Healthy brain - memory and forgetting
Brain and neuron basics
The more we know about the brain, the more we will understand about Alzheimer’s. It is a 3-pound mass of 100 billion cells – or neurons, the consistency of firm tofu. The human brain uses 20% of your body energy when you are at rest! The brain has two hemispheres and all the substructures (except one, the pineal gland) are paired left and right. This picture shows a slice through the brain from your forehead to the back of your head.
There are many kinds of neurons; let’s focus on the dendritic type. Each has a microscopic cell body, a long projection called the axon, and dendrites, like tree branches. Axons can be long, reaching down the spinal cord to activate muscles, for example.
The cell bodies gather to form substructures, called grey matter because they appear grey. The axons join to form adjoining layers we call white matter because the axons are coated with a waxy protective substance myelin, which appears white.
Neurons connect to each other and the brain has 40 quadrillion connections, making one human brain more powerful than all the computers that we have in the world wired together! (Bartol, eLife 2015:e10778)
from: Science Photo Library - PASIEKA Brand X Pictures Getty Images
We learned in school that once it reaches maturity, the brain does not make new neurons, but in 1998 Erickson showed this is wrong – the brain does make new neurons in some areas. Brain Derived Neurotrophic Factor (BDNF) grows them. How do we increase BDNF? K. Ericksson showed in 2011 that exercise increases the size of the hippocampus and improves memory. (See Erickson K PNAS 108 (2011) 3017-3022. "Exercise training increases size of hippocampus and improves memory.”)
Three parts of the brain
There are 3 major parts of the brain. The brain stem includes our spinal cord and cerebellum, which is the part of the brain for balance and rote motions. The brain stem is evolutionarily the oldest part and we have this in common with animals - responsible for breathing, heartbeat, digestion, reflexes, sleeping and arousal. It is the first to develop in a fetus, and the last to be affected by Alzheimer’s.
The midbrain in the center is the emotional brain, containing the limbic system, which regulates sex hormones, sleep cycle, hunger, emotions and addictions. The midbrain also contains the pleasure center/the reward circuit that makes us feel good. The amygdala is responsible for the fight or flight impulse, anger and fear. The hippocampus – the name means sea horse because it was thought to resemble a sea horse – is the gatekeeper for short and long-term memories. The hippocampus is the first place that is affected by Alzheimer’s, which is why the first symptom of Alzheimer’s is usually loss of short-term memory.
The wrinkly folded exterior, the cerebrum or cortex, is the thinking brain. It is evolutionarily the newest part and in humans is massive compared to other animals. Here is the seat of our thoughts, reasoning, language, planning and imagination. Parts of the cortex also process our senses, music, temperature, movement, reading and mathematics. It is affected by dementia in the middle and late stages.
Brain as electrochemical system
The neurons communicate by sending electrical pulses that travel down their axons. The rate of the pulses– faster or slower – contains the information the brain is trying to transfer.
The midbrain in the center is the emotional brain, containing the limbic system, which regulates sex hormones, sleep cycle, hunger, emotions and addictions. The midbrain also contains the pleasure center/the reward circuit that makes us feel good. The amygdala is responsible for the fight or flight impulse, anger and fear. The hippocampus – the name means sea horse because it was thought to resemble a sea horse – is the gatekeeper for short and long-term memories. The hippocampus is the first place that is affected by Alzheimer’s, which is why the first symptom of Alzheimer’s is usually loss of short-term memory.
The wrinkly folded exterior, the cerebrum or cortex, is the thinking brain. It is evolutionarily the newest part and in humans is massive compared to other animals. Here is the seat of our thoughts, reasoning, language, planning and imagination. Parts of the cortex also process our senses, music, temperature, movement, reading and mathematics. It is affected by dementia in the middle and late stages.
Brain as electrochemical system
The neurons communicate by sending electrical pulses that travel down their axons. The rate of the pulses– faster or slower – contains the information the brain is trying to transfer.
From: http://www.slideshare.net/noor_faiza/bio-psychology
There is also chemistry in the brain. The electrical pulses stimulate the release of chemicals, which travel a short distance from one cell to the next across so-called synapses, wiring these two cells together. The chemicals have various effects, like excitatory (e.g. acetylcholine) – wakefulness, attentitiveness, anger, aggression, etc. There is also inhibitory – calming of anxiety, inducing sleep, etc.
With electrical signals traveling all the possible synapses in the many neurons, and the many chemicals involved, the agility of the brain is enormous! It was also found by Candace Pert that neurotransmitter receptors are found throughout the whole body, and she termed the phrase “liquid brain.” Thus the information system in our body extends beyond the boundaries of what we traditionally call the brain.
It is natural that some of the first therapies for dementia focus on the brain chemicals that can affect brain activity. One common Alzheimer’s medication, Aricept (donepezil), increases acetylcholine in the brain to increase activity. Namenda (memantine) is thought to block excess glutamate that can kill neurons.
The senses and how they work
It’s important to look at the senses because they are very important in communicating with a person with dementia, and many continue to work well throughout dementia, especially touch. Touch is the first sense we have as a newborn, and often the last to be lost in dementia. Our bodies are covered with a network of six to ten million sensors. Keep in mind that the hands, feet and the face take up more than half! So holding hands is good! Don’t forget passive touch – like the sun on our faces as well as active touch, like eating a mango.
From: http://stories.barkpost.com/19-dogs-sunbathing
Smell is separated by just 2 or 3 synapses to the hippocampus. Thus smells may be quickly and strongly associated with memories and their emotions than other senses. A 2015 study correlated possible loss of smell with early Alzheimer’s.
As for vision, every second, retinal cells transmit one billion pieces of information to the brain! The brain then sorts out what information to attend to. We tend to pay attention more to changes in our visual field. People with Alzheimer’s tend to lose peripheral vision, thus it is important to get your face right in front of their face and get eye contact before speaking. People with Alzheimer’s also may lose contrast between colors and cannot see blue and purple as well. Use red, orange, yellow.
The ear has the fewest sensory cells of any sensory organ, only about 3500. You often see people shouting at people with dementia. Now, they may have hearing loss. But consider first that they may hear OK, they are just having trouble processing; ask a short question, then wait 30 secs! You will be surprised that an answer will come if you wait. If their hearing is pretty good, music can be important! We’ll talk about music later.
Memory
What is memory? Memory is not just one thing. There is short-term memory, we’ll talk about working memory, which lasts under a minute. It can hold 7-10 items. You may be taking notes, and you can write down what was said a few seconds ago and signals are firing to your hippocampus. But after awhile, the new information displaces the old information. Short-term memory has a limited capacity. It’s like a scratch-pad. After information enters short-term memory, it gets transferred to long-term memory. Transfer is aided by two things – repetition, and by giving it a meaning or association. Consider learning a person’s name. Say it out loud. Think to yourself, Robert, I have a favorite cousin named Robert. And you’ll be more likely to remember that name.
As for vision, every second, retinal cells transmit one billion pieces of information to the brain! The brain then sorts out what information to attend to. We tend to pay attention more to changes in our visual field. People with Alzheimer’s tend to lose peripheral vision, thus it is important to get your face right in front of their face and get eye contact before speaking. People with Alzheimer’s also may lose contrast between colors and cannot see blue and purple as well. Use red, orange, yellow.
The ear has the fewest sensory cells of any sensory organ, only about 3500. You often see people shouting at people with dementia. Now, they may have hearing loss. But consider first that they may hear OK, they are just having trouble processing; ask a short question, then wait 30 secs! You will be surprised that an answer will come if you wait. If their hearing is pretty good, music can be important! We’ll talk about music later.
Memory
What is memory? Memory is not just one thing. There is short-term memory, we’ll talk about working memory, which lasts under a minute. It can hold 7-10 items. You may be taking notes, and you can write down what was said a few seconds ago and signals are firing to your hippocampus. But after awhile, the new information displaces the old information. Short-term memory has a limited capacity. It’s like a scratch-pad. After information enters short-term memory, it gets transferred to long-term memory. Transfer is aided by two things – repetition, and by giving it a meaning or association. Consider learning a person’s name. Say it out loud. Think to yourself, Robert, I have a favorite cousin named Robert. And you’ll be more likely to remember that name.
There are two kinds of long-term memory. Conscious memory includes facts and concepts, like the multiplication tables – usually no emotion is associated with these. There are also events and experiences, which often do have emotions associated. Those memories with a lot of emotion tend to last a long time. For example, many remember clearly what they were doing on September 11, 2001, but few remember what they were doing the day before that. This is how we store our autobiography, orchestrated by the hippocampus.
There is also unconscious memory, in other words, we do not perceive it. Examples include procedural tasks like brushing your teeth, riding a bike or playing the piano. You don’t need to think about the details, you just do it. It’s interesting that these bypass the hippocampus and are stored in other parts of the brain. Remember we said that the hippocampus is damaged by Alzheimer’s. You might see a person with Alzheimer’s who cannot remember much about themselves, but they can still play the piano. That is not all that surprising since their memories about how to play the piano are procedural and bypass the hippocampus, thus are not affected by the disease.
Long term memory is stored in different parts of the brain. Progressive losses in Alzheimer’s can be correlated with the progress of the disease throughout the brain.
Long term memory is the outcome of increased activity between neurons. Here we have a few neurons in the hippocampus firing together.
Neurons that fire together wire together. This increased activity chemically changes the neurons to allow electrical charges to travel particular routes. Think of a long term memory as a network of neurons (maybe 100’s or 1000’s) wired together throughout the brain. Repetition, e.g. reminiscing, allows strengthening of the pathway that allows one to recall. For example, if you recall a favorite church service when you were a kid, there would be a network of neurons in the visual, olfactory and emotional sections of the brain connected to each other to produce the sights, smells and feelings of that time, with the hippocampus orchestrating the information into a coherent story.
From: http://neurosciencenews.com/psychology-mental-task-reminiscing-1471/
Forgetting
For short-term memory, forgetting means that a nerve impulse has ceased being transmitted through a particular neural network. For long-term memory, it means that the chemical modification is lost, e.g. the protein that was modified decays because of a random event or the cell that has the chemical information dies through illness. Or because the hippocampus that recreates the episode from information in different parts of the brain is damaged. The memories may still be there, just not accessible!
Even the healthy brain prunes itself – getting rid of connections not used very often. Thus the phrase, use it or lose it! This is the theory behind doing brain gym exercises (for example BrainHQ from Posit Science) to help keep the mind active.
Sleep
Sleep must be extremely important because if you think from an evolutionary view, not being conscious puts a person or animal at very high risk in terms of safety. It would be prime time for the saber-tooth tiger to attack us! But the real reason for sleep and dreaming is not fully understood. What does sleep have to do with memory?
For short-term memory, forgetting means that a nerve impulse has ceased being transmitted through a particular neural network. For long-term memory, it means that the chemical modification is lost, e.g. the protein that was modified decays because of a random event or the cell that has the chemical information dies through illness. Or because the hippocampus that recreates the episode from information in different parts of the brain is damaged. The memories may still be there, just not accessible!
Even the healthy brain prunes itself – getting rid of connections not used very often. Thus the phrase, use it or lose it! This is the theory behind doing brain gym exercises (for example BrainHQ from Posit Science) to help keep the mind active.
Sleep
Sleep must be extremely important because if you think from an evolutionary view, not being conscious puts a person or animal at very high risk in terms of safety. It would be prime time for the saber-tooth tiger to attack us! But the real reason for sleep and dreaming is not fully understood. What does sleep have to do with memory?
From: http://www.prweb.com/releases/NWF_Guide/sleep_disorder/prweb8776322.htm
It is thought that sleep has two main functions. One is to consolidate memories better in our brain. The second, discovered only in the past few years, is that the brain cleans itself at night. The janitor comes in and sweeps out all the molecules and metabolites that build up due to all our thinking and learning and functioning during the day. Thus sleep is extremely important for our brain health.
Sleep researchers say you should sleep 8-9 hours and if you are going to nap, a 90 minute nap is ideal because you can complete one sleep cycle in that time. If you can’t do 90 minutes, a 20-minute nap is ideal for giving you some rest.
Dementia is associated with disturbed sleep. We don’t know if the lack of sleep contributes to the illness or the illness disrupts sleep.
Music
Music obviously involves the auditory areas but also the limbic system – the emotional center of our brain. It boosts endorphins that can lift our spirits and even cause euphoria. For non-musicians, the right hemisphere is dominant for appreciation of melody and harmony, and the left for rhythm and language. The playing of an instrument is good because it also involves even more of the brain - the motor system, the same is true for dance.
Everyone has seen videos of dementia patients reacting very happily to old familiar music (see the work of Oliver Sacks and Naomi Feil). These effects can last for hours or days and can stimulate memories. A 2015 study (Brain 2015: 138; 2438–2450) showed that there are two primary areas for long-term musical memory shown in red in the top graphic. These areas are surprisingly spared in Alzheimer’s, as shown by the brain maps showing Alzheimer’s damage in two ways – grey matter atrophy and hypometabolism (with orange, yellow, green the higher damage and blue and purple the lower damage.)
Sleep researchers say you should sleep 8-9 hours and if you are going to nap, a 90 minute nap is ideal because you can complete one sleep cycle in that time. If you can’t do 90 minutes, a 20-minute nap is ideal for giving you some rest.
Dementia is associated with disturbed sleep. We don’t know if the lack of sleep contributes to the illness or the illness disrupts sleep.
Music
Music obviously involves the auditory areas but also the limbic system – the emotional center of our brain. It boosts endorphins that can lift our spirits and even cause euphoria. For non-musicians, the right hemisphere is dominant for appreciation of melody and harmony, and the left for rhythm and language. The playing of an instrument is good because it also involves even more of the brain - the motor system, the same is true for dance.
Everyone has seen videos of dementia patients reacting very happily to old familiar music (see the work of Oliver Sacks and Naomi Feil). These effects can last for hours or days and can stimulate memories. A 2015 study (Brain 2015: 138; 2438–2450) showed that there are two primary areas for long-term musical memory shown in red in the top graphic. These areas are surprisingly spared in Alzheimer’s, as shown by the brain maps showing Alzheimer’s damage in two ways – grey matter atrophy and hypometabolism (with orange, yellow, green the higher damage and blue and purple the lower damage.)
From: Jacobsen, Jorn-Henrik et al. "Why musical memory can be preservedin advanced Alzheimer's disease” Brain 2015: 138; 2438–2450.
To take advantage of this long-term musical memory, enjoy songs with a person with Alzheimer’s from the person’s youth, hymns, top 10 hits, oldies and even nursery rhymes.
The self and spirituality
A new brain map was released in July 2016 with 100 new areas marked (New York Times, July 20, 2016).
From: Glasser, Matthew et al., Nature (2016) doi:10/1028/nature18933
With all this research, notice that we have not identified a part of the brain that is the center of self or “soul.” When you wake up in the morning, how do you know it’s you? Many parts of the brain contribute to the sense of self. The hippocampus handles experiences and stories and therefore our autobiography. Also in the midbrain, our amygdala and limbic system provide our unconscious parts that act on our behavior and shape who we think we are – our demeanor, emotional temperature, tendency to worry, get angry, how we find pleasure. On the surface of the brain, our cerebrum plays a huge role in who we think we are – because it is the seat of thought. The prefrontal cortex has our thoughts, plans, imagination and ability to solve problems. The orbitofrontal cortex gives us goals, a sense of morality and ethics and is possibly the seat of conscience. The temporal lobe of the associative cortex allows us to recognize scenes, objects and faces, and to process sounds and language. Our talents, e.g. music, art, sports, lay in various parts of the brain, also constitute part of who we think we are. Because there is no one part of the brain that is our “self” it is not even possible for dementia to destroy that self!
Secondly, there is no part of the brain that is the center of spirituality. Andrew Newberg’s and other’s work on neurotheology has attempted to “measure” spirituality in the brain. Whether he is observing monks meditating or sisters doing centering prayer while they are getting a brain scan, there are multiple areas of the brain that “light up” during spiritual experiences. There is no one clear substructure that is the internal “cell phone” to God, at least not one that has yet been identified. Again, because there is no one part of the brain that is responsible for our spirituality, it is not even possible for dementia to destroy spirituality. It’s even possible that spirituality could increase in some ways!
Music, humor, spirituality, the self – these are spread throughout the brain and the disease doesn’t remove them. Alzheimer’s is a disease of an organ of the body, no more, no less. So why the stigma? We don’t treat heart patients or kidney patients that way, why should those with dementia be treated differently?