In a recent Knowing Neurons piece, we explored the exotic visual abilities of other animals, while lamenting the limitations of human color vision. In this article, we stretch those limits and celebrate some peculiarities of trichromatic color vision.Continue reading
How long is the coast of Britain? It doesn’t matter how good your geography is — the answer depends on the size of your measuring stick. The coast of Britain has twists and turns at all spatial scales, from kilometers to millimeters. And the smaller the measuring stick used, the longer the measured length of the coastline.Continue reading
What would the world be like without color? Imagine you are a neurophysiologist, who studies color perception. You know that light is a wave and that humans perceive color according to differential activation of color receptors, known as cones, in the retina. You know that red cones are sensitive to long wavelengths, green cones are sensitive to medium wavelengths, and blue cones are sensitive to short wavelengths. There’s just one issue: your entire life, you have been confined to a dark room where your only access to the outside world is a black and white television monitor. You have never seen color.Continue reading
Some questions cannot be addressed by science. Like parallel universes, the consciousness of others is not something that can be directly observed, measured, or experienced. Rene Descartes famously said,
“I think, therefore I am.“
a declaration that only knowledge of one’s own consciousness is absolute. You assume that friends and neighbors have subjective, internal experiences similar to your own. And yet, you will never know that these individuals are not mindless automatons, behaving in a manner similar to yourself yet lacking conscious experience.Continue reading
Pictures are powerful tools for illustrating quantitative data and capturing public interest. Each year, NASA releases many beautiful images of Martian dunes and distant nebulae which help win public funding. Likewise, when it comes to grabbing headlines and commanding public attention, noninvasive studies of functional brain activity often do best when they beautifully illustrate said activity as colorful pixels dancing on the convoluted surface of the cerebral cortex.Continue reading
Stem cells have two characteristic and essential properties:
- Self-renewal. They can divide to give rise to another stem cell.
- Potency. They are capable of differentiating into specialized cells.
Imagine that you’re driving down a road undeterred, no red lights or stop signs to slow you down. While that may seem like a very exciting idea, it is obviously very dangerous, since our roads are not all parallel, but interconnected in a number of different ways. For traffic to go smoothly in all directions, we have stop signs, red lights, speed bumps and police cars to make sure no accidents occur. Continue reading
It is easy to assume that if a car has a gas pedal, it needs to have brakes, and similarly, if our brain has excitatory neurons, it needs inhibition too. For a long time, the field of neuroscience had thought of inhibitory interneurons as the “brakes” of the brain, providing suppression to neuronal activity. However, in my conversation with Dr. Gordon J. Fishell, I learned that interneurons are far more fascinating cell types than merely being inhibitory! Their multifarious morphology can be attributed to a palette of functions in brain developmental and regulation.Continue reading
Snap! Crackle! Pop!
Those are the sounds that Professors David Hubel and Torsten Wiesel heard in the early 1950s when they recorded from neurons in the visual cortex of a cat, as they moved a bright line across its retina. During their recordings, they noticed a few interesting things: (1) the neurons fired only when the line was in a particular place on the retina, (2) the activity of these neurons changed depending on the orientation of the line, and (3) sometimes the neurons fired only when the line was moving in a particular direction.Continue reading
One night, Mark withdraws $200 cash from an ATM. He is on his way to meet his family, and intends to treat everyone to a special dinner at his favorite restaurant for his wife’s birthday. Just as he finishes his transaction, Dan rounds the street corner, pulls out a knife, and threatens Mark to hand over the cash. Mark, without hesitation, hands over the money, but Dan stabs him in the stomach anyway. Dan runs off, leaving Mark injured on the sidewalk.Continue reading