Animal Behavior seeks to understand why animals behave the way they do. Advances in understanding the underlying mechanisms, from the reception and processing of input signals to the effectors of animal behavior, can help to better understand the differences in behavior from one individual to another according to their age, internal state, sex, or condition. It can allow us to compare physiological and pathological functions in the context of neurological disorders, which are often associated with behavioral changes, in order to better diagnose and treat them. Attention deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), obsessive compulsive disorder (OCD), and Tourette syndrome (TS) are all well-known neurobehavioral disorders in which social behavior is impaired. Neurodegenerative diseases, such as Alzheimer’s disease (AD) or Parkinson’s disease (PD), also significantly affect behavior.

To study behavior in an organism, one can focus on a wide range of behavioral aspects, such as movements (motor behavior), conditioning responses (learned behavior), or interactions between animals (social behavior). In Dulac’s lab, researchers are particularly interested in understanding social behaviors in mice, including parenting, mating, and aggression. They have been able to show that the same neuronal cluster associated with parenting behavior is activated in mothers, fathers, and virgin females when they show parenting behavior toward pups, but not in virgin males who do not show parenting behavior but infanticide behaviors (Wu et al., 2014). They were also able to further identify molecularly and spatially defined neuronal populations associated with specific social behavioral states at a given time point in the preoptic area (POA) of the hypothalamus and surrounding regions (Moffitt et al., 2018). The hypothalamus is a region of the brain located just above the optic chiasma, and the preoptic area is located in the anterior part of the hypothalamus. This region contains many small nuclei that are known to be involved in social behavior as well as homeostasis functions such as thermoregulation and fever, sleep, thirst, appetite and so on. Recent studies in the Dulac lab using spatial transcriptomics identified molecularly defined neuronal clusters in the POA that correlate with their involvement in specific social and instinctive behaviors. Several clusters defined by the expression of specific gene markers have been shown to regulate various behaviors: the POAGal+/Calcr+ cluster regulates parenting behaviors (Wu et al., 2014; Kohl et al., 2018), the MPNSlc32a1+/M c4r+ and MPNSlc17a6+/T rhr+ clusters dynamically regulate social homeostasis (Lui et al., 2023), and the VMPOGal+/Calcr+/Amigo2+ cluster regulates sickness behaviors (Osterhout et al., 2022). In order to shape and display an appropriate behavior, an organism must assimilate its internal state, external cues and learned representations, and simultaneously process and integrate multiple streams of information encoding all these states of need . In 1943, Abraham Maslow described these needs in a hierarchical manner, in which physiological needs must be met before safety and social needs. Later he noted that individual motivational drives do not always occur independently of each other, so that several needs probably work together to direct appropriate behavioral outcomes.

Given these facts, one can ask two sets of questions: How do the different behaviors and homeostatic circuits in the POA work together to produce a given behavior, how are they functionally and structurally related, do they have an order of priority, some kind of hierarchy that can be observed? What distinguishes two individuals who do not behave in the same way in the same situation, are there molecular changes, structural and functional changes in neurons or circuits?