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futurity_sci_tech 00134.txt

#Scientists use light to make mice asocial California Institute of technology rightoriginal Studyposted by Jessica Stoller-Conrad-Caltech on September 19 2014scientists have discovered antagonistic neuron populations in the mouse amygdala that control whether the animal engages in social behaviors or asocial repetitive self-grooming. This discovery may have implications for understanding neural circuit dysfunctions that underlie autism in humans. Humans with autism often show a reduced frequency of social interactions and an increased tendency to engage in repetitive solitary behaviors. Autism has also been linked to dysfunction of the amygdala a brain structure involved in processing emotions. This discovery which is like a eesaw circuitwas led by postdoctoral scholar Weizhe Hong in the laboratory of David J. Anderson biology professor at Caltech and an investigator with the Howard hughes medical institute. The work appears online in the journal Cell. e know that there is some hierarchy of behaviors and they interact with each other because the animal can t exhibit both social and asocial behaviors at the same time. In this study we wanted to figure out how the brain does thatanderson says. Anderson and his colleagues discovered two intermingled but distinct populations of neurons in the amygdala a part of the brain that is involved in innate social behaviors. One population promotes social behaviors such as mating fighting or social grooming while the other population controls repetitive self-grooming#an asocial behavior. Interestingly these two populations are distinguished according to the most fundamental subdivision of neuron subtypes in the brain: the ocial neuronsare inhibitory neurons (which release the neurotransmitter GABA or gamma aminobutyric-acid acid) while the elf-grooming neuronsare excitatory neurons (which release the neurotransmitter glutamate an amino acid). To study the relationship between these two cell types and their associated behaviors the researchers used a technique called optogenetics. In optogenetics neurons are altered genetically so that they express light-sensitive proteins from microbial organisms. Then by shining a light on these modified neurons via a tiny fiber optic cable inserted into the brain researchers can control the activity of the cells as well as their associated behaviors. Using this optogenetic approach Anderson s team was able to selectively switch on the neurons associated with social behaviors and those linked with asocial behaviors. With the social neurons the behavior that was elicited depended upon the intensity of the light signal. That is when high-intensity light was used the mice became aggressive in the presence of an intruder mouse. When lower-intensity light was used the mice no longer attacked although they were engaged still socially with the intruder#either initiating mating behavior or attempting to engage in social grooming. When the neurons associated with asocial behavior were turned on the mouse began self-grooming behaviors such as paw licking and face grooming while completely ignoring all intruders. The self-grooming behavior was lasted repetitive and for minutes even after the light was turned off. The researchers could also use the light-activated neurons to stop the mice from engaging in particular behaviors. For example if a lone mouse began spontaneously self-grooming the researchers could halt this behavior through the optogenetic activation of the social neurons. Once the light was turned off and the activation stopped the mouse would return to its self-grooming behavior. Surprisingly these two groups of neurons appear to interfere with each other s function: the activation of social neurons inhibits self-grooming behavior while the activation of self-grooming neurons inhibits social behavior. Thus these two groups of neurons seem to function like a seesaw one that controls whether mice interact with others or instead focus on themselves. It was unexpected completely that the two groups of neurons could be distinguished by whether they were excitatory or inhibitory. f there was ever an experiment that carves nature at its joints'says Anderson his is it. his seesaw circuit Anderson and his colleagues say may have some relevance to human behavioral disorders such as autism. n autismanderson says here is a decrease in social interactions and there is often an increase in repetitive sometimes asocial or self-oriented behaviors#a phenomenon known as perseveration. ere by stimulating a particular set of neurons we are both inhibiting social interactions and promoting these perseverative persistent behaviors. tudies from other laboratories have shown that disruptions in genes implicated in autism show a similar decrease in social interaction and increase in repetitive self-grooming behavior in mice Anderson says. However the current study helps to provide a needed link between gene activity brain activity and social behaviors nd if you don t understand the circuitry you are never going to understand how the gene mutation affects the behavior. oing forward he says such a complete understanding will be necessary for the development of future therapies. But could this concept ever actually be used to modify a human behavior? ll of this is very far away but if you found the right population of neurons it might be possible to override the genetic component of a behavioral disorder like autism by just changing the activity of the circuits#tipping the balance of the seesaw in the other directionhe says. The Simons Foundation the National institutes of health and the Howard hughes medical institute supported the work. Source: Caltechyou are free to share this article under the Creative Commons Attribution-Noderivs 3. 0 Unported license i

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