In this series, I dig a little deeper into the meaning of psychology-related terms. This week’s term is amnesia.
Amnesia is a memory deficit that can go in two different directions. Retrograde amnesia goes backward, affecting previously stored memories. Anterograde memory loss goes forward, affecting the ability to move short-term memory information into new long-term stored memories.
There are multiple types of amnesia that can have retrograde or anterograde effects. Typically the effect is on declarative memory (factual information) rather than procedural memory (how to complete tasks).
Alzheimer’s disease and other forms of dementia are degenerative diseases that cause memory loss as a result of physical changes in the brain.
Post-traumatic amnesia occurs following a traumatic brain injury such as a concussion. While it lasts, new events can’t be stored in memory. The effects can be both retrograde and anterograde. The Galveston Orientation Amnesia Test (GOAT) is the most commonly used test for post-traumatic memory disruptions.
Transient global amnesia is a neurological disorder with attacks that last several hours and involve short-term memory being effectively knocked out, along with difficulties retrieving older memories. Aside from that, though, the person is cognitively intact. The cause isn’t understood, but it has been linked to migraines and epilepsy.
Dissociative amnesia can result from periods of dissociation, such as in dissociative identity disorder, or repressed memories. Memory loss may occur during traumatic situations like sexual assault. Some of the event memories may consolidate after a couple of nights sleep.
Korsakoff’s syndrome can result from a severe deficiency in thiamine due to long-term alcoholism. People with this disorder tend to confabulate, meaning their brain unconsciously makes up stories to fill gaps in memory. This is not conscious lying; rather, it is an involuntary process.
Related to medical treatment
Drug-induced amnesia can be useful during medical or dental procedures to reduce memories of the procedure once it’s done. Colonoscopies and wisdom tooth removal are examples of procedures where amnestic drugs like the benzodiazepine midazolam may be used.
Electroconvulsive therapy (ECT) can potentially cause anterograde and retrograde memory loss. I experienced both. The anterograde effects didn’t bother me all that much, and I didn’t tend to notice it as much as my family did, since they hadn’t forgotten that I’d already asked the same question 10 times. The retrograde effects more disturbing. Some of those memories came back eventually, but others didn’t. It was a strange feeling, especially if I was looking at photographs of myself doing things I felt certain I’d never done.
Between all of these potential causes for amnesia and the cognitive biases that tend to skew our thinking and memory, it really is quite amazing that our memories work as well as they do and as often as they do.