Positive and negative memories and behaviors are split up in the brains of mice

October 17, 2016, RIKEN
Cerebellum of CIVM postnatal rat brain atlas. Credit: Neurolex

Like broccoli and ice cream on a toddler's plate, the brain also keeps nice and nasty information in separate places. 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. As reported on October 17 in Nature Neuroscience, these opposing neurons in the amygdala are not only physically separated but also genetically distinct.

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. Anterior and posterior BLA neurons are also capable of disrupting expected behaviors if they are turned on or off with optogenetic light stimulation, according to the new study from the RIKEN-MIT Center for Neural Circuit Genetics.

To identify the 'negative' and 'positive' neurons, researchers exposed male mice to either footshocks 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. The activated neurons were genetically profiled, revealing two distinct genetic markers—Rpso2 for negative neurons and Ppp1r1b for positive neurons. Rspo2 was observed almost exclusively in the anterior BLA, while expression of the Ppp1r1b gene was concentrated in the posterior BLA. These spatially distinct positive and negative neurons differed in their size, shape, and electrical properties as well. 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, anterior and posterior neurons not only responded to the value of rewards, but were crucial for associated negative and positive behaviors, respectively. Mice were trained either to respond to footshocks by freezing in place (the ) or to perform a light-cued nose poke to receive water (the positive behavior). Using optogenetics, a method for manipulating genetically tagged cells with light, the researchers could weaken these behaviors, simply by targeting either the anterior or posterior BLA with precise bursts of light while the mice were trained.

Finally, the positive and negative neurons could even interfere with how well mice learned the associated positive and negative behaviors. The expected freezing behavior was reduced by light stimulation of positive neurons during the footshock training, and activation of negative neurons impaired the mice in the water reward task. These neurons could effectively drown out the positive or negative meaning of powerful external stimuli like water or shocks, and this is achieved through mutual inhibitory neural signaling between the anterior, or negative, and posterior, or positive BLA. The basolateral amygdala thus has an important role in associating negative and with appropriate behaviors.

Explore further: Neurons can be reprogrammed to switch the emotional association of a memory

More information: Kim J, Pignatelli M, Xu S, Itohara S, Tonegawa S (2016) Antagonistic negative and positive neurons of the basolateral amygdala. Nature Neuroscience, DOI: 10.1038/nn.4414

Related Stories

Neurons can be reprogrammed to switch the emotional association of a memory

October 24, 2014
Memories of experiences are encoded in the brain along with contextual and emotional information such as where the experience took place and whether it was positive or negative. This allows for the formation of memory associations ...

Both sides now: Brain reward molecule helps learning to avoid unpleasant experience, too

February 29, 2016
The brain chemical dopamine regulates how mice learn to avoid a disagreeable encounter, according to new research from the Perelman School of Medicine at the University of Pennsylvania. "We know that dopamine reinforces 'rewarding' ...

Study shows different brain cells process positive, negative experiences

May 27, 2016
Combining two cutting-edge techniques reveals that neurons in the prefrontal cortex are built to respond to reward or aversion, a finding with implications for treating mental illness and addictions.

Scientists identify neurons devoted to social memory

September 30, 2016
Mice have brain cells that are dedicated to storing memories of other mice, according to a new study from MIT neuroscientists. These cells, found in a region of the hippocampus known as the ventral CA1, store "social memories" ...

Neuroscientists identify brain circuits that could play a role in mental illnesses, including depression

March 31, 2016
Some mental illnesses may stem, in part, from the brain's inability to correctly assign emotional associations to events. For example, people who are depressed often do not feel happy even when experiencing something that ...

Brain circuitry for positive vs. negative memories discovered in mice

April 29, 2015
Neuroscientists have discovered brain circuitry for encoding positive and negative learned associations in mice. After finding that two circuits showed opposite activity following fear and reward learning, the researchers ...

Recommended for you

Sensitive babies become altruistic toddlers

September 25, 2018
Our responsiveness to seeing others in distress accounts for variability in helping behavior from early in development, according to a study published September 25 in the open-access journal PLOS Biology by Tobias Grossmann ...

Immune cell pruning of dopamine receptors may modulate behavioral changes in adolescence

September 25, 2018
A study by MassGeneral Hospital for Children (MGHfC) researchers finds that the immune cells of the brain called microglia play a crucial role in brain development during adolescence, but that role is different in males and ...

Scientists reverse a sensory impairment in mice with autism

September 25, 2018
Using a genetic technique that allows certain neurons in the brain to be switched on or off, UCLA scientists reversed a sensory impairment in mice with symptoms of autism, enabling them to learn a sensory task as quickly ...

Why it doesn't get dark when you blink

September 25, 2018
People blink every five seconds. During this brief moment, no light falls on the retina, yet people continue to observe a stable picture of the environment with no intervals of darkness. Caspar Schwiedrzik and Sandrin Sudmann, ...

Researchers identify new cause of brain bleeds

September 25, 2018
A team of researchers including UCI project scientist Rachita Sumbria, Ph.D. and UCI neurologist Mark J. Fisher, MD have provided, for the first time, evidence that blood deposits in the brain may not require a blood vessel ...

Lung inflammation from childhood asthma linked with later anxiety

September 25, 2018
Persistent lung inflammation may be one possible explanation for why having asthma during childhood increases your risk for developing anxiety later in life, according to Penn State researchers.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.