Written by Cognitive Neuroscientist, Anna Maria Matziorinis
Neurobehavior explores the intricate interplay between the nervous system and behavior, focusing on how the brain and nervous system modulate and are modulated by cognitive functions, emotions, and behaviors. The term “behavior” encompasses observable responses, actions, or reactions to environmental stimuli. These behaviors can be innate or hardwired, learned, voluntary, or involuntary (automatic responses occurring without conscious control).
In the domain of social behavior, defined as interactions between individuals or groups that confer benefits to one or more participants (Wilson, 1975), relationships can vary in form, duration, and function (Blumstein et al., 2010). Social behaviors encompass a spectrum including aggression, cooperation, altruism, competition, communication, affiliation, imitation, courtship, and parental behaviors, among others. Building on the foundational work of Tinbergen (1963), four orthogonal explanations account for behavioral variations observed in nature: (1) immediate causation, (2) development, (3) function, and (4) evolutionary history. When analyzed integratively, these frameworks provide a comprehensive understanding of social behavior across multiple disciplines (Blumstein et al., 2010).
By examining social behaviors through the lens of neurobehavior, we can better understand how the nervous system governs these complex interactions, providing a bridge between individual neural processes and collective social dynamics.
For example, neurobehavior also includes a wide array of individual behaviors, each intricately regulated by the nervous system in response to internal and external stimuli. Motor behavior, for instance, involves the body’s movements and actions, which can be either voluntary, such as walking, or involuntary, such as reflexes. Sensory processing refers to how the nervous system interprets sensory information, leading to appropriate responses; for example, detecting a hot surface and immediately withdrawing the hand. Memory and learning are processes by which experiences are encoded, stored, and retrieved, enabling adaptive behaviors based on past experiences, like avoiding certain foods after a bad experience. Attention is the cognitive process of selectively focusing on specific stimuli while ignoring others, such as concentrating on a conversation in a noisy room. Emotional regulation involves managing and responding to emotions in adaptive ways, such as calming oneself after feeling angry. Executive function refers to higher-order cognitive processes that guide goal-directed behavior, like planning or impulse control, as seen in the decision to study instead of going out. Fear and anxiety responses are triggered by perceived threats, leading to behaviors like the fight-or-flight response, which are modulated by the brain’s amygdala. Sleep and wakefulness are behaviors regulated by circadian rhythms, influencing patterns of rest and activity. Motivation is driven by neural processes that initiate and sustain goal-directed behaviors, such as the drive to eat when hungry. Attachment and bonding behaviors, influenced by neurochemicals like oxytocin, form emotional connections between individuals, exemplified by the strong bond between a mother and her child. Addictive behavior involves compulsive engagement in rewarding stimuli, such as drugs or gambling, due to changes in the brain’s reward circuits. Lastly, imitative behavior refers to replicating actions observed in others, as when a child mimics a parent’s expressions, a behavior crucial for learning and social development. These examples illustrate the complex ways in which the nervous system governs various aspects of behavior.
When closely examined, these neurobehaviors can be seen as interconnected through the three fundamental pillars of neurobehavior—stress, reward, and social bonding. Each behavior is influenced by, and in turn influences, these core processes. For instance, stress impacts memory, attention, and emotional regulation; reward mechanisms underlie motivation, addictive behaviors, and motor actions; while social bonding drives attachment, imitation, and affiliative behaviors. By analyzing neurobehavior through the lens of these three pillars, we can gain deeper insights into how our actions, thoughts, and emotions are shaped and regulated by the nervous system.
Stress Response: HPA and SAM Systems The body’s response to stress is mediated by two primary systems: the Hypothalamic-Pituitary-Adrenal (HPA) axis and the Sympathetic-Adrenomedullary (SAM) system. The HPA axis involves a cascade of hormonal signals starting from the hypothalamus, triggering the pituitary gland to release adrenocorticotropic hormone (ACTH), which then stimulates the adrenal cortex to produce cortisol. This stress hormone helps the body manage and adapt to stress. The SAM system, on the other hand, activates the sympathetic nervous system, leading to the release of adrenaline and noradrenaline from the adrenal medulla. These neurotransmitters prepare the body for a "fight or flight" response, increasing heart rate, blood pressure, and energy availability.
In essence, these systems equip the body with the ability to respond swiftly and effectively to stress, ensuring survival and the ability to adapt to changing environments.
Reward Mechanisms The brain’s reward system is key to understanding motivation, pleasure, learning, and addiction. Central structures like the ventral tegmental area (VTA), nucleus accumbens, and prefrontal cortex work together, with dopamine playing a crucial role. When engaging in rewarding activities—such as eating, socializing, or drug use—dopamine is released, reinforcing behaviors and facilitating learning by strengthening the connection between actions and their positive outcomes.
However, when this system is dysregulated, it can lead to significant issues. Overactive dopamine responses can drive addictive behaviors, as the brain becomes fixated on activities that provide excessive dopamine, creating a cycle of dependency. Conversely, low dopamine levels are linked to depression, where diminished reward and motivation hinder both learning and daily functioning.
In summary, dopamine not only drives pleasure and motivation but is also essential for learning through reward. Its imbalance can lead to disorders like addiction and depression, highlighting the importance of understanding and managing this critical neurotransmitter system.
Social Bonding Social bonding is essential for human survival and well-being. It involves complex neurobiological processes that foster attachment, trust, and cooperative behavior. Oxytocin and vasopressin, neuropeptides produced in the hypothalamus, are critical for social bonding. Oxytocin, often referred to as the "love hormone," enhances bonding in relationships, maternal behaviors, and social recognition. Vasopressin is associated with social behaviors, including aggression and territoriality. These hormones interact with brain regions such as the amygdala and prefrontal cortex to modulate social interactions and emotional responses.
This document provides a visualization of the neurobehavioral systems involved in stress response, reward, and social bonding. We use category theory to represent the Hypothalamic-Pituitary-Adrenal (HPA) axis, the Sympathetic-Adrenal-Medullary (SAM) system, the reward system, and the social bonding system. Each system is presented with its objects and morphisms, followed by a combined diagram that shows how these systems interact to influence neurobehavior.
Stress Perception: A stressor is perceived by the brain.
Hypothalamus Activation: The hypothalamus is activated, releasing corticotropin-releasing hormone (CRH).
Pituitary Gland Activation: CRH travels to the anterior pituitary gland, stimulating it to release adrenocorticotropic hormone (ACTH).
Adrenal Cortex Activation: ACTH travels through the bloodstream to the adrenal cortex.
Cortisol Release: The adrenal cortex releases cortisol into the bloodstream.
Physiological Effects: Cortisol helps mobilize energy, suppresses non-essential functions (like immune response), and helps restore homeostasis.
Stress Perception: A stressor is perceived by the brain.
Hypothalamus Activation: The hypothalamus is activated, signaling the sympathetic nervous system.
Sympathetic Nervous System Activation: Nerve signals are sent to the adrenal medulla.
Adrenal Medulla Activation: The adrenal medulla releases adrenaline (epinephrine) and noradrenaline (norepinephrine) into the bloodstream.
Physiological Effects: These catecholamines increase heart rate, blood pressure, and energy availability.
- Stress perception to Hypothalamus activation
- CRH (Corticotropin-Releasing Hormone) released by the hypothalamus
- ACTH (Adrenocorticotropic Hormone) released by the pituitary gland
- Adrenal Cortex to Cortisol release
- Cortisol feedback loop
- Cortisol to Physiological Effects
- Stress perception to Hypothalamus activation
- Hypothalamus to Adrenal Medulla activation via Sympathetic Nervous System
- Adrenal Medulla to Epinephrine/Norepinephrine release
- Epinephrine/Norepinephrine feedback loop
- Epinephrine/Norepinephrine to Physiological Effects
HPA Axis:
SMA Axis:
When a stressor is perceived, the brain initiates the stress response by activating both the SAM system and the HPA axis.
The SAM system provides an immediate response to stress, often termed the "fight-or-flight" response. This involves the rapid release of catecholamines (adrenaline and noradrenaline) from the adrenal medulla, which increases heart rate, blood pressure, and energy availability.
While the SAM system deals with the immediate stress response, the HPA axis is activated almost simultaneously to provide a more prolonged response.
The hypothalamus releases corticotropin-releasing hormone (CRH), which stimulates the anterior pituitary to secrete adrenocorticotropic hormone (ACTH). ACTH then travels to the adrenal cortex, prompting the release of cortisol.
Cortisol helps sustain the body’s alertness and energy levels, modulates the immune response, and restores homeostasis over a longer period.
Feedback Mechanisms: Both systems have feedback loops to regulate their activity. High levels of cortisol from the HPA axis can inhibit the release of CRH and ACTH, preventing an overreaction to stress. Similarly, catecholamines from the SAM system can influence the activity of the HPA axis.
Complementary Roles: The SAM system’s quick response allows the body to deal with immediate threats, while the HPA axis ensures that the body can manage prolonged stress without exhausting its resources.
Integrated Response: In many situations, the body needs both immediate and sustained responses to effectively manage stress. For example, in a threatening situation, the immediate effects of adrenaline prepare the body for quick action, while cortisol ensures that energy supplies are replenished and maintained for as long as the stressor is present.
The HPA and SAM axes work together by providing a balanced and effective response to stress. The SAM system handles the immediate needs of the body in response to acute stress, while the HPA axis manages the longer-term effects, ensuring that the body can sustain its response without harm. Their coordination ensures that the body can adapt to and recover from stress in a comprehensive manner.
: Social Interaction
: Oxytocin Release
: Oxytocin Action
: Brain Regions Activation
: Bonding Experience
: Social interaction leads to oxytocin release.
: Oxytocin release leads to oxytocin action.
: Oxytocin action leads to brain regions activation.
: Brain regions activation leads to bonding experience.
The three pillars of neurobehavior—stress, reward, and social bonding—are intricately connected to the formation and strengthening of social networks, which in turn lead to enhanced social ties, improved well-being, and resilient communities. Social bonding, facilitated by neuropeptides like oxytocin, fosters trust, cooperation, and emotional connections between individuals, which are essential for building and maintaining strong social ties. The reward system reinforces these bonds by associating positive social interactions with pleasurable experiences, motivating individuals to engage in and nurture these relationships. Additionally, effective management of stress through supportive social networks enhances resilience, as these networks provide emotional support and resources that mitigate the impact of stress. The synergy between these pillars not only fortifies individual psychological health but also contributes to the overall robustness of social networks. Strong social ties fostered through these mechanisms lead to enhanced social cohesion, where individuals feel more connected and supported. This improved sense of community directly contributes to better well-being, as individuals are less likely to experience the detrimental effects of stress when they have strong social support. Moreover, resilient social networks emerge as these interconnected relationships provide a buffer against life’s challenges, ensuring that communities can adapt and thrive even in the face of adversity.
These three pillars also serve as crucial tools in studying social entanglements and the complex topologies that arise from them. Social entanglements refer to the intricate and often overlapping relationships and interactions within a social network. By examining these entanglements through the lens of stress, reward, and social bonding, researchers can uncover the underlying structures that define how individuals and groups connect and interact. Network theory helps us map these connections, revealing patterns such as clustering, centrality, and bridging ties, which are essential for understanding the flow of information, resources, and influence within a network. The topology that emerges from these social entanglements often reflects the strength and dynamics of these connections, with certain individuals or groups acting as hubs or connectors within the network. These hubs can amplify the effects of stress or reward, or they can be focal points for social bonding, thus shaping the overall behavior and resilience of the network. Understanding this topology allows us to predict how changes in one part of the network might affect the entire system, providing insights into how social networks evolve, adapt, and respond to challenges. Through the study of these pillars and the resulting topologies, we gain a deeper understanding of the social structures that drive creativity, cohesion, and resilience in social groups, leading to more effective strategies for fostering healthy and dynamic communities.
Blumstein, D. T. (2010). Towards an integrative understanding of social behavior: New models and new opportunities. Frontiers in Behavioral Neuroscience. https://doi.org/10.3389/fnbeh.2010.00034
Cannon, W. B. (1915). Bodily Changes in Pain, Hunger, Fear and Rage. An Account of Recent Researches Into the Function of Emotional Excitement. New York, NY and London: Appleton Co.
Godoy, L. D., Rossignoli, M. T., Delfino-Pereira, P., Garcia-Cairasco, N., & De Lima Umeoka, E. H. (2018). A Comprehensive Overview on Stress Neurobiology: Basic Concepts and Clinical Implications. Frontiers in Behavioral Neuroscience, 12, 127. https://doi.org/10.3389/fnbeh.2018.00127
Selye, H. (1950). Stress and the general adaptation syndrome. Br. Med. J. 1, 1383–1392.
Selye, H. (1976). The stress concept. Can. Med. Assoc. J. 115:718.
Tinbergen, N. (1963). On aims and methods of ethology. Zeitschrift für Tierpsychologie, 20(4), 410-433. https://doi.org/10.1111/j.1439-0310.1963.tb01161.x
Wilson, E. O. (1975). Sociobiology: The new synthesis. Belknap Press of Harvard U Press.
Young, L. J., & Wang, Z. (2004). The neurobiology of pair bonding. Nature Neuroscience, 7(10), 1048–1054. https://doi.org/10.1038/nn1327