Relationship Between Emotions, Learning, and Appetite
Each motivation is experienced subjectively and is accompanied by a specific emotional reaction. The biological significance of such experiences is that they allow an individual to quickly and reliably assess their needs without resorting to detailed analysis. Subjective experiences associated with metabolic needs are always negative in character. Their main task is to stimulate the search for objects to satisfy the need.
In their pure form, negative emotions accompany a need only in the early stages of ontogenesis or upon its initial appearance. Further behavioral shaping is closely linked to the mechanism of learning:
- Repeated satisfaction of a need evokes positive emotions.
- The animal or human remembers these sensations.
- Positive emotions begin to weave into the structure of motivational arousal by an anticipatory principle.
Thus, appetite arises—the subject's anticipation of the positive emotion that will occur when the current need is satisfied. Appetite is a powerful stimulus for goal-directed activity. The expectation of a "reward" forces more active behavior, more successful overcoming of obstacles, and determines the selective direction of motivation.
What is the Chemical Specificity?
From an electrophysiological standpoint, motivational arousals of different biological qualities (e.g., hunger, thirst, or fear) are characterized by completely identical changes in the electrical activity of brain structures—so-called EEG activation.
However, each motivation possesses marked specificity, which manifests in emotional sensations, features of cortico-subcortical integration, and, most importantly, in chemical mechanisms. Neuropharmacological analysis using selective blockers proves that different motivations rely on distinct neurotransmitter systems:
- Defensive motivation (fear) is selectively suppressed by $\alpha$-adrenoceptor blockers (e.g., chlorpromazine). This fact was established in studies by V.A. Gavlicek and A.I. Shumilina.
- Feeding motivation (hunger) is selectively blocked by anticholinergics (atropine, amizyl).
Experimental Evidence
Chemical selectivity is clearly demonstrated in classic animal experiments.
Motivational Conflict (Rabbit Experiment) A rabbit is trained to eat in a specific room. Then, in the same setting, it is subjected to electrocutaneous stimulation. As a result, a conflict arises: despite strong hunger, fear motivation dominates. The rabbit refuses food and cowards in a corner. However, if chlorpromazine is administered intravenously (0.5 mg/kg), adrenergic mechanisms are blocked. Fear is instantly eliminated, the previously suppressed feeding motivation is disinhibited, and the rabbit immediately begins to eat. This proves that hunger and fear are built on different chemical pathways.
EEG Analysis (Cat Experiment) After two days of food deprivation, a cat is placed under urethane anesthesia. An EEG of the anterior cortical regions shows selective "hunger" activation, while slow activity typical of drug-induced sleep is registered in the parieto-occipital regions. If nociceptive (pain) stimulation is applied, generalized activation of the entire cortex occurs.
- Administration of chlorpromazine blocks only pain-induced activation without affecting the "hunger" activity of anterior regions.
- Administration of anticholinergics exclusively eliminates hunger-related activation.
Pharmacological agents allow for a peculiar "chemical dissection" of ascending subcortical influences on the cerebral cortex.
Complexity of Neurochemical Organization
The mechanisms of chemical specificity are significantly more complex than the primitive scheme of "one neurotransmitter — one motivation." Experiments show high variability in reactions: anticholinergics block hunger not in all animals, just as adrenoceptor blockers do not always eliminate fear.
According to V.G. Zilov's concept, whole complexes of various systems (adrenergic, cholinergic, dopaminergic) are involved in the formation of motivations. This holds true both for feeding motivation (upon stimulation of the lateral hypothalamus) and defensive motivation (upon stimulation of the ventromedial hypothalamus).
Conclusion: Chemical specificity is determined not by one specific substance, but by a specific chemical integration of physiologically active substances. Neurotransmitters combine into unique combinations across different brain structures, forming a concrete, irreproducible motivational state.