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Neurophysiology of Emotions

 (Humans vs. Animals)



By: Dr Anthony Alsayed

No piece of our mental life is more imperative to the quality and sense of our existence than emotions. This mental state arising spontaneously rather than through conscious effort is a subjective feeling based objectively on the organism-environment relation with respect to the wale-organism integration. Generally researches agree that emotions have the following parts: subjective feelings, physiological responses, and expressive behavior. Contemporary views suggest emotions are brain states that quickly allocate values to outcomes and provide a simple plan of appropriate actions.


It’s very important to make a distinction between emotions and mood. The main difference between emotions and mood are emotions, such as anger, fear, sadness, joy, disgust, curiosity/interest, surprise, and acceptance, are usually of somewhat short duration, while moods, such as happiness or frustration, for a longer time.


So it’s not surprising that most of the great classical philosophers such as Aristotle, Descartes, and Hobbes, recognized the theory of emotion as typical conscious phenomena which typically: involve more pervasive bodily manifestations than other conscious states; vary along a number of dimensions (intensity, valence, etc); play an indispensable role in determining the quality of life and the regulation of social life; contribute crucially to defining ends and priorities; have a central place in moral education and the mores life.


The debates is still very active among neuroscientists, physiologists, ethnologists, philosophers, and others to determine the emotional processes  and states in humans and animals, i.e. the neurophysiological activities  and  the similarities between them.

Despite the variance of the species in which the brain is found there are many common features in its cellular make-up, structure and function. On a cellular level, the brain is composed of two classes of cells, neurons and glia. Both contain several different cell types which perform different functions. Interconnected neurons form neural networks (similar to man-made electrical circuits). These highly specialized circuits (the chemical and electrical impulses) make up systems which are the basis of perception, action and higher cognitive function.


Neurons, the cells that generate action potentials and convey them to other cells, constitute the essential class of brain cells. Although the histology of the brain is common to all those who have one, the structural anatomy is not. There are further dissimilarities within invertebrates (although vertebrates tend to share certain commonalities). For example in insects, the brain can be divided into four parts, the optical lobes, the protocerebrum, the deutocerebrum, and the tritocerebrum. In cephalopods, the brain is divided into two regions: the supraesophageal mass and the subesophageal mass. In vertebrates, there are three major parts: hindbrain (medulla oblongata and metencephalon), midbrain (mesencephalon) and forebrain (diencephalon and telencephalon).


Vertebrate nervous systems are distinguished by encephalization and bilateral symmetry. According to the hierarchy based on embryonic and evolutionary development, chordate brains are composed of the three regions that later develop into five total divisions:

  • Rhombencephalon (hindbrain)- Myelencephalon and Metencephalon

  • Mesencephalon (midbrain)

  • Prosencephalon (forebrain)- Diencephalon and Telencephalon


The brain can also be classified according to function, including divisions such as:

  • Limbic system

  • Sensory systems- Visual system, Olfactory system, Gustatory system, Auditory system, Somatosensory system

  • Motor system

  • Associative areas


Vertebrate brains receive signals through nerves arriving from the sensors of the organism, interpret those signals and formulate reactions based on built-in programs and learned experiences.


The brain cells, brain molecules, neurotransmitters and synapses are almost identical in all animals.  The human brain is quite convoluted (progressive evolution) and because of their complexities that even up to know the comprehensive picture is not yet complete. The animal brain is likely to be adept at simply driving self-preservation (limited and dependable evolution).


The chemical neurotransmitters of animals are the same as humans- dopamine, serotonin, opioids. Also, the same hormones are similar. In addition, scientists recently pointed that human nuclear DNA appears to be 98.4 percent identical to chimpanzee.  In fact, animals have been used in experimentation for medical and psychological issues for a long time precisely because of these similarities.


From a behavioral perspective, it makes sense animals experience emotions. According to many researchers, the main difference between animal emotions and human emotions is that animals don’t have mixed emotions (such as love-hate) the way people do. Perhaps, animals respond to the environment much as human do, reacting emotionally to others and even becoming stressed and anxious in times of danger, but they cannot express their feelings linguistically. Researchers have found that, unlike humans, animal emotions can be expressed by actions only.


Researchers working in different fields stated that animals widely experience feelings and emotions such as fear, jealousy, grief, anger and love. But the human brain and the animal brain control these emotions differently.  Researchers consider that the human emotion is cortical and the animal emotion is sub-cortical, but they argue on the level of dimensions such as sociability, affection, emotional stability and competency.


The most flexible emotion which has been studied by physiologists, psychologists and others is fear. Based on brain structures (amygdala, prefrontal, anterior cingulated, venttral striatum, and insula) currently though to be most involved in emotion, fear has been described as a warning signal transferred from the brain to the cortex and depending on the environmental factors. Subsequently, the cortex will send these signals to the sub-cortical structures and body organs as an action. Then cortex receives the reaction from the physiological turbulent of the body in the form of fear. 


The center of the fight/flight response is in the periaqueductal gray (central gray) which surrounds the cerebral aqueduct of the midbrain. The central gray is under tonic inhibition from the medial hypothalamus, which receives input from the central nucleus of the amygdala, which receives signals from the orbitofrontal cortex. The central gray activates the autonomic nervous system elevating heart rate, raising blood glucose and adrenaline, etc.


The sympathetic nervous system is dedicated to what might be called emotional responses, whereas the parasympathetic nervous system is more concerned with localized regulation of organ function. Nonetheless, parasympathetic involvement is seen in emotion when, for example, a fearful person involuntarily urinates or defecates.


Electrical stimulation of the amygdale can produce fear or anger, depending on the spot stimulated. Stimulation of the septum usually results in delight and sexual-arousal. Stimulation of the globus pallidus and the mid-center of the thalamus can produce a feeling of joy.


Fear seems to be the most widely evident emotion in the animal kingdom, although the emotional repertoire of other species may be as distinct as their physiologies. So far, it’s known animals have physiological responses that are analogous to human emotional responses. Budiansky believes animals are aware of their emotions, but they are limited in their awareness by not being able to formulate their feelings into words and express them consciously.


According to the conclusions from various research studies, some behaviors, structures, and brain chemistry is similar in humans and animals. Also, evidence from different fields of anatomy, physiology, ethnology, neurochemistry, DNA analysis and psychology show support for the idea that, on some emotional level, animals are somehow like humans. Furthermore, all these evidences, theories and studies give the impression to be by an evolutionary process themselves, which makes any absolute conclusions currently unfeasible.  



Sources, References and Bibliography


  1. 1997. “Reconciling Cognitive and Perceptual Theories of Emotion: A R. P.” Philosophy of Science. 64:555-579

  2. Darwin, Charls. 1998 [1986]. The Expression of the Emotionin Man and Animals. Introduction, Notes and Commentaries by Paul Ekman. London: Harper Collins.

  3. Tangley, Laura. Animal Emotion. Issue 001030.

  4. Steindorf, Sara. Unbeastly Behavior. Christian Science Monitor. 05-29-2001.

  5. Thagard, Paul. 2005. Coherence in Thought and Action. Cambridge, MA: MIT Press.

  6. Thagard, Paul. 2006. Hot Thought: Mechanisms and Applications of Emotional Cognition. Cambridge, MA: MIT Press.

  7. Goldie, Peter, (ed.). 2002. Understanding Emotions. Aldershot: Ashgate Publishing.

  8. Aristotle/ cognitive science

  9. Descartes, Rene/ Epicureanism  

  10. 2006. Emotions: A brief History. Oxford: Blackwell.

  11. 2008. The biology of the brain/id/1286752.

  12. Rossano/2003. Evolutionary Psychology: The Science of Human Behavior and Evolution. Wiley.

  13. Beridge/2001. Comparing the emotional brain of humans and other animals. In Handbook of affective sciences, R. Davidson, K. Scherer, H. Hill Goldsmith (Eds.), Oxford University Press, N.Y., 2003.

  14. 2003. Animal News Center, Inc.

  15. Robert C., Rberts. Propositions and Animals Emotion. PP147 (10)

  16. P. V. Simonov. The Emotional Brain: Physiology, Neurology, Psychology, and Emotion. Translated from Russian by Marie J. Hall.

  17. Rosenzweing, Mark R. Biological Psychology. University of California, Berkeley.

  18. Other Related sources


© Dr. Anthony Alsayed 2017

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