AP Biology class blog for discussing current research in Biology

Tag: fear

Are Fish Mind Readers?

Several inherited behavioral mechanisms in humans and animals are deeply rooted in prehistoric animals. Some of these mechanisms, for example, fear, as well as the ability to fall in or out of love, humans have possessed for thousands of years and are found in our ancient genetic pathways. Although scientists are hesitant to attribute human-like feelings to animals, it has been proven that many animals, including fish, have moods. A recent study published in the journal; Science, demonstrated that fish can identify fear in other fish. This ability is regulated by the hormone oxytocin. This is the same “brain chemical” that controls the feeling of empathy in humans. The researchers discovered that fish could detect fear in other fish by deleting genes linked to producing and absorbing oxytocin. These fish became fearful as well.


Deleting genes involves various techniques, which is specific to the organism and the purpose for the deletion. Generally, there are two main approaches for deleting genes: Targeted Deletion and Random Deletion. In Targeted Deletion, very specific regions of the DNA sequence are removed or replaced to eliminate the gene of interest. Random Deletion occurs when large sections of the DNA sequence are randomly deleted in the hope of removing the gene of interest. The research focused on zebrafish brains; a small tropical fish often used for such research. The fish used in this experiment became practically antisocial and failed to change their behavior and could no longer detect when other fish were anxious. Scientists then injected oxytocin into some of the altered fish, and the fish’s ability to sense and react to the feelings of other fish was re-established. Fish behave just like humans in that they respond to other individuals being frightened. During this experiment, fish were seen paying considerably more attention to previously stressed or frightened fish.

Oxytocin is a hormone that plays a key role in social bonding and emotional communication in mammals, including humans. It is produced in the hypothalamus and released into the bloodstream by the pituitary gland. One of the primary functions of oxytocin is to produce social bonding between individuals. It has been shown to increase trust and cooperation between people, and it is often referred to as the love hormone because of its role in promoting feelings of love and intimacy.

Oxytocin with labels

Hans Hofmann, an evolutionary neuroscientist at the University of Texas at Austin, said that it’s less of a “love hormone” and more of a “scale” that helps fish recognize the most noticeable social situation. This recognition activates neural circuits that may make one run from danger or engage in behavior that results in mating. This ability is essential to certain species of fish survival.

Fight or Flight? A stroll down memory lane…

Everyone handles fear differently. Have you ever wondered why some people are fearless, while others are afraid of their own shadows? Fear is a natural human emotion that arises when we feel threatened or harmed. Fear can be rational or irrational. In some cases, like post-traumatic stress disorder (PTSD) or anxiety-related disorders, fear responses can be uncontrolled or exaggerated. Researchers have been trying to figure out what specifically triggers fear and how it turns into a long-term memory. 

Depression - a lonely alcoholic in fear covers his face with his hands

This study from researchers at Linköping University investigated the biological mechanisms that impact fear-related memories in the brain. They used rats and discovered potentially groundbreaking data behind anxiety-related disorders and alcohol dependence. For those of us who need a quick lesson on the brain, the amygdala regulates emotions and is activated by endangerment or threats. The nerve cells connect the frontal lobe to the amygdala. Interestingly, the research found that these connections are changed in people with anxiety-related disorders. 


Specifically, they investigated a protein known as PRDM2. This protein encodes a zinc finger protein that can bind to different types of proteins and receptors. Levels of PRDM2 seem to play an important role in exaggerated stress responses and are also lower in those who are alcohol-dependent. It is common for anxiety-related disorders and alcohol dependency to be present at the same time, and the researchers suspect that this is caused by the protein. 


A little more review on the science of the brain is needed before we continue.  The formation of memories are complex and may be connected to our fear responses.  Consolidation is when new memories are formed and preserved into long-term memories. Increased activity between the frontal lobes and amygdala increases learned fear reactions. The decrease in PRDM2 increases the consolidation of fear-related memories. 

Mental Health - The Noun Project

The research suggests that patients with anxiety-related disorders may benefit from treatments that weaken fear memories. Researchers have discovered a way to down-regulate PRDM2, but do not have a way of increasing it, yet. This mechanism could be a part of the explanation as to why individuals have a greater susceptibility to anxiety-related disorders and why these disorders are commonly associated with alcohol dependency. 

Protein PRDM2 PDB 2JV0

One thing we have learned thus far in AP Biology class is that ribosomes are protein factories located free in the cytosol or bound to the rough endoplasmic reticulum or nuclear envelope. Within the rough endoplasmic reticulum, proteins are produced to either be secreted outside the cell, membrane-embedded proteins, or proteins to go inside organelles. 


Although they have not discovered a way to increase PRDM2, it is very interesting for us to be able to understand how our fear memories turn into long-term memories and what causes individuals to be more vulnerable to mental health disorders. Hopefully, with the continued research on the biological mechanism that may cause fear, we can reverse engineer the cause and create new innovative medicines to treat and, perhaps, completely cure them. 

The Woman who cant be Afraid teaches us about Fear

A lot of people say they aren’t scared of anything, but the reality is every body is scared of something. Everybody, except a woman known as SM.

SM had a rare illness that caused damage to the part of her brain associated with fear. The amygdala “is involved in many of our emotions and motivations, particularly those that are related to survival”.  In the same way that pain is a warning sign in attempt to protect you from danger, fear is a function of protection. Without fear you would constantly place yourself in dangerous situations with out responding to an impulse of survival.

The Amygdala- the area of the brain responsible for fear

The damage to SM’s amygdala caused her to lose the ability to feel fear. Scientists tested her on several simulated and real life situations such as being held up at gunpoint, watching scary movies, watching domestic violence. SM felt no fear what so ever in any of these situations. Scientists naturally would predict that with the loss of a functioning amygdala, SM would never feel fear again.

Yet, one day SM had a panic attack. The panic attack was brought on in an experiment where SM inhaled a small amount of carbon dioxide that created a short feeling of suffocation.

The fact that SM felt fear from a panic attack without an amygdala “illuminates some of the brain’s most fundamental processes and may have practical value in the study of panic attacks.” Additionally, it suggests that there may be an alternative center for fear responding to internal threats- such as suffocation or a heart attack.

This study is particularly fascinating because it shows just how little we know about ourselves and the world around us. It illuminates the flaws in our apparent definitive knowledge and encourages further research and speculation about what we know concerning the brain.


Link to Main Article:

Link to additional Articles:

Link to Picture used:

Powered by WordPress & Theme by Anders Norén

Skip to toolbar