Dr. David Berson, a professor at Brown University, discusses the peripheral nervous system and its role in our daily experiences. He provides a detailed understanding of the nervous system, explaining how individual circuits work and how they function together as a whole. He also delves into topics such as how we see, color vision, "strange" vision in animals, how we orient in time, body rhythms and melatonin, spending time outdoors and its impact on eyesight, sensation, mood, and self-image, the sense of balance, why pigeons bob their heads, popping ears, the midbrain and blindsight, why tilted motion feels good, reflexes vs. deliberate actions, the basal ganglia and the "2 Marshmallow Test," suppressing reflexes with the cortex, neuroplasticity, connectomes, and how to learn more about the brain. Overall, Dr. Berson provides a comprehensive understanding of the nervous system and its various functions.
Dr. David Berson
Dr. David Berson, a professor at Brown University, is known for his discoveries regarding the cells in the eye that regulate circadian rhythms. He has also made significant contributions to understanding how our perceptions of the outside world translate into motor action. In this podcast episode, he discusses the peripheral nervous system and its role in our daily experiences.
- Dr. David Berson is an expert in neuroscience and provides a detailed understanding of the nervous system.
- He explains how individual circuits work and how they function together as a whole.
- His insights go beyond what can be found in textbooks or popular books.
- By the end of the podcast, listeners will have a comprehensive understanding of the nervous system.
How We See
The brain is responsible for our visual experience, processing information from the eyes to create our conscious visual experience. Ganglion cells are key neurons that communicate between the eye and the brain, and the cortex is where our conscious visual experience occurs.
Color Vision
Color vision is enabled by the detection and decoding of different wavelengths of light by neurons in the retina.
Key points:
- Light is a form of electromagnetic radiation that can be perceived as particles (photons) and waves.
- Neurons in the retina detect different frequencies within the electromagnetic spectrum, resulting in the experience of different colors.
- Proteins in the retina absorb light with different frequencies, allowing the nervous system to compare and contrast these signals to extract information about the composition of light wavelengths.
The perception of color is a result of our brain interpreting the different composition of light that reaches our eyes.
Key points:
- The biological mechanisms for seeing color are similar across humans and animals.
- However, the subjective experience of color cannot be fully explained through scientific approaches.
- There are five different cone types involved in color vision.
“Strange” Vision
The most profound aspect of the topic of "Strange" Vision is the differences in vision between humans and animals, particularly dogs.
Key points:
- Animals, such as dogs, can see things that humans cannot.
- Dogs see reds more as oranges due to having fewer types of cone cells for color vision.
- Humans typically have three cone types, allowing us to see a wider range of colors.
- Dogs only have two cone types, limiting their color perception.
- Other types of pigments, such as rod cells for dim light vision and melanopsin pigment, are also mentioned.
- Colorblindness is briefly discussed and the challenges it poses in a world designed for people with normal color vision.
- Individuals missing one cone type may have a visual limitation where they are blind to certain contrasts.
- This limitation is not as damaging as not being able to see acutely or read fine print.
- Color is meaningful to humans, but other mammals like dogs and cats can function well without it.
- An odd photopigment is mentioned in the video.
How You Orient In Time
The specialized ganglion cells in the eye, called intrinsically photosensitive cells, convey information to the brain about brightness in the environment. These cells have pigment located in the outermost layer of the retina, where the photoreceptors are located. The surprising discovery is that photoreceptor cells in the innermost part of the retina, called ganglion cells, can directly absorb light and convert it into neural signals. The brain uses this information to orient in time, regulating the circadian clock. The circadian clock is present in almost all cells of the body and needs synchronization with the natural rhythms of the environment to avoid issues like insomnia.
Body Rhythms, Pineal function, Light & Melatonin, Blueblockers
The circadian clock, coordinated by the suprachiasmatic nucleus (SCN), regulates the body's rhythms and is present in most tissues. The SCN receives input from the retina to coordinate activities of other organs. The SCN impacts the autonomic nervous system, affecting alertness and calmness. The pineal gland, a major source of melatonin, is influenced by light signals received by the SCN. Exposure to bright light, especially blue light, suppresses melatonin release. It is advised to avoid bright light at night. Blue light is the optimal signal for shutting down melatonin, but any light can affect the system. Wearing blue blockers during the day is not recommended. Lack of light can lead to seasonal affective disorder and depression. Expose oneself to bright light when wanting to be alert and avoid bright light when wanting to sleep. The incidence of myopia is related to body rhythms, pineal function, light, melatonin, and blueblockers.
Spending Times Outdoors Improves Eyesight
- Spending time outdoors is strongly linked to improved eyesight, especially in reducing nearsightedness in children.
- The exact reason behind this connection is not fully known, but it could be due to increased exposure to light or the process of focusing on near or far objects.
- It is recommended to use a device to measure photon exposure throughout the day to optimize eye health.
Sensation, Mood, & Self-Image
The peri-habenular, a part of the brain, serves as a link between peripheral sensory input and the cortex, connecting to the thalamus. There is a side pathway from the retina to a different part of the cortex through a different part of the thalamus, influencing mood and light-related aspects.
Key points:
- The peri-habenular acts as a linker between peripheral sensory input and the cortex.
- A side pathway from the retina to a different part of the cortex exists through a different part of the thalamus.
- This side pathway plays a role in mood and other aspects of light.
- The pathway from the eye to the frontal lobe affects higher-level functions like self-perception and planning.
- Activation of this pathway at the wrong time of day can lead to depression.
- Silencing this pathway can prevent negative effects of certain lighting cycles.
- Intrinsically photosensitive cells regulate basic functions, including mood and circadian rhythm.
Sense of Balance
The vestibular system in the inner ear is responsible for our sense of balance and detects our movement in relation to the world. It functions as a gravity sensing system and detects rotational movements through hair cells stimulated by fluid motion. The brain encodes the sense of balance through three axes of encoding, allowing it to determine the direction of head movement. The brain differentiates between self-induced movement and external motion, and visual information is combined with balance information for image stabilization. This stabilization is similar to image stabilization technology in cameras. Rapid eye movements and periods of rest are made to stabilize the image on the retina. Other animals also exhibit similar stabilization behaviors.
Why Pigeons Bob Their Heads, Motion Sickness
Pigeons bob their heads to stabilize the image on their retina while their body moves, demonstrating a better understanding of vision and balance than humans. Motion sickness occurs when there is a conflict between the visual and balance systems in the brain, causing nausea. The cerebellum plays a crucial role in combining visual and balance input, and damage to it can result in difficulties in motor learning and coordination. The flocculus, a part of the cerebellum, is responsible for stabilizing movements and has a learning function to compensate for any loss in the vestibular system. To prevent motion sickness, it is advised to avoid using phones in moving vehicles.
Popping Ears
Popping Ears: Techniques to Relieve Discomfort and Equalize Pressure
- When ascending or taking off in an airplane, the ears may feel plugged due to increased pressure.
- To relieve discomfort, plug the nose and blow out to equalize the pressure.
- When descending or landing, the pressure decreases, causing the air behind the eardrum to expand.
- To equalize the pressure, plug the nose and suck in.
- Blowing out when not supposed to may also work, as long as the passageway is open.
Midbrain & Blindsight
The midbrain is a crucial area beneath the cortex that controls unconscious functions and reflexes, serving as a link between the peripheral nervous system and the cortex. It contains the superior colliculus, an important visual center. The optic tectum or superior colliculus in the midbrain is a reflex center that interprets visual input and helps animals reorient their gaze and body. It handles reflexive responses to visual stimuli and integrates input from other sensory systems. Rattlesnakes and flies have specialized sensory systems in the midbrain for heat detection and taste receptors, respectively. The midbrain plays a crucial role in cross-correlating sensory information from different systems, allowing the brain to pay attention to corroborated information. Conflicting information can lead to confusion and motion sickness. Overall, the midbrain is a fascinating area of study.
Why Tilted Motion Feels Good
Why Tilted Motion Feels Good
- Tilted motion, such as skateboarding, cornering in cars or bikes, running, dancing, and surfing, brings pleasure to many people.
- The exact reason for this phenomenon is unknown, but dopamine may be involved.
- Roller coasters provide a thrill and activate the falling reflex.
- Children tolerate vestibular craziness more than adults, and some enjoy being shaken by their parents.
- Moving through space may activate the reward systems in the brain.
- The feeling of agency and mastery that comes with choosing to move and tilt contributes to the pleasurable sensation.
Reflexes vs. Deliberate Actions
Reflexes and deliberate actions are controlled by different parts of the brain. Reflexes are automatic movements that occur without conscious thought and are designed to keep us safe. Deliberate actions involve higher-level cognitive centers and decision-making. The brain has mechanisms to override automatic movements if they are inappropriate, but also allows reflexes to work quickly in life-threatening situations. There is constant communication between these different levels of the brain to ensure both reflexes and deliberate actions are coordinated effectively.
- Reflexes are automatic and instinctive responses trained through repetition.
- Overthinking can disrupt reflexive actions and lead to mistakes.
- Deliberate actions involve conscious thought and consideration of the situation.
- The basal ganglia is an important brain structure involved in deliberate actions.
Basal Ganglia & the “2 Marshmallow Test”
The basal ganglia are a group of structures in the forebrain that play a crucial role in controlling go-type behavior and no-go type behavior. They work together with the cerebral cortex to make decisions about whether to withhold or execute behavior.
Key points:
- The cortex is involved in decision-making and self-control.
- The marshmallow test demonstrates the involvement of the cortex in delaying gratification.
- Some individuals find it easier to engage in tasks and have low activation energy, while others struggle with task completion.
- The basal ganglia is a complex network that implements and influences plans generated by the cortex.
- It is involved in decision-making, restraint, and initiating actions.
- The basal ganglia and the cortex work in parallel and interact with each other.
- The "2 Marshmallow Test" refers to the ability to delay gratification and make choices that are not based on instant gratification.
- This ability can be developed through mental practice and discipline.
Suppressing Reflexes: Cortex
The cortex is responsible for suppressing reflexes and adding nuance, context, and experience to our actions. It allows us to learn from others through communication and creates a map of the visual world in our brain. The visual cortex processes visual information and contains multiple maps that specialize in encoding various features. Different parts of the cortex are responsible for different tasks and involve the cooperative activity of many neurons. The brain's logic and function involve a complex interplay between specialized neurons and network activity. It is a highly interconnected and interactive system with both specificity and non-specificity in its functioning.
Neuroplasticity
Neuroplasticity is the brain's ability to reorganize and adapt to changes in sensory input. It can lead to the repurposing of brain regions for different functions, as observed in a blind woman who developed exceptional braille reading skills. The visual cortex, normally responsible for processing visual information, was reallocated for tactile processing in her case. This extreme level of plasticity highlights the versatility of the visual cortex in adapting to different sensory inputs. Neuroplasticity can occur in both positive and negative ways, affecting the structure and function of the brain in response to experiences and learning. Understanding neuroplasticity involves studying connectomes, which are similar to genomes.
Key points:
- Neuroplasticity refers to the brain's ability to reorganize and adapt to changes in sensory input.
- The visual cortex can be repurposed for tactile processing in blind individuals with exceptional braille reading skills.
- Neuroplasticity can occur in both positive and negative ways, affecting brain structure and function.
- Connectomes, similar to genomes, play a role in understanding neuroplasticity.
What is a Connectome?
A connectome refers to the structure of nervous tissue at a very fine scale, down to the level of individual synapses and synaptic vesicles. It involves creating a complete description of the synaptic wiring of a chunk of nervous tissue. This provides a wiring diagram of the tissue, allowing for a comprehensive understanding of its connectivity. Connectomics, specifically the serial electron microscopy reconstruction of neurons, allows for the study of the brain's anatomy and connectivity. By understanding the structure, researchers can make predictions about the function of specific circuits. The connectome combines both the structural and functional aspects of the brain, allowing scientists to understand how different cells communicate and process information. Without knowledge of the cell types and connections in the connectome, it would be impossible to explore the workings of the brain.
How to Learn (More About the Brain)
Learning more about the brain can be overwhelming due to the abundance of information available. However, there are ways to navigate this vast field and participate in neuroscience research without formal education or extensive resources. Here are some key points to consider:
- The Huberman Lab Podcast and other sources provide valuable information on the nervous system.
- Projects like Eyewire allow individuals to contribute to neuroscience research from home.
- Seeking guidance from knowledgeable people and reading accessible books on neuroscience can enhance understanding.
- Resources like Wikipedia and libraries offer valuable knowledge on the subject.
- Neuroscience is a diverse field with various branches dedicated to different aspects of the brain, making it an exciting area to explore.
Book Suggestion, my Berson Appreciation
The most profound aspect of the conversation between Andrew Huberman and Dr. David Berson is their discussion of a book suggestion, "We Know It When We See It" by Dick.
Key points from the conversation include:
- Dr. Berson's extensive knowledge of the nervous system and his ability to educate others.
- Andrew's gratitude for Dr. Berson's guidance and his tendency to seek his advice when exploring new problems related to the nervous system.
- Both Andrew and Dr. Berson express their enjoyment of the session.