Your Brain's Trash Bin: What's in It and Why

Pay close attention to your butt.

As you sit there reading this, feel your posteriorand the back of the top of your thighspress into your chair. Notice that, until I called attention to it, you werent aware what was happening with your butt and thighs.

This same lack of awareness applies to the majority of sensations pouring into your brain . You werent focusing on the feel of your clothes against your body or background sounds such as the hum of your refrigerator or the change in temperature of your breath each time you breathe in and out (the air going in always feels cooler than the air going out). Similarly, while you read, a tremendous amount of visual information in your peripheral vision goes un-noticed.

Your brain automatically chucks all this sensory information into a mental trash can so that you don't accumulate clutter that will get in the way of perception, thought or memory.

Tomorrow, you might remember the sensations on your butt and thighs or the feel of your breath today (because I made you pay attention to these things), but you dont remember years and years of similar sensationsbecause your brain flushed them away before they could be stored.

Raw sensations are not the only information your brain relegates to the re-cycle bin.

Think back over your life. If you pick any random day, say August 12th 2013, its very unlikely that you can remember events that happened that day, unless you check a calendar and think hard about where you were and what you were doing. Even after going through this exercise, you probably can only recall vague factoids, such as, that particular day was a Monday so I was probably at work and probably commuted back and forth to work," etc.

The sad truth is that you dont remember the vast majority of your life becauselike the pressure on your buttyour brain has thrown most of your life experiences into a trash can, then emptied that can.

Yes, you remember the day you graduated high school, got married, had a child, lost a parent or watched two planes fly into the World Trade Towersso some things do escape the trash bin. But most days of your life are either a vague haze or gone entirely.

How does your brain decide what to keep and what to throw away?

A quick experiment will provide clues.

Grab a pencil and paper, then scan your eyes quickly over each of the 9 images below, allowing no more than 3 seconds to look at all of the photos (1 second per row ofimages). Close your eyes, count to 20, then open your eyes andwithout looking back at the imageswrite down a brief description of each photo you remember.

Source: Hiromitsu Morimoto, Geoffery Beall, John Bulles, Karlyne,Hywell Williams, Eric Haseltine, Oolong's photojournal,

Odds are that you wont remember all of the pictures, but even if you do, the photos at the top of your list will probably be the rabbit with a waffle on its head, the cheetah, the building with a tree growing out its side and the 17th century musician with a guitar.

Why? Because those images represent a departure from normal,"whereas its not unusual to see objects in the remaining images. You recall details surrounding births, marriages, deaths, major news stories precisely for the same reason: They represent a major departure from the normal flow of your life

In other words, your brain likes to hang on to information thats abnormal," and trashes information thats normal.

Your brain does this because retaining abnormaldata keeps you out of trouble. Events that are everyday occurrences rarely cause you problems because you can predict, and prepare for expected eventssuch as heavy rush hour traffic, bad weather in the winter or drunk drivers on New Years Eve. What could threaten your well-being the most are unpredictable or abnormal events for which you are unprepared, such as a mugging in a safe part of town, a sudden rainstorm on a sunny day, or a cheetah lounging on a neighborhood tree.

Thus it makes perfect sense for your brain to remove normal memories so that they dont interfere with abnormal information that could prevent nasty surprises. As amazing as our brains are, they can only store and quickly retrieve limited amounts of information; so its a good idea for that stored information to maximize the odds of our survival.

Recent research suggests that mental trash removal is so important that it does not happen passively by gradual decay, but is an active process in which your brain selectively erases memories it believes are of little value. Neuroscientist Oliver Hardt and colleagues at McGill University recently found that this process of selective active memory erasure takes place while we sleep .

It seems that we go to bed knowing more than when we wake up the next day, but what we remember in the morning is the important stuff.

If you think your brain is erasing more memories than youd like, you dont have to let it make automatic trash removal decisions. You can intervene to retain more memories by manually telling your brain to store them. The simplest way to do this is to pay close attention to details you want to recall. Your brain wont throw out datasuch as the fact that your breath is cooler going in than coming outthat you take time to actively notice. Your brain will also keep information that you repeat over and over (like a phone number someone just gave you). Finally, if there are particular memories, say of a pleasant vacation, that you want to keep, revisit those memories often. Each time you call up a memory, your brain will take notice, and will avoid erasing it while you sleep.

One way or another, you can best preserve memories by telling your brain they're important.

Ron Davis, of the Scripps Research Institute has examined the neurotransmitters involved in memory formation and forgetting and concluded that dopamine plays an active role in erasing unimportant memories almost as soonas they are formed.

According to Davis: "The study suggests that when a new memory is first formed, there also exists an active, dopamine-based forgetting mechanismongoing dopamine neuron activitythat begins to erase those memories unless some importance is attached to them, a process known as consolidation that may shield important memories from the dopamine-driven forgetting process.

Nowsince Id like your brain to avoid erasing this article from memory with dopamine (or while you sleep)Ill leave you with a thought that is (hopefully)sufficiently abnormal.

Ill end the article the same way I began it,with your butt. Specifically,by erasing memories about your rear end, your brain is in the best position to save it.

https://www.psychologytoday.com/blog/long-fuse-big-bang/201504/your-brains-trash-bin-whats-in-it-and-why