Memory Leak: Black Holes Decrypted

The potentially explosive situation is an inexhaustible source of comedy: a hero wakes up one morning with a huge hangover, and with no memory of what the old woman might have done. All he can remember is overdoing the vodka. Then nothing. The black hole. However, the videos and friends are formal: he did not fall asleep – the loss of memory does not correspond to a loss of consciousness – and he even continued to enliven the evening, in a more or less appropriate way.

“Even in a state of amnesia, the drinker can hold a conversation, talk about the past and make decisions, but won’t remember them the next day”explains Aaron White, a neuroscientist at National Institute on Alcohol Abuse and Alcoholism (NIAAA) American. These alcohol blackouts would be far from uncommon. While no data exists for adults, a 2016 British survey showed that among 2,140 teenagers who had used alcohol in the past six months, 20% had experienced some form of amnesia.

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Drinking can derail our “memory map.” In question, a neural bug in the hippocampus, this small brain structure in which the transfer of memories from short-term memory to long-term memory takes place, and which therefore allows the lasting recording of facts and events. “Alcohol slows down the electrical impulse in hippocampal neurons and other important areas of the brain by increasing the activity of a receptor, that of gamma-aminobutyric acid (Gaba), the main inhibitor of the central nervous system. It also blocks another receptor, called the NMDA receptor, which is essential for making new memories.”adds Aaron White.

With the hippocampus struggling, the encoding of new memories falls by the wayside. In most cases, however, the fragments of the evening that have still managed to print will be able to return. “We are talking about a piecemeal or partial blackout, continues the neuroscientist. ‘Islands’ of scattered memories remain, separated by large empty commemorative spaces. ” Complete amnesia is known as a complete blackout or en bloc. In this case, there is no point in trying to remember the events. It’s a waste of time: memories don’t exist and never did.

“Alcohol slows electrical impulses in hippocampal neurons and blocks the NMDA receptor, which is essential for making new memories”

THE EFFECT OF BENZODIAZEPINES

When faced with alcoholic amnesia, we are not the same. One thing is certain: it’s not just for young fans of get plastered. Any drinker can experience it, regardless of age and relationship to alcohol. But large amounts of alcohol, especially if absorbed very quickly, still predispose to memory lapses.

“Mild memory impairment appears at 0.5 g/L of blood alcohol and memory loss tends to occur at around 1.5 g/L, says Aaron White. Women weigh less on average than men and their bodies contain less water, their blood alcohol level increases often higher and faster. That would explain why they are more at risk.”

Another dangerous cocktail: mixing wine or gin and tonic with benzodiazepines, a family of drugs prescribed for anxiety and insomnia. They can also enhance the action of Gaba, a neurotransmitter that inhibits neuronal activity. But they don’t bring about that image of drunkenness: difficulty keeping balance, slurring, etc. – typical of alcohol poisoning, making them ideal substances for abuse.

“Rohypnol and Mogadon, two highly amnesic benzodiazepines, have also been withdrawn from the market, because they were used in rape cases brought before the courts” recalls Catherine Thomas-Anterion, neurologist, doctor of neuropsychology and research associate at the Laboratory for the study of cognitive mechanisms at the University of Lyon 2.

GHB: HOW DOES MEMORY LOSS HAPPEN?

GHB, another sedative and hypnotic substance misused for criminal purposes, can produce retrograde and anterograde amnesia: it is more difficult for a person who has consumed it to remember what happened immediately before the drug was administered, or to retain any new information within hours to take it. “The pharmacological mechanisms of action of GHB are not yet clear.

It is possible that there is a specific receptor for GHB. But the drug certainly also activates the Gaba receptors, numerous in the hippocampus, as well as in the cerebral cortex and in the amygdala”, explains Harry Sumnall, professor of toxicology at John Moores University in Liverpool. Again, the memories will perhaps be written in dotted lines. “Anterograde amnesia can be partial or complete, so that some events can be remembered”, nuance the specialist.

“Anterograde amnesia can be partial or complete, so that some events can be remembered”

MEMORY LOSS: AMNESIC STROKE

But you don’t need alcohol or drugs to definitively ′′ hoe ′′ a few hours of your life. Everyone, in absolute terms, is susceptible to being affected by transient amnesia, also called amnesiac stroke.

“LThe neurons in the hippocampus are very fragile and other factors can prevent them from functioning normally.”, adds Catherine Thomas-Anterion. A physical shock – the sudden onset of a severe cold, an unusual effort – or a psychological shock – severe stress or the announcement of bad news – or even certain pathologies such as migraine can suspend the work of neurons. A parenthesis during which amnesiacs are perfectly able to drive, talk and go about their business normally.

Until they realize something is wrong, and they panic: “We often see lost and panicked people who come to the emergency room for this reason. We reassure them: the situation naturally returns to normal after 4-24 hours.”, specifies the neurologist. More fear than harm. But a page will definitely remain blank for some.

“There are still ‘islands’
of scattered, separate memories
from large empty commemorative spaces”

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