The temporal lobe, the emotional and homeostatic center of the brain

brain-science-2-pic-1Thalamus: Relays sensory information to the cortex. While this is critical for eating behavior, the thalamus plays a relatively minor role in controlling energy homeostasis when compared to the hypothalamus, which has a crucial role in feeding.

Hypothalamus: The body’s thermostat. The hypothalamus responds to circulating signals of hunger and energy balance. Close to the amygdala, and sharing many connections with it, the essential role of the hypothalamus is to keep all things in our bodies equal. The hypothalamus tells us to drink when we are dehydrated, to sleep when we are fatigued, to take off our sweater when we are hot, and to eat when our bodies are running low on calories. It helps us achieve homeostasis.

This latter role of the hypothalamus was essential to our survival when living in hunter-gatherer society, perpetually on the brink of starvation, and never knowing when the next meal (usually vegetable matter and only occasionally lean meat) would be available. In an environment where malnutrition posed a constant threat for infertility and death, we therefore evolved a pre-disposition to be in a constant, calorie-seeking, overdrive, and to derive an excessive amount of pleasure from eating foods rich in calories and fat. As if this weren’t enough, we also developed an incredibly efficient mechanism of laying down any excess calories consumed at one time as fat, for use at a later time when food was again scarce.

Amygdala: A key part of emotional regulation, the amygdala controls our reactions to events that are key to survival. From events that signal immediate danger to the presence of food, sexual partners, rivals, or children in pain or danger.

There is evidence that the basolateral area of the amygdala is responsible for allowing learned cues to control eating. This means when we see a cue for food, we respond by eating. This is increasingly problematic when our environment is rife with food related cues, as it is now.

It has been suggested that the relationship between eating behavior is mediated by the connectivity between the basolateral amygdala and the lateral hypothalamus. Thus, some researchers have suggested that an amygdalohypothalamic system is specific for our “see food, eat it” response to food advertisements, emotional eating, or any other eating that occurs outside of physiological necessity.

Hippocampus: Memory and learning

The hippocampus is largely regarded as the memory center, responsible for consolidating short- and long-term memory and spatial navigation. It is a major component of the human brain, and is located within the limbic system.

In the context of eating behavior, the hippocampus helps respond to the dynamic changes which are a part of our ever-changing environment. Environmental changes or cues can control which motivational state will guide behavior toward natural or drug rewards; the memory for the location of a highly rewarding substance (like cookies!) is rarely forgotten, thanks to the hippocampus.

How Complex is Eating Motivation?

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Taken from: Berthoud (2011) Metabolic and hedonic drives in the neural control of appetite: who is the boss? Current Opinions in Neurobiology (21) 888-896.

The motivation to eat is controlled by other factors that are not directly related to energy homeostasis. Food consumption is regulated by internal, physiological signals from the body (e.g., deficit signals, hormones, circadian rhythm), as well as by external, environmental signals (e.g., sensory, reward, experiential, cognitive, emotional, social).

What underpins pleasure?

In the most simplistic terms, hormones are released when we engage in rewarding activities or consume rewarding things. For example, eating delicious food, getting a raise, finding money, winning at gambling, or the feeling after a yoga class or run. Two key hormones are dopamine and serotonin, and the pathways they follow explain how we begin to learn, think, and remember rewarding experiences and their consequences. The pathways can be traced through the brain as follows:

brain-science-2-pic-3Credit: ABPI

In our contemporary world, environmental cues that influence food intake are becoming increasingly more powerful. Why fewer and fewer of us are able to maintain a “healthy” relationship with food is among one of the most difficult questions in science today. Trying to understand how and why the obesity epidemic has occurred requires collaborative physiological, medical, and neuroscientific research, in addition toinsights from professionals in social and clinical psychology, economics, and public health and policy.

Learned cues are initially arbitrary cues from the environment that gain the ability to control feeding through associations with reward or punishment. Food-predictive cues can stimulate eating despite satiety, which is a burgeoning issue in health policy. The more we learn about the effects of food advertising, stress and overeating, and the addictive properties of food, the more important this issue becomes. Obesity has serious health implications, so the more we understand the role of the brain in guiding our eating behavior (and key factors that influence it) the better prepared we are in our current “obesigenic” environment.

The act of impulsive eating is a risk-based decision that could be explained by an overactive reward system and underactive inhibitory system in the brain.Or rather, defective signaling from the amygdala to the orbitofrontal cortex and nucleus accumbens.

What activities are also rewarding but won’t produce the same kinds of dependencies? Exercise, learning a new language, or travelling. While each can be done to access, time and money restrictions will often serve as a way to limit your access. Also, I’ve yet to meet a person who became compulsive about language learning.

Each of these activities can stimulate the brain and generally reduce stress. Since there is a strong connection between stress, impulsivity, and overeating, engaging in behaviors known to reduce both stress and impulsivity may contribute to healthier eating behavior in addition to protecting your brain from the damaging effects that compulsive behavior can cause.