Summary: According to researchers, adult born neurons play a critical role in the identification of sensory stimulus and the positive values associated with sensory experience.
Source: Institute Pasteur.
Although we have known for several years that the adult brain can produce new neurons, many questions about the properties conferred by these adult-born neurons were left unanswered. What advantages could they offer that could not be offered by the neurons generated shortly after birth?
Scientists from the Institut Pasteur and the CNRS have demonstrated that the new neurons produced in adults react preferentially to reward-related sensory stimuli and help speed up the association between sensory information and reward. Adult-born neurons therefore play an important role in both the identification of a sensory stimulus and the positive value associated with that sensory experience. The neurons generated shortly after birth are unable to perform this function.
These findings are published in the journal PNAS on February 19, 2018.
Although most neurons are generated during embryogenesis, some brain regions in mammals are capable of constantly regenerating their neurons in adulthood. The existence of these adult-born neurons has been proven, but many questions about their function and the way in which they integrate into their target areas remain unanswered.
Research carried out by the Perception and Memory team (Institut Pasteur/CNRS), directed by Pierre-Marie Lledo, a CNRS Director of Research, has recently revealed the specific role of these neurons produced in the adult brain. This study demonstrates that assigning positive values to sensory experiences is closely based on the activity of adult-born neurons, and not the neurons formed shortly after birth. It is these new neurons that may enable individuals to anticipate the delivery of a reward.
The scientists focused on the production of new neurons in adult mice, in particular those neurons that integrate into the olfactory bulb, the brain region responsible for analyzing odors. These new neurons are thought to play a major role in providing flexibility for learning and memorizing olfactory sensory experiences.
The scientists from the Institut Pasteur and the CNRS observed that the new neurons were able to react differently to an odor depending on the consequences associated with that sensory experience, such as whether or not there would be a reward. They also demonstrated that olfactory learning, in which the mice had to associate an odor with positive reinforcement, became easier once the new neurons had been activated. Finally, simply activating these adult-born neurons could be assimilated with a reward-predicting odor.
In short, this research shows that adult-born neurons are involved in the value associated with sensory stimuli rather than just the identification of the nature of a given sensory stimulus. It demonstrates that reward-motivated learning depends largely on adult neurogenesis.
Transferred to humans, these findings could improve our understanding of the role played by new neurons in the adult hippocampus in associative learning processes.
Source: Aurelie Perthuison – Institute Pasteur
Publisher: Organized by NeuroscienceNews.com.
Image Source: NeuroscienceNews.com image is credited to Mariana Alonso and Pierre-Marie Lledo – Institut Pasteur.
Original Research: Abstract in PNAS.
Adult-born neurons boost odor–reward association
Olfaction is an important sensory modality driving fundamental behaviors. During odor-dependent learning, a positive value is commonly assigned to an odorant, and multiple forms of plasticity are involved when such odor–reward associations are formed. In rodents, one of the mechanisms underlying plasticity in the olfactory bulb consists in recruiting new neurons daily throughout life. However, it is still unknown whether adult-born neurons might participate in encoding odor value. Here, we demonstrate that exposure to reward-associated odors specifically increases activity of adult-born neurons but not preexisting neurons. Remarkably, adult-born neuron activation during rewarded odor presentation heightens discrimination learning and enhances the ability to update the odor value during reversal association. Moreover, in some cases, activation of this interneuron population can trigger olfactory learning without sensory stimulation. Taken together, our results show a specific involvement of adult-born neurons in facilitating odor–reward association during adaptive learning.