So you're walking along, minding your own business, playing with your iPod in a neutron storm next to a nuclear plant during the equinox, and suddenly some Applied Phlebotinum grants you a magnificent gift: an entire library's worth of information is downloaded directly into your head, along with all the intellect, memories and wisdom needed to use it. You become an instant genius at everything from knitting to astrophysics, and you can suddenly Techno Babble your way out of any problem!
Except... for this problem:
The thing about super-human knowledge and intellect, is that often you don't get a super-human brain to put it in, and there's only so much room in there. As your brainpower goes up, your survival rate goes down. Time is running out, and you either have to figure out a way to ditch your new super-smarts or die — either by hemorrhage, cranial explosion, or body strain.
Occasionally dying isn't the problem: It might be non-fatal, but have some other significant drawback if you don't get rid of it soon, such as madness, head-splitting migraines, overwriting of memories or knowledge, or permanent brain damage. This often leads to Flowers for Algernon Syndrome when the character returns to normal, warning others about the dangers of get-smart-quick schemes.
Compare Deadly Upgrade. Also compare The Fog of Ages, where an immortal being has been collecting memories for so long that they're overwriting the oldest ones. Not to be confused with My Brain Is Big, where the skull literally runneth over and the brain shows outside it. See also Super Intelligence.
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In Silent Mobius, Holonic, a computer virus that consumed almost all of Tokyo's data, was going to attempt to enter a visionary's brain and escape physically, and this trope is what Lebia Maverick described as what would happen if it did.
At the end of Divergence Eve LeBlanc gets all of the information about the entire universe (and the alternative one) downloaded to his brain. Then his head explodes.
In Ghost Sweeper Mikami, Dr. Chaos's brain really is completely full with information. So what happens when he learns something new? Rather than expand and strain itself, his brain simply overwrites the earliest thing it can. So while he is an occult genius who can readily comprehend many mystic things, he can easily forget such basic things as what 2+2 results in (hint: not 5).
Played for laughs in K-On!, where Cloudcuckoolander Yui forgets all the chords she learned after cramming for an exam.
It's a recurring issue for Yui through both seasons.
Yuiafter being greeted by the others the morning before a final exam: "Don't talk to me. Everything I memorized will fall out." (trips)
The titular character of Naruto faces this downside to his Shadow Clone training strategy. With hundreds of clones he can experience years of training in one day, but the backlash when the clones disperse is enough to render him unconscious while his brain tries to process the information.
In Osamu Tezuka's Phoenix story "Civil War", the historical figure Taira no Kiyomori desires the blood of the titular bird so he can become immortal and continue to lead the Taira Clan, instead of letting it get run into the ground by his incompetent sons. He starts having second thoughts, however when he has a vision of himself in the 21st century, where he's become an invalid due to his brain having run out of space for new memories and has to be periodically hooked up to an "Amnesia Machine" or he'll go crazy. Other characters who do gain immortality, or at least very long lifespans don't seem to have this problem, but that might just be because they usually end up becoming hermits whose lives are largely monotonous.
This is pretty much the plot of the first arc of To Aru Majutsu no Index. The titular character, Index Librorum Prohibitorum, is being used by the church as a library of every magic tome in the world, using her eidetic memory. However, because it uses up most of her brain, they periodically wipe her other memories (ie: her memories of her own life). Later subverted when it turns out that this was all just an excuse to wipe her memories for the purpose of preventing her from developing too much independence and possibly becoming a threat.
In Omamori Himari, back when Kuesu Jinguuji was a student mage, her only friend in the school got her to read a forbidden tome of knowledge. Then it turned out that the only reason that Vilma befriended Kuesu in the first place was because she thought that reading the book through a second person would allow her to acquire the tome's infinite knowledge without going mad like every other person who'd tried to read the book. Unfortunately for her, Kuesu was so suited for use as a medium that she absorbed knowledge faster than Vilma's mind could process it, resulting in her brain exploding.
Several cards in Magic: The Gathering provide extra draws (and thus, potentially knowledge of additional spells in-game) at the expense of life points, making overuse of them naturally dangerous. And not all of them can be easily "turned off" once in play...
The other danger of excessive card drawing is that you lose the game if you have to draw from an empty deck. There are several tournament strategies that involve generating obscene amounts of mana, then dropping a Stroke of Genius or similar card to make an opponent draw their entire deck plus one card.
Also, the hand size limit may be a less lethal example of the trope. A player can technically end up with any number of cards in his or her hand for a time... but at the end of his or her turn, he or she has to discard any in excess of his or her current maximum hand size (which usually starts at seven and stays there unless modified by specific effects), presumably reflecting how much arcane knowledge his notional brain can safely hold for long.
The card Rush of Knowledge mentions this; "Limitless power is glorious until you gain limitless understanding", the picture shows a mage receiving knowledge, much to his discomfort.
In an issue of The Sandman, "Calliope", Dream punishes an author by giving him an overload of ideas, so much so that he starts writing them on the walls with his bloody fingers.
In PS238, a scientist managed to both figure out time travel and learn all of the world's knowledge up to the late 90s by uploading an encyclopedia into his brain. It made him so crazy that he used his time travel abilities to be both a superhero and his own nemesis.
In the Captain Atom / Wildstorm crossover, Cap does this to Voodoo when she tried to invade his mind. He uses his neural uplink to the Pentagon's computer net to basically KO her with the Internet.
In his first appearance, The Leader - superintelligent enemy of the Incredible Hulk - was after an Ultimate Machine containing all the knowledge in the Universe. When he obtained it and downloaded the information in his mind, this proved too much even for his super brain and killed him. Seemingly.
In With Strings Attached, the first time Ringo uses his mindsight, his brain is overloaded with a million brilliant details all screaming for his attention. Luckily, before he can go nuts, “A reflex he didn't know he had kicked in and narrowed his vision back down before anything permanent happened.”
For a moment he stood, swaying. "Whoa," he mumbled. "Whatta trip."
In We Are Pokemon Trainers, the reaction of gaining two sets of memories from the Alternate Timeline and the original is a temporary brain overload.
The film version of Johnny Mnemonic, with the additional kick that the protagonist doesn't actually have access to the downloaded knowledge that's killing him — he's a courier hired to carry data securely in his own "wetware".
The Computer Wore Tennis Shoes (1995 version). It was not going to destroy him in this case, but got erased with a "magical noise virus over the phone".
Subverted in Flash Gordon, in that Zarkov's brain was to be erased and reprogrammed, but Klytus ordered it to be done "only to Level 3", as he doubted Zarkov's Earth brain could take any higher level. After he leaves his assistant orders him programmed to Level 6. Further subverted in that Zarkov managed to also keep his original memory.
Batman Forever: Though a bit vague, Riddler seems to be doing this (or using other people's brainpower to amp his own mental function, or both.) It makes him a megalomaniac and a malfunction of the machine physically warps him.
The Butterfly Effect: Thanks to Mental Time Travel, the hero suffers mental instability, migraines, and institutionalization when the doctors find out "he has four lifetimes' worth of memories in his head!"
Charly, an adaptation of the classic Flowers for Algernon, has an intellectually handicapped man undergo a treatment that boosts his intellect up to normal and then far beyond. Unfortunately, as he discovers from checking out the test rodent Algernon, it'll cause him to burn out and wind up even stupider than before, possibly brain-dead.
In Rain Man, Dustin Hoffman's character is an autistic savant who has superhuman memory retention and computational skills, offset by severe social disability; based on a Real Life person.
In Flight of the Navigator, an alien research computer travelling near Earth, hearing that humans "only use 10% of our brains," wanted to find out if it could use the other 90% to backup its data. When the abducted experimental subject asked it what happened after it filled his brain to the max, the computer replied "You leak." Fortunately, there were no dangerous side-effects.
In Fred Hoyle's novel The Black Cloud, scientists communicating with the Cloud are given a recording of its knowledge. An initial attempt to download the knowledge into one of them proves to be quickly fatal; a second attempt seems more promising at first but also ends in mental breakdown and death.
The book Ender's Shadow, a companion novel to Ender’s Game, features a very, very dark version of this trope. It is revealed about halfway in that Bean, a diminutive but fiercely intelligent kid, has been genetically altered at birth to have an almost infinite capacity for learning, because his brain continues to grow like an infant's. His brain will never stop growing; neither will his skull, his bones, or the rest of his body. It's only a matter of time before he becomes far, far too big to support himself and one of his organs gives out. This remains a major plot point over the rest of the "Shadow" novels.
Worse, it's discovered that Bean's genetically engineered traits are inheritable. It's estimated that about any children of Bean have at least a fifty-fifty chance of inheriting the genetic traits responsible for his unceasing growth. Naturally, Bean and Petra go to great lengths to prevent their children from being given the same death sentence as Bean. Equally naturally, Achilles deliberately screws with their preventative measures. At the end, it's implied that one of Bean's kids - one of the ones who's inherited the genetic trait - was taken off-planet by the surrogate mother, who was under the impression that she was carrying Achilles' heir. This is later confirmed, both by Word of God, and in the latest book.
In A Study In Scarlet, Sherlock Holmes claims that the reason he is so ignorant of such things as astronomy is that he's trying to save brain-space for forensic knowledge.
In Small Gods, the illiterate Brutha nevertheless has Photographic Memory. He experiences discomfort after visually memorizing the contents of an entire library. The discomfort comes from one of the recurring themes in the Discworld series: Knowledge is power. Knowledge is found in books. Therefore, libraries have immense power. And Brutha had all of one in his head, even if he could not read it.
While he doesn't have a brain in the biological sense, Death often finds his vast Photographic Memory to be a psychological burden. At such times, he tends to get drunk and/or go AWOL while Susan takes care of the family business.
In the James Allan Gardner book Radiant, the "Balrog" hive-mind spore colony infecting Youn Sue's mind grant her wish to see and think as they do... by spreading her mind slowly to absorb more information while retaining the detail of her original perspective. She pleads for them to stop, but they continue until she blacks out from brain damage. The Balrog then moves in and reconstructs the damaged bits to bring her out of her coma.
In David Brin's Kiln People, a widespread technology is the creation of "dittoes", short-lived clay-based copies of a person that share their knowledge and upload their memories into their original at the end of the day. The problem is that the human brain only has space for a few hundred years' worth of memories — ordinarily not that big a problem, since over your lifetime you'd only add maybe a century or so of memories. One character, however, has become a "queen bee" — she stays in one place and sends out dozens of dittoes at a time to live her life for her — and arranges for an elaborate suicide when she realizes she's almost out of room.
Averted by the titular immortal of The Vampire Tapestry, who remains active for roughly one human lifespan at a time, then goes into hibernation for an undetermined period, always waking as an amnesiac.
In the novella Starplex, this is the cause of one species' (the Ibs) natural death—the crystals that store their memories become full, and new memories begin overwriting their autonomic functions. Other species, once they develop immortality, eventually have to start discarding portions of their memories once they reach a certain age, though it's not clear what the side effects of not doing so would be.
In Bruce Coville's My Teacher Is an Alien series, Duncan goes from dumb bully to super-genius after using an alien machine. However, his brain soon begins to pick up information like radio and TV signals out of the air, making it impossible for Duncan to think. Justified: it turns out the alien's plan was to make his brain into a communication device so she could contact her leaders in space.
The Dark Templar trilogy of books from StarCraft has this as one of the main plot threads. Human archaeologist Jacob Ramsey gets the entire mind and consciousness of a Protoss transferred to him, except this Protoss is a Preserver, who has the memories of the entire race. This results in Jacob having several brain tumors develop, and he must find a way to get the Protoss out of his head.
A short story and script for several anthology series: a man invents a memory enhancement drug, but finds that the result drives the adult insane. A baby/young child takes the drug, and their developing brain adapts to the new load. As a result, the child becomes a rich genius and take control of his parents and then the world.
In Poul Anderson's World Without Stars, humanity has achieved near immortality, but because our brains weren't designed to hold centuries of memories, every hundred years or so, people have to go in and decide what memories they want to keep, and what they want to forget.
In The Ellimist Chronicles (an Animorphs prequel), Toomin (The Ellimist) is captured by "Father", a giant squid-like alien who connects his tentacles into the brains of his victims, and thus, having a network of hundreds of minds, has ridiculous intelligence (and the faculties to handle it). After decades of Father using Toomin as his plaything, Toomin finds a way to defeat him by absorbing all the thousands of minds that Father uses... into his one brain. The strain of having so many minds meant for so many body types caused him to hallucinate. Rather than finding a way to return to normal, however, he spends years building a spaceship/supercomputer to plug himself into (and escape Father's planet), which makes him capable of handling his newfound superintelligence. He is still mostly Toomin, however.
A Science Fiction story released in one of Asimov's anthologies had people suddenly going catatonic because the new invention of TV stored a memory for every frame shown on-screen, causing people to run out of storage space. The President, advised of the problem, held a live teleconference to warn people of the problem and froze up while watching himself on the monitor opposite him.
In Foundation and Earth, Daneel is revealed to suffer from a bad case of this.
In a variant, Kate in The Long Dark Tea-Time of the Soul once read that the human brain can juggle a maximum of seven trains of thought or observation at once. Sure enough, when an eighth thought occurs to her, a plot-relevant detail she'd just begun to notice pops out of her head and is forgotten.
In Time Enough for Love, part of Robert A. Heinlein's Future History series, this is noted as an issue when a computer seeks to download its personality into a Wetware Body in order to experience life as a human. The computer's mentor and confidant has to remind it that it won't have nearly the same processing power or capacity for information storage, and indeed once the feat is accomplished, the now-female human Minerva discusses the choices she made in terms of which memories to discard and which to keep in order to avoid this trope.
In Inheritance,Galbatorix is defeated this way. Realizing that Galbatorix and his infinite amount of power would be unable to kill with any amount of attacks thrown at him, Eragon decided to just cast a spell that would make him understand all the pain he has caused. He Goes Mad From The Revelation. It's cooler and more epic than it sounds.
The Bruce Sterling short story "Our Neural Chernobyl" is written as a review of a monograph studying the social and cultural effects on the world after an engineered virus is released that causes rampant dendritic growth - essentially, making people's brains extremely plastic and adaptive so they can constantly learn and think at faster and faster rates. It also frequently causes lethal burnout, nicknamed "chernobyling" after the Chernobyl power plant disaster in the '80s. Eventually, the virus even jumps species, with some animals showing signs of increased yet distinctly inhuman intellect.
A character in M. John Harrison's Viriconium stories can only remember the last two centuries of his life, although evidence suggests he is far, far older. He lives in a vast underground complex full of machines he doesn't remember building — or what they do — and entire wings he forgot existed.
In the book Flowers for Algernon, the title-giving mouse and protagonist Charlie Gordon both are given extreme intelligence from an operation. However, as time goes on both Algernon and Charlie Gordon start to degrade in intelligence before finally dying, with any way to stop this from occurring lost when Charlie started losing his intelligence.
In Lois McMaster Bujold's Vorkosigan Saga, Barrayaran Imperial spymaster Simon Illyan was one of a host of low-ranking officers who'd had an eidetic memory chip implanted by order of the previous Emperor. Illyan was the only one not to suffer schizophrenia or worse as a result of the chip, largely by maintaining as small and pointless a personal life or personal opinions as possible. In the novel Memory, however, the chip malfunctions and makes Illyan a massive security risk as he begins spouting countless secrets whenever he's not sedated, and it is slowly killing him. After the chip is removed, his memory is now much worse than a normal person's due to having leaned on the chip's capabilities for so long.
The title character in Borges Funes the Memorious is this.
The "total perspective vortex" in The Restaurant at the End of the Universe appears to do something like this; by stuffing the entire vastness of the Universe into the victim's head, their personality is squashed into a nice compact ball of insanity.
In The Adventures of Tom Sawyer, Tom mentions a boy who had an incredible memory, seeming to know every verse in the Bible. Until one day the mental strain of it broke his mind.
There's a short story entitled "The Last Master of Limericks" that invokes this trope. The eponymous Last Master is, basically, a brain in a jar operating the defenses of the Solar System. It's kept "asleep" when not actually needed because of the trope. It muses at one point during the story that it long ago reached maximum capacity and now must continuously grow in order to have space to store new memories ... fortunately (or maybe not; it's got one of those endings), it's a large jar.
In Stargate SG-1, there are Ancient Repositories, where if you stick your head in you get all the (possibly nearly infinite) knowledge of the Ancients, but a human mind will slowly degrade for as long as the information is still in there. Jack O'Neill got nailed twice by those devices.
Also in Stargate SG-1, Orlin, an ascended Ancient, takes a human body in order to help the main characters with the current Big Bad. Unfortunately, he holds onto the necessary knowledge for too long; he ends up suffering massive brain damage, and has to be institutionalized.
When RepliCarter tried to download that same ascended knowledge from formerly ascended Daniel's brain, she was confident that the combined storage space of the Replicators would be sufficient to contain it. She was wrong. Nothing bad happened specifically because of it, but the distraction was enough for Daniel to get the better of her and seize control of the Replicators for a few minutes.
In Stargate Atlantis, a hyper-evolution machine gives Rodney McKay amazing mental powers (including psychic ones such as mind reading and telekinesis) - but at the cost of it eventually killing off the part of his brain that controls the lower functions, such as his heartbeat. It's at the last moment of his life that he manages to figure out (using his amazing intellect) how to reverse the process to return to normal.
This almost happened to Max in an episode of Dark Angel which involved her taking a rival series clone's neural implant and installing it into her own brain. The strain nearly burnt out her nervous system.
Russell T Davies is clearly very fond of this — back in the first series finale, Rose absorbs the time vortex, making her effectively a goddess, but is in danger of being "burned up" by the power and whispers, "I can see everything. The sun and the moon, the day and the night — but why do they hurt? My head... is killing me."
In a fatal example from"Forest of the Dead" River Song uses her own brain as a data buffer to download the Library survivors out of the core, killing her in the process
In The Second Coming, Steve (played by Christopher Eccleston, who would later play the ninth Doctor) discovers that he's literally the son of God. He compares the experience of accessing divine omniscience with a human brain to "downloading fifty-million megabits into a pocket calculator," and, though it doesn't seem to be actually dangerous, he admits that it hurts.
Lt. Barclay in Star Trek: The Next Generation episode "The Nth Degree", although the newly gained super-intelligence doesn't seem to be dangerous in itself. The problem comes when he connects his brain directly to the ship's computer. He uploads himself and uses the extra processing power to expand his intelligence, but then realizes that his brain alone would be too small to contain it, so he's stuck in the computer until the end of the episode—at which point, the Cytherians (who had sent the probe that zapped Barclay) removed most of the extra intelligence, though Barclay did seem to end the episode with a slight—but noticeable—permanent boost to his intellect.
On Andromeda, Harper had a database downloaded into his brain (he has a computer port on his neck), and it played out similar to SG-1, only instead of being directed to a single goal like O'Neill, Harper began and abandoned dozens of projects.
In the Buffy the Vampire Slayer episode "Earshot", where Buffy accidentally gets telepathy, she starts hearing everyone's thoughts all the time. This not only overwhelms her, but it will inevitably cause her to go crazy unless the telepathy is removed. There was one other person to have gotten this, and he ended up in complete isolation, away from any other people.
In Heroes, Matt Parkman has this problem when he gets his telepathy, but after a while he learns to control it better and the problems stop.
Until Ando super-charges Matt's power, causing a temporary but disabling case of this trope.
Joan of Arcadia had an episode where a child Joan had babysat earlier in the season died. In the middle of a Rage Against the Heavens rant at God, God offers to show her what he sees and hears every day. Fifteen seconds later, she's on the floor, unable to deal with the downsides of omniscience.
Cordelia from Angel is given the "gift" of visions that turned out to cause her brain to slowly deteriorate since humans weren't meant to have them. She keeps it secret for years before slipping into a coma and learning that she will eventually die from this if she doesn't agree to become half demon to compensate. She is also shown other examples of what happens because of the visions: one girl whose head literally blew out the back, and an alternate-universe Angel who was driven completely insane by them.
Firefly's River Tam got along pretty well being incredibly intelligent with a bit of psychic ability. Then the governmentgets a hold of her. They make her undeniably kickass, but one consequence is that now her greatly increased psychic abilities make her insane, unable to filter out what she hears.
"Make them stop! They're everywhere. Every city, every house, every room; they're all inside me! I can hear them all and they're saying... NOTHING! GET UP! Please, get up!... Please God, make me a stone."
Chuck entirely averts this until it's revealed that the reason Chuck was sent the Intersect was because he was one of the few people who wasn't immediately killed by this. After a few years it seems to finally be hurting him.
And then, there's the instances where characters aside from Chuck gain the Intersect. When Morgan had it, his memories were being fried and his normal personality was being "corrupted" by it. Moreover, in the series' final Story Arc, Sarah had to upload the Intersect in order to rescue Chuck from the Big Bad, who had kidnapped him. However, much like Morgan, her memories took a hit and she ended up losing all that she remembered of the past five years. This gave the villain a chance to use the amnesiac Sarah as a weapon of sorts against Chuck. Keep in mind, that these instances involved variations of the Intersect that were tampered with "trojan horses".
And even moreso of Dead At 21, in which the hero has one year to keep the intellect-enhancing chip in his brain from frying it.
In Red Dwarf, episode "Holoship", Rimmer has all the knowledge and experience of two officers of the ship transferred into his own mind so as to pass an exam. Kryten warns him, however, that it could "reduce him to a gibbering wreck". It doesn't, and the result is slightly unnerving.
In another episode, the ship's computer Holly finds a way to boost her intelligence and undo three million years of "computer senility". Overclocking it, she gets an IQ of 12,368 (over her original IQ of 6,000) at the cost of reduced run-time: about 3 and a half minutes.
On one episode of Scifi's The Invisible Man, Hobbes was accidentally stabbed with a serum that would cause his intelligence to rapidly increase. However, he'd go through several stages, gradually becoming an Insufferable Genius, then a crazy genius, then, with this trope, his brain would become so advanced he would retreat into his own mental world of absolute knowledge, and stop using or caring about his body at all. Fortunately, it was stopped and reversed at the Insufferable Genius stage.
One of the college students who was injected committed suicide and took the creator of the serum with her. The other three ended up catatonic. According to the Keeper, "they found them [[their minds]] and it was more than they could handle."
Star Trek: Voyager: Seven of Nine downloads huge amounts of data straight into her head, but can't handle it, and starts creating wild conspiracy theories.
The scary thing is how much sense most of them make, given the evidence she provides.
Until she starts using the exact same evidence to create different, contradictory theories.
The Doctor tries it by uploading the knowledge of many geniuses, but he also ends up getting their dark sides too. He gains an Evil GeniusSplit Personality.
An episode of Amazing Stories, "One for the Books", had a man involuntarily soaking up all the knowledge contained in the library in which he worked, which quickly drove him towards madness. In the end it's learned that it was done by aliens, as a way to gather all that info; they "squeezed" it out of him and went on their way.
On Married... with Children Kelly Bundy goes on a tv trivia game show on the subject of sports. Her father Al & brother Bud teach her quite a lot of trivia, but they're careful because they know that if her brain gets full then something she already knows will fall out. Unfortunately, when she appears on the show she "learns" something new and sure enough, the audience hears a "ping" as an old piece of knowledge falls out of her brain. Come the $1,000,000 question and Kelly doesn't know the answer. The question: Who once scored four touchdowns in a single game for Polk High School in Chicago? The answer: Al Bundy.
The Far Side spoofs this in one comic. A student with a comically tiny head raises his hand in a classroom and asks the teacher, "May I be excused? My brain is full."
In Wizardry: Bane of the Cosmic Forge, one NPC is a moderately evil wizard who wished on the Cosmic Forge that "I shall know everything." The artifact's solution to the trope was to split him into two consciousnesses and divide the knowledge between them. However, as it chose to concentrate data in the one that got the body, he went insane anyway. The one who got the understanding (the "hows" and "whys") relates the story to your party.
It has become an open secret that that Arakune of BlazBlueWas Once a Man, but a good portion of his dementia comes from a Runneth Overing Skull. He acquired so much knowledge that his mind began dumping random parts of his psyche, and the process is ongoing. Of course, that means the knowledge he possesses about everything—including himself—is essentially random at all times. This makes all the attempts to save him with The Power of Love more tragic.
In Mass Effect, the Prothean Beacons were designed to easily transfer information across their Empire. However, due to no other race posesses the Prothean's natural empathic abilities, viewing them can potentially run the risk of destroying a weak-willed individual's mind entirely.
Homestuck - Sollux is a high-level psionic. The mind honey which boosts his lusus from idiocy completely overloads his brain when he eats it. note YOU DO NOT UNDER ANY CIRCUMSTANCE EAT THE MIND HONEY. He recovers, but there are terrible consequences.
Mindmistress gets her super-intelligence from a Phlebotinum pulse that kills the target in two weeks unless reversed (the brain grows so much that it is analogous to brain cancer). Her non-super self is mentally challenged.
Also used in a different way in a later story, where the villains of the week attempts to steal her knowledge. They all go insane — the human mind cannot handle that much knowledge.
Forthought is an ordinary man who underwent the same process. He is considerably smarter than MM and with his more advanced mental capacity he wills his brain to not have cancer rather than transform back.
In Schlock Mercenary a race of Immortal aliens are found on a backworld planet. The collapse of the civilization nearly a million years ago was due to their experiments with immortality, leading to this trope as many of them went insane due to too many days going by too similar for the mind to sort out. Amongst the many measures they tried, only one worked - upgrade their brains to make them controllably forget or ignore vast swathes of their memories.
Apparently, this is what happen to humans coming in contact with the mysterious being SCP-606 residing at the SCP Foundation, resulting in coma and death from overload of information. The entity doesn't seem to do it out of malice, instead calling it "enlightening" its victims.
Code Lyoko example: Jérémie once tried to use the same quantum memory technology that powered the Supercomputer to enhance his own brainpower. Of course, it backfired due to both the immense physical strain and the fact that XANA introduced the possibility of that maneuver as a Red Herring.
At one point, Jimmy calculates the maximum possible number Sheen's IQ could grow to. It hits infinity.
This is the entire reason why Freakazoid! is so damn zany: the accident that empowered Dexter also uploaded all information from the Internet into his brain. Maybe that wasn't that big of a deal back then, considering the volume of info had yet to reach the terabytes (perhaps even gigabytes), but even at that time, that was still a lot for a single brain to handle.
Though it could also have to do with what all the information from the Internet encompasses...
This is used against a villain in one episode of Darkwing Duck. In the final showdown, DW and Launchpad get their hands on the Norma Ray, a device that increases your IQ and gives you psychic powers as long as you clear your mind of all thought (or else you get a literal and figurative "swelled head"). They bombard the villain with rays while asking him a bunch of tough questions at once, causing him to lose his concentration and make his head so big that it blows up.
Happens to Sponge Bob Square Pants of all people, in the episode "Squilliam Returns". Squidward turns the Krusty Krab into a fine dining establishment to impress Squilliam, and Spongebob is to wait tables. After learning everything associated with fine dining, his skull runneth overbadly — he cannot even remember his own name any more! The only thing he can remember, except for fine dining, is breathing.
Not sure how cartoon sponges operate, but most creatures don't need to remember to breathe, it's automatic (autonomic?).
In The Batman, Dr. Strange gets all the knowledge in the universe in return for helping the Joining - when he receives it, he ends up comatose (though The Martian Manhunter can still read his mind to get the information they need to defeat The Joining)
Bulkhead of Transformers Prime, after getting the Cybertronian data cylinder's contents uploaded into his brain becomes much smarter, but the influx of knowledge threatens to erase his memories and override his original personality.
In Xiaolin Showdown, using the Shen Gong Wu named Fountain of Hui grants the user insight to anything and everything. However, without its sister-Wu the Eagle Scope, which is mostly an uber-telescope, the Fountain of Hui will only grant the user a humongous head and random facts, such as the length of the world's largest toenail, which they will babble incessantly for about a week.
It also seems to be imply that using the Fountain of Hui without the Eagle Scope results in pain accompanying the above huge head and random facts spouting given that Omi's immediate action after saying the length of the world's largest toenail is to grip his head and complain "Ow…"
In X-Men: Evolution, Rogue's power absorption eventually left her with fragments of all the people she absorbed, such that she couldn't help randomly using their powers occasionally. Then she went and bumped into Mystique, providing a handy outlet for those fragments in the form of shapeshifting. A rampage ensued. Xavier had to telepathically purge her of all the accumulated personalities to get her back under control.
In The Simpsons, Homer believes that mundane learning has this effect on him, citing as an example a time when he took a home wine-making course and forgot how to drive. Marge points out the more obvious cause of this loss of ability.
Marge: That's because you were drunk! Homer:And how!
People with bipolar disorder often go through a period of high creativity, fast and often quite clever thinking before the sleep-deprivation psychosis kicks in. The feeling of being on such a high can often be like one's skull literally overflowing with energy; and sleep deprivation doesn't need to happen. The insomnia can be controlled with medication, for a start.
Also people with Eidetic Memory can set off a memory at any time by some random thing, be it good or bad.
Subverted by people who have suffered the loss of a substantial portion of their brains, due to strokes, tumors, accidents or surgery, yet continue to function and accumulate memories normally throughout their lives. Even patients who have entire cerebral hemispheres removed to halt their epileptic seizures don't "run out" of memory-space, despite having only 50% storage capacity.
In either Ripley's Believe It Or Not, or Guinness Book Of Records, there was an account of a girl who at age 14 had learned fluency, and was writing papers in about twelve different languages. She ended up dying at about age 16 (possibly from a seizure).
Which actually isn't the trope at all, since there are plenty of people that can speak at least that many languages (J. R. R. Tolkien was one; he could understand at least 20 languages, along with dialects of several of them and was fluent in over a dozen) without any similar issues, and it's pretty well-established that learning languages as a child is considerably easier than doing so as an adult (learning more than one language as a child seems to make it easier to learn additional ones later; Tolkien, for example, learned four of his as a young child, from his mother).
Certain kinds of autistic patients known as savants make up for their seemingly handicapped social skills with superhuman computational ability.
Solomon Shereshevskii, a Russian mnemotist (who did not, in fact, have an Eidetic Memory) had the ability to remember things so well that he became dislocated in time; he eventually became unable to tell whether the thing you just told him happened 5 minutes or 5 years ago. He had to literally learn to mentally remove facts from his memory (in other words, deliberately forget). It didn't help that he had fivefold synaesthesia, an extremely strong form of synaesthesia in which stimulating one sense meant a reaction from them all. That Other Wikihas an article on him.