Why Does Time Fly as We Get Older?

Originally posted at Scientific American MIND.

Another year; another Christmas around the corner.

The conversation around the watercooler these days has evolved into the annual “where has the time gone?” discussion—how quickly the neighborhood kids have become high school graduates; how our hot July beach vacations seem like they were just yesterday; and how we haven’t baked cookies or sent cards or bought gifts yet because time has just been flying by.

It’s become a common complaint—almost a joke—that time seems to whiz by faster and faster as we get older.

Of course, aging doesn’t grant us the power to disrupt the space-time continuum, so it’s not a real problem. But why do we perceive it to be?

'Twas the Neural Pathway of Christmas

The following is an original and extraordinarily nerdy rendition of the classic Clement Clarke Moore poem adapted by yours truly, describing the basic pathway of happiness one feels when one sees a pleasant image—like Santa Claus!

Ornament by Neverland Jewelry.

'Twas the neural pathway of Christmas as my eyes do behold
A vision of St. Nicholas—red, so jolly, and bold.

His image burns into my retina, transmitting down optic nerve
Before the optic chiasm crosses in an unexpected swerve.

From optic tract to LGN—the sensory relay
Of six alternating layers; a complex neural highway.

Radiation to layer 4 of the visual cortex comes next—
But what follows leaves even the greatest minds perplexed.

For this vision becomes a signal, signal becomes a sense
Conversion of molecule to emotion—a feeling so intense.

Glutamatergic synapses fire onto the VTA—
A group of tiny neurons on the floor of the midbrain.

But wrong you are if you believe the brain to be tired,
For from VTA to nucleus accumbens dopamine is fired.

It is from this tiny region that glimpsing Santa brings such joy—
Pleasant emotional perception for every girl and boy.

So fleeting this emotion, as your auditory cortex hears,
 "A brainy Christmas to all—now, onward, reindeer!"