Thursday, May 6, 2010

Eight Intriguing Facts about the Human Brain

(1) The mind IS what the brain does. That is to say, your sense of Self, your consciousness, your emotions, language, moral reasoning, ability to write a symphony or paint a sunset, are all ONLY the products of neural firing and activity in your brain (if you accept the scientific mechanistic view of human nature), and not the result of some ethereal mind (if you reject Cartesian dualism).

(2) "The difference between seeing words, hearing words, reading words and generating words can correspond to different aspects of what part of your brain is active. To some extent, if we put you in an fMRI scanner and observed what you're doing in real time, by looking at the activity patterns in your brain we can tell whether you are thinking about music or thinking about sex. To some extent we can tell whether you're solving a moral dilemma versus something else. And this is no surprise if what we are is the workings of our physical brains" (Bloom, 2007).

(3) The basic unit of the brain, the neuron (which you have about 1000 billion of), is the only type of cell in your body that can remain with you from birth until death - all other cell types are replenished after about 7 years. Furthermore, even though this is the case, dead neurons can grow back, even in very late stages of life.

(4) It is never the actual drugs you take, for medical or recreational purposes, that make you feel calm, euphoric, or otherwise - it is rather the neurotransmitters, like serotonin, dopamine, and norepinephrine, which psychopharmacological substances trigger, that are the source of drug-induced moods and sensations. Hence Dan Gilbert's quote, "We have within us the capacity to manufacture the very commodities we are constantly chasing."

(5) Is the human brain the same thing as your laptop? Does it work in the same way? There are a number of similarities between computing machines and your 3lb. fleshy mental universe, but there are two key differences. First, brains can take a lot of damage and still maintain relatively high levels of functioning. Computers on the other hand, as many of us are all well aware, are very temperamental and fragile. Second, brains are exceedingly faster than your Dell, despite the fact that you Dell is using considerably more conductive equipment. If the human brain were wired like a PC with the type of fatty equipment it uses to process information, it would take around 4 HOURS just to recognize a face. Luckily for us, our brain functions through extraordinarily efficient massively parallel distributive processing.

(6) Although as this post makes clear, we ARE our brains, there are a number of activities we are capable of even when decapitated (thank the French for this evidence). Research has found that all of the following phenomenon are possible without a brain: newborn sucking, limb flexation in withdrawal from pain, vomiting, and yes, even getting an erection of the penis (although I do not quite understand the evolutionary purpose of this).

(7) There are topological maps of you body encoded in your brain, so that body parts which are near one another, like your foot and your ankle, are closer together on the maps than parts which are farther apart, like your eyelids and your fingertips. Interestingly, the size of each part of your body in these brain maps is directly related to the potency of sensation in any particular body area (e. g., the mouth, fingertips, and genitals take up a very large portion of these maps, and your back and shoulders, although much larger in real life, take up much smaller sections).

(8) People who are right-handed create and process language in the left lobe of their brain. This seems relatively straightforward. However, some people who are left-handed create and process language in the right side of their brain, while for other lefties language is located in the left side of their brain - and yet there are a third group of lefties whose language centers are scattered throughout various parts of their brains!

There will be more to come in this new series on Intriguing Facts about the Human Brain.

Source: Foundations: This is your Brain

Saturday, May 1, 2010

The Building Block of the Social Brain: Single Neurons

Watching a Living Brain in the Act of Seeing -- With Single-Synapse Resolution

"When light falls on the retina of the human eye, it hits 126 million sensory cells, which transform it into electrical signals. Even the smallest unit of light, a photon, can stimulate one of these sensory cells. As a result, enormous amounts of data have to be processed for us to be able to see. While the processing of visual data starts in the retina, the finished image only arises in the brain or, to be more precise, in the visual cortex at the back of the cerebrum.

Pioneering a novel microscopy method, neuroscientist Arthur Konnerth and colleagues from the Technische Universitaet Muenchen (TUM) have shown that individual neurons carry out significant aspects of sensory processing: specifically, in this case, determining which direction an object in the field of view is moving. Their method makes it possible for the first time to observe individual synapses, nerve contact sites that are just one micrometer in size, on a single neuron in a living mammalian brain.

Focusing on neurons known to play a role in processing visual signals related to movement, Konnerth's team discovered that an individual neuron integrates inputs it receives via many synapses at once into a single output signal -- a decision, in essence, made by a single nerve cell. The scientists report these results in the latest issue of the journal Nature. Looking ahead, they say their method opens a new avenue for exploration of how learning functions at the level of the individual neuron.

Neuroscientists speculate that a neuron might be caught in the act of learning a new orientation. Many nerve endings practically never send signals to the dendritic tree of an orientation neuron. Presented with visual input signals that represent an unfamiliar kind of movement, formerly silent nerve endings may become active. This might alter the way the neuron weighs and processes inputs, in such a way that it would change its preferred orientation; and the mouse might learn to discern certain movements better or more rapidly. 'Because our method enables us to observe, down to the level of a single synapse, how an individual neuron in the living brain is networked with others and how it behaves, we should be able to make a fundamental contribution to understanding the learning process,' Konnerth asserts."

Read the whole article here