01/23/2013 10:44 pm ET Updated Mar 25, 2013

New Facts and Old Habits: How Your Brain Sculpts Your Memories

Like many large companies, MusclePharm has seen its share of both positive and negative press. Over the past two years the nutritional supplements manufacturer has battled lawsuits alleging price discrimination, environmental violations and patent infringement -- all while bringing home boatloads of best-product awards and celebrity athlete endorsements. In short, it's a company whose popularity has so far managed to drown out the cries of naysayers.

With a little reflection, we could all probably name one or two companies like MusclePharm, companies whose products remain popular, thanks to their addictiveness or usefulness, despite the occasional accusatory headline. By the same token, we've all had the experience of going sour on a company or product when we learn that they've "crossed the line," decorating toys with lead-based paint, say, or treating animals cruelly. And as anyone who grew up around certain religious communities knows, sometimes "the line" is a spiritual one: Rumors of donations to the church of Satan, or support of same-sex marriage, can get a company blacklisted and boycotted by some fundamentalist groups.

Although we don't all share the same standards for corporate behavior, most of us realize that it's pointless to shake our pitchforks at every negative mark on every company's record. Over time we learn to filter out information that isn't particularly significant to our purchase choices, while holding on to tidbits that support those decisions. This is known as confirmation bias, and whether we like it or not, even the smartest of us are vulnerable to it.

But how do our brains get rid of information we think is "useless" -- and why does that label seem to apply to more information the older we get?

A new study offers some tantalizing clues. In the hippocampus, a brain structure that helps you form and retrieve memories, researchers have isolated a particular class of chemical receptors that shape connections between neurons. These chemical receptors, known as NMDARs, are made up of two types of smaller subunits: one known as NR2A, which tends to reduce communication between neurons, and one called NR2B, which lengthens and strengthens interneural communication.

Researchers have known for a while that kids' brains have more NR2B subunits than NR2As, which helps their brains form lots of long-term memories. However, as kids age, their receptors' NR2A subunits start to outnumber the NR2Bs, reducing neural communication times and making memory storage more efficient, a process known as "information sculpting."

And now, as described in a study published in the journal Scientific Reports, a team led by Joe Tsien at Georgia Regents University has discovered just how this shift from NR2Bs to NR2As changes the way we remember new information as we grow older. The researchers genetically modified mice to match the adult ratio of NR2B to NR2A subunits, then they ran the little guys through some trials. As it turned out, mice with childlike brain chemistry were still great at forming strong neural connections but had serious trouble holding on to useful memories at the expense of useless ones. In other words, "[i]f you only make synapses stronger and never get rid of the noise or less useful information, then it's a problem," Tsien says.

In fact, other experiments have found that mice -- and humans -- with ultra-powerful memories actually do worse on many tests than those with merely average memories do. It seems that when it comes to effective learning, selective forgetfulness is at least as important as skillful memorization, and what's more, our brains get sleeker as we grow older. After a lifetime of experience, your neurons have become master information sculptors, trained to hold on to habits that work and discard details that seem less important, even if those "unimportant" details sometimes include the last known location of your car keys.

In any brain, though, whether that brain belongs to a mouse running a maze or a human choosing an energy drink, habits and loyalties die harder the older we get. So next time you're about to try a new brand or make a big purchase, try asking (or googling) around and checking up on the latest press. After all, it's never too late for an old dog to learn a new trick or two.