neurodudes

Human neural stem cells differentiate and promote locomotor recovery in spinal cord-injured mice — PNAS

This article has some very promising results. I haven’t read the paper in detail, but here’s the executive summary. Human neural stem cells (hNSCs) were injected into mice that received a precision contusion (laminectomy) injury at spinal level T9. Control groups had vehicle and human fibroblast cell injections after receiving the same injury.

The group receiving hNSCs showed a significant functional recovery from the vehicle group. The fibroblast group did not. Then, to prove that the functional recovery was due to the new neurons and glia from the hNSC, the investigators injected the recovered mice with diptheria toxin, which affects human neurons while essentially leaving mouse neurons alone. After the toxin injection, the recovered mice with hNSC regressed back to the same behavioral performance as the vehicle group. That is, the functional recovery reversed after selective de-activation of the hNSC-derived neurons.

Additionally, the hNSCs produced both neurons and oligodendrocytes (myelin producers) in the mice. Through EM, it was verified the hNSC-derived neurons formed synapses with endogenous mouse neurons.

Amazing. Work like this shows how genetically similar mouse and human neurons (well, at least spinal cord neurons) must be. And, with regard to the race to understand and control stem cell development, this provides further evidence of how strongly the local environment can influence differentiation.

Almost Before We Spoke, We Swore – New York Times

Fun article from the NYT about swearing through the ages and its biological basis. Some relevants parts:

Reporting in The Archives of General Psychiatry, Dr. David A. Silbersweig, a director of neuropsychiatry and neuroimaging at the Weill Medical College of Cornell University, and his colleagues described their use of PET scans to measure cerebral blood flow and identify which regions of the brain are galvanized in Tourette’s patients during episodes of tics and coprolalia.

They found strong activation of the basal ganglia, a quartet of neuron clusters deep in the forebrain at roughly the level of the mid-forehead, that are known to help coordinate body movement along with activation of crucial regions of the left rear forebrain that participate in comprehending and generating speech, most notably Broca’s area.

The researchers also saw arousal of neural circuits that interact with the limbic system, the wishbone-shape throne of human emotions, and, significantly, of the “executive” realms of the brain, where decisions to act or desist from acting may be carried out: the neural source, scientists said, of whatever conscience, civility or free will humans can claim.

And some input from Frans about angry chimps:

Indeed, chimpanzees engage in what appears to be a kind of cursing match as a means of venting aggression and avoiding a potentially dangerous physical clash.

Frans de Waal, a professor of primate behavior at Emory University in Atlanta, said that when chimpanzees were angry “they will grunt or spit or make an abrupt, upsweeping gesture that, if a human were to do it, you’d recognize it as aggressive.”

Such behaviors are threat gestures, Professor de Waal said, and they are all a good sign.

The Aug 4 issue of Neuron has an interesting article (news & views) on fMRI of the ventral (“what”/perception) and dorsal (“where”/motor) visual pathways.

Subjects in the fMRI were either shown images of objects alone or hands grasping these objects. Reliably, the object-only stimuli activated the contralateral ventral visual pathway. In the case of grasping stimuli where the hand was presented in the opposite visual hemifield from the object, contralateral activation of the dorsal and ventral visual pathways was seen. When subjects were asked to focus their attention on either object or grasping hand, activation was pronounced in the ventral or dorsal visual streams, respectively.

Most importantly, the study affirms that there really isn’t a single fundamental visual representation in the brain — the representation used to recognize an object is not the same as the representation used to pick up that object. Because of the different functions of these tasks, this probably doesn’t sound too surprising but, to me, it is surprising! What we consciously see is neurally separate from what our motor system is “seeing” and the break between the two pathways happens quite early in visual processing.

Like the mirror neuron work, this provides further evidence in the “seeing is believing/doing” vein. As the author of the news and views summary points out, this work

remind[s] us once more that (ultimately) the brain did not evolve to enable us to think; it evolved to enable us to act.

Lastly, this type of idea is the basis of Rodolfo Llinas’s elegant book i of the vortex, which I’ve been reading recently. So far, it’s great and I recommend it highly!

Daniel Moran, Andrew B. Schwartz, and G. Anthony Reina “…created a virtual reality video game to trick the monkeys into thinking that they were tracing ellipses with their hands, though they actually were moving their hands in a circle.

They monitored nerve cells in the monkeys enabling them to see what areas of the brain represented the circle and which areas represented the ellipse. They found that the primary motor cortex represented the actual movement while the signals from cells in a neighboring area, called the ventral premotor cortex, were generating elliptical shapes.”

http://news-info.wustl.edu/tips/page/print/652.html