[@hubermanlab] How Your Thoughts Are Built & How You Can Shape Them | Dr. Jennifer Groh

Link: https://youtu.be/tb6ApBIXr1k

Short Summary

Dr. Jennifer Gro discusses the brain's sensory integration, particularly how vision and hearing merge to create a unified perception of the world. The conversation covers topics like sound localization, 3D sound, the influence of physical spaces on auditory experience, and the surprising connections between vision, attention, and even the ear itself. The podcast concludes with a discussion of the neurological basis for thinking, with a focus on how our brains run sensory simulations and the role of the environment, attention and technology.

Key Quotes

Here are 5 quotes from the transcript that I found particularly valuable:

1. "What goes on in our brains when we think might be that we're running simulations related to the thought using that sensory sensory motor infrastructure of the brain."

   • This encapsulates the central theory about the nature of thought being explored, suggesting that our mental processes are deeply rooted in sensory and motor experiences.

2. "Maybe you need to shift some resources away from processing the conversation and towards some, you know, actually dealing with the here and now sensory motor task."

   • This insightful explanation of why distractions impair focus during demanding tasks connects abstract cognitive processes to concrete sensory-motor resource allocation in the brain.

3. "If we live long enough, 80% of us will get hearing loss at some point in our lives."

   • This stark statistic is a sobering reminder of the prevalence of hearing loss and the importance of protecting our hearing.

4. "I often take off my glasses to measure the distance between my two ears that way. And it's something like about a half a millisecond is the largest delay you can experience."

   • This perfectly summarizes the incredible speed at which our auditory system works!

5. "They're stuck in that cone of attention...our attention tends to follow our vision, not necessarily the other way around."

   • This describes the direct link between vision and focused brain states.

Detailed Summary

Here's a detailed summary of the YouTube video transcript in bullet points, highlighting the key topics, arguments, and information discussed:

Introduction and Guest:

• The Huberman Lab Podcast features Dr. Jennifer Gro, a professor of psychology and neuroscience at Duke University.
• Dr. Gro studies how the brain represents the world, focusing on sensory integration, attention, learning, and how eye movements influence brain function.
• The podcast aims to provide useful definitions of thoughts and how to control them, and explain how to use experiences and knowledge of the brain to become a better thinker.

Sensory Integration (Auditory & Visual):

• The conversation starts with sensory integration, specifically auditory and visual integration.
• The initial point of integration is discussed, leading to the "superior colliculus" as a key brain structure.
• Superior Colliculus: This area responds to both visual and auditory stimuli. Eye position influences how neurons in this region respond to sound.
• Dynamic Maps: Dr. Gro's initial interest was in how the brain creates dynamic maps of sound location relative to eye position, considering the constant shifts in visual scenes due to eye movements.
• Even though the visual scene is shifting massively on the retina, we are mostly not aware of it, indicating that the brain is doing a lot of computation under the hood.
• Adaptation: The brain can rapidly remap the visual-auditory world in milliseconds.

Merging Sight and Sound:

• Discussion of how the brain merges visual information (e.g., lip movements) with auditory information, even when the sound source doesn't perfectly align with the visual source (e.g., movies, ventriloquism).
• Ventriloquism is used as an example of how perception can be tricked by manipulating visual and auditory cues.
• This ability to merge senses is learned during development and continuously updated until adulthood.

Sound Localization:

• Explanation of how we localize sound using timing and level differences between the two ears.
• The maximum delay a sound can experience reaching one ear before the other is half a millisecond, a very short duration.
• A baby's head is about half the width of an adult's head. That means that that you know half millisecond for me is you know a quarter of a millisecond for for a baby and it's going to change as they grow.
• The brain uses differential delays for the sound to arrive at one ear versus the other, timing cues, the distance of the ears, and speed of sound to detect the location of sound.
• Ear structure (folds) filters sound, affecting frequency content and influencing sound localization. People with damage to their ears will likely have an initial deficit, but likely adapt over time.

Voice Perception:

• Discussion of why our own voice sounds different recorded versus how we perceive it in real-time.
• Reasons include: Recordings don't capture the full frequency range, the brain actively manipulates sound transduction in the ears, and bone conduction contributes to how we hear our own voice.
• The brain may "turn down the volume" in anticipation of our own speech to avoid being "blasted" by the sound.

Hearing Loss and Safety:

• Hearing loss correlates with dementia. Less sensory information coming into the brain leads to cognitive decline.
• The amount of radiation coming from Bluetooth headphones is considerably lower than the radiation one is exposed to all day.
• The sensitivity of the neural sensory space of the bones for bone conduction.
• If your headphones are loud enough for somebody besides you to hear, you're inflicting hearing damage, probably permanent hearing loss at some level.
• Discussion of bone conduction headphones and their safety (leaving ears open).
• Concern about excessive sound exposure and its impact on hearing loss in younger generations.
• The volume turned up loud enough to block out surrounding sound is a cause for concern. Noise cancelling headphones help.

Sound and Space:

• Difference between listening to music through headphones versus speakers in a room.
• Headphones create the sensation of sound originating inside the head.
• 3D sound and how the brain computes distance using loudness, echoes, and other cues.
• Sounds are "bendy" and move around objects.
• The loudness cue requires knowing the initial stimulus.
• Shorter path sound travels straight from the mouth to the ear.

Vibration and Emotion:

• Objects have resonant frequencies.
• The relationship between vibration and sound is important given that our ears contain the apparatus to detect sound frequency, and have to do with balance and vibration.
• Humans also have a resonant frequency. Certain frequencies of sound can shape our emotional state. (Music)
• Gongs as an ancient tool for orienting people's emotional state.
• Lower frequencies bend more easily. Low frequencies are audible to more people and are louder.

Music and Emotion:

• The universality of music and its evolutionary purpose are discussed.
• Music and rhythm may have evolved to help humans act in concert, scaring off predators and competitors.
• Evolution could have increased the fitness of cooperating together through rhythm.
• Song and body movement evolved to signal what one was feeling or what their intention was.
• The haka as a vigor display, stomping.
• People are captured by other people's attention by the certainty of what they say and the tamber of their voice.

Music and Memory:

• Music makes it easier to remember things. If you know the first couple of words of a verse, you've got the rest of the verse.
• The ABC song as a good example.
• Musicians who write lyrics have to start the first two or three words of the verse and the rest kind of spills out of me.

Brain Structures and Auditory Integration:

• Discussion of brain structures involved in auditory integration.
• The ear is like a frequency separator.
• Eye movements affect auditory signals even in brain areas traditionally considered primarily auditory.
• Top-down input from the brain carries information about eye position, influencing ear structures.
• The eardrum moves with every eye movement, creating sounds that can be measured.
• There are descending connections from the brain to the retina itself that are are potentially related to circadian influences.

Physical Environment and Sound Perception:

• Examples of physical spaces like Grand Central's whispering gallery and cathedrals, and how they shape sound perception.
• The Grand Central arches: Diagonal corners are easily 25 feet away from the other person and can hear each other whisper due to the way the sound wave travel along the ceiling on that parabola.
• People understand sound intensity and frequency and localization completely differently.
• High ceilings in churches amplify aspects of music.
• Sounds in settings are a combination of all the reflective surfaces in the setting.
• When people join together in sound, you're communicating something very important, that's the most effective way to communicate a feeling.
• Music to bring people together. Need for very primitive music.

Science and Disagreement:

• Scientists are able to have a comfort with argumentation but also go where the facts lead us.
• Science has agreements on how to evaluate strength of evidence.

Focus, Silence, and the Voice in Our Head:

• Question about the optimal thing to listen to in order to be able to focus. Silence may be best.
• Thoughts on the use of sound as a way to change brain state.

Theory of Thought:

• A theory of thought in our brain may be running simulations related to the thought using the sensory sensory motor infrastructure of the brain.
• Thinking about a cat might involve simulations in visual and auditory cortex.
• Fractured thoughts jump around.
• It is really tough to come up with a word completely unrelated to something being talked about.
• The theory of thought may provide an explanation for why speech impairs you from visual motor. Shifting resources away from processing conversation and towards sensory motor task.

Brain States and Flow:

• Brain states are context-dependent.
• Brain described as a ball bearing on a flat surface. The more fatigued you are, the more unbalanced the surface is.
• ADHD might not necessarily be a clinical diagnoses but a matter of not allowing a narrow enough set of sensory inputs and context to drop into the trench.
• Changing immediate environment can get out of a little rut.
• Discussion of the idea that attending scientific conferences, moving seats can anchor attention.
• Whether effects of binaural beats or other frequencies improving focus has to do with just needing to fill the auditory sensory space.

Personal Strategies for Focus:

• Having an ideal work environment, having the right physical space.
• Some people think they can't focus, but that there's a sensory space that needs filling. People need to hack themselves.
• Music needs to be interesting. Classical music is what you listen to.
• There is so much infiltration through devices.
• Musicians make a playlist for a particular project, that those songs become a cue.
• One should have an understanding of what works for a particular person for a particular project.

Acetlycholine and Attention:

• Mentioned of experiments that the cortex is rich with nerve endings that release acetylcholine. Nucleus basalis releases acetylcholine.
• Acetylcholine creates attentional spotlighting.
• Need to integrate vision, sound, context, thinking, intention, and action.
• Norepinephrine is used to raise alertness.
• Dopamine does many different things in different areas.
• It is so clear that a sphere of intention is necessary.
• A lot of people can't focus because acetylcholine is a resource that is spent out and replenished in sleep.

Interval Training and Mental Work:

• Discussed doing interval training with physical workouts.
• The attention span of athletes directly maps onto the duration of their event.
• You can write a sentence and then check one new site.
• Let go of working efficiently as a goal in and of itself.

Distraction and System Trust:

• Phones have made it such that there is a step function.
• Need rest and recovery for physical exercise.
• Brain and muscles are not that different from each other.
• Trust the brain state shifting. Don't fight it.
• Certain times of day when things are going to come to you and that certain things aren't ready.
• "Being blocked can mean you don't know yet what needs to come next".
• People try to drop into that deep trench as quickly as possible.

Jennifer's Experience as a Musician:

• Started off with flute and now plays the banjo and sings.
• Attention is anchored for the duration of the performance.
• Singing is better in performance.
• Banjo playing has the adrenaline effect that can hurt the finger movements.
• Songs can only be rehearsed once because she can't remember the words the second time through.

Pressure and Neural Basis of Choking:

• Discussion about the pressures that can affect neural basis.
• If there is a potential low payoff if you get something right and then high payoff if you do it really right, the performance on the high stakes condition is always worse.
• Choking turns out to be recruitment of too many motor units. It is an overinvestment of motor effort.
• "Perfectionism is a trap." Have to mentally convince self that the stakes are lower.

Chickens and Vision Attention:

• Has banttom meal flur chickens. Little guys. bred to be pets.
• Non-invasive experiment to try: draw a line in the dirt for the chickens.
• They can hypnotize chickens, but they are just hyperfocused.
• View horizons and relax the autonomic nervous system.
• Hypnosis is a state of hyperfocus.
• When we do virgins eye movement, our eyes together in a particular point there's a really interesting increase in output of areas like Locus Ceruius.
• Birds who eat off the ground and undergo virgin eye movements get locked there.
• Vision drives brain state.

Phones and Attention Control:

• The phone can be helpful but should not be used when bored.
• Phone makes it hard to stay in the present.
• It is helpful to be aware of what you want to get out of your phone.
• Have exit paths for the phone.
• Seamless on ramp and no end point is the dangerous thing.
• Social media is the slot machine.
• Set up the phone.
• Log out and use a specific phone for those apps.

Conclusion:

• The conversation covered auditory and visual systems, their integration, and how the physical environment shapes brain function.
• The brain is creating its own environment.
• We have a lot more control over the environment that we may not realize.