Author: auj239

Classical Conditioning and PTSD

Classical conditioning is a type of learning that involves forming associations between different stimuli, such as different things in the environment. It’s the reason why we flinch when we see lightning in response to the coming thunder or why we feel anxiety when we enter a doctor’s waiting room in fear of receiving an injection. Classical conditioning is even used in advertising, which is why we salivate after seeing an advertisement for McDonald’s on television. 

John Watson’s experiment with Little Albert provides a useful model in identifying the different forms of stimuli and responses involved in classical conditioning that leads to fear. In the experiment, Watson exposed the child, Little Albert, to a white rat. At first, the white rat elicited no response from Little Albert. However, when the white rat was also presented with a loud banging noise, Little Albert began to cry because he feared the noise. Eventually, Little Albert began to cry after seeing just the white rat alone because he was conditioned to associate the fear of the accompanying loud noise with the appearance of a white rat. 

In this case, Little Albert’s unconditioned response was crying when exposed to an unconditioned stimulus in the form of loud banging noise. After all, it’s only natural that a young child should cry after hearing a loud noise. The conditioned stimulus was the white rat, which Little Albert learned to fear after conditioning, which elicited the newly conditioned response of crying whenever he saw the white rat. 

There are other instances in which classical conditioning can make us fear the simplest things. I grew up hearing stories of how my grandfather was a prisoner of war for two years in the early 1960s. For two years he lived in a constant state of fear while enduring extremely uncomfortable conditions, including eating the same unhygienic, foul-tasting lentil dish every single day. When he was finally released and returned home, he asked my grandmother never to cook lentils in the house because he was conditioned to associate that particular dish with his time in the camp. In my grandfather’s case, the unconditioned response was fear of the unconditioned stimulus of living in the camp as a POW. The conditioned stimulus became the lentil dish he was served every day and his conditioned response was irrational fear and discomfort associated with those lentils because it brought back painful memories.  This example shows how unintentional classical conditioning can be detrimental to people’s psyches. 

 

Memory Retrieval: Forming Associations

The basic memory process consists of three steps: encoding, storage, and retrieval. And while all three steps are necessary for memory storage, retrieval is arguably the most relevant of the three as it demonstrates that a certain memory has been successfully stored into our long-term memory. 

So what exactly does retrieval entail? It’s defined as the act of getting information out of memory storage and back into our working memory and conscious thought. There are three forms of retrieval: recall, recognition, and relearning. 

Recall, which is what we typically think of when we discuss retrieval. It is the ability to access information without cues and is a skill we often use during exams while answering short answer questions. 

Recognition occurs when you identify information that has been previously learned. We use recognition when trying to choose the correct answer, like during a multiple-choice test. We choose the correct answer after comparing it with other choices and picking the solution that is familiar to us and fits in the context of the question. 

Relearning is likely the most cumbersome of the three forms of memory retrieval as it involves learning information that has been previously learned. There are several concepts that we have been taught over and over again over our many years of schooling. Relearning can help measure the time saved while learning a familiar concept again. For example, a person who took piano lessons as a child but didn’t play again until adulthood will likely be surprised at how quickly they are able to pick up the skill again because of the concept of relearning. 

Whatever the form of recall, retrieval cues can help us remember through the web of associations that hold our memories together in storage. State-dependent and Mood-dependent memory explain how our things such as our physical setting and emotional state of mind can trigger the process of retrieval. 

Though the concepts of retrieval and understanding the importance of retrieval cues are useful to apply while studying for exams, it can also have some interesting consequences. For example, in middle school, I loved reading books in the car while my dad drove me to school. While reading, he would often play music to entertain himself. In fourth grade, I remember that my dad went through a phase of playing old Pakistani songs from the 70s and 80s while I was reading the Percy Jackson series. Amazingly, almost ten years later whenever I hear those old songs I immediately begin to think about the books I was reading. My brain automatically goes through the process of retrieval because of the cues presented by the music! It is a strange association of memories that I will likely recall for the rest of my life. 

Neurotransmitters and their effect on the brain: Dopamine and Parkinson’s Disease

What are Neurotransmitters?

It’s a well-known fact that neurotransmitters have a profound impact on the brain. But how exactly do they work? Neurotransmitters are chemical substances released in vesicles at the end of a nerve fiber (at the terminal branches of an axon) with the arrival of a nerve impulse. They diffuse across the gap between two neurons, also called the synaptic gap or cleft, and are received by receptors on the receiving neuron (at the dendrite), which transfers the impulse from one nerve to another. The image below shows this process in greater detail.

Image 1: Neurotransmitters and the Synaptic Cleft

It helps to think of neurotransmitters and receptors like a lock and key mechanism: receptors act like locks, accepting some neurotransmitters and rejecting others that don’t “fit”. Neurotransmitters are the “key” that fits into its designated receptors. After a receptor accepts a neurotransmitter, it begins a chain reaction of events that locally charges the cell membrane, sending a signal along the length of the neuron and on to the next. 

Dopamine and Parkinson’s Disease

Now that we have a basic understanding of how neurotransmitters work, we can discuss what effects a neurotransmitter imbalance would have on the brain. The neurotransmitter dopamine has pathways involved with Parkinson’s disease. Parkinson’s is considered a degenerative disorder and begins when cells in the part of the brain known as the substantia nigra begin to die. These nerve cells are responsible for dopamine production and relay messages that control body movement. In some people, these dopamine-producing nerve cells begin to die. When approximately 80% of dopamine is lost, symptoms such as tremors, slow movement, stiffness and loss of balance occurs in the body. 

Parkinson’s is the second most common age-related disease after Alzheimer’s disease. It is estimated that 7-10 million people worldwide suffer from Parkinson’s, including my grandmother. As I’ve visited her frequently over the years, I’ve watched her symptoms manifest in several ways. She walks slowly and with a shuffling gait and relies on her walker to get around the house. Her hands often tremble even when she is not cold or scared and sometimes, she stutters in her speech. These are all classic symptoms of Parkinson’s as they all relate to a loss of motor function. This is likely because of the lack of dopamine in her brain. Her body movement is interrupted because the cells in the substantia nigra are unable to send nerve impulses as frequently between the spinal cord and the brain due to the lack of dopamine. 

Image 2: Dopamine levels in a normal and a Parkinson’s affected neuron

Treating Parkinson’s Disease

While the initial cause of cell death in the brain remains unknown, scientists have been using their knowledge of dopamine and its pathways to create drugs that mimic how dopamine is supposed to work in the brain. My grandmother has recently begun using one of these drugs, which are also known as Dopamine-receptor agonists, to treat her symptoms. Like dopamine, they fit into the receptors that receive dopamine and are able to complete the neural pathway the leads to smooth body movement. The diagram below shows how dopamine agonists mimic the effects of dopamine. 

Image 3: How dopamine-agonists mimic dopamine in the brain

While agonist drugs can help ease the symptoms of diseases like Parkinson’s, it is our hope that researches will soon be able to identify the source of this degenerative disease. One thing is certain: we must never underestimate the importance of neurotransmitters and their effect on our body and mind.

 

Links:

https://www.lexico.com/en/definition/neurotransmitter

https://mayfieldclinic.com/pe-pd.htm

https://parkinsonsnewstoday.com/parkinsons-disease-statistics/

Image 1: https://www.verywellmind.com/the-chemistry-of-depression-1065137

Image 2: https://www.atrainceu.com/course-module/1874200-080_antiparkinson-strategies-module-03

Image 3: https://parkinsonsdisease.net/medications/