December 1, 2018 | David F. Coppedge

Wonders of the Equipment in Your Head

Look at what scientists are finding you can do, or is being done automatically for you.

How sounds going into our ears become words going through our brains (University of Maryland). Did you ever think about the fact that the words you hear are only sound waves hitting your eardrum until your brain receives the electrical signals and processes them into messages? There’s nothing lexical about the signals until they arrive in the brain. First you have to pick out the sound you want to hear (this can be difficult in a party room), recognize phonemes or syllables, and then piece them together to make sense out of what you are hearing. This has to be done really fast, because your conversational partner can be speaking 3 words per second. A paper by UMD neuroscientists in Current Biology announces that, yes indeed, the process of brain analysis from signal to meaning is very rapid. How rapid? Well, it’s “surprisingly early,” they say; in fact, “this happens pretty much as soon as the linguistic information becomes available.”

We may hear others’ footsteps, but how do we ignore our own? (Science Daily). We marvel at the new-fangled noise-canceling headphones, but you already have some of that technology in your head. All mammals appear to have this ability; mice, naturally, want to hear that cat’s footsteps and not its own. To figure out how we cancel unwanted sounds, scientists publishing in Nature developed an “acoustic virtual reality system” where they could teach a mouse to associate a novel sound with its own movements. Here’s what Live Science says about the findings. Look how complicated and rapid it is:

Amazing FactsTheir imaging and measurements showed a strong coupling between the motor cortex — an area of the brain that’s involved with movement — and the auditory cortex. During training, the motor cortex begins forming synapses, or connections to the auditory cortex. These connections end up serving as a noise filter.

So-called inhibitory neurons, or brain cells, in the motor cortex began to send out signals to cancel out the firing of neurons in the auditory cortex that make us aware of the sound. This process is so quick that it is “predictive,” Mooney said, meaning the cancellation signal happens at the same time that the brain commands a movement.

How attention orchestrates groups of nerve cells to enrich the brain’s symphony (German Primate Center). That’s an attention-getting headline. If you like Mozart, you will enjoy their description of how your brain hears music, and how vision joins the symphony to give a more complete experience.

Diagram of the human ear.

Silence in the concert hall. The conductor raises the baton and the strings begin. They play the first four bars of Mozart’s “A Little Night Music”. All together they play a single melody, which is probably one of the best known in the music world. Then the voices divide. Different string instruments play separate melodies and the “Little Night Music” thus becomes a complex work of art. Scientists from the German Primate Center (DPZ) – Leibniz Institute for Primate Research in Göttingen and Institute for Research in Fundamental Sciences in Tehran, Iran, recently discovered in a study with rhesus monkeys that nerve cells assume the role of musicians in visual perception in our brain. Usually many cells are active together (synchronously) when they process simple stimuli from our environment. The researchers were able to show that visual attention desynchronizes these nerve cells’ activity and thus enables more complex information processing.

Gravity Perception: The Role of the Cerebellum (Current Biology). It’s not just the inner ear that helps you know which way is up. This paper ascribes a prominent role to the cerebellum, a part of the brain evolutionists tend to view as primitive. This paper should increase the respect it is due.

The cerebellum is known to support motor behaviors, including postural stability, but new research supports the view that cerebellar function is also critical for perception of spatial orientation, particularly because of its role in vestibular processing.

The otoliths in the inner ear contribute signals due to linear motion; the semicircular canals in the ear contribute information about rotational movement, and the eyes (when open) watch the motion – but the cerebellum is where the processing of all this information is done, the paper explains.

Eyes Have a Natural Version of Night Vision (Duke University). Young people like playing with the night-vision goggles they get for Christmas, but we actually have a natural version of it. How? The “Cells in retina change their duties to help the brain detect motion.” Stargazers know that it takes a few minutes for the eyes to get adjusted to darkness, but a lot of teamwork is going on in the back of the eyeball to make this possible.

To see under starlight and moonlight, the retina of the eye changes both the software and hardware of its light-sensing cells to create a kind of night vision. Retinal circuits that were thought to be unchanging and programmed for specific tasks are adaptable to different light conditions, say the Duke scientists who identified how the retina reprograms itself for low light.

“To see under starlight, biology has had to reach the limit of seeing an elementary particle from the universe, a single photon,” said Greg Field, an assistant professor of neurobiology and biomedical engineering at Duke University. “It’s remarkable at night how few photons there are.”

The ability to detect single photons with the eye shows ultimate engineering. It can’t get better than that. These researchers show that many things have to work in concert to make it possible: the cells involved in detecting motion have to reprogram themselves to aid in the detection of those photons.

Tapping into the brain’s star power (Nature). Let’s end with marveling at an under-appreciated type of brain cell: the astrocyte [“star cell”]. “No longer just ‘brain glue’, astrocytes are coming to the fore as a broadening toolset reveals the cells’ complexity and diversity,” this article begins. Astrocytes make up 20-40% of a mammalian brain. Discovered in the late 19th century, they have been largely ignored in favor of the jazzier neurons whose signals we can probe electrically. But look at them:

One astrocyte can have tens of thousands of connections (UCSD)

Unlike neurons, astrocytes are electrically quiet, so their activity goes undetected by conventional electrophysiology methods. They’re also astoundingly complex: a single astrocyte can connect to tens of thousands of neurons.

Tens of thousands! That’s astonishing for one cell to have that many connections. We can’t relate all the wonders these cells do, but suffice it to say in summary that “Glossed over as mere support cells for more than a century, astrocytes actually have crucial roles in the brain,” including controlling neurotransmitter levels, regulating extracellular potassium ions to influence thresholds for nerve-cell firing, and releasing molecules that promote the formation and pruning back of synapses. They basically keep the brain wiring from going haywire. We quote one of the researchers, whose use of new techniques to study these cells have given him “unparalleled appreciation of the richness and dynamics in how astrocytes contribute to the function of the brain as an organ.”

Evolution only sounds reasonable when you look at the big, glittering generalities. When you realize that all these exquisitely-tuned complex systems would have had to arise by a long series of mistakes over millions of years, evolution makes no sense at all. That’s why we love to report on the details of biological systems, so you can become inoculated against the storytelling of Darwin charlatans. Now let’s go use those eyes, ears, and brains for their intended use: to serve God and enjoy the blessings He has richly given us.

 

 

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