#cerebral cortex

[biologist4ever]

Illuminating the brain through art and science

[quotesfrommyreading]

One study concluded that humans have five times the information-processing capacity of cetaceans, whom they placed beneath chimps, monkeys, and some birds. But in the same study, horses—with smaller brains than chimps—were found to have five times the number of cortical neurons. Does this mean horses are smarter than chimps? A major confounding factor in these types of comparisons appears to be that every factor is itself quite confounding. Estimating numbers of neurons is a very rough science, so the raw number comparisons are crude. There are lots of different kinds of neurons, and they are arranged in different configurations and proportions in different species. We know all these variations mean something, that they will determine what brains are capable of, but we don’t know yet quite what, or how that might change from one moment to the next in different parts of the brain. There are a lot of assumptions at play, and it can be misleading to extrapolate from one brain to another.

This also applies to comparing cognitive ability. Trying to infer from brains and their structures which animals are “better” at cognition and ranking animal brains in order of “intelligence” is as treacherous as it is tempting. Stan Kuczaj, who spent his lifetime studying the cognition and behavior of different animals, put it bluntly: “We suck at being able to validly measure intelligence in humans. We’re even worse when we try to compare species.” Intelligence is a slippery concept and perhaps unmeasurable. As mentioned earlier, many biologists conceive of it as an animal’s ability to solve problems. But because different animals live in different environments with different problems, you can’t really translate scores of how well their brains perform. A brain attribute is not simply “good” or “bad” for thinking, but rather varies depending on the situation and the thinking that brain needs to undertake. Intelligence is a moving target.

What confounds this dilemma further is that individual animals within a species have varying cognitive abilities. To quote the Yosemite National Park ranger who, when asked why it was proving so hard to make a garbage can that bears couldn’t break into, said, “There is considerable overlap between the intelligence of the smartest bears and the dumbest tourists.”

 —   In the Mind of a Whale

[er-cryptid]

[yoan-le-grall]

[drchristophedelongsblog]

Penfield's homonculus: a fascinating map of our brain

What is Penfield's homonculus?

Penfield's homonculus is a simplified but highly illustrative graphic representation of how our brain ‘sees’ our body. It is a neurological map that shows how the different parts of our body are represented in the cerebral cortex. Imagine a deformed little man, with disproportionately large hands and mouth: that's the homunculus!

Two homunculi, two functions

There are two main types of homunculus:

- The motor homunculus: This corresponds to the area of the cerebral cortex that controls voluntary movements. In this homunculus, the parts of the body that we use with precision (hands, lips) occupy a much larger surface area than the parts that we use less (trunk, for example). This is because these areas require finer neuronal control.

- Sensory homunculus: This is the area of the cortex that receives sensory information from our body. As with the motor homonculus, the most sensitive areas (skin, lips) are disproportionately represented.

 Why is this representation so distorted?

The distortion of the homonculus does not reflect the actual size of the different parts of the body, but rather their functional importance in the brain. The more sensitive an area of the body or the more precise the motor control required, the larger the surface area it occupies on the homonculus.

How was the homonculus discovered?

It was the Canadian neurosurgeon Wilder Penfield who developed this mapping in the 1930s. While operating on epileptic patients, he electrically stimulated different areas of the cerebral cortex. He realised that stimulating certain areas triggered movements or sensations in specific parts of the body. By repeating these experiments, he was able to establish a correspondence between the different regions of the brain and the different parts of the body.

What are the implications of homonculus?

The discovery of the homonculus has had a major impact in several areas:

- Neurology: It has led to a better understanding of the mechanisms behind motor or sensory disorders, such as paralysis or loss of sensitivity.

- Neurosurgery: It helps neurosurgeons to plan their operations in such a way as to avoid damaging essential areas of the brain.

- Functional rehabilitation: It guides therapists in setting up rehabilitation programmes tailored to patients who have suffered brain damage.

Beyond the homonculus: brain plasticity

It is important to note that the homonculus is a static representation of the brain, but our brain is a dynamic and plastic organ. The connections between neurons can change throughout our lives as a result of learning and experience. For example, the homonculus of someone who plays the piano will be slightly different from that of someone who does not.

In conclusion

Penfield's homonculus is a valuable tool for understanding how our brain works. It reminds us that our brain is a complex, organised structure, in which each part has a precise function. Although this representation is simplified, it offers us a fascinating vision of how our body and mind are interconnected.

Go further

[ptchwkstaccato]

thinking about that one time i promised to do a rap battle with the gaming society president on discord not expecting him to go through with it BC ive never met him irl

then i get to the meetup and this genuinely incredibly attractive cute guy stands up and SCREAMS "WHERE IS RUBY" to demand a rap battle in front of 50 people and then they all turned to the fucking dork in a deadpool jumper should i kill myself ?

(i did not end up doing it but ive PROMISED to do it next year as long as he buys me a drink)

((i probably would have done it if he wasn't genuinely hot LMAO))

[jcmarchi]

Neuroscientists create a comprehensive map of the cerebral cortex

New Post has been published on https://thedigitalinsider.com/neuroscientists-create-a-comprehensive-map-of-the-cerebral-cortex/

Neuroscientists create a comprehensive map of the cerebral cortex

By analyzing brain scans taken as people watched movie clips, MIT researchers have created the most comprehensive map yet of the functions of the brain’s cerebral cortex.

Using functional magnetic resonance imaging (fMRI) data, the research team identified 24 networks with different functions, which include processing language, social interactions, visual features, and other types of sensory input.

Many of these networks have been seen before but haven’t been precisely characterized using naturalistic conditions. While the new study mapped networks in subjects watching engaging movies, previous works have used a small number of specific tasks or examined correlations across the brain in subjects who were simply resting.

“There’s an emerging approach in neuroscience to look at brain networks under more naturalistic conditions. This is a new approach that reveals something different from conventional approaches in neuroimaging,” says Robert Desimone, director of MIT’s McGovern Institute for Brain Research. “It’s not going to give us all the answers, but it generates a lot of interesting ideas based on what we see going on in the movies that’s related to these network maps that emerge.”

The researchers hope that their new map will serve as a starting point for further study of what each of these networks is doing in the brain.

Desimone and John Duncan, a program leader in the MRC Cognition and Brain Sciences Unit at Cambridge University, are the senior authors of the study, which appears today in Neuron. Reza Rajimehr, a research scientist in the McGovern Institute and a former graduate student at Cambridge University, is the lead author of the paper.

Precise mapping

The cerebral cortex of the brain contains regions devoted to processing different types of sensory information, including visual and auditory input. Over the past few decades, scientists have identified many networks that are involved in this kind of processing, often using fMRI to measure brain activity as subjects perform a single task such as looking at faces.

In other studies, researchers have scanned people’s brains as they do nothing, or let their minds wander. From those studies, researchers have identified networks such as the default mode network, a network of areas that is active during internally focused activities such as daydreaming.

“Up to now, most studies of networks were based on doing functional MRI in the resting-state condition. Based on those studies, we know some main networks in the cortex. Each of them is responsible for a specific cognitive function, and they have been highly influential in the neuroimaging field,” Rajimehr says.

However, during the resting state, many parts of the cortex may not be active at all. To gain a more comprehensive picture of what all these regions are doing, the MIT team analyzed data recorded while subjects performed a more natural task: watching a movie.

“By using a rich stimulus like a movie, we can drive many regions of the cortex very efficiently. For example, sensory regions will be active to process different features of the movie, and high-level areas will be active to extract semantic information and contextual information,” Rajimehr says. “By activating the brain in this way, now we can distinguish different areas or different networks based on their activation patterns.”

The data for this study was generated as part of the Human Connectome Project. Using a 7-Tesla MRI scanner, which offers higher resolution than a typical MRI scanner, brain activity was imaged in 176 people as they watched one hour of movie clips showing a variety of scenes.

The MIT team used a machine-learning algorithm to analyze the activity patterns of each brain region, allowing them to identify 24 networks with different activity patterns and functions.

Some of these networks are located in sensory areas such as the visual cortex or auditory cortex, as expected for regions with specific sensory functions. Other areas respond to features such as actions, language, or social interactions. Many of these networks have been seen before, but this technique offers more precise definition of where the networks are located, the researchers say.

“Different regions are competing with each other for processing specific features, so when you map each function in isolation, you may get a slightly larger network because it is not getting constrained by other processes,” Rajimehr says. “But here, because all the areas are considered together, we are able to define more precise boundaries between different networks.”

The researchers also identified networks that hadn’t been seen before, including one in the prefrontal cortex, which appears to be highly responsive to visual scenes. This network was most active in response to pictures of scenes within the movie frames.

Executive control networks

Three of the networks found in this study are involved in “executive control,” and were most active during transitions between different clips. The researchers also observed that these control networks appear to have a “push-pull” relationship with networks that process specific features such as faces or actions. When networks specific to a particular feature were very active, the executive control networks were mostly quiet, and vice versa.

“Whenever the activations in domain-specific areas are high, it looks like there is no need for the engagement of these high-level networks,” Rajimehr says. “But in situations where perhaps there is some ambiguity and complexity in the stimulus, and there is a need for the involvement of the executive control networks, then we see that these networks become highly active.”

Using a movie-watching paradigm, the researchers are now studying some of the networks they identified in more detail, to identify subregions involved in particular tasks. For example, within the social processing network, they have found regions that are specific to processing social information about faces and bodies. In a new network that analyzes visual scenes, they have identified regions involved in processing memory of places.

“This kind of experiment is really about generating hypotheses for how the cerebral cortex is functionally organized. Networks that emerge during movie watching now need to be followed up with more specific experiments to test the hypotheses. It’s giving us a new view into the operation of the entire cortex during a more naturalistic task than just sitting at rest,” Desimone says.

The research was funded by the McGovern Institute, the Cognitive Science and Technology Council of Iran, the MRC Cognition and Brain Sciences Unit at the University of Cambridge, and a Cambridge Trust scholarship.

[anauthorslife]

This week, on Living with Disabilities, I had the opportunity to sit down with a friend of mine Tracy Jackson. When she was younger, she earned the title of champion. She was a horse trainer back in the day.

[covenawhite66]

Outer layers of the brain produce high frequency brain ways associated with sensory stimulation

Deeper regions of the brain produce low frequency alpha waves associated with control signals.

Studying six layers of the brain's Cerebral Cortex in 14 regions.

The Cerebral Cortex is responsible for higher cognitive function.

Cognitive function is a broad term that refers to mental processes involved in the acquisition of knowledge, manipulation of information, and reasoning.

Lamination is the biological process by which cells are arranged in layers within a tissue during development

[thatwriterwiththeblock]

Created a God out of a human brain at the laundromat today

[biologist4ever]

Illuminating the brain through art and science!

[margotricordeau]

[quotesfrommyreading]

I’d learned by this point that comparing brains is a difficult business in general. In explaining how clever humans are, we often point out the extraordinarily large size of our thinking organs. Their bulk is the bane of childbirth and consumes 90 percent of the glucose in our blood. But size itself is not a clear guide for comparing animal intelligences, as some bigger animals with larger brains seem to lack the cognitive abilities of smaller ones. Size, as the saying goes, isn’t everything. Relative brain-to-body size, how wrinkled and complex brains are, the thickness of their layers, the structures within them, and the types of neurons these are made of are all helpful—though our human brains are, naturally, the yardstick that other brains are measured against. And yet it is impossible to look at a whale brain and not be surprised by its size. When Hof first saw one, despite knowing they were big, its mass still shocked him. The human brain is about 1,350 grams, three times larger than our big-brained relative, the chimpanzee. A sperm whale or killer whale brain can be 10 kilograms. These are the biggest brains on Earth and possibly the biggest brains ever, anywhere. It’s perhaps not a fair comparison: in relation to the size of our bodies, our brains are bigger than those of whales. Ours are similar in proportion to our body mass, as are the brains of some rodents; mice and men both invest a lot of themselves in their thinking organs. But we both lag far behind small birds and ants, which have much bigger brains compared to their body size than any big animals.

The outer layer of a mammal’s brain is called the cerebral cortex. In cross section, it looks a little like a wraparound bicycle helmet sitting on top of the other parts of the brain. This is the most recently evolved part of our brains, and it was by using their own cerebral cortexes that brain scientists have learned that this area is responsible for rational, conscious thought.

It handles tasks like perceiving senses, thinking, movement, figuring out how you relate to the space around you, and language. You are using yours now to read and think about this sentence. Many biologists define “intelligence” as something along the lines of the mental and behavioral flexibility of an organism to solve problems and come up with novel solutions. In humans, the cerebral cortex, acting with other bits of the brain (the basal ganglia, basal forebrain, and dorsal thalamus), appears to be the seat of this form of “intelligence.” The more cortex you have and the more wrinkled it is, the more surface area available for making connections—and voila! More thinking.

Humans have a really large neocortex surface area, but it’s still just over half that of a common dolphin, and miles behind the sperm whale. Even if you divide the cortex area by the total weight of the brain to remove the cetacean size advantage, humans still lag behind dolphins and killer whales. But there are other measurements in the cortex that seem to be associated with intelligence, and here, dolphins and whales lag behind humans.

The more neurons are packed in, how closely and effectively they are wired, and how fast they transmit impulses are also extremely important in brain function. Just as the composition and layout of the chipset in your tiny, cheap cellphone allows it to pack more computing power than a five-tonne room-sized 1970s supercomputer. Both cetaceans and elephants, the biggest mammals on sea and land, seem to have large distances between their neurons and slower conduction speeds. In raw numbers of neurons, humans here, too, have the edge, with a human cortex containing an estimated 15 billion neurons. Given the larger size of cetacean brains, you’d think they’d have more, but in fact their cerebral cortex is thinner, and the neurons are fatter, taking up more room.

Nevertheless, some cetaceans such as the false killer whale are close behind human levels with 10.5 billion cerebral neurons, about the same as an elephant. Chimps have 6.2 billion and gorillas 4.3 billion. Further complicating comparisons, whales have huge numbers of other kinds of cells, called glia, packing their cortexes. Until recently, we believed these glial cells to be an unthinking filler, but we’ve now discovered that they actually seem important for cognition, too. I don’t know about you, but all this cortex measurement and comparison makes my own feeble organ hurt.

 —   In the Mind of a Whale

[biglisbonnews]

Study finds a connection between fructose and Alzheimer's disease Scientists from the University of Colorado have found a link between fructose and Alzheimer's disease. They say the sugar shuts down parts of the brain that deal with memory and attention to time and causes people to focus on finding food. — Read the rest https://boingboing.net/2023/02/16/study-finds-a-connection-between-fructose-and-alzheimers-disease.html

[drchristophedelongsblog]

Anatomy of the brain: A journey to the heart of our control center

Let's delve into the intricacies of our brain, the fascinating organ that governs all our thoughts, emotions and actions.

The human brain is a complex structure made up of billions of interconnected neurons. These neurons communicate with each other via specialized pathways, forming a complex network that enables us to perceive the world, think, learn and act.

Major brain regions

The brain can be divided into several major regions, each with specific functions:

- Cerebral cortex: This is the outer layer of the brain, made up of gray matter. It is responsible for higher functions such as thought, language, memory and perception.

- Limbic system: Involved in emotions, memory and learning.

- Brain stem: Connects the brain to the spinal cord and controls vital functions such as breathing and heart rate.

- Cerebellum: Involved in movement coordination, balance and posture maintenance.

Key structures for information transmission

Within these large regions, many structures play a crucial role in the transmission of information:

- White matter: Composed mainly of myelinated axons, it ensures communication between different brain regions.

- Basal ganglia: Involved in movement control, learning and emotions.

- Thalamus: Relays most sensory information to the cerebral cortex.

- Hypothalamus: Regulates many vital functions such as body temperature, appetite and sleep.

Communication pathways

Information circulates in the brain via specific nerve pathways. Among the most important are :

- The pyramidal pathway: Responsible for voluntary control of movement.

- Sensory pathways: transmit sensory information from the body to the brain.

- Associative pathways: Connect different regions of the cerebral cortex, enabling the integration of information and the performance of complex cognitive functions.

Neurotransmitters: the brain's chemical messengers

Communication between neurons takes place via molecules called neurotransmitters. These chemical substances transmit signals from one neuron to another, enabling the transmission of information.

In conclusion, the brain is a complex and fascinating organ, whose functioning relies on precise organization and efficient communication between its different structures. Understanding the mechanisms of information transmission in the brain is essential to our understanding of the basis of our behavior and cognitive abilities.

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