a coconut,
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  Speaker 1: remember the reality. The brain is not a television set
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  Speaker 1: that can be repaired by hitting it twice. And that's
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  Speaker 1: it for now.