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Scientists recently used treadmill exercise, drugs, and electrical stimulation to train paralyzed rats to walk once again, demonstrating a way to possibly treat spinal injuries in humans, which at present are basically untreatable.

In a spinal injury, the neural circuits connecting the brain to the muscles that control walking become damaged or severed, leaving an individual paralyzed. In able-bodied people, these “walking circuits” spring into action when they receive a signal from the brain, but if the spinal cord is damaged, the message from the brain never arrives. When contact with the brain is lost, the circuits shut down [The Guardian]. In the study, published in Nature Neuroscience, researchers manipulated these circuits and produced movement that was “almost indistinguishable” from normal walking. See for yourself in the embedded video.

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Experiments conducted on squid brains in the early days of neuroscience created misunderstandings about the workings of the human brain that have persisted for 70 years, according to a new study. While the squid experiments did shed light on how messages are transmitted between brain cells with electrochemical signals (and led to a Nobel Prize for the experimenters), researchers are just now realizing that the results gave scientists a confused idea about the efficiency of neurons.

The story begins seventy years ago when a pair of British physiologists, Alan Hodgkin and Andrew Huxley, took the first stab at figuring out how neurons transmit electrical signals, known as action potentials. Because most neurons are small–in humans, a cubic millimeter of gray matter can contain 40,000 neurons–the duo turned to squid, which contain a giant axon, the long thin part of a neuron through which action potentials travel [ScienceNOW Daily News]. Those early experiments found that transmitting the action potential along the axon was a very inefficient process that used a great deal of energy, and neuroscientists ever since have assumed that mammal brains had the same inefficient wiring.

Researcher Henrik Alle, lead author of the new study published in Science, decided to reexamine the old assumptions. “I saw this old work,” says Alle. “I thought I cannot believe personally that nature would waste such energy.” Alle figured that nature would have made the process more efficient in mammals, whose brains send a huge number of messages [NPR News].

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A chemical compound similar to the blue food dye found in blue M&Ms and blue Gatorade could one day be used to treat people with spinal injuries, and could reduce damage and improve mobility, according to a new study. Researchers found that when they injected the compound Brilliant Blue G (BBG) into rats suffering spinal cord injuries, the rodents were able to walk again, albeit with a limp. The only side effect was that the treated mice temporarily turned blue [CNN].

The same research team had previously shown that ATP, a vital energy source that keeps the body’s cells alive, quickly pours into the area surrounding a spinal cord injury after it occurs. Unfortunately, the release of ATP at hundreds of times the normal level kills off healthy, uninjured motor neuron cells by flooding them with a deluge of molecular signals, making the initial injury worse [BBC News]. In the new experiment, described in the Proceedings of the National Academy of Sciences, the blue compound prevented ATP from latching on to the motor neuron cells, and therefore prevented the secondary damage that occurs in the hours after a spine injury.

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In a new study, researchers attached electrodes to individual neurons in monkeys’ brains and then rerouted those neuronal signals through a brain-machine interface, which converted them into electrical signals that controlled the monkeys’ own paralyzed muscles. Researchers say this roundabout feat of bioengineering could eventually lead to new treatments and prosthetics for paralyzed people.

The implant exploits the fact that even when the neural connection between a brain region and the muscles it controls is severed or damaged by, say, a stroke or spinal injury, the controlling neurons remain active. For example, people living with quadriplegia who try to move their arm still generate arm-movement signals in the motor cortex of their brain, even after several years of paralysis [New Scientist]. The new study is the first to send the signals back to the user’s own muscles, as opposed to related research in which the signals are fed into electronic devices.

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A small study has found that the brains of men and women are wired differently in a region that is related to speech, memory, and hearing. Researchers studied the brain tissue from four men and four women who were all having a small portion of their brains excised as a treatment for epilepsy. They found that in the brain region called the temporal neocortex, men have a higher density of synapses, which are the connection points between brain cells.

For many years, scientists have searched for structural variations between men’s and women’s brains to explain psychological studies showing that, overall, the sexes think and act differently. Past studies found differences in brain mass and neuron density, but “they were hyped and untrustworthy,” [neuroscientist Edward] Jones says. This study is meticulously detailed, he notes. It is the first to show gender differences on such a fine scale — at the synapse [Science News].

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Researchers have gotten an amazingly close look at the human brain’s methods of short-term memory formation and recollection. A new study has examined the activity of individual brain cells, and found that the same neurons that fire when a person gets their first look at something fire again when they recall it.

Scientists at the University of California, Los Angeles, (U.C.L.A.) showed 13 volunteers—epilepsy patients with therapeutic electrodes implanted in their brains—several five- to 10-second clips from videos such as The Simpsons. The researchers found that a small sample comprising some 50 neurons in the hippocampus and entorhinal cortex (memory centers in the brain) fired in distinctive repeatable patterns that differed for each clip [Scientific American]. A few minutes later, when researchers asked the volunteers to think back to the film clips and say what came to mind, the neurons fired in the same distinct patterns when they mentioned each clip.

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Researchers have built a “biological brain” for a robot using a dish full of rat neurons, and have harnessed the neurons’ electric signals to navigate the robot around a pen. Researchers say the experiment should add to their understanding of how brain cells function, and could provide insight into what goes wrong in neurons affected by diseases like Alzheimer’s and Parkinson’s.

The robot’s controller nestles inside a small pot containing a pink broth of nutrients and antibiotics. Inside that pot, some 300,000 rat neurons have made – and continue to make – connections with each other. As they do so, the disembodied neurons are communicating, sending electrical signals to one another just as they do in a living creature [New Scientist]. The neurons’ automatic drive to connect and communicate may be an indication of how sturdy brain cells are; researcher Steve Potter, who has been involved in similar experiments, says that brain cells have “evolved to reconnect under almost any circumstance that doesn’t kill them” [Telegraph].

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