system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What happens when one “blacks out” when drinking too much alcohol?
gpt
The medical term for a blackout is ‘anterograde amnesia’, essentially meaning that it’s memory loss acting forward in time (whilst the substance is affecting you), so it’s difficult or impossible to form new memories.

Alcohol belongs to a drug class called the GABAergics, which are drugs that affect GABA and/or its receptors (the main neurotransmitter which acts to ‘calm’ the brain/body down). Other similar drugs include benzodiazepines (like Valium and Xanax), and barbiturates. These drugs work by affecting how nerves communicate with each other, especially in the brain, by essentially slowing down signals between neurons. An analogy would be like a hose connected to a water supply, where taking alcohol is essentially turning down the tap so it’s just a trickle. This happens differently depending on the specific area of the brain.

Because nerve communication is so vital for memory formation, due to it requiring strengthened connections between neurons, taking a substance which decreases that will inevitably have an impact on how well you’ll be able to remember events while under the influence.

As a side note, it’s also possible to cause a blackout through high doses of drugs that act against the neurotransmitter systems responsible for causing nerves to transmit to each other - namely NMDA/glutamate. This is why people usually don’t remember surgeries where general anaesthesia is used, and also when using certain recreational drugs like ketamine (a dissociative depressant, medically used as an anaesthetic). It’s not a matter of neurotoxicity when you don’t drink often, although this is definitely a reason why alcoholics often struggle with memory issues over long periods.