AsianScientist (Oct. 20, 2016) – Like broccoli and ice cream on a toddler’s plate, mice brains also keep nice and nasty information in separate places, which are genetically distinct, researchers in Japan have found. The paper was published in Nature Neuroscience.
Within the amygdala, an important memory center in the brain, pleasant experiences, tastes, and smells are confined to the back of the basolateral nucleus (BLA), while unpleasant ones are stored at the front. These anterior and posterior regions also interact in a push-pull manner, regulating behaviors tied to negative and positive stimuli respectively.
While there is previous evidence for a positive/negative division in the brains of mice and fruit flies for smell and taste memories, the link from this split to positive and negative behaviors had not been established.
To identify the ‘negative’ and ‘positive’ neurons, researchers from the RIKEN-MIT Center for Neural Circuit Genetics exposed male mice to either electrical shocks to the foot or the company of a female mouse. These specific experiences leave their mark in the amygdala in the form of higher expression levels of the gene c-Fos, a marker of neural activity. Genetic profiling of the activated neurons revealed two distinct genetic markers—Rpso2 for negative neurons, observed almost exclusively in the anterior BLA, and Ppp1r1b for positive neurons, concentrated in the posterior BLA.
The positive neurons were activated when mice were exposed to pleasant smells and water rewards, while negative neurons became active in response to pain and unpleasant smells. Moreover, the researchers found that anterior and posterior neurons not only responded to the value of rewards, but were crucial for associated negative and positive behaviors, respectively; and that the positive and negative neurons could even interfere with how well mice learned the associated positive and negative behaviors.
The BLA thus has an important role in associating negative and positive stimuli with appropriate behaviors, the authors concluded.
The article can be found at: Kim et al. (2016) Antagonistic Negative and Positive Neurons of the Basolateral Amygdala.
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Source: RIKEN Brain Science Institute; Photo: Shutterstock.
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