How Your Nervous System Works & Changes | Huberman Lab Podcast #1
Podcast Summary
Today’s episode provides an introduction to how the nervous system works to create sensations, perceptions, emotions, thoughts and behaviors, as well as how we can change our nervous system— a phenomenon known as neuroplasticity. The information sets the stage for all Huberman Lab Podcast episodes that follow by covering neurons, synapses, brain chemicals and the rhythms that control our ability to focus, learn and sleep… and more.
Key Takeaways
Our entire experience of life is filtered by our sensory receptors
Contrary to popular belief, humans are able to effectively multi-task
Thoughts can be both reflexive or deliberate - we can decide what and how to think
Impulsivity is a lack of top down processing, particularly in kids
Our ability to change our neuroplasticity, and ultimately our behavior, depends on how well rested we are
Neuroplasticity (changes in behavior) occur during sleep - if you want to get better at something, you must sleep
Twenty minutes of deep rest following sustained effort accelerates neuroplasticity
We can use neuroplasticity to both add new behaviors, but also remove behaviors that we dislike
Memories can't be erased but emotional load associated with them can be reduced
Sleep is critically important for immune system, wound healing, learning, as well as our longevity
Our entire existence occurs in ninety minute intervals called ultradian cycles - pay attention to the way your body operates
(00:05:00) What is the Nervous System?
The nervous system includes the spine, brain, connections between the organs and everything in between
The brain is a part of the nervous system
The nervous system is responsible for everything you think, feel and imagine
The nervous system is a continuous loop of communication between the brain, spinal cord, and the body
The nervous system is like a Möbius Strip - it all loops together
The nervous system dictates how the body should behave
If you have a stomach ache - that is a function of the nervous system
The nervous system governs all other functions of the body. At the same time, the nervous system is also influenced by other functions of the body
At the turn of the 19th century, scientists believed that our nervous system was one giant cell
Spanish physician Santiago Ramon y Cajal “neuron theory” proposed that the nervous system was made up of microscopic cells (neurons), each independent from one another but that establish complex patterns of connections
Neurons are connected by synapses
The body is a flow of electricity between different nerve cells and responds based on inputs
How does the nervous system work? It is kind of like keys played on a piano in a specific order to make a song
The hippocampus is involved in memory
(00:08:55) What is Deja Vu?
Déjà vu, pronounced is French for “already seen.” Déjà vu describes the fascinating and strange experience where you feel that something is very familiar but you also know that this feeling of familiarity should not be as strong as it is.
Deja vu occurs when neurons in one circumstance are firing again in a similar, but not exactly the same, situation
(00:10:50) How War, Guns & Soap Shaped Our Understanding of the Brain
Events throughout history have provided great insight into how our brain works
In World War 1, advancements in artillery and bullets made it such that bullets would enter and exit the body very discretely, producing leisons in the nervous system
People would return from war with holes in their brain and nervous system
At the same time, advancements in healthcare and science meant that more people survived war and returned home with medical issues to study and treat
Patients would say "I recognize these faces, but I don't who they are"
Other times people would return from war speaking gibberish. However, they were completely adept at understanding language
(00:13:30) Jennifer Aniston Neurons
A study published in Nature found that various pictures of Jennifer Aniston elicited a response in a single neuron inside the medial temporal lobe of another patient
(00:14:30) How does the brain process sensations?
The brain is a map of our experience and sensations
Our entire experience of life is filtered by our sensory receptors
What does the nervous system do?
The nervous system is the body's command center. The nervous system controls movements, thoughts, and automatic responses to the world around you.
The nervous system controls the body's major systems and functions:
Sensation is a non-negotiable element of the nervous system
Neuron in eyes perceive certain colors
Neurons in skin perceive certain types of touch
Neurons in ear to perceive certain sounds
(00:16:10) Magnetic Sensing & Mating
Are there experiences that humans are unable to perceive due to physical limitations? YES
Some snakes have infrared vision - they are unable to detect shape, but they can detect heat profile
Some turtles and birds have neurons in their noses that can detect magnetic fields in order to go one from one particular location to a particular destination so that they can mate and lay eggs
Humans do not have receptors to sense magnetic fields, nor do they have heat vision
(00:17:30) Perceptions & The Spotlight of Attention
Focus and spotlight is the ability to take what we are sensing and then focus on it
Example of the difference between sensation and attention:
Pay attention to the bottom of your feet and whatever they are in contact with
Sensation is always happening, but perception is under the control of attention
Attention is like a spotlight, it can focus more or less on certain things
Contrary to popular belief, humans are able to effectively multi-task
(00:20:10) Bottom-Up vs. Top-Down - How to Control Behavior
When we are well-rested, we can direct our attention in very deliberate ways
Nervous system is two way street composed of reflexive and deliberate behaviors
Reflexive Behaviors: if you know how to walk already, you don't need to to think about walking
This is called a bottom up process - information is flowing though the senses and guiding automatic behavior
Now if a car were to come to a screeching halt, you would pause, moving you into a deliberate behavior
Deliberate behaviors are top down and require focus, but will always require effort and strain
The nervous system is wired to do actions with low metabolic demand
Feelings & Emotions
To this day, scientists and philosophers argue about exactly what are feelings and emotions and and how feelings and emotions work
Feelings involve both neurons and chemicals
Chemicals (neuromodulators) bias which neurons are activate or inactive
Simple way to think about neuromodulators is that they are like playlists
Dopamine makes certain neurons and neural circuits more active, and others less active
Serotonin makes us feel grateful about what we have
(00:24:30) Antidepressants & Anti-Psychotics
Through the discovery of antidepressants, we discovered that we can regulate chemicals in the body
However, taking antidepressants can cause impacts to the body
For example, reducing serotonin may also reduce dopamine
All of the chemical receptors are very sensitive to changes
Different receptors on different parts of the body have different impact
Many antidepressants increase serotonin but have side effects on motivation, appetite or libido because serotonin is binding to receptors in the brain that control other things
Emotions can also be cultural/contextual
(00:27:40) Thoughts & Thought Control
We tend to believe that thoughts and emotions are not under our control
Thoughts are somewhat reflexive - we experience them passively
Thoughts are like perceptions. They also take into account the past, as well as the future
Thoughts can be both reflexive or deliberate - we can decide to think something
Thought patterns can be deliberately controlled
(00:28:35) How does the nervous system influence our actions?
Actions are the most important aspect of our nervous system
Sensations and feelings are entirely in our heads, unless we take concrete action based on them
"Movement is the final common pathway"
Almost everything we experience, including thoughts and experience, play a part in the action we take or do not take
Like thoughts, movement can also be deliberate or reflexive
Deliberate Action requires attention to:
Duration: how long will I do something?
Path: what should I be doing?
Outcome: what will happen at the conclusion?
The moment you decide to learn something, resist speaking, or otherwise fighting impulse, you are engaging in deliberate actions
(00:33:20) How to control impulses
Perhaps somebody says something that is triggering/upsetting to you, but you want to avoid saying something
You are now actively biting your tongue - you may feel physical agitation
The forebrain is actively suppressing a circuit, causing you to feel agitation
Children do not have forebrain circuitry to suppress actions until around twenty five
Kids will see candy and immediately reach out and grab it, whereas adults might ask for permission
Impulsivity is a lack of top down processing
Removal of inhibition through alcohol is the actual removal neural inhibition
(00:36:25) What is Neuroplasticity? The Holy Grail of Neuroscience
What is neuroplasticity? Plasticity is a process by which neurons change the connections and how they work
This allows for things to go from deliberate to automatic
Neuroplasticity is generally referring to adaptive neuroplasticity. In particular, self-directed plasticity (eating healthier, going to the gym, and much more)
From birth to around age twenty-five, the brain is incredibly plastic. Kids can learn new things and adapt very easily. This is more difficult for adults
For adults looking to increase neuroplasticity, need to ask two questions:
What particular aspect of my nervous system am I trying to change?
How exactly do I plan on changing neuroplasticity?
The answer to second question is governed by how awake or sleepy we are
(00:41:20) The Portal to Neuroplasticity
We can direct our own neural changes. We can do this for our brain, but can't do so for other parts of our body.
For example, we can't say that we want our stomach to be better at digesting spicy food
The adult brain can change as it relates to experience - there is an interest in learning more about neuroplasticity
Plasticity in the adult human nervous system is controlled by neuromodulators
Neuroplasticity is able to be achieved under traumatic circumstances due to large release of chemical
Epinephrine creates alertness and increased attention
Acetylcholine marks neurons that are active during marked period of alertness
We need alertness to have focus
We need focus in order to direct neuroplastic changes within our nervous system
(00:46:40) How to learn while sleeping
The dirty secret of neuroplasticity is that no neuroplasticity occurs during the actual effort
All of the neuroplasticity and connections between nerve cells occurs during sleep and non-sleep deep rest
Neuroplasticity depends on how much attention and focus someone can continuously sustain
This could be to the point of agitation and a feeling of strain are required for neurplasticity to occur
Twenty minutes of deep rest following sustained effort accelerates neuroplasticity
If people are learning a particular skill and they hear a tone in the background and that tone is played during deep sleep, learning increases. The sound cues the nervous system even during sleep
The bell is a Pavlovian cue to the brain
(00:50:20) The Pillars of Plasticity
We can use neuroplasticity to both add new behaviors, but also remove behaviors that we dislike
For example, it is possible to eliminate agoraphobia
Memories can't be erased but emotional load can be reduced
Neuroplasticity is a two-phase process involving the autonomic nervous system (also known as the sympathetic/parasympathetic nervous system)
The autonomic nervous system works like a see-saw. Every twenty four hours we wake up energized and get tired at night
Every twenty-four hours, we have a phase of our day that is optimal for thinking, focus and neuro-plasticity
In another part of our day, we have little ability to learn and focus
Both phases of day are critical to neuroplasticity
We must master the transition from sleep to wakefulness and wakefulness to sleep
Sleep is critically important for immune system, wound healing, learning, as well as our longevity
How to get better at sleeping and staying asleep
Not only do we need to sleep more, we also need to optimize the time when we go to sleep as well as the quality of sleep
The non-traditional Uberman sleep schedule has been studied, but is not effective for everyone
Our culture has not explored the rhythms that occur during our waking states such as when the brain is optimized for learning and growth
There is vast data that points to ultradian rhythms
(00:55:00) Leveraging Ultradian Cycles & Self Experimentation
What are ultradian rhythms?
In chronobiology, an ultradian rhythm is a recurrent period or cycle repeated throughout a 24-hour day.
Ultradian rhythms include ninety minute rhythms of focus
Sleep is broken into ninety minute rhythms - throughout the night we cycle through diffferent cycles of sleep
When we wake up in the morning, ultradian cycles continue
For the first five minutes of an ultradian cycle, the brain and neural circuits are not optimally tuned to whatever you are trying to do. As you continue to engage, the brain catches up
Ultradian cycles occur during sleep and wakefulness, and frequently see-saw
It is vitally important to understand that our entire existence is occurring in ninety minute intervals. We must lean into the ninety minute intervals
Focused learning should be ninety minute intervals, with the first few minutes being difficult
We should pay attention to when our brain is most anxious and perceptive:
When am I most focused? When am I least focused?
When am I most motivated? When am I least motivated?
Asking these questions allows us to shift our abilities to engage in different types of work