Biological Bases of Memory

Description of Biological Bases of Memory

Like our other biological processes, our memory relies on a network of brain and body functions to take in information from the environment, process it, store it, and later retrieve it. Where do we process memories in our brains? How do we make a memory out of something we learn or experience that bombards our senses?

There are several major biological players in the networking team of memory. We know this thanks to data from electrophysiology, neuroimaging, computational modeling, and neuropsychology. Studies from these fields show that memory is a process that happens throughout the brain, but there are specific regions that are more active in short-term or long-term memories.

The Hippocampus and the Frontal Lobes

The captains of the memory team in our brains are the hippocampus, the frontal lobe, and the temporal lobe. The hippocampus is located in the limbic system, and it is in charge of forming (but not storing) our long-term explicit memories. These explicit memories can be images, events, or names and require conscious effort for us to recall them. Both the frontal and temporal lobes work with our memory, and each lobe is in charge of different kinds of memories.

HIPPOcampus and Memory, pexels.com

While your hippocampus and two of your lobes are busy with your explicit memories, there are other areas of the brain that are responsible for your implicit memories. These types of memories are unconscious processes based on past experiences or learned skills and behavior that are stored in our long-term memory and require little to no effort for us to recall. Since they are based on past experiences, implicit memories can impact our current thoughts, feelings, and behaviors (such as being afraid of dogs because you were bitten as a child).

The Cerebellum and the Basal Ganglia

Next on the networking team of memory are the cerebellum and the basal ganglia. These two areas of the brain control memories associated with classical conditioning and motor skills. The cerebellum is in charge of storing information and memories that we learn through classical conditioning. These memories and skills become unconscious reflexive responses. We use many of these every day! Damage to the cerebellum can result in severe deficiencies in basic motor skills and common tasks.

Next up is the basal ganglia, which are responsible for the deep brain functions of motor skills. During procedural learning, the brain cortex sends information to the basal ganglia, and the basal ganglia store the information. Reward and punishment learning (operant conditioning) is also processed here. Remember, these are all unconscious processes or memories. Once you learn them, you never forget!

The Amygdala

The emotional powerhouse of the team is the amygdala. The amygdala uses our emotions to make memories (or sensory memories). Have you noticed that times you are very angry stick in your memory vividly? The same goes for events that make you extremely happy. Hormonal changes happen during these events and impact the way the memory is processed by the amygdala.

Our memory can help protect us by forming predictions of future events based on past experiences. They are only predictions, though, and they may not be true. This is why major emotional events in our lives are more likely to be remembered than those with less emotional content. You are more likely to forget a boring event than a really fun one! The amygdala uses our emotions to form new memories and process new experiences, but it also uses old memories to inform new decisions.

Neurotransmitters and Memory

Biologically speaking, memories are created thanks to neurotransmitters and synaptic plasticity in our brains. Synaptic plasticity is the continuous change in the amount, type, and strength of our neural connections. The strength of our neural network increases when we persistently activate certain connections. Connections that are used less often or not at all become weaker until they no longer exist.

Examples of Biological Bases of Memory

Memory formation happens constantly as we simply exist in the world. There are so many examples of how our biology impacts our memory. How we process and remember things that people tell us and things we experience through our senses are two of these processes.

It all begins with the speech input (listening to someone else talking). The noise of someone speaking to us enters the acoustic-phonetic process of the brain, also called the processing center for spoken words. When does creating a memory take place in this process? If we can make sense of the words we are hearing, they will travel to the echoic memory portion of our brains. Languages and syllables that make sense to us are processed here. What if you can't make sense of the words you hear? No memory is created!

Amnesia and Memory Loss

What happens when there is damage to our hippocampus? Does it affect our memory processes? When the hippocampus is damaged, you might experience amnesia or memory loss. There are two types of amnesia.

Anterograde amnesia is the inability to create new memories. You still remember everything from your past. Anterograde amnesia is also called short-term memory loss. Retrograde amnesia involves memory loss for a segment of the past, usually around the time of an accident (like a blow to the head). You can still create new memories, but you forget what happened during some or all of your past.

Factors Influencing Biological Bases of Memory

Like the blow to the head we mentioned earlier, life experiences can cause problems with memory. Health problems and diseases are the primary culprits. How do they affect our memory functions, and what are the potential outcomes for memory functioning?

Depression & Memory

Those who are affected by depression may experience impairment in their memory capabilities. Most often these problems take the form of forgetfulness and confusion. Stress and depression have a huge impact on our short-term memory. Depression affects our working memory and the chemical exchanges of neurotransmitters such as serotonin and dopamine. If there is a chemical disruption in our brain, it can make memory formation more difficult.

Dementia & Memory

Two other common medical issues that disrupt memory are the onset of dementia or Alzheimer's disease. Many people experience dementia, regardless of culture, economic status, or gender.

For those with Alzheimer's, memory recall becomes very slow. Even if the brain is still storing the memories, it is difficult to access them. What the person remembers can often be inaccurate (addresses, names, etc.). Sometimes those with dementia become stressed, anxious, or angry when this happens (understandably!), which increases difficulties in memory recall even more.

In Alzheimer's disease, neurons in the brain are injured and die. When they die, the connections between networks of neurons break down. Many areas of the brain begin to shrink in size. This causes what is called brain atrophy: a widespread and significant loss of brain volume.

Why does this happen? Neurotransmitters seem to be the culprit. Remember, there are many different neurotransmitters with their own functions. In the brains of those with Alzheimer's disease, there seems to be a lack of acetylcholine (ACh). This neurotransmitter helps control muscle movements and move memories between the brain and spinal cord.

Alzheimer's and Memory, pexels.com

Biological Bases of Learning and Memory

What if we added learning to the process of memory? How does learning and remembering what we learn work in the brain? It all begins within our neurons or brain cells. Learning happens when there is a change in the strength and number of neural pathways in the brain. This process of creating neural pathways is known as synaptic plasticity.

The more you do something or repeat information, the stronger those neural pathways become, and the less likely you are to forget those things! The less you do something or repeat information, the weaker those neural pathways become, until the brain prunes those connections entirely (gets rid of them). If you want to become really good at something, use those brain connections as much as possible!

If neuron A continuously communicates with neuron B, there is constant energy flowing through that connection. When neurons constantly communicate with each other, this is called long-term potentiation (LTP). If neuron A never talks to neuron B, no energy flows between those two connections. This is called long-term depression (LTD). The less energy that flows between two neurons, the weaker the connection becomes. The more energy that flows, the stronger the connection becomes!

Practicing, pexels.com

Biological Mechanisms of Long-Term Memory

Our hippocampus is the brain's version of a save button, but it's not a permanent storage center for our memories. Instead, the hippocampus is more of a transitional storage unit for memories (smells, feelings, or sounds) that will move on later. The hippocampus also likes to work overtime. While we sleep, our hippocampus is working hard to solidify our memories. What else happens in our memory while we sleep?

If you look at a brain scan of someone who is sleeping, you will see a conversation happening in the neural connections between the hippocampus and the cerebral cortex. During sleep, our hippocampus replays memories from the day and transfers them to the cerebral cortex for storage in long-term memory.

Sleep is important for many reasons, but it is especially important in memory. When we do not get enough sleep, it can negatively affect our memory! Sleep helps maintain the plasticity of neural connections, which are super important for storing and retrieving memories. Sleep also helps with consolidation: putting together new memories from the day before with older material.