Neurobiology: linear.

The analysis of the sensory circuits of the nematode worm elegans revealed that the circuitry was gender-specific and was generated by eliminating the initial connection between the sexes. See page 206

If a person’s brain is presented, even the most detailed neuroanatomist can hardly determine the gender of its former owner. There are obvious differences between men and women in some areas of the brain, but these differences may be subtle, variable, and the causes and consequences are largely unknown. Over the past five years, some organisms have worked on 1,2,3 suggesting that changes in neural connectivity between regions of the brain may be a sign of differences between men and women. This is on page 206, oren souza’s. 4. Clear evidence is provided for the gender difference of the roundworm nerve wiring in caenia elegans. In addition, they reported that these differences were caused by gender-specific eradication of neural connections and were controlled by the genetic gender of the nervous system itself.

In the elegans, males are males and females are called androgynous. They produce sperm reserves that can be reproduced by self-fertilization or by mating with men. A very detailed study of the neural systems of the sexes. An adult hermaphrodite has 302 neurons, and the entire connectome between these neurons was mapped to five in the 1980s. These connections are called synapses, and connecting neurons to circuits is crucial for brain function. A complete hermaphrodite connectome is still the only one and provides unmatched information about neural circuits and behavioral control.

Oren souza et al. Start with a comparison of the hermaphroditic wiring diagram and the adult male tail 6, identified in 2012. The author focuses on the circuitry of a connected neuron that receives and interprets the input of tiny sensory organs from the tail of the phasmid. Surprisingly, they found seven synapses instead of another, a phenomenon known as sexual dimorphism. For example, although two neurons, called PHB and AVA, are contiguous in both sexes, synaptic connections between them seem to exist only in hermaphroditism. In men, PHB is linked to nearby neurons called AVG (figure 1).

Figure 1: losing maturity.

Figure 1

Oren souza et al. 4 to determine gender specificity of the roundworm c. elegans seven synaptic connections between neurons, including called PHB and AVA between neurons and PHB and AVG the synaptic connections between neurons. In young animals, these synapses can be seen in males and hermaphrodites. As the worm matures, the inherited synapses of each neuron are eliminated. In men, the connection between PHB and AVA was lost. The connection remains hermaphroditic, and the connection between PHB and AVG is lost. The genetic change in PHB is enough to reverse this pattern.

Full-size images.

The researchers used the genetic tool fluorescence to mark the seven synapses to make the connection visible in the activity. Oren-suissa and her colleagues asked how gender affects synaptic patterns after confirming that these relationships are indeed sexual dimorphism. A key insight comes from examining sexual underage animals. Among the five synapses, young animals have a specific relationship between males and androgyny, suggesting that both sexes initially adopt the intermediate state of sex. The sexual dimorphism is produced by eliminating a specific connection – a process known as synaptic pruning.

Although mutation pruning not well described in the worm, but it in mammalian nervous system plays an important role in development, so as to make learning, memory and cognitive change mature connectivity. Cells called microglia, which specialize in synaptic pruning, are involved in the production of sex differences in the mammalian brain. Therefore, pruning can play an evolutionary conservative role in shaping gender differences in circuit connectivity. In addition, the destruction of synaptic pruning has been credited with helping to show gender bias in neuropsychiatric disorders, such as autism 8 and schizophrenia 9. Perhaps the difference in clipping a particular relationship may make a sex – in these cases, men – more susceptible to disease.

Oren souza et al. The basic mechanism for associating sex with pruning is investigated. In the elegans, the sex of the individual depends on the number of X chromosomes it carries. In the nervous system – even in individual neurons – reversing this genetic signal has been shown to change the physiology and behavior of the circuit 10. Using this method, the researchers found that the heritability of individual neurons could also determine whether to trim a particular synapse. For example, PHB neurons, which are genetically “young” and androgynous, usually lead to the elimination of phb-ava connections. In addition, the phb-avg synapses normally pruned in hermaphrodites are retained (figure 1). Therefore, the stability of specific synapses is related to heredity.

At first glance, the genetic effect seems to be irrelevant for mammals, including information about state by hormones such as testosterone and estrogen) throughout the body. However, the sex differentiation of the mammalian brain also depends on its own genetic gender 11. The details of the differences are still mysterious, and studies of invertebrates can provide insight.

Oren souza et al. Next, consider the consequences of sexual behavior. In hermaphroditism, trim produces a phasmid circuit, which provides for the avoidance of toxic chemicals. In men, however, pruning will connect phasmid to neurons that represent the presence of a mate. Therefore, the author wants to know whether the phasmid circuit may be used for male sexual behavior. Although they did not test the behaviour of men with a female phasmid circuit, they did find that phasmid was destroyed by disabling PHB neurons to destroy male mating ability.

The study leaves some unexamined questions and raises intriguing new questions. It is easy to understand why young men benefit from avoiding toxic chemicals and provide reasons for the relationship between men and women. However, it is not obvious why young males and females have a male relationship, just for later pruning. It is not yet clear how a given neuron “knows” which of its many synapses needs pruning. In mammals, pruning is usually the result of decreased synaptic activity; Perhaps this phenomenon also plays a role in nematodes. Finally, heredity also cuts connections to the head of the worm, which contains circuits that control more complex decisions. What might be the consequences?

Research by oren-suissa and colleagues provides critical support for the structure and function of the biological gender regulating neural circuits. In more complex animals, the gender differences in pruning may regulate functional connectivity, disease susceptibility and cognition. Further study of natural variability in the brain may provide important insights into the workings of the neural circuits. They should also shed light on the interaction between society and biological processes, and even tell us something about what makes us human.


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