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.

Bacterial speech bubbles : Nature

Bacteria secrete signals to other bacteria of the same species through vesicle packets.

Mashburn and Whiteley describe the unexpected convergence of two seemingly unrelated areas of microbiological research: how bacteria talk to their friends, and how they attack their enemies. The authors studied the bacterial pathogen Pseudomonas aeruginosa, which releases a hydrophobic molecule called the ‘pseudomonas quinolone signal’ (PQS) to send messages to other bacteria of the same species. The surprise is that, rather than being secreted as single molecules, PQS is released in bubble-like ‘vesicles’ that also contain antibacterial agents and probably toxins aimed at host tissue cells as well.

I wonder if this is evolutionarily connected to synaptic vesicles or if this is a case of something like convergent evolution…

Microcephalin, a Gene Regulating Brain Size, Continues to Evolve Adaptively in Humans — Evans et al. 309 (5741): 1717 — Science

Although the finding itself isn’t terribly shocking, the analysis is interesting and raises some even more interesting ethical questions. Methodology: The researchers tracked the occurence of a particular haplotype, which “increased in frequency too rapidly to be compatible with neutral drift [and] this indicates that it has spread under strong positive selection.” Strikingly this gene is not very old (37,000 years) and it has been changing rapidly… the real message: make no mistake, we’re still evolving!

Another interesting issue involves this figure from the paper:

Fig. 3. Global frequencies of Microcephalin haplogroup D chromosomes (defined as having the derived C allele at the G37995C diagnostic SNP) in a panel of 1184 individuals. For each population, the country of origin, number of individuals sampled, and frequency of haplogroup D chromosomes are given (in parentheses) as follows: 1, Southeastern and Southwestern Bantu (South Africa, 8, 31.3%); 2, San (Namibia, 7, 7.1%); 3, Mbuti Pygmy (Democratic Republic of Congo, 15, 3.3%); 4, Masai (Tanzania, 27, 29.6%); 5, Sandawe (Tanzania, 32, 39.1%); 6, Burunge (Tanzania, 28, 30.4%); 7, Turu (Tanzania, 23, 15.2%); 8, Northeastern Bantu (Kenya, 12, 25%); 9, Biaka Pygmy (Central African Republic, 32, 26.6%); 10, Zime (Cameroon, 23, 8.7%); 11, Bakola Pygmy (Cameroon, 24, 10.4%); 12, Bamoun (Cameroon, 28, 17.9%); 13, Yoruba (Nigeria, 25, 24%); 14, Mandenka (Senegal, 24, 16.7%); 15, Mozabite [Algeria (Mzab region), 29, 53.5%]; 16, Druze [Israel (Carmel region), 44, 60.2%]; 17, Palestinian [Israel (Central), 40, 63.8%]; 18, Bedouin [Israel (Negev region), 44, 54.6%]; 19, Hazara (Pakistan, 20, 85%); 20, Balochi (Pakistan, 23, 78.3%); 21, Pathan (Pakistan, 23, 76.1%); 22, Burusho (Pakistan, 25, 66%); 23, Makrani (Pakistan, 24, 62.5%); 24, Brahui (Pakistan, 25, 78%); 25, Kalash (Pakistan, 24, 62.5%); 26, Sindhi (Pakistan, 25, 78%); 27, Hezhen (China, 9, 77.8%); 28, Mongola (China, 10, 100%); 29, Daur (China, 10, 85%); 30, Orogen (China, 10, 100%); 31, Miaozu (China, 9, 77.8%); 32, Yizu (China, 10, 85%); 33, Tujia (China, 10, 75%); 34, Han (China, 41, 82.9%); 35, Xibo (China, 9, 83.3%); 36, Uygur (China, 10, 90%); 37, Dai (China, 9, 55.6%); 38, Lahu (China, 10, 85%); 39, She (China, 9, 88.9%); 40, Naxi (China, 10, 95%); 41, Tu (China, 10, 75%); 42, Cambodian (Cambodia, 11, 72.7%); 43, Japanese (Japan, 27, 77.8%); 44, Yakut [Russia (Siberia region), 25, 98%]; 45, Papuan (New Guinea, 17, 91.2%); 46, NAN Melanesian (Bougainville, 18, 72.2%); 47, French Basque (France, 24, 83.3%); 48, French (France, 28, 78.6%); 49, Sardinian (Italy, 26, 90.4%); 50, North Italian [Italy (Bergamo region), 13, 76.9%]; 51, Tuscan (Italy, 8, 87.5%); 52, Orcadian (Orkney Islands, 16, 81.3%); 53, Russian (Russia, 24, 79.2%); 54, Adygei [Russia (Caucasus region), 15, 63.3%]; 55, Karitiana (Brazil, 21, 100%); 56, Surui (Brazil, 20, 100%); 57, Colombian (Colombia, 11, 100%); 58, Pima (Mexico, 25, 92%); 59, Maya (Mexico, 25, 92%).

Haplogroup D describes a set of mutations in the gene encephalin that, according to the study, have been selected for. The figure/caption above shows that this haplotype occurs at a much lower rate in sub-Saharan populations and highest in East Asian, European, and Latin American populations. Let me be clear: The paper is intended to demonstrate the selective pressure for this haplogroup. Although the authors suggest it, this does not necessarily give us the causal connection that encephalin was selected for because the gene results in a bigger brain.

It is known that encephalin definitely plays a role in determing brain size, but, as this well done NYT article (highly recommended for those unable to access the original Science article) points out, there could be another function of the gene product (perhaps even some non-neural role) that explains the selection.

I do feel strongly that this kind of science is interesting and needs to be done, both for improving our understanding of the world and for public health benefits, but it will be only more controversial as we find more genes and evolutionary scenarios like this. One very nice side-effect I think is that these new levels of individual genotyping precision will really challenge what we think of as race. Once we discover everyone is a genetic mutt, can anyone really be said to belong to one race? .

This was news to me, but maybe not to everyone. Everyone’s all impressed with the regularity of cerebellar wiring. Well, how much neater it is when you hear that that architecture may not be just in the cerebellum; in various species, there are a handful of structures similar to cerebellums. And they may have similar functions.

These are separate structures found in species which also have cerebellums (all vertebrates have cerebellums, by the way). At this point, it is debatable how “similar” they really are, but they tend to have:

• analogs to granule cells
• analogs to Purkinje cells
  • with spiny apical dendrites and also either basilar dendrites or smooth proximal regions of the apical dendrites
• sensory input to the Purkinje-like cells organized in a topographic map. The afferents synapse onto the basilar dendrites or the proximal parts of the apical dendrites.
• parallel fibers going from the granule cells to the Purkinje cells, each one contacting many Purkinje cells in many parts of the topographic map.
• embryological origins in the alar or sensory plate

Some of them have also been shown in in vivo experiments to have electrophysiological responses which learn in ways similar to the way the cerebellum does in classical conditioning (think rabbit eye puff experiment).

A notable difference between these structures and the cerebellum is that they don’t have climbing fibers.

Curtis Bell (below) theorizes that all of these structures’ function is to filter expected patterns out of incoming sensory signals.

Quoting/paraphrasing from the paper below, the structures are:

• medial octavolateral nucleus (MON) (in most basal aquatic vertebrates and in some myxinoids)
• dorsal octavolateral nucleus (DON) (in most of the same basal aquatic vertebrates as the MON, except for the bony fish (neopterygii), where it is entirely absent)
• marginal layer of the optic tectum (in all ray finned fish (actinopterygii)
• electro-sensory lobe (ELL) (in a few groups of advanced bony fish (teleosteii))
• the rostrolateral nucleus (RLN) of the thalamus (in a few groups of bony fish)
• dorsal cochlear nucleus (DCN) (in almost all mammals)

For more about this, check out this paper:

Curtis C. Bell. Evolution of Cerebellum-Like Structures. Brain, Behavior and Evolution 2002;59:312-326 (DOI: 10.1159/000063567)

See also:

Anna Devor. Is the cerebellum like cerebellar-like structures?. Brain Research Reviews, Volume 34, Issue 3, December 2000, Pages 149-156.

Have You Heard? Gossip Turns Out to Serve a Purpose – New York Times

From the article:

Gossip not only helps clarify and enforce the rules that keep people working well together, studies suggest, but it circulates crucial information about the behavior of others that cannot be published in an office manual. As often as it sullies reputations, psychologists say, gossip offers a foothold for newcomers in a group and a safety net for group members who feel in danger of falling out.

In this very interesting article, Martin Sereno argues that rather than evolving out of inflexible, hardwired emotion-linked calls, language may have evolved out of complex, flexible learned vocalization patterns which at first had no meaning attached to them (something like birdsong).

Sereno, M. I.(2005) Language origins without the semantic urge. Cognitive Science Online, 3, pp. 1-12.

Read on for the abstract.
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Fascinating NYTimes article on how birds may be as intelligent as primates, and how the assumption that a layered cortex is the hallmark of higher intelligence may be wrong. Mentions the work of the Avian Brain Nomenclature Consortium (see avianbrain.org) to modernize avian anatomical nomenclature.
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