How does prefrontal cortical function impact the hedonic continuum?
By Dana Morales’ UA 25 and Jim Stellar
What is the hedonic continuum and how does it relate to approach-withdrawal?
The hedonic continuum is a device psychologists use to arrange happiness on a scale, allowing researchers to measure preferences. This came from food science research, using a 1 – 7 point scale, where individuals are able to rate things with a happy, neutral or sad expression.
Approaching and Withdrawing in the lower brain in rats
We think this idea of a hedonic continuum, is a reflection of the balance between two systems in the brain perhaps even at the hypothalamic level. Weak electrical stimulation of the lateral hypothalamus increases approach behavior in rats. Also, rats will press an operant lever to initiate the electrical stimulation, indicating that the stimulation produced a reward. We see this phenomenon in humans from some poorly run experiments long ago, which would not be ethical to conduct today. When this hypothalamic stimulation point was placed in the medial or midline part of the hypothalamus, the opposite effects were observed. This stimulation induced withdrawal behaviors, and the rats oriented away from the stimuli, working to turn off the lever, to terminate the stimulation. This experiment was not conducted in humans.
This lateral-medial difference was also reflected in feeding behavior in rats. Destroying the lateral hypothalamus resulted in a reduction in feeding in rats which also caused significant weight loss. Destroying the medial hypothalamus, produced a reduction in satiety and instead released feeding behaviors leading to obesity.
Long ago in the 1970s, JS conducted his PhD thesis on these effects of approaching and withdrawing behavior in rats stimulating and lesioning the lateral and medial hypothalamus, and he proposed the idea then that these systems mediated approaching and withdrawing behaviors. As reflected in the title of our blog.
Human emotions
Researchers such as Friedrich Nietzsche and Lisa Barrett suggest that human emotions begin with two fundamental expressions: the good and the bad. From these basic feelings, a range of complex emotions develops through learning and labeling. One aspect of this emotional labeling often involves visual input (e.g. facial emotions), which help us understand various emotional states of others. This understanding allows us to predict others’ behaviors or emotions by inferring their mental states, a concept known as mentalizing.
How we label emotions can significantly influence our perception of them, even extending to sophisticated emotional terms like “schadenfreude” – the pleasure derived from another’s misfortune. Interestingly, Nietzsche views suffering as essential for personal development and the establishment of individual values. Barrett argues for constructed emotions that are made and can foster our understanding of the complexities of human experience. Our perception of these mental states impacts our motivations (the good and the bad) when considering the approach and withdrawal concept.
What is the role of the prefrontal cortex in evaluating the hedonic continuum?
The prefrontal cortex (PFC), particularly the left PFC, sometimes called the “personality center,” distinguishes us as humans because it uniquely involves the complex spectrum of human emotions and thinking. It processes and interprets these emotions cognitively, making it a critical player in human affectome. In the use of higher-order functions, we see an interplay between cortical function and the hedonic continuum, influencing how these network components are processed and communicated. A prior blog post discussed cognitive re-representation of limbic (emotional) processes.
When considering the role of the PFC in evaluating the hedonic continuum, it is essential to understand that the PFC may provide a cognitive framework integrating these higher-order cognitive functions with affective (emotional) responses. In considering this idea, note that the left prefrontal cortex is also implicated in emotional and affective functions (e.g. behavioral goal representations and positive emotions). It holds information value in problem-solving, planning, and reasoning. However, the left PFC also helps inhibit impulsive actions and negative emotions. It also plays a role in approach-related emotions such as enthusiasm and motivation. Thus the left PFC is overseeing the hedonic continuum even if it originates in the hypothalamus.
The left PFC can interact with the hedonic continuum
First, consider Aristotle’s concept of eudaimonia, which emphasizes the moral and ethical virtues necessary for leading a good life. He suggests that true happiness involves a more profound sense of fulfillment. Rather than viewing pleasure as the sole goal, Aristotle believes it is a byproduct of virtuous living.
Aristotle differentiates between higher and lower pleasures, arguing that not all pleasures contribute equally to well-being. He notions that higher pleasures—specifically intellectual and moral pleasures—are what truly contribute to eudaimonia. This leads to the distinction between two happiness types: mere pleasure-based and virtue-based happiness.
When exploring our motivations, the PFC helps us navigate the spectrum of pleasure by assessing our emotions and finding a balance between our immediate desires and the quest for a fulfilling, virtuous life—an idea rooted in Aristotle.
When experiencing mixed emotions (positive and negative) simultaneously they can differ in valence and arousal. This influences the cognitive role of the left PFC involving executive function.
Conclusion
The hedonic continuum is an intriguing concept that helps us understand the interactions between two opposing emotional and motivational states represented in brain structures. The key question is how these brain structures, associated with approach and withdrawal, relate to one another. Do they inhibit each other, functioning like a seesaw where one is elevated while the other is lowered? This idea of reciprocal inhibition seems overly simplistic when considering the complexity of emotions and a complicated brain.
In our next blog, we will explore the experience of mixed emotions simultaneously and how the brain processes these feelings.
