Rat cortexThree significant announcements in one week!  Neuroscience is galloping ahead, thanks to improved scanning techniques, and also to Moore’s Law, which allows bigger and bigger data sets to be acquired and analysed.  You need that when you’re studying the most complex thing known to man.

Perhaps the most interesting of the three is a review of what happens in the brain when its owner loses consciousness.  A team at the University of California at Los Angeles (UCLA) used functional magnetic resonance imaging (fMRI) on 12 healthy volunteers to see how information flows changed inside their brains as they lost consciousness under anesthesia with propofol.

They concluded that communication between areas of the brain becomes extremely inefficient when we lose consciousness, as if each area of the brain becomes very distant from every other.  Consciousness, it seems, does not reside in a particular place within our brains, but rather in the way that our billions of neurons communicate with one another.
The second announcement may help solve the age-old riddle of why animals sleep.  Since sleeping makes us vulnerable, it must have an important function.  Recent research had provided evidence for the theory that it enables the brain to sort out memories and preserve the important ones for the long-term, but this didn’t seem enough.

New research at the University of Rochester Medical Center (URMC) in New York state supports the view that the most important function of sleep is waste removal.   The system responsible for disposing cellular waste in the rest of the body – the lymphatic system – does not extend to the brain, which maintains its own closed ecosystem behind the so-called the blood-brain barrier.  The brain’s unique method of waste removal – the glymphatic system – is highly active during sleep, pumping cerebral spinal fluid (CSF) through the brain, flushing waste back into the circulatory system where it eventually makes its way to the general blood circulation system and, ultimately, the liver.  The toxins that are removed are responsible for Alzheimer’s disease and other neurological disorders.  The brain’s cells can reduce in size by as much as 60% during sleep, allowing waste to be removed more effectively.

The brain’s process of clearing waste can only be observed in a living brain, which was not possible before the advent of a new imaging technology called two-photon microscopy.

It seems that given the limited energy at its disposal, the brain must choose between two different functional states — awake and aware, or asleep and cleaning up.

Finally, the picture above may look like a handsome brush head, but is actually a reconstruction of five neighbouring barrel columns in a rat’s vibrissal cortex, which processes information obtained from whiskers located along the animals’ snout.  Each column corresponds to one whisker.
Scientists at the Max Planck Institute at Florida and Germany have shown that the number of neurons varies between cortical columns according to their function: the number of nerve cells per cortical column increases with the distance of the respective whisker from the ground.
It has been suggested that this is bad news for brain-builders because it makes it harder to model numerous cortical columns by mapping just one.  But hey, who doesn’t like a challenge?

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