The neural mechanisms involved in behavioral responses related to emotions

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One of the most conspicuous characteristics of any organism is its ability to react to salient stimuli with an appropriate behavioral response that maximizes survival and minimizes threatening or unpleasant events. In mammals, emotions are considered as an evolutionary strategy to detect changes from the environment to direct proper behavioral responses. Emotions are generated by the complex interaction of interconnected brain structures part of the limbic system. The dorsal raphe nucleus (DRN), the main serotonergic nucleus of the brain, receives signals from different nuclei of the limbic system and in return regulates emotions and behavioral responses by releasing the neuromodulator serotonin (5-HT) in different parts of the central nervous system. Experimental results suggest that the 5-HT would be important to process aversive signals that are important to orchestrate behaviors when something aversive is expected. However, the mechanisms by which 5-HT controls emotions and behaviors is still elusive. This can be explained by the technical difficulties in specifically measuring and controlling serotonergic pathways in vivo.In this research proposal, we use innovative optogenetic and photometric approaches that will allow us to dissect the serotonergic circuitry involved in the processing of emotions. By using several behavioral tests commonly used in mice, we can correlate neural activity and behaviors. Using innovative optogenetic manipulation, we can also artificially activate or inhibit specific neural pathways and see how these manipulations can change behavioral responses. Specifically, in this program, we are interested in understanding how the lateral habenula (LHb) controls the activity of the main serotonergic center of the brain, the dorsal raphe nucleus (DRN). The LHb has been suggested to be the main disappointment center of the brain; it is activated by aversive stimuli or in absence of expected rewards (i.e. a condition that should produce “disappointment”). My preliminary results lead me to believe that it plays is central role in sending aversive signals to the DRN that may have a central role in directing proper behavioral responses in aversive contexts or when a punishment is expected. Our objectives in the longer term is to have a better understanding of the central nervous system and its function at the cellular, synaptic and its neural pathways important in the processing of emotional signals crucial to orchestrate our behaviors.