Introducing Time Perception, Note on Fasting & Supplements
In this podcast, Andrew Huberman, a professor of neurobiology and ophthalmology at Stanford School of Medicine, discusses time perception and how it can be manipulated. Our perception of time is linked to our neurochemical states and can affect our mood, stress, and happiness. He talks about how we can dilate or contract our experience of time, and provides tools and protocols to help us do this. He also answers some questions related to fasting and time-restricted feeding, such as whether supplements can break a fast. Generally, those without sugar or protein content, such as Athletic Greens and fish oil, do not break a fast.
Entrainment, Circannual Entrainment, Melatonin
Time perception is linked to something called entrainment, which is when internal processes, biology, and psychology are linked to some external thing. Circannual rhythms are an example of this, where neurons within the eyes, brain, and body mark off the passage of time throughout the year. Light seen by the eyes reduces the amount of melatonin released in the brain, which has an effect on energy levels and mood. Melatonin correlates with day length, with more light resulting in less melatonin and vice versa. This is why most people feel more energetic in the spring and less in the winter, as the amount of melatonin that corresponds to the length of the day changes. Entrainment is not limited to this example, as other external events can also be linked to internal states.
Seasonal Oscillations in Testosterone & Estrogen, Tool 1
Humans tend to produce varying levels of testosterone and estrogen depending on the length of the day, which can affect their behavior and mood. Last year, Parrack published in Cell Reports, a journal of Cell Press, an excellent example of this. They showed that two hours of sunlight exposure to the upper body was associated with significant increases in testosterone and estrogen. Sunscreen does not seem to inhibit this effect, but it is important to prioritize skin health. Our perception of time is both conscious and slower oscillatory events related to day length, which influence hormones like melatonin, testosterone and estrogen. Bright lights can override some of these processes and affect our mood and behavior.
Circadian Timing, Tools 1, 2, 3 (for Circadian Entrainment)
Circadian entrainment is the process of the body's cells synchronizing to the 24 hour light/dark cycle. Each cell has a 24 hour timer where a gene is expressed, inhibited by a particular protein. This cycle is regulated by light, with morning sunlight, evening sunlight, and lack of light in the middle of the night. To ensure precise circadian entrainment, it is important to get 10-30 minutes of bright light, ideally sunlight, in the morning and afternoon, and to limit bright light in the evening. Disruptions in circadian entrainment can cause a number of health problems, so it is important to synchronize the body to the 24 hour light/dark cycle.
Tool 4: Timing Physical Activity; Tool 5: Timing Eating Window
Circadian entrainment is the process of aligning one's internal perception of time with the external events of the world, such as exposure to sunlight. To entrain your circadian clock, you should engage in physical activity at fairly regular times of day and eat within more or less the same time window each day. You don't have to eat your meals at exactly the same time, but rather have a consistent period or phase of each 24 hour cycle. Additionally, you should also be exposed to sunlight in the morning and avoid bright light at night. When your circadian clock starts to get disrupted, it can have negative effects on your time perception.
When Circadian Entrainment is Disrupted, Time Perception Suffers
This classic 1985 study by Ashcroft has been repeated many times and looks at how people perceive the passage of time in isolated environments with no clocks, windows or watches. People generally underestimate how long they have been in the environment and their perception of shorter time intervals, such as minutes and seconds, is also disrupted. This can have an effect on how well people can perform tasks if their circadian entrainment is disrupted, as it affects their perception of time. Accurately perceiving time is important for being able to work and complete tasks effectively.
Tool 6: Ultradian (90min) Cycles & Focus
Circannual entrainment is the matching of the cells and tissues and organs of our body to the 365 day journey that the earth takes around the sun each year. Circadian entrainment is the way that the 24 hour genetic and protein clocks of each and every one of our cells is matched to the rotation of the earth on its axis and the exposure or lack of exposure to the sun because of that rotation on its axis. Ultradian rhythms are rhythms of about 90 minutes or so, and all of our existence is broken up into these 90 minute ultradian cycles. It has been established that these 90 minute cycles also control our ability to focus and perform work in wakeful states. These ultradian rhythms are ones that you set and at around a hundred minutes or 120 minutes, no matter who you are, you're going to see a diminishment in performance. It is recommended to do no more than three and ideally it would be two or just one of these 90 minute cycles and they should be spaced by at least two to four hours.
Our Sense of the Passage of Time: Present, Prospective, Retrospective
Time perception involves three forms: our perception of the present, prospective timing, and retrospective timing. We can measure off intervals in the future and reconstruct events in the past using memory. The human nervous system is regulated by two main molecules, dopamine and norepinephrine, which modulate how we perceive time. Serotonin is also released from a different area of the brain and has a different effect on time perception. Studies have shown how dopamine and serotonin can affect time perception.
Dopamine (& Nor/epinephrine) Lead to Time Overestimation; Frame Rate
In summary, dopamine and norepinephrine are released in the brain and cause us to overestimate the passage of time. This is because they cause a phenomenon known as "fine slicing of time", which is similar to increasing the frame rate of a camera to show slow motion. Experiments have shown that the more dopamine or norepinephrine released, the more people tend to overestimate the amount of time that has passed. Dopamine and norepinephrine are also related, as dopamine can be converted into norepinephrine. This phenomenon is seen in both humans and animals.
Serotonin & Time Underestimation; Decreased Frame Rate
Serotonin is a neuromodulator that can cause people to underestimate the amount of time that has passed. Experiments have been done with drugs that increase serotonin, as well as cannabis, which increases serotonin and activates cannabinoid receptors. When people have elevated levels of serotonin, they tend to underestimate how much time has passed when asked to guess how much time has elapsed. This is due to serotonin slowing the brain's frame rate from 4000 frames per second to 20 frames per second. Additionally, there are variations in levels of dopamine, norepinephrine, and serotonin in the body during the 24-hour circadian cycle. This evidence suggests that these molecules play a role in time perception during wakefulness.
Dopamine vs. Serotonin Across the Day; Tool 7: When to Do Rigid vs. Creative Work
Our perception of time is affected by the levels of dopamine, norepinephrine, and serotonin in our brain, body, and bloodstream. In the first half of the day, dopamine and norepinephrine levels are higher and people tend to overestimate how much time has passed. In the second half of the day, serotonin levels are higher and people tend to underestimate how much time has passed. This affects how we should structure our day and prioritize tasks. Creative tasks should be done in the serotonergic second half of the day, while hard tasks should be tackled early in the day when dopamine levels are higher. This will help us to better parse difficult problems due to our higher resolution perception of time.
Example of Tool 7
Doing precision-based tasks like math, recipes, or physical skills require a high resolution brain, which can be found in the early part of the day due to dopamine and norepinephrine impacting time perception. On the other hand, afternoon is a better time for brainstorming and creativity as there is more flexibility in terms of how one batches time. The neurotransmitters dopamine and norepinephrine play an important role in how we perceive time, and thus how well we can perform certain tasks. Rigid tasks such as math and recipes require a higher resolution brain and should be done in the early part of the day. In the afternoon, we are better at brainstorming and creative works due to the serotonergic state of the brain.
How Sleep Deprivation Degrades Performance
The circadian rhythm plays a critical role in our sleep and waking patterns. When sleep is disrupted, it causes dysregulation of dopaminergic, neurogenetic, CIC, and serotonergic states which can lead to difficulty concentrating. Keeping the dopaminergic neurons and adrenergic state limited to the early part of the day, and the serotonergic state to the second half, could help keep this sense of time regulated. This could help to improve concentration and overall wellbeing. Poor sleep is linked to long-term health problems and so it is important to prioritize good sleep hygiene.
Trauma, “Over-clocking” & Memories; Adjusting Rates of Experience
People who have experienced trauma, like car accidents, can experience an increase in dopamine and norepinephrine levels during the event, which can cause them to perceive things as happening in ultra slow motion. This is known as overclocking and the information of the event gets stamped down into their memory system. The hippocampus and neocortex both take part in storing the memory, which involves both a space code of the particular neurons that fired, as well as a rate code of how quickly they fired. Treatments such as EMDR, ketamine therapies, and cognitive behavioral therapy can help to reduce the emotional weight of the memory by allowing the person to control the rate of playback of the memory. Overclocking is an extreme example of this phenomenon and it can be difficult to shake the memory and the emotions associated with it.
Why Trauma Involves Dopamine & Epinephrine, Arousal
Dopamine is not necessarily a molecule of reward, but a molecule of motivation and drive. It is closely related to the norepinephrine system and both are increased during heightened states of arousal. We don't know if dopamine is released during trauma, but it has been associated with changes in time perception during both positive and negative events. This could explain why dopamine is seen during trauma as it is a common hallmark of elevated arousal.
Dopamine, Spontaneous Blinking & Time Perception; Tool 8
There is a very interesting relationship between arousal, dopamine, time perception, and blinking. It is based on a paper titled ‘Time Dilates After a Spontaneous Blinking’ published in Current Biology Cell Press Journal. It is suggested that heightened states of arousal are associated with heightened levels of dopamine, which leads to a slicing of time through blinking. It is also said that cognitive attention follows visual attention, and increases in dopamine are associated with increases in spontaneous blink rate, which shifts our perception of time. It is suggested that if you want to slow down your perception of time, you should blink less, and if you want to speed it up, you should blink more. Time perception is a distributed phenomenon, with dopamine controlling the frame rate on our experience.
Deliberate Cold Exposure, Dopamine, Tool 9: Adjusting Frame Rate in Discomfort
Cold exposure, such as cold showers, ice baths, immersion in cold water tanks, lakes and oceans have many positive effects when done properly. A study published in the European journal of physiology showed that cold exposure can increase baseline levels of dopamine 2.5 times and it appears to be a healthy increase. When experiencing cold exposure, dopamine levels are high which can cause a person to experience the discomfort at a higher resolution. To cope with this, a person can focus on an external cue, think of something else, or sing a song in their head or out loud. This can help to divorce the person from the sensation and perception of their experience.
Fun “Feels Fast” BUT Is Remembered as Slow; Boring Stuff “Feels Slow,” Recall As Fast
Dopamine and serotonin can impact how we perceive the passing of time. Our experience in the moment can be vastly different than our retrospective perception of the event. When something is fun and varied, dopamine is increased and it can make the experience feel like it passes by quickly. Conversely, if something is boring or unenjoyable, then it can feel like it takes a long time. Studies have shown that if people are in a boring environment and isolated from time cues, it can feel like time is passing much more slowly than it is. Our perception of time is influenced by our level of excitement, and this is determined by dopamine and serotonin levels. Therefore, it is important to remember that two different stopwatches can be used to measure our experience, depending on our state of mind.
Retrospective Time, Context Variation & Enhanced Bonding with Places & People
Neuromodulators such as dopamine and novelty can influence our perception of time and memory. The more novel experiences we have in a certain place, the more we feel that we know it and the longer we feel we have been there. To illustrate this, if someone were to move to a new city and have a hundred different, exciting experiences, they would feel like they have lived there for longer than if they only lived in one place. The same concept is true for social interactions, if we experience several novel environments with someone, we tend to feel like we know them better, even if the total amount of time together is the same. This shows how our perception of time and neuromodulators can shape our relationships with places and people.
Dopamine Release Resets the Start of Each Time Bin on Our Experience
The neurochemicals dopamine and its associated neural circuits and areas of the brain have a major influence on how we perceive time. A study conducted by Neuron journal entitled Behavioral Physiological and Neural Signatures of Surprise During Naturalistic Sports Viewing demonstrated this by using brain imaging on subjects watching basketball games. The release of dopamine in the mesolimbic reward pathway, specifically the nucleus accumbens and the ventral tegmental area, occurs when an expected event happens and when a surprise occurs. This dopamine release serves as a marker that predicts the frame rate of the perception of the events. It can be concluded that dopamine and its release are responsible for how we divide up our experience and perceive the passage of time.
Habits & Time Perception; Tool 10 (Setting Functional Units of Each Day)
In this podcast, it is suggested that habits can be used to invoke a release of dopamine, which can help to mark the passage of time. This means that by engaging in specific habits at specific intervals throughout the day, one can structure their day in smaller or larger functional units. Habits can help us to feel motivated and to perceive time in a more structured and organized way. The Human Lab Podcast puts out a newsletter with an example protocol on how to use habits and dopamine to structure one's day.
Synthesis & Book Suggestion (Your Brain Is a Time Machine by D. Buonomano)
Dopamine is a chemical in the brain that contributes to forming habits and routines. These habits and routines can affect how we perceive time. Dr. Dean borne Amano is an expert in the neuroscience and physics of time and has written a book on the topic called "Your Brain is a Time Machine". This book covers how the brain perceives time and offers ways to adjust our perception of it. I hope to have Dr. Amano on the podcast soon to discuss his book further.