Understanding Fear: The Pavlovian Approach

The discovery of classical conditioning by Ivan Pavlov, a Russian physiologist, came about by chance while he was exploring digestion. He observed that certain environmental stimuli could elicit behavioral responses in dogs, revealing that one stimulus could signal another. This groundbreaking realization significantly influenced the fields of psychology and neuroscience.

Classical conditioning, also referred to as associative learning, describes how both animals and humans learn to respond to new stimuli that typically wouldn’t provoke a reaction. This occurs through association with stimuli that do elicit a response. For instance, a dog may begin to salivate at the sound of a bell if it has been trained to associate that sound with food.

Fear, one of the most basic human emotions, can be effectively acquired through this type of associative learning. A famous experiment involved conditioning a 9-month-old infant named Albert to develop a fear of a white rat. Initially, Albert displayed no fear toward the rat, but after several instances of pairing the rat with a loud noise, he became frightened when seeing the rat. If left unaddressed, such fears can transform into persistent, debilitating memories akin to traumatic experiences. These memories are remarkably resilient, with a lifetime prevalence reaching 29%. However, the mechanisms behind the long-term storage of these fearful memories and how they may diminish over time remain largely unexplored.

The challenge of alleviating these enduring fears intrigued me deeply. During my doctoral research, I aimed to bridge this knowledge gap. I was particularly interested in whether alleviating fear involved replacing the fear memory with a sense of safety—a process known as “fear extinction”—or if it required modifying the original fear memory with new information, termed “memory updating.”

Fear extinction involves gradually exposing an individual or animal to a feared stimulus in a safe and controlled setting, ultimately leading to a reduction or elimination of the fear response. This approach helps to associate the previously feared stimulus with safety, thereby weakening the initial fear.

To delve into how fear memories are stored and reduced within the brain, we utilized a genetically modified mouse model that enabled us to track the neurons responsible for both fear and safety memories. The mice underwent an experiment similar to what little Albert experienced, where they learned to associate a specific environment with a foot shock. This exposure was sufficient to establish a fear memory. After a month, we tested the mice in the same environment, this time without the foot shock, to assess their recollection of the fearful experience. Their freezing behavior, a common response to fear, indicated active recall of the fear memory. Subsequently, we implemented fear extinction training to diminish this fear memory, and we observed that the mice no longer froze in the previously feared context.

Our study revealed new insights into the brain's mechanisms for processing and reducing fear memories. Surprisingly, we discovered that some neurons involved in storing fear memories are reactivated during the memory attenuation process rather than being suppressed.

During extinction training, when the mice recalled the fear, the same neurons that encoded the fear initially were reactivated. This reactivation proved crucial for the attenuation of fear. When we interfered with the fear neurons to prevent their reactivation, the attenuation process faltered. Conversely, sustaining their activity enhanced fear attenuation.

Ultimately, we found that the ongoing activity of the neurons associated with fear plays a vital role in diminishing the intensity of the fearful memory. This finding provides insight into why exposure therapy, which involves gradual exposure to fears, can effectively mitigate the impact of traumatic memories. In summary, confronting our fears and replacing them with positive, reassuring experiences is the first step toward achieving safety.

The first video titled "How to 'overcome' fear | Trevor Ragan | TEDxCedarRapids" explores various strategies to face and conquer fear, emphasizing practical methods to transform anxiety into empowerment.

The second video, "One simple trick to overcome your biggest fear | Ruth Soukup | TEDxMileHigh," discusses a straightforward yet effective technique for addressing and overcoming significant fears, providing viewers with actionable insights.