The Reopfr eMseemntoartiioens. How Do We Recognize what We Like?

The complexity of the human brain and memory bears a remarkable similarity to the complexity of the universe: both systems span multiple orders of magnitude, where their components interact in extraordinary ways. This intricate network explains how the functions of the nervous system involve coordinated actions between various brain regions, while this system both influences and is influenced by other bodily systems (cardiovascular, endocrine, gastrointestinal, and immune).

Advances in neuroscience reveal that relevant daily events induce functional and morphological remodeling in neural circuits. These changes, the product of associations between lived experiences, translate into behavioral modifications through learning, shaping everything we do, think, feel, and even imagine.

When an experience—or the set of associations it generates—repeatedly activates brain circuits, these changes become permanent, crystallizing into long-term memories that can persist for days, months, or a lifetime. This process, known as memory consolidation, involves lasting transformations in neural networks: from adjustments in synaptic transmission and modifications of chemical receptors to alterations in gene expression that produce new proteins to strengthen neuronal connections. Basically, without these cellular changes, there would be no consolidation, and without consolidation, there would be no lasting memory.

THE EMOTIONAL CONTEXT DURING FOOD INTAKE INFLUENCES THE INTENSITY AND PERSISTENCE OF THE MEMORY

A MODEL FOR STUDYING LONG-TERM MEMORY: FLAVOR RECOGNITION MEMORY
Flavor, which integrates taste and smell, plays a key evolutionary role: guiding consumption toward nutrients and away from toxins. Taste cells send information to the brain, where it is processed in a multisensory way in plastic networks that integrate the hedonic value of flavor, the body’s internal state, and its context. This synthesis activates brain regions specialized in consolidating memories, which are constantly updated based on gastrointestinal experiences, satiety levels, and expectations.

Decades of research have identified critical structures and circuits for flavor memory, such as gustatory and visceral pathways (Núñez-Jaramillo et al., 2010). These circuits, operating in an orchestrated manner, allow us to recognize flavors associated with caloric load, pleasure, or aversive consequences. A milestone in this field was the discovery of taste aversion conditioning (TAC) by John García et al. in 1955. Their paradigm explains why, after consuming a novel food followed by gastrointestinal discomfort, we develop an aversion to its flavor, drastically reducing its future consumption.

Using the TAC and its variants, in our lab we have studied in rodents brain structures of three fundamental regions: the gustatory cortex, the amygdala, and the basal forebrain (BF), which are key to acquiring, consolidating and storing gustatory memories, both emotionally charged and incidentally acquired.

The gustatory cortex functions as a multimodal center: its neurons respond not only to flavors, but also to temperature, texture, pain, and visceral state. Its plasticity allows it to adapt to the changing hedonic value of foods, updating memories even years later. Initially aversive flavors—such as beer or certain cheeses—can become pleasurable after repeated exposure.

TAC modulates learning through cholinergic neurons (a form of neuronal communication based on the neurotransmitter acetylcholine), which regulate cortical excitability towards new stimuli. Our studies demonstrate that the release of acetylcholine in specific cortical areas depends on a dynamic balance between GABA (an inhibitory neurotransmitter) and hypothalamic histamine, a balance influenced by taste familiarity, craving, or aversion. In parallel, the amygdala plays a central role in modulating the consolidation of emotional memories linked to flavor, since the emotional context during food intake influences the intensity and persistence of the memory.

The recognition of aversive tastes occurs through the simultaneous activation of the amygdala and the gustatory cortex. The amygdala coordinates specific neuronal patterns in the cortex, inducing chemical (modifications in neurotransmitters) and morphological (synaptic reorganization) changes that strengthen long-term memory. Furthermore, the amygdala collaborates with the frontal and prefrontal cortices—multisensory regions that integrate smell, taste, motivational state, and hedonic value—to predict consequences (pleasurable or harmful) based on previous experiences. Thus, when we evoke a taste, we not only recognize it, but we also evaluate its potential impact.

We have documented neurochemical changes involved in progressive familiarization with stimuli. Since taste memory is constantly updated based on changing food experiences, gastrointestinal consequences, satiety levels, or expectations, the formation of eating habits appears to depend on the hedonic content of the flavor. The data show that the greater the hedonic content, the greater the change in preference for a flavor after prolonged familiarization. This familiarization correlates with alterations in the neurochemical activity of structures involved in the formation, recall, or relearning of specific stimuli.

Our work proposes that appetizing foods like sugar increase consumption due to the activation of brain reward circuits and positive feedback that consolidates the memory as “relevant” through neurochemical changes in structures responsible for its representation, inducing neuroadaptations that promote progressive increases in consumption. Confirmation of this hypothesis would help us understand how overeating with appetizing foods—a daily reinforcer—induces changes in brain chemistry that eventually lead to inflexibility in the reward system when adapting to new circumstances.

OVEREATING WITH APPETIZING FOODS INDUCES CHANGES IN BRAIN CHEMISTRY THAT LEAD TO INFLEXIBILITY IN THE REWARD SYSTEM

DYNAMIC HEDONIC PERCEPTION AND THE INTEROCEPTIVE SYSTEM
The hedonic perception of a food is not fixed; it varies according to satiety or hunger. The same flavor can be pleasurable during fasting (“hunger is the best sauce”) or neutral after satiety. This flexibility depends critically on the interoceptive system (Craig, 2009)—with key nuclei in the insula and anterior cingulate—a neural network that monitors internal signals (heart rate, satiety, gastrointestinal discomfort) and acts as a bridge between bodily homeostasis and conscious experience. During eating, it integrates visceral signals (gastric distension, glucose levels) with sensory (smell, texture) and emotional (aversion or pleasure) information, thus adjusting eating behavior.

Food consumption, far from being a simple act, recruits intricate bodily functions whose regulation includes homeostatic and metabolic balances, conscious processes, and emotional responses, with cognitive properties such as memory and decision-making. In individuals on restrictive diets, the interaction between these processes becomes critically important: the ability to stop consumption despite sensory pleasure depends on accurately integrating the hedonic value of food and internal satiety signals. Recent studies highlight its role in eating disorders; for example, in obesity or anorexia, interoceptive dysfunction can alter satiety recognition, prioritizing sensory pleasure over metabolic signals (Khalsa et al. 2018).

CONCLUSION: TOWARDS A COMPREHENSIVE VISION
These findings underscore the need to interpret taste memory from a holistic perspective that considers the multimodality of stimuli, their emotional charge, and interactions with the interoceptive system. Only in this way will we be able to understand complex behaviors where multiple stimuli intertwine under diverse emotional contexts. This approach is key to deciphering phenomena such as the formation of eating habits or the pathological rigidity of the reward system, paving the way for more effective interventions in eating disorders.

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