Think About the Brain
The human brain keeps surprising scientists with its unfathomable complexity as well as its nifty algorithms.
The Supporting Roles
‘Little Brain’ or Cerebellum Not So Little After All (San Diego State University). The cerebellum, or “little brain” located next to the brain stem, has gotten short shrift for years compared to its superior, the cerebral cortex with all those folds of gray matter. Scientists at SDSU are finding out it is more complex than expected. It now is seen as a highly versatile portion of the brain with complexity of its surface giving the cerebral cortex a run for its money.
It’s essentially a flat sheet with the thickness of a crepe, crinkled into hundreds of folds to make it fit into a compact volume about one-eighth the volume of the cerebral cortex. For this reason, the surface area of the cerebellum was thought to be considerably smaller than that of the cerebral cortex.
By using an ultra-high-field 9.4 Tesla MRI machine to scan the brain and custom software to process the resulting images, an SDSU neuroimaging expert discovered the tightly packed folds actually contain a surface area equal to 80% of the cerebral cortex’s surface area.
The scientists in the article are calling the cerebellum “quite the jack of all trades” because of its “versatile role, contributing to our five senses as well as pain, movements, thought, and emotion.”
Mapping the brain’s sensory gatekeeper (MIT News). Many readers may be unfamiliar with the “thalamic reticular nucleus” or TRN. It is “believed to act as a gatekeeper for sensory information flowing to the cortex,” this article says. Problems with this region seem to be associated with autism and other attention disorders.
When sensory input from the eyes, ears, or other sensory organs arrives in our brains, it goes first to the thalamus, which then relays it to the cortex for higher-level processing. Impairments of these thalamo-cortical circuits can lead to attention deficits, hypersensitivity to noise and other stimuli, and sleep problems.
When functioning correctly, the TRN serves its users well by “blocking out distracting sensory input.” Without that filter, we could easily be overwhelmed with sensations coming too fast to process. For more on that, see last year’s MIT News article, “How we tune out distractions: Neuroscientists trace a brain circuit that filters unwanted sensory input.” Thanks to these automatic circuits, we are able to focus on a conversation despite constantly changing background noise. Such marvels don’t just happen.
Brain Builds and Uses Maps of Social Networks, Physical Space, in the Same Way (UC Davis). Scientists are finding that the brain constructs physical maps (like paths through a city) and virtual maps (like social networks) in much the same manner. This is because we typically sample a space and infer relationships between samples. Participants given network puzzles to solve were found to build them piecemeal, whether they were physical or virtual networks. Solving the networks called on secondary players in the brain:
They were later asked about relationships between new pairs of people in the grid while the researchers used functional magnetic resonance imaging to measure brain activity. Without being prompted, based only on pairwise comparisons, the volunteers organized the information into a two-dimensional grid in their brains. This two-dimensional map was present across three brain regions called the hippocampus, entorhinal cortex and ventromedial prefrontal cortex/medial orbitofrontal cortex.
We tend to fit new data around a template with a few landmarks, and build up a “map” that can integrate new data into the template. It’s an intelligent way to design, the team found:
That allows us to quickly adapt to a new situation based on past experience. This may help to explain humans’ remarkable flexibility in generalizing experiences from one task to another, a key challenge in artificial intelligence research.
“We know a lot about how the neural codes for representing physical space,” Boorman said. “It looks like the human brain uses the same codes to organize abstract, nonspatial information as well.”
New role for white blood cells in the developing brain (Babraham Institute). The brain needs help from the immune system during development. Scientists in the UK and Belgium found that white blood cells, formed in the thymus and usually found in the blood, are able to pass through the blood-brain barrier to aid microglia during development. In fact, the white blood cells ferry information from the gut microbiota into the brain as well. These “new roles” for immune cells open up more doors of discovery.
The findings open up a whole new range of questions about how the brain and our immune system interact. “It has been really exciting to work on this project. We are learning so much about how our immune system can alter our brain, and how our brain modifies our immune system. The two are far more interconnected than we previously thought,” says Dr Emanuela Pasciuto (VIB-KU Leuven).
Is There a ‘Female Brain’?
Brain scientists haven’t been able to find major differences between women’s and men’s brains, despite over a century of searching (The Conversation). Ari Berkowitz gives the answer in the headline: men’s and women’s physical brains look the same, except for being slightly larger in men on the average. It’s not the size, of course, but the wiring: “John Stuart Mill pointed out, by this criterion, elephants and whales should be smarter than people,” Berkowitz quips. Whatever brain differences there are between the sexes, which some will insist are real, apparently cannot be traced to physical differences in brain structure or tissue. He concludes,
So it’s not realistic to assume any human brain sex differences are innate. They may also result from learning. People live in a fundamentally gendered culture, in which parenting, education, expectations and opportunities differ based on sex, from birth through adulthood, which inevitably changes the brain.
Ultimately, any sex differences in brain structures are most likely due to a complex and interacting combination of genes, hormones and learning.
Gina Rippon explores this topic a bit further in her piece on The Conversation, “The ‘female’ brain: why damaging myths about women and science keep coming back in new forms.” Her emphasis is less on neurobiology and more on culture: i.e., how to combat stereotypes.
Did the Brain Evolve?
Inside the Paleolithic mind (Science). Carolyn Ash looks at a collection of scraping tools, presumably made out of hippopotamus bone by Homo erectus. As she considers the precision marks on the tools, she tries to infer what might have gone on in the minds of their makers.
Sano et al. show how this large (>10 centimeter) fragment was intentionally shaped by a controlled knapping technique and turned into a handaxe. This breakthrough represents a step-change from the conservative thinking of previous tool makers. By analyzing the scarring around the edges of the superbly preserved tool, the authors inferred that the maker, probably Homo erectus, was able to adjust the thickness on both sides of the material by a distinctive flaking technique. This allowed it to be used for precise purposes, such as butchering animal carcasses.
At least she differentiates the mind from the brain, and recognizes intelligent design from its effects.
Evolution of the human brain (Science). Here it comes, kiddos: the daily just-so storytelling hour. Line up a marmoset brain to a human brain, and you can tell opposite tales whether you look at the data with a bottom-up plot (evolution) or a top-down plot (creation). Colette Dehay and Henry Kennedy, naturally, take the bottom-up storytelling plot. (They have to; this is Science Magazine with its historically anti-creationist tradition.)
The crucial observation is that there is a selective increase in the numbers of neurons in the supragranular layers. This “humanization” of the marmoset fetal cortex demonstrates that expression of ARHGAP11B in bRGs in a primate substrate has the capacity to contribute to neocortical expansion and supragranular complexification during human evolution. ARHGAP11B-induced expansion of the cortical progenitor pool is mediated by metabolic changes in mitochondria, particularly increased glutaminolysis, a characteristic of highly mitotically active cells. This illustrates how cell metabolism—one of the most ancient of biological networks—participates in shaping the human lineage.
It sounds believable when you don’t think about it. Didn’t John Stuart Mill remind Ari Berkowitz that if size (or number of cells) caused brain differences, whales would be the smartest animals on the planet? Or is your mind simply a function of cell metabolism? They why doesn’t your physical heart do the thinking? Do you think better when sprinting down the track, when your mitochondria are revved up to the max? Dehay and Kennedy apparently didn’t think about their thesis very hard. But that’s the nature of Darwinism: just say “It evolved,” and your work is done.
That’s enough evolution for this article. We don’t want to spoil the Lord’s Day, when we should be obeying the words of Jesus, who taught that the greatest commandment was to love the Lord your God with all your heart and with all your soul and with all your mind (Matthew 22:37). Mind your brain so that it thinks about that.