NOTICE: Posting schedule is irregular. I hope to get back to a regular schedule as the day-job allows.

Thursday, March 24, 2011

Amnesia who?

Note: The following appeared last year as a guest post to "Mad Genius Club", a daily blog which rotates between science fiction/fantasy authors. This take on amnesia, as well as the appeal to authors to *not* overuse the cliche, seemed appropriate to the current topic being covered in The Lab Rats' Guide to the Brain, so I present this as my as last "canned" post while on vacation.


"Mrs. Smith?"

"Yes Doctor?"

"Your husband suffered a terrible head injury. He's in a coma."

"Oh, Doctor, will he be all right?"

"We'll only know once he wakes up."

"Ashley? It's me, Melissa!"

"Where am I? Who are you? What happened? Who am I?"

"Oh, no!"

It's a familiar theme, amnesia as a plot device. Overused, trite, cliché, yes; but also terribly *mis*-used.

Hi, the bloggers of the Mad Genius Club have asked me to contribute a series on the science behind science fiction/fantasy. I don't claim to be a Mad Genius, nor am I necessarily a Mad Scientist – a bit upset at times, but not truly Mad! Bwahahahaha! (I think we can safely save that label for Dr. Freer.) However, I am a neuroscientist, currently employed as a faculty member at a medical school.


What? Oh, yeah. This is Ratley, an intelligent lab rat. Actually that's LabRat, they insist on the capitals. Ratley and his friends will help me with these blogs.

So, on to today's topic: SF/F clichés regarding the brain with particular emphasis on amnesia.

Amnesia is little understood by the lay public. The most common experience of amnesia is the soap-opera scene with which this column opened. But what is amnesia, and how does it *really* happen?

OK, classroom time.


What? I said, class…

[Squeak, squeak, squee…]

OK, if you insist,*you* tell them.

[Ahem. OK, y'all, I got the stuffy Doc out of the way. As the Doc said, I'm Ratley, and I've *experienced* amnesia in the lab. Let me tell ya, it ain't no picnic. Amnesia means "without memory," and there's two typical types – retrograde amnesia, meaning a loss of memory from the past. The other kind is called anterograde amnesia and it means loss of memory "forward" into the future. I've had 'em both, and they result when a part of the brain that processes memory ain't workin'. ]

Excuse me, Ratley?


Are you going to explain what you mean by "future" memory? Shouldn't you tell them that anterograde amnesia is a lack of ability to make *new* memories?


I will, thanks.

In fact, anterograde amnesia is the most common form of amnesia, even though the retrograde form (poor Ashley, above) is better known. Imagine, trying to remember a phone number but never quite managing it; reading the same newspaper over and over again, never recalling the previous read; or never being able to remember where you'd left your keys, your car, your kids, your wife…

How can this be, how can it happen? Well, let's start by looking at how amnesia happens.

Take Ratley for instance.


Not literally, calm down, please! I'm just giving an example!

When Ratley said he had experienced amnesia, he means that in the lab, scientists use a chemical to temporarily put part of the brain to sleep, causing amnesia – which type depends on the brain area affected. In humans, amnesia usually results from damage to the brain. Oh, but not just any damage! It has to be specific type of damage and specific areas of the brain. Damage can be a traumatic head injury: Ashley's tragic soap-opera car crash, or the angsty teen's headfirst dive into an empty swimming pool. Damage to specific brain areas can also occur due to epilepsy, stroke, tumor, hemorrhage, infection (meningitis or encephalitis) or drug interactions.


Yes, Ratley, just like Ratface. See folks, Ratface did a bit too much LDS in the 60's. He's harmless – really – but not all there.

And what are those brain areas? Well, in scientist language, they are the pre-frontal and frontal cortex (for retrograde amnesia); hippocampus, medial temporal lobe and diencephalon (for anterograde amnesia). Traumatic injury, tumor and stroke can affect any of these areas; infection and hemorrhage are most likely to involve the frontal and prefrontal cortex, while epilepsy and drugs are most likely to affect the hippocampus, temporal lobe and diencephalon.


Yes, I know. Go ahead. Ratley wants to show you how to tell the brain areas apart.

[[sq…] Oh, sorry about that. Okay, humans. You've got those big hands with nice opposable thumbs. So, unhand that mouse and keyboard! Now, place your index fingers on your temples, yes, the soft areas at the side of the forehead. Feel that? It is the most direct access to your brain except from the inside. From your fingers to the center of your forehead is frontal cortex. If you draw a line between your forefingers across the top of your head – that's the prefrontal cortex. Move your fingers straight back until they are directly in front of your ears – that's the medial temporal lobe and hippocampus. Move the fingers below and behind the ears – straight in from there at the center, bottom of the brain is the brain stem, also known as the diencephalon.

[What about the other areas, the top of the head, the back, the base of the skull? You humans just *love* to make movies where the bad guy hits the hero on the top or back of the skull with the butt of a gun – he (or she) loses consciousness and wakes up in the hospital with amnesia. Silly humans. Listen to the rat, now: it's not gonna happen that way.

[Next exercise, put your thumbs directly in front of your ears and lace your other fingers over the top of your head. That's the sensory and motor areas – controlling all sense of touch, position and pain, and moving the various muscles of the body. From there to the back of the skull is visual area, responsible not only for sight, but also interpreting what you see. Run your fingers down from top, center of your head, to the very back the skull. Feel that slight dimple? That bony area right below it protects the cerebellum, responsible for coordinating all of the muscles involved in any movement. ]

Thanks, Ratley!

So, in our story brave Ashley foils the terrorist, gets cold-cocked at the base of his skull for his troubles, and wakes up with amnesia, right? Well, no. He might wake up with some coordination problems, blurred vision or possibly "agnosia" a specific type of amnesia for words or faces, but not full scale retrograde amnesia.

What about that mysterious alien parasite that "wraps itself around the cerebral cortex" and takes over its host, leaving total amnesia in its path?


No, Ratley, I know what you're going to say, but I'm *not* talking about Ratfink!

Leaving aside the fact that there is no *room* for such a parasite without sacrificing so much brain tissue that the host is clearly impaired in more than just memory, the description is not specific enough to suggest any particular type of amnesia. No, the more likely result will be pressure on the other parts of the brain causing the hapless host to stop thinking and breathing well before any amnesia could set in.

On the other hand, just about any surgery on the brain carries risk of damage to neighboring area. Anterograde amnesia is a common side effect, although retrograde amnesia is rarer. In fact, to get total retrograde amnesia requires trauma – massive infection, crushing injury to the central-to-frontal part of the skull, concussive blast injury. Anything less is unlikely to give total amnesia. Oh, sure, falling off a horse and hitting your head on a curb will likely cause a bit of amnesia – certainly for the 10 minutes or so immediately preceding the injury – but not the total "Who am I?" kind. Typically the amnesia lasts as long as the brain swelling that accompanies the concussion (about 24-48 hours) but usually only extends to memories from a few hours to a few months prior to the accident.

So, how *do* you incorporate brain damage and/or amnesia into a plot? Ratley?

[First, keep it simple. If the big dumb hero takes a glancing blow to the head, he's not gonna have total amnesia and lead a complete second life for 20 years. Keep it simple, and keep it short. Give the big dummy amnesia for the day leading up to the accident, and only lasting a few days to a week. However, you *can* leave the actual events of the accident permanently forgotten.

[Second, avoid the obvious. Instead of giving the dude full amnesia, consider an alternative.


Right, Ratley. Alternatives to amnesia might be: (1) agnosia– inability to remember faces or the names of common objects, (2) aphasia - the inability to speak certain words or names (we also call this the "tip of the tongue" phenomenon), or (3) neglect – an apparent inability to consciously notice objects that occur in particular places in our field of vision.

Back to you, Ratley.

[Thanks, Doc.

[Third, remember that total retrograde amnesia is *rare*. Instead of amnesia, give your character vision, hearing or coordination problems. There's a bunchaton of other stuff that happens after head injury.

[Fourth, keep in mind the differences in those different types of amnesia: give a human anterograde amnesia and they may not remember that they had the exact same conversation 15 minutes ago, but they can still remember the name of their 10th grade crush. Likewise, retrograde amnesia still leaves the ability to make new memories.

[Ah, excuse me a sec…

[HEY RATFACE! The cheese is over THERE!

[Ah, sorry about that, maybe Doc needs to finish this while I go clean up a mess...]

So, folks, Ratley's final point is to keep the perspective. Amnesia typically means loss of memory for facts. Skills such as reading, riding a bike, speaking a foreign language, complex logic puzzles – those memories are processed and stored in a different manner and not subject to the same injuries as amnesia. Just like Ratface can't remember where he left the cheese just now, he still remembers how to run mazes and get under Ratley's fur.

Finally, don't be too stuck on the rules (or clichés). Try something new, or figure out a way to let your protagonist function with just a partial injury. If you want help, don't hesitate to contact an expert –


- Or a LabRat! In fact, many scientists would be flattered to help out.

1 comment:

  1. I once fell backwards in a high school class and struck the back of my head on the floor hard enough to draw blood. My memories of that morning were gone forever. I had no memory of getting up and going to school or my classes before that one. I also temporarily could not find my locker. I took the phone away from them in the office and told my mom to come get me although the school was telling me I was fine and just needed to hustle my butt to my next class. I was temporarily unable to remember my classes or locker combination. But the next day I did.


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