neurodudes

Echolocating kid, who had both his retinas surgically removed at an early age:

This dramatic example of human neural plasticity is amazing! Someone should go study this kid and his parents and find out more about how he developed his echolocation strategy. Are there other examples of this occurring in the medical literature? I’ve heard that blind people have very good hearing (and other senses) but this seems like a little more than “good hearing.” Also, thanks to Ben Huh for pointing me to this!

Viren tipped me off to this fascinating result that reinforces the idea that we really have no clue about what is happening in the earliest stages of neural development. This recent PNAS study found that the strongest predictor of a man being homosexual is the number of biological, older brothers. The effect is independent of non-biological brothers and still holds when the brothers are reared apart. As presented in the paper, the evidence suggests that the early development in the uterus might be different for later children.

Abstract after the jump. (more…)

Social isolation delays the positive effects of running on adult neurogenesis - Nature Neuroscience

From the Apr 9, Nature Neurosci:

Social isolation delays the positive effects of running on adult neurogenesis
Alexis M Stranahan, David Khalil & Elizabeth Gould

Social isolation can exacerbate the negative consequences of stress and increase the risk of developing psychopathology. However, the influence of living alone on experiences generally considered to be beneficial to the brain, such as physical exercise, remains unknown. We report here that individual housing precludes the positive influence of short-term running on adult neurogenesis in the hippocampus of rats and, in the presence of additional stress, suppresses the generation of new neurons. Individual housing also influenced corticosterone levels—runners in both housing conditions had elevated corticosterone during the active phase, but individually housed runners had higher levels of this hormone in response to stress. Moreover, lowering corticosterone levels converted the influence of short-term running on neurogenesis in individually housed rats from negative to positive. These results suggest that, in the absence of social interaction, a normally beneficial experience can exert a potentially deleterious influence on the brain.

We’ve heard in the past about neurogenesis in adults, but as far as we understand, this only happens in limited locations throughout the brain. However, what if those new neurons migrate to different places?

New evidence in mice suggests that after being born, new neurons can travel along the flow of spinal fluid to end up in the olfactory bulb.

If there is migration to other locations in the brain, the ramifications for computational models of brain systems are significant.

–Stephen

In the August PLoS Biology, there is an article showing the production of pure neural stem cells from human embryonic stem cells.

The procedure is quite simple: Add growth factors FGF-2 and EGF to the ES cells and you get pure NS cells, which overcomes several of the limitations of previous neurosphere-based assays [Nature Methods].

Some recent work in Neuron (full article; easy to read summary) shows how hippocampal neurons can cause neural progenitor cells to produce new neurons in the hippocampus. I find this fascinating since the network literally is replacing itself through its own dynamics.

The mechanism seems to be that GABAergic cells synapse onto progenitor cells and cause calcium entry due to the depolarization. (GABAergic synapses are often excitatory in young cells which have elevated intracellular chloride levels.) The increased calcium entry leads then to activation of genes coding for neuronal differentiation-related proteins.

Also, here’s some earlier work from Malenka’s lab along the same lines.

This research suggests that neuronal variety within a single person may be partly due to “jumping genes” which change their position from cell to cell.

Alysson R. Muotri, Vi T. Chu, Maria C. N. Marchetto, Wei Deng, John V. Moran and Fred H. Gage. Somatic mosaicism in neuronal precursor cells mediated by L1 retrotransposition p903. Nature 435, 903-910 (16 June 2005). doi: 10.1038/nature03663

News and Views

“…a difference in concentration of a single molecule across the tip of an axon can measurably impact the direction in which the axons grow”

Press release: http://gumc.georgetown.edu/communications/releases/release.cfm?ObjectID=2670

Journal article:

• actual article
• Pubmed entry with link to commentary and errata